Download acinetobacter

Important Microorganisms in Foods
Aims:
(1) Introduce important spoilage microorganisms and pathogens in foods
(2) The introduction includes the morphology, biochemical characteristics, growing temperature and pH,
habitat, roles in foods for each microorganisms.
(3) It’s better to be familiar with the names of Genus for the spoilage microorganisms. However, for some
important industrial microorganisms and pathogens, you are recommended to know their scientific
names.
Outline:
(1) Important bacteria in foods
(2) Important molds in foods
(3) Important yeasts in foods
_______________________________________________________________________________________
1. Important bacteria in foods
Acinetobacter
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
Neisseriaceae
Gram(-)
rods short and plump approaching cocci – pairs and chains – also large
irregular cells and filaments noted in all cultures.
oxidative metabolism, oxidase(-),catalase(+), no flagella but twitching
motion on solid media, strict aerobes, resistant to penicillin
30 to 32℃ optimum
optimum pH 7.0
soil and water
usually not identified
psychrotrophic
spoil meat, poultry, fish, eggs and dairy products; also suggested for single
cell protein to utilize ethanol and gas oil
same as Pseudomonas
2-1
Aeromonas
1)
2)
3)
4)
Vibrionaceae
gram (-)
rods with rounded ends to cocci occurring singly, in paris or chains
facultative anaerobes that can either be fermentative or oxidative; motile by
polar flagella or non-motile; oxidase (+); catalase (+); casein; starch and
gelatin hydrolyzed
5) 0 to 41℃ range with 20 to 30℃ optimum
6)
7)
8)
9)
range pH 5.5 to 9.0
water
A. hydrophila
frequently mistaken for members of Enterobacteriaceae but oxidase (+)
and nitrate reduction are characteristic of Aeromonas speies; can grow in
psychrotrophic range
10) cause enteric infection from contaminated fish; spoil fresh meat, poultry,
and fish; cause black rot in eggs
11) Isolate on enteric media and follow by biochemical and serological tests
Alcaligenes
1)
2)
3)
4)
Genera of uncertain affiliation
Gram(-)
single rods to cocci
respiratory metabolism, never fermentative, oxidase (+), obligate aerobe,
motile with peritrichous flagella, non-pigmented, alkaline reactions
5)
optimum 20 to 37℃
6)
7)
8)
optimum pH 7.0
intestinal tract, water and marine environments, dairy products
most species that appear in the literature are no longer recognized as
distinct species except for A. faecalis
9) alkaline reaction, especially in litmus milk
10) spoil meat, poultry, eggs, fish; produce ropy milk and slimy cottage cheese
11) same as Pseudomonas
2-2
Alteromonas
1)
2)
3)
4)
Genera of uncertain Affiliation
gram(-)
straight or curved rods
respiratory metabolism, motile by single polar flagellum, require seawater
for growth
5)
optimum of 20-30℃, some grow at 4℃ and none at 45℃
6)
7)
8)
9)
10)
optimum near neutral
marine environments
usually not given
need seawater
spoilage of fish, produce sulfur-containing compounds (mercaptans, H2S,
dimethyl sulfide)
11) seawater needed in media (see Bergey’s Manual of Systemic Bacteriology
Volume 1, 1984)
Acetobacter
1)
2)
3)
4)
Acetobactereaceae
Gram(-)
straight or curve ellipsoidal to rod shaped; single, pairs or chains
respiratory and never fermentative, strict aerobes, motile by peritrichous
flagella or nonmotile, oxidize ethanol to acetic acid, catalase (+), oxidase
(-)
5)
5 to 42℃ with 25-30℃ optimum
6)
7)
8)
9)
10)
4 to 7.0 with 5.4 to 6.3 optimum
on fruits and vegetables
A. aceti – vinegar production
oxidize acetate and lactate to carbon dioxide plus water
vinegar production, cause ropy and sour beer due to acetification, rot in
apples and pears
11) medium with 0.5% yeast extract, 1.5% ethanol, and 2.5% agar
2-3
Aerococcus
1)
2)
3)
4)
Streptococcaceae
Gram(+)
cocci, tetrad formation if grown in suitable media
catalase absent or weak, microaerophilic (anaerobic growth is frequently
absent), homofermentative, D-lactic acid, non-motile, growth on solid
media is usually sparse and beaded, complex growth factors
5)
growth at 10 but not 45℃
6)
7)
8)
9)
similar to lactics
air, meat brines, raw and processed vegetables
A. viridans
growth in 40% bile, 10% NaCl, 0.01% potassium tellurite, pH 9.6,
produces H2O2
10) grow in meat brines and cause disease in lobsters
11) isolate in rich broth under aerobic conditions
Arthrobacter
1)
2)
3)
Coryneform group
Gram(+) to Gram (-) variable – granules retain stain if cell loses it
pleomorphic (cells change form during life cycle) – irregular rods change
to coccoid cells
4)
catalase (+), strict aerobes, respiratory metabolism ＆ never fermentative,
cellulose not attacked
5)
0 to 37℃, optimum 20 to 30℃
6)
7)
8)
9)
10)
11)
optimum neutral to alkaline
soil
species usually not identified
psychrotrophic, pectinolytic, some thermoduric
spoil meat and poultry
same as Corynebacterium
2-4
Actinomyces
1)
2)
3)
4)
Actinomycetaceae
Gram(+)
diphtheroid cocci or rods that form branched filaments and also form V, Y,
T shapes
facultative anaerobes, produce acids (acetic, lactic, formic, succinic) but no
gas form carbohydrate, CO2 needed for best growth
5)
optimum 35 to 37℃
6)
7)
8)
9)
10)
11)
optimum near neutral
soil
not usually identified
thermophilic strains
thermophilic spoilage of grains, cause of food-borne illness uncertain
brain heart infusion agar or blood agar in anaerobic atmosphere
Bacillus
1)
2)
3)
4)
Bacillaceae
Gram(+), can also stain gram variable
rods – single or chains with endospores
catalase (+), usually motile, strict aerobes or facultative anaerobes, some
are proteolytic and/or lipolytic, few form gas
5)
-5 to 75℃ (depends on species)
6)
7)
2 to 9.3
Soil, water, air, dust
8)
B. subtilis – strict aerobe, pH 5.5 to 8.5, temp. 5 to 55℃ with 30℃
optimum, reduces nitrate to nitrite, cause ropy bread, rancid salad dressing
＆ used to manufacture amylases ＆ proteases
2-5
B. licheniformis – ferments glucose anaerobically, temp. 15 to 55℃ with
optimum 30-50℃, grows in salt of 7.5 to 15%, reduces nitrate to nitrite, red
pigment if iron present, cause ropy bread and gas in canned meat under
anaerobic conditions in presence of sugar and nitrate
B. cereus – temp. 10 to 45℃with optimum of 30℃, pH 4.9 to 9.3,
aerobic or facultative anaerobic, gas under anaerobic conditions if nitrate
present, proteolytic (sweet curdles milk-clot ＆ no acid), found in spices,
food poisoning (spores survive 100℃ for 3 minutes)
B. megaterium – temp. 3 to 45℃, aerobic, usually pigmented (yellow,
pink, brown), usually motile, spoils salad dressing, sours fresh meat ＆
hams
B. polymyxa – temp. 5 to 45℃, facultative anaerobe (acid ＆ gas
anaerobically), bulging spores, needs biotin, grows on proteose peptone
agar, minimum pH 3.8 to 4.0, gassiness in cheese, spoilage of acid foods
due to under-processing or entrance due to defective seals
B. macerans – temp. 5 to 50℃, facultative anaerobe, bulging spores,
needs biotin and thiamine, dose not grow on proteose-peptone agar,
minimum pH 3.8 to 4.0, spoilage of acid foods due to under-processing or
entrance due to defective seals
B. stearothermophilus – obligate thermophile temp. 30-75℃, growth at
65℃= stable characteristic, spores need 121℃ for 20 minutes to destroy,
dose not grow at pH 5.0, sensitive to azide ＆ some acid, thermostable
enzymes & ribosomes (70℃ for 24h), “thermophilic flat sour” in canned
foods that are low acid
2-6
B. coagulans – temp. 15 to 60℃, pH 4.0 to 6.0 optimum, spores (121℃ for
0.7 minutes to destroy),”flat sour” in canned foods, used to produce lactic
acid commercially
9) produce spores that are more heat resistant than vegetative cells (generally
the higher the temperature of growth, the more heat resistant the spores are)
10) See #8 above
11) Sporeformers – heat at 80℃ for 10 minutes, plate and incubate under
aerobic conditions, do biochemical tests
Flat sour – steam or boil food for 5 minutes and plate on medium
containing glucose and acid-base indicator and incubate aerobically
B. cereus – plate on phenol-red-egg yolk-polymyxin agar; incubate at 30
℃ for 24 to 48h; do Biochemical tests (gram stain, sugar broths, nitrate
broth, litmus milk, gelatin, starch, buffered glucose broth)
Bacteroides
1)
2)
3)
4)
Bacteroidaceae
Gram(-)
nonsporeforming rods
obligately anaerobic, catalase(-), nonmotile or motile with peritrichous
flagella, fermentation products (succinic, lactic, acetic, formic and
propionic acids)
5)
best at 37℃
6)
7)
8)
9)
10)
11)
optimum 7.0
oral cavity, sewage, intestinal tract
usually not identified
anaerobic; suggested as fecal indicator but not used for foods
cause fresh meat spoilage but overlooked since anaerobic
isolate anaerobically on plate count or trypticase soy agars; do biochemical
tests
2-7
Bdellovibrio
1)
2)
3)
4)
Genera of Helical/Vibroid Cells
Gram(-)
comma shaped rods
predatory nongrowing phase and intracellular reproductive phase, motible
by single polar flagellum, obligate aerobe, respiratory metabolism, need
host to growth although some strains are prey-independent
5)
range 10 to 37℃ with optimum of 28 to 30℃
6)
7)
8)
9)
10)
11)
optimum near neutral
soil, sewage, marine environments
not usually identified to species
parasites for bacteria and lyses bacterial cells
unknown role in foods
needs host in most cases and depends on environment
Bifidobacterium
1)
2)
3)
4)
Actinomycetaceae
Gram(+)
variable rod shapes that may be branched; club, Y or V forms
saccharoclastic, glucose fermented to L (+) lactic and acetic in 2:3 ratio,
catalase(-), benzidine (-), anaerobic but slightly oxygen tolerant if CO2
present
5)
optimum 36 to 38 and none at 20 or 46.5℃
6)
7)
8)
9)
10)
11)
optimum 6 to 7 with little growth below pH 5.5
alimentary and instestinal tracts of humans and animals
B. bifidum suggested for colonizing intestinal tract of infants
anaerobic
possible fecal indicators
anaerobic conditions in presence of CO2
2-8
Brevibacterium
1)
2)
3)
4)
Coryneform Group (uncertain affliation)
Gram(+)
short, non-branching, non-sporeforming rods that resemble
Corynebacterium spp.
B. linens may be synonymous with Arthrobacter globiformis, orange-red
pigment
5)
optimum of 20 to 30℃
6)
7)
8)
9)
optimum around 7
soil, water, dairy products
all species are uncertain
may be reclassified as Corynebacterium or Arthrobacter species
10) surface of soft ripened cheese (Limburger ＆ Brick)
11) same as Corynebacterium
Brucella
1)
2)
3)
Genera of uncertain affiliation
Gram(-)
single coccobacilli or short rods
4)
respiratory metabolism, nonmotile; require thiamin, niacin ＆ biotin;
catalase (+), oxidase (±), strict aerobes
5)
20 to 40℃ with 37℃ opitumum
6)
7)
8)
optimum 6.6 to 7.4
raw milk from sick animals
B. abortus – brucellosis in dairy herds
B.melitensis – involved in cheese
9) mammalian parasites and pathogens
10) “Malta” fever in humans
11) isolate on nutritive selective media by incubating in 10% CO2 atmosphere,
do biochemical tests
2-9
Campylobacter
1)
2)
3)
4)
Spirillaceae
Gram(-)
slender spirally curved rods, old cells forms coccoid bodies
respiratory metabolism, microaerophilic to anaerobic, motile with single
polar flagellum at one or both ends, oxidase (+), energy form amino acids
or TCA cycle intermediates and not carbohydrates
5)
growth at 25℃, but usually not 42℃, optimum = 37℃
6)
7)
optimum = pH 7.0
infected animals, intestinal tract, water
8)
Campylobacter fetus subsp. Jejuni opt. 42℃, not grow at 25℃
Campylobacter fetus subst. intestinalis
9) motile by corkscrew action, growth best in 5% O2 and 10% CO2
10) food gastroenteritis from water, raw milk, undercooked pork and poultry
11) complex, see current literature
Cellulomonas
1)
2)
3)
4)
5)
Coryneform Group
Gram(+); decolorize easily and Gram (+) granules observed in Gram (-)
cells
irregular rods that are straight, curved, club-shaped, or arranged in V-shape
but can become more coccid on aging
aerobic to facultative anaerobes, require biotin and thiamine, attack
cellulose, motile (usually polar) or nonmotile, oxidase (-)
optimum 30℃
6)
7)
8)
9)
10)
optimum pH 7.0
soil
C. flavigena – spoils olives by degrading cellulose
degrades cellulose
attacks cellulose in vegetable products, studied for single cell protein (SCP)
from waste products
11) isolate in medium containing a cellulose substrate
2-10
Citrobacter (one of coliforms)
1)
2)
3)
4)
Enterobacteriaceae
Gram(-)
rods
uses citrate as sole carbon source, motile with peritrichous flagella, grows
on KCN, carbohydrate fermented to acid ＆ gas (CO2 + H2 ),IMVC
(±+-+)
5)
optimum 30 to 37℃
6)
7)
8)
9)
optimum around neutral pH
water, feces, urine, intestinal tract
usually not identified
can be psychrotrophic, common in fecal matter
10) spoils fresh meat ＆ poultry
11) same as for Escherichia
Clostridium
1)
2)
3)
4)
Bacilaceae
Gram(+) (especially in early stages)
rods – with oval spore that distends the bacilli, with endospore
catalase(-), nonmotile or motile with peritrichous flagella, anaerobic,
saccharolytic or proteolytic, produce acid and gas
5)
0 to 70℃, optimum depends on species
6)
7)
3.0 to 8.5
Soil, water, intestinal tract
8)
C. butyricum – temp. optimum 25 to 37℃, requires biotin, gaseous
spoilage of acid foods, butyric fermentation in fruits and vegetables, stormy
fermentation in milk and hams
C. pasteurianum – optimum. 37℃, spores not heat resistant, gassiness in
cheese and acid foods
2-11
C. sporogenes – optimum temp. 30 to 40℃, digests milk, putrefactive
anaerobe that spoils acid and low acid foods, 【PA 3679】is a tested
organism for heat processing canned foods, causes explosion in chocolates
C. botulinum – optimum temp. 30 to 40℃, putrefactive, produces potent
neurotoxin, food intoxication mainly form home processed foods and
usually is type A. Type E from fish, spores 120℃ for 4 minutes to destroy,
toxin Type A 80℃ for 6 minutes to destroy
C. perfringens – optimum temp. 45℃, nonmotile, require amino acids
and growth factors, pH 5 to 8, H2S produced in most media, spores need
minutes to 6h at 100℃ for inactivation, produced toxin (α-in US) in
intestine from cooked meat and related foods causes food poisoning
C. thermosaccharolyticum – obligate thermophile with optimum at 55℃,
thermophilic anaerobe (TA) causing hard swell in non-acid canned foods,
coagulates milk, degrades sugar
C. putrefaciens – optimum temp. 20 to 25℃ with 0 to 30℃ range,
nonmotile, produce H2S and gas, putrefactive, spores 100℃ for 10 minutes
to destroy, spoil ham and other meats
9) Most strains are strictly anaerobic; carbohydrates usually fermented with
gas production; protein degradation yields H2S, mercaptans, etc
10) See #8 above
11) Sporeformers – heat at 80℃ for 10 minutes, plate and incubate
anaerobically at appropriate temperature
Sulfide-spoilers – use sulfide-containing medium and incubate under
appropriate conditions
C. botulinum – enrich in medium containing trypsin and incubate at 26℃
for 5 days and then streak on liver-veal egg yolk agar; characterize
biochemically (gram stain, morphology and sporulation), inject mice
intraperitoneally to observe toxigenicity
2-12
C. perfringens – plate on tryptose-sulfite-cycloserine (TSC) agar and
incubate at 35℃ for 24h; do biochemical tests (thioglycollate, iron-milk,
motility-nitrate, lactose-gelatin, sporulation broth, etc.), check for α-toxin
production
Corynbacterium
1)
2)
3)
4)
Coryneform Group
Gram(+) – can lose stain easily and only granules remained
straight and curved rods frequently showing club-shaped swelling, produce
palisade layers
catalase (+), facultative anaerobic or aerobic, non-motile or motile
5)
0 to 40℃
6)
7)
8)
5 to 7.5
soil, water, air, plants, intestinal tract
C. bovis – mastitis in cows
C. diptheriae – diphtheria – may be transported by food
Most mesophiles, some psychrotrophs
9)
10) Corynebacterium species – various plant disease (rots ＆ wilting);
spoilage of meat, poultry and seafoods
11) use media such as trypticase soy agar, plate count agar, etc,; characterize by
biochemical tests and morphology
Desulfotomaculum
1)
2)
3)
4)
Bacillaceae
Gram(+)
straight or curved rods with rounded ends, single or sometimes in chains;
spores are oval to round, terminal to subterminal, and cause swelling of
cells
anaerobic, catalase (-), sulfate reduced to sulfide, respiratory metabolism,
motile by peritrichous flagella
5)
30 to 70℃ with optimum of 35 to 55℃
6)
7)
sensitive to acid, grows at pH 6.0 or above
soil, fresh water, waste water, rumen
2-13
8)
D. nigrificans – thermophilic temp. 45-70℃ with optimum of 55℃
9)
Reduces sulfate, sulfites, and other sulfur compounds to H2S; thermophilic
sporeformer
10) causes sulfate spoilage of canned foods (peas, corn)
11) use anaerobic conditions and thermophilic temperatures
Desulfovibrio
1)
2)
3)
4)
Sulfur-Reducing Bacteria
Gram(-)
curved, straight or spirolloid rods (influenced by age and environment)
usually respiratory metabolism with sulfate compound as terminal electron
acceptor, sometimes fermentative metabolism, motile by single polar
flagellum, obligate anaerobe, need reducing agent for growth, moderately
halophilic
5)
range 0 to 44 ℃ with optimum of 25 to 35℃
6) optimum pH 7 to 7.5
7) soil, water, marine environments
8) not usually identified
9) reduction of sulfate to H2S which reacts with iron to form FeS
10) odor of manure pile imparted in pickling brines
11) anaerobic conditions in salt medium containing carbon source and sulfate
with pH of 7.5
Edwardsiella
1)
2)
3)
4)
Enterobacteriaceae
Gram(-)
rods
facultative anaerobe, motile by peritrichous flagella, H2S produced, citrate
not used as sole C source, indole (+), catalase (+)
5)
37℃ optimum
6)
similar to other enterics
7)
isolated from humans with diarrhea, from blood ＆ urine, and water
8)
9)
10)
11)
E. tarda
H2S produced on TSI agar
proof not conclusive for causing enteritis by transmission in foods
isolate on enteric media, then do biochemicals and serology
2-14
Enterobacter (one of coliforms)
1)
2)
3)
Enterobacteriaceae
Gram(-)
short rods
4)
catalase (+), oxidase (-), no H2S, IMVC (--++), acid ＆ gas by 2,3
butanediol fermentation, motile by peritrichous flagella, citrate ＆ acetate
used as sole carbon
5)
optimum 30 to 37℃
6)
4.5 to 8.5
7)
plants, soil, water ＆ sometimes intestinal tract
E. aerogenes – ropy milk, gas in cheese
E. cloacae – early sauerkraut manufacture
9) coliform group of plant origin, predominant in absence of oxygen in
refrigerated foods (vacuum packed meats)
10) see 8 and 9 above, also spoil meat, fish and milk
11) same as Escherichia
8)
Erwinia
1)
2)
3)
4)
Enterobacteriaceae
Gram(-)
single straight rods
catalase (+), oxidase (-), acid but gas weak or absent, facultative anaerobes,
motile by peritrichous flagella, degrade pectins, rarely produce urease or
lipases, pigment yellow to red
5)
optimum 27-30℃, range 1to 40℃
6)
7)
8)
9)
10)
11)
4 to 8.8, optimum 6.0 to 7.0
plants
E. carotovora
plant pathogens
cause soft rot, wilt, and necrosis in fruits and vegetables
isolate on standard plate count agar and do biochemicals
2-15
Escherichia (one of coliforms)
1)
2)
3)
4)
Enterobacteriaceae
Gram(-)
single or paired rods
facultative anaerobes, catalase (+), oxidase(-), motile by peritrichous
flagella or nonmotile, uses acetate but not citrate as sole carbon source,
lactose fermented by most; glucose fermented to lactic, acetic and formic
acids plus gas (H2+CO2); KCN not used, H2S not produced on TST, IMVC
reaction (++──)
5)
0-46℃ optimum 30 to 37℃
6)
7)
8)
4.5 to 8.5
intestinal tract
E. coli
Enteropathogenic E. coli (EEC), Enterotoxigenic E. coli (ETEC), E. coli
O157:H7
9) used as fecal indicator for water foods
10) spoils meat, poultry, fish, eggs, dairy products; EEC causes diarrhea food
poisoning especially in infants and travelers; ETEC causes traveler’s
diarrhea; E. coli O157:H7 causes hemorrhagic colitis
11) use EMB of Violet Red Bile agars and confirm with biochemical tests and
serology
Flavobacterium
1)
2)
3)
4)
Genera of uncertain affiliation
Gram (+)
coccibacilli to slender rods
respiratory metabolism, motile by pertitrichous flagella or nonmotile,
pigmented (yellow, red, orange, brown), some facultative anaerobes
5)
grow best below 30℃
6)
7)
8)
9)
10)
11)
5 to 9, optimum 7.0
soil, water, vegetation, dairy products
usually not identified
many psychrotrophic
spoil fish, poultry, eggs, meat, dairy products
same as Pseudomonas
2-16
Gluconobacter
1)
2)
3)
4)
Acetobacteraceae
Gram (-) to Gram variable
elliposoidal to rod-shaped, occur in pairs, chains or singly
respiratory metabolism, never fermentative, catalase (+), strict aerobes,
motile with 3 to 8 polar flagella or nonmotile, oxidizes ethanol to acetic
acid
5)
optimum 25 to 30℃, no growth at 37℃
6)
7)
8)
9)
10)
3.6 to 7 with 5.5 to 6.0 optimum
flowers, fruits and vegetables
G. oxydans
will not oxidize lactate to CO2
causes ropiness and souring of beer by acetification; occur in baker’s yeast,
honey, fruits soft drinks; cause rot in apples and pears
11) medium: yeast extract (0.5%), glucose (5%), actidione (0.01%), and
bromophenol blue (0.006%)
Hafnia
1)
2)
3)
4)
Enterobacteriaceae
Gram (-)
rods
facultative anaerobe, motile by peritrichous flagella, citate not used as sole
C, glucose fermented to acid and gas, no H2S
5)
optimum 37℃
6)
7)
8)
9)
similar to other enterics
feces of humans and animals, soil, water, sewage, dairy products
H. alvei
may use malonate as carbon source, some grow at refrigeration
temperatures
10) off-flavor in beer as phenols, spoil vacuum packaged meats
11) same as other Enterobacteriaceae members
2-17
Halobacterium
1)
2)
3)
4)
Halobacteriaceae
Gram (-)
single rod
respiratory metabolism, never fermentative, catalase (+), oxidase
(+),carotenoid pigments (yellow ＆ red), need 15% salt for growth;
sodium , magnesium, and chloride needed to maintain cell structure and
rigidity; motile by tuft of polar flagella or nonmotile
5)
30 to 50℃with 40℃ optimum
6)
7)
8)
9)
10)
5.5 to 8.0 with optimum 7.2 to 7.4
salt water
H. salinarium – obligate halophile that discolors salted fish
alkaline reactions due to deamination or decarboxylation of amino acids
spoils seafood and fish
11) use medium with 15% salt and incubate at 40℃
Halococcus
1)
2)
3)
4)
Halobacteriaceae
Gram (-)
cocci in pairs, tetrads or clusters
growth in 2.5M NaCl or high, respiratory metabolism, non-motile, aerobic,
pink to red pigment, catalase (+), oxidase (+)
5)
range 30-37℃
6)
7)
8)
9)
10)
optimum 7.2; some growth at pH 5.5 but not at pH 8.0
wherever salt is highly concentrated, especially ocean waters and solar salt
H. morrhuae
need 2.5M (15%) salt for growth, produce red pigment or bacteriorubein
spoil salted fish
11) medium with 15% salt and incubation at 30-35℃
2-18
Klebsiella (one of coliforms)
1)
2)
3)
4)
Enterobacteriaceae
Gram (-)
capsulated rods – single, pairs or chains
oxidase (-), catalase (+), acid &gas by 2,3 – butanediol fermentation, H2S
not produced, nonmotile, IMVC (D,D,D,D), resistant to penicillin
5)
optimum 35 to 37℃
6)
7)
8)
9)
10)
11)
optimum 7.2
respiratory and intestinal tracts
K. pneumoniae – causes pneumonia
one of coliforms – can be used as fecal indicator
food-borne spread of pneumonia not usually noted
isolate on enteric medium, such as MacConkey’s; then do biochemical and
serological tests
Kurthia
1)
2)
3)
4)
Coryneform Group
Gram (+)
regular unbranched rods with rounded ends that; occur in chains
catalase (+), respiratory metabolism & never fermentative, strict aerobes,
motile
5)
5 to 37℃ with optimum at 25 to 30℃
6)
7)
8)
9)
10)
11)
near neutral optimum
plants and meat
species usually not identified
grow in 4 to 6% salt
found on fresh and vacuum packed meats
same as Corynebacterium
Lactobacillus
1)
2)
3)
Lactobacillaceae
Gram (+)
rods – single or chains
2-19
4)
catalase (-), Homo- or heterofermentative, nonmotile, nonsporeforming
facultative anaerobes, rarely pathogenic, D,L or DL-Lactic Acid, complex
nutritional requirements
5)
5 to 53℃; optimum 30 to 40℃
6)
7)
8)
3 to 9.6 optimum 5.5 to 5.8
plants, dairy products & intestinal tract
*L. brevis – pickles, olives, bloaters in pickles, sausage
L. bulgaricus – Swiss cheese, buttermilk, yogurt, thermophile
L. casei – ropy milk, bread starter
L. lactis – thermoduric
L. plantarum – pickles, olives
L. helveticus – Emmental & Gruyere cheese
L. delbrueckii – soy sauce fermentation, beer & distilled spirits – sour
mash
*L. fermentum – gas in cheese (false eyes in Swiss)
L. leichmannii – Kumiss (fermented milk of Russia)
*L. viridescens – greening of meat
*L. hilgardii – deterioration of wine
*L. tricodes – deterioration of wine
L. acidophilus – acidophilus milk
*L. buchneri – deterioration of wine, sausage fermentation
9) must have fermentable carbohydrate, ferment sugars to considerable acid
10) see #8 above * = Heterofermenters
11) same as Streptococcus
Leuconostoc
1)
2)
3)
4)
Streptococcaeae
Gram (+)
cocci in pairs & chains
catalase (-), heterofermentative, nonmotile, complex growth and amino
acid requirements, facultative anaerobes, L- lactic Acid
5)
10 to 40℃ but some species vary
6)
7)
3 to 9.6
plant surfaces, milk
2-20
L. cremoris – diacetyl (buttermilk, etc.)
L. mesenteroides – pickles, olives & sauerkraut, slimy syrups & sugars
L. oenos – spoil wines
L. lactics – milk & dairy products, thermoduric
L. dextranicum – spoils orange juice
9) must have fermentable carbohydrate, relatively inactive in litmus milk (no
reduction or clot)
10) mainly fermented foods – see #8 above
11) same as for Streptococcus
8)
Listeria
1)
2)
3)
4)
Genera of Uncertain Affiliation
Gram (+); may strain Gram (-) if cells are old
coccoid rods in chains of 3 to 5 cells or in filamentous forms; diptheroid
palisade layers can be seen when stained
aerobic to microaerophilic (reduced O2 and 5 to 10% CO2), motile by
peritrichous flagella (20 to 25℃), catalase (+), growth slow in absence of
carbohydrate, ferments sugars (glucose, trehalose, salicin) to acid,
hydrolyze esculin and polysorbate 80, produces small zone of β-hemolysis
on blood agar, H2S(-), O- and H-antigens used to differentiate serotypes,
grows in 10% salt
5)
range of 2.5 to 38℃; optimum 35 to 37℃
6)
7)
8)
9)
pH range 5.5 to 9.6
feces of animals and humans, vegetation, silage, soil
L. moncytogenes
able to grow at refrigeration temperatures, produces gastroenteritis and
leukocytosis and moncytosis (mild influenza-like illness to meningitis,
bacteremia endocarditis, and central nervous system infection; many
patients have other medical disorders or are on immunosuppressive drugs)
with a mortality rate of around 50%
10) microorganism transported through milk or infected meat (rare)
11) isolate on sheep’s blood agar, McBride’s Listeria agar using atmospheres of
10% CO2, 5% O2 and 85% N2 and 35℃
2-21
Methylococcus
1)
2)
3)
4)
Methylomonadaceae
gram (-)
spheres in pairs with cyst in resting stage
aerobic, respiratory metabolism, grow only on methane or methanol or
formaldehyde
5)
range 30 to 50℃ with optimum at 37℃
6)
7)
8)
9)
10)
optimum near neutral
soil and water
M. capaulatus
growth on methane or methanol
use methanol from food waste fermentation and make single cell protein
11) nitrate mineral salts plus methane at 37-45℃in oxygen atmosphere
Methylomonas
1)
2)
3)
4)
Methylomonadaceae
Gram (-)
straight, curved or branched rods
aerobic, respiratory metabolism, motile by single polar flagellum, cysts in
resting stage, energy sources (methane, methanol, formaldehyde), catalase
(+), oxidase (+)
5)
range 20 to 35℃
6)
7)
8)
9)
10)
range 6.8 to 8.0 in presence of sodium nitrate
soil and water
usually not given
grow on methane or methanol at 20% O2 or greater
utilization of methanol produced from food waste fermentation for single
cell protein
11) need methane or methanol in nitrate mineral salts and enrichment with soils
and oxygen atmosphere
2-22
Microbacterium
1)
2)
3)
4)
Coryneform Group (uncertain affiliation)
Gram (+)
small diptheroid rods with rounded ends; angular & palisade layers are
typical
catalase (+), weakly fermentative, nonmotile, aerobic, produce lactic acid
5)
15 to 35℃ with optimum at 30℃
6)
7)
8)
9)
10)
11)
optimum 6.8 to 7.5
dairy products
all are uncertain
resemble Corynebacterium and Arthrobacter spp.
spoil meat, poultry, fish, milk, also thermoduric
same as Corynebacterium
Micrococcus
1)
2)
3)
4)
Micrococcaceae
Gram (+)
cocci-irregular clusters, single or pairs
catalase (+), tolerates 5-15% salt, water soluble pigment (yellow, orange &
red), lysostaphin (-), nonmotile, strict aerobe
5)
optimum = 25-30℃, range = 0 to 45℃
6)
7)
range = 5 to 8.5
fresh & salt water, air, soil, sewage plant surfaces, skin of humans &
warm-blooded animals (essentially on all raw foods)
M. luteus –yellow
M. roseus – pink
M. varians–thermoduric
M. radiodurans/irradiation–resistant to irradiation
selective advantage: (a) high salt foods, (b) use nitrate ion in place of
oxygen – cured meats, (c) survive heating – milk pasteurization, (d) more
resistant to dehydration & radiation; (e) sensitive to acid – inhibited at pH 5,
(f) grow at refrigeration temperatures, (g) produce lipolytic & proteolytic
enzymes, reduce nitrate to nitrite, and oxidize organic substrates, (h)
discolor food (yellow, pink) Note: Rarely primary source of spoilage
since unable to grow rapidly & compete with other microorganisms – can
be problems in above 8 cases if conditions are optimum.
8)
8)
2-23
10) (a) Brick & Surface ripened cheese-oxidize lactic acid & increase pH, (b)
Cheddar Chinese – flavor, (c) Salt cured meat products – reduce nitrate
which affects color fixation and also spoils bacon, ham & bologna, (d) dry
fermented sausage – controlled European fermentations
11) (a) medium with added salt, (b) medium for lipolytic and proteolytic
microorganisms, (c) thermodurtic – 30 minutes at 62.8℃ and then plate
milk, (d) medium designed for specific food product in mind.
Moraxella
1)
2)
3)
4)
Neisseriaceae
Gram(-)
short plump rods often approaching cocci; in pairs or chains
oxidative metabolism, strict aerobes, oxidase (+), catalase (+), sensitive to
penicillin, no flagella but may have twitching motility on solid surfaces,
carbohydrates not utilized
5)
32 to 35℃optimum
6)
7)
8)
9)
10)
7 to 7.5 optimum
soil and water
usually not identified
parasitic on mucous membranes
spoilage of meat, poultry and fish – usually initiate spoilage with
Acinetobacter and then Pseudomonas predominate
11) same as Pseudomonas
Mycobacterium
1)
2)
3)
4)
Mycobacteriaceae
gram (+), but not readily stained
slightly curved or straight rods which may show filamentous branching
aerobic, acid-alcohol fast, slow growing, catalase (+), nonmotile, pigment
(yellow to red)
5)
optimum 30 to 40℃
6)
7)
optimum 6.4 to 7.0
soil, water, warm & cold-blooded animals
2-24
8)
9)
10)
11)
M. tuberculosis – tuberculosis may be spread by foods
acid-fast at some stages of growth
can cause tuberculosis, previous basis for pasteurization of milk
grow slowly (up to 2 weeks) on media containing egg or coagulated serum
Nocardia
1)
2)
3)
4)
Norcardiaceae
Gram (+)
coccoid cells with branched filaments and microcyts or chlamydospores
obligate aerobes, nonmotile, carotenoid pigments produced, resists
lysozyme, virulent phage know for few species
5)
range 10 to 45℃ with optimum 25 to 35℃
6)
7)
8)
9)
10)
range 5 to 10 with optimum of 7 to 7.5
soil
N. steroids
filamentous forms produced
produce vitamin B12, N. steroids can infrequently produce mastitis in
cows, suggested for single cell protein
11) depends on source
Pediococcus
1)
2)
3)
4)
Streptococcaceae
Gram (+)
cocci in pairs & tetrads
catalase (-), homofermentative, nonmotile, DL-Lactic Acid, facultative
anaerobes, complex nutritional requirements
5)
7 to 45℃ with optimum 25 to 32℃
6)
7)
8)
9)
10)
4 to 9.6
plant materials
P. cerevisiae
must have fermentable carbohydrate, grow in salt to 5.5%
fermentation of pickles; sauerkraut; summer sausage; cause ropiness,
turbidity & sourness in beer
11) same as Streptococcus
2-25
Peptococcus
1)
2)
3)
Peptococcaceae
Gram (+)
cocci as single, pairs tetrads or irregular mass
4)
catalase (±), heterofermentative, anaerobic, carbohydrate not required, uses
peptones and amino acids for energy, sensitive to penicillin G
5)
range 25 to 37℃, optimum of 35 to 37℃
6)
7)
range 6 to 8, optimum of 7 to 8
mouth and intestinal and respiratory tracts of humans and animals and in
soil
8) usually not identified
9) use protein degradation compounds for energy and anaerobic
10) uncertain, isolated from skin of humans
11) anaerobic conditions similar to Clostridium species
Peptostreptococcus
1)
2)
3)
4)
Peptococcaceae
Gram(+)
cocci occurring in pairs or short to long chains
catalase(-), anaerobic, heterofermentative, lactate not produced, ammonia
produced
5)
range 25 to 38℃, optimum of 35 to 37℃
6)
7)
8)
9)
range 6 to 8, optimum of 7 to 7.5
oral cavity and respiratory and intestinal tracts in humans and animals
usually not identified to species
anaerobic and do not produce lactic acid but acetic formic, propionic,
butyric, isobutyric, valeric, isovaleric caproic, isocapptoic, and succinic
acids
10) uncertain
11) same as Peptococcus species
Photobacterium
1)
2)
3)
Vibrionaceae
gram(-)
plump, straight rods
2-26
4)
respiratory or fermentative metabolism, motile by one to three unsheathed
polar flagella, grow in mineral medium plus seawater, sodium needed for
growth
5)
growth at 4℃ and 35℃ used to differentiate species, usually grow at 20℃
6)
7)
8)
9)
optimum near neutral
marine environments
usually not given
need sodium for growth, use seawater, produce luciferinase and produces
light
10) isolated from fish
11) similar to Alteromonas species
Planococcus
1)
2)
3)
4)
Micrococcaceae
Gram(+)
cocci-single, pairs or tetrads
catalase(+), metabolism respiratory, strict aerobes, motile with one to four
flagella, hydrolyze gelatin
5)
optimum = 20 to 37℃
6)
7)
8)
9)
10)
11)
optimum pH 6 to 7.0
isolated from poultry and seawater
P. citreus – yellowish orange water-insoluble pigment
not often associated with food
part of normal flora
nutrient broth or sea water
Propionibacterium
1)
2)
3)
4)
Propionobacteriaceae
Gram(+)
nonsporeforming, pleomorphic, diptheroid (club-shaped) rods
anaerobic to aerotolerant, fermentative yielding propionic and acetic acids
and carbon dioxide, catalase (+)
5)
optimum 30 to 37℃
6)
7)
optimum pH 7.0
dairy products and intestinal tract
2-27
8)
9)
10)
11)
P. freundenreichii subsp. Shermanii
Production of propionic acid
forms characteristic eyes in Swiss cheese, also contributes to flavor
isolate on yeast extract lactate medium and incubate anaerobically with 5%
CO2 for 7 to 10 days at 30℃
Proteus
1)
2)
3)
4)
Enterobacteriaceae
Gram(-)
rods in chains or pairs that can give coccoid or filamentous forms under
special conditions
catalase(+), oxidase(-), motile by peritrichous flagella, nonpigmented, acid
& sometimes gas from glucose, IMVC(+ + + D), urease(+), grows in KCN
5)
10 to 43℃
6)
7)
8)
9)
10)
11)
optimum 6 to 7
soil, water, intestine
usually not identified
produces swarming on solid media
spoil meat, eggs, seafood & dairy products; also proteolytic (putrefactive)
same as Klebsiella
Pseudomonas
1)
2)
3)
4)
Pseudomonadaceae
Gram(-)
single straight or curved rods
respiratory metabolism, never fermentative, strict aerobes, catalase(+),
oxidase(+), motile by one or more polar flagella, some produce diffusible
and/or fluorescent pigments(red, blue, green, yellow)
5)
4 to 43℃
6)
7)
most do not grow below pH 5.3-6.0
soil, water, intestinal tract, and on plants
2-28
P. fluorescens – fluorescent pigment
P .aeruginosa – of clinical importance
considerable regrouping of the gram negative rods has changed many of the
names that appear in literature
9) (a) psychrotrophic growth is important; (b)use variety of noncarbohydrate
compounds for energy; (c)lipolytic and/or proteolytic; (d)ability to
synthesize own growth factors; (e)aerobic – grow fast & cause surface
spoilage; (f)pigment formation discolors surface; (g)most important low
temperature spoilage microorganisms
10) spoilage of meats, poultry seafood, eggs, dairy products
11) use trypticase soy agar or plate count agar and do biochemical tests
(oxidase, catalase, penicillin sensitivity, flagella stain, etc.)
8)
Sarcina
1) Peptococcaceae
2) Gram(+)
3) cocci in packets of eight or more
4) strict anaerobes, nonmotile, fermentative metabolism (CO2, H2, acetic acid,
require numerous amino acids and few vitamins)
5)
optimum = 30 to 37℃
6)
7)
8)
9)
10)
11)
range = 1 to 9.8
salted fish, ham, surface of cereal grains
species usually not identified
spoil salty foods
spoilage of ham and salty fish
anaerobic conditions; salt for selective purpose
Salmonella
1)
2)
3)
4)
Enterobacteriaceae
Gram (-)
rod
acid & gas from glucose but not lactose, motile by peritrichous flagella,uses
citrate as sole carbon sauce, oxidase (-), produces H2S, IMVC (- + - +),
mixed acid fermentation (lactic, formic acetic & succinic), catalase (+)
2-29
5)
7 to 47℃ with optimum at 37℃
6)
7)
8)
4-9 with optimum at 6.5 to 7.5
intestinal tract
S. typhi – typhoid fever
S. typhimurium – most often in food poisoning outbreaks
9) causes food infection due to ingestion of large number of cells, classified
by serology (O, K, and H antigens)
10) all species can cause food poisoning; spoils meat, poultry & eggs in
mesophilic range
11) use pre-enriched lactose broth for 24h 35℃ followed by selective
enrichment in selenite-cystine and tetrathionate broths; streak on selective
agars (Hektoen enteric, xylose lysine desoxycholate, bismuth-sulfite);
characterize by biochemistry (TSI, LIA urease, etc.) and serology (O, H, K
antisera)
Serratia
1)
2)
3)
4)
Enterobacteriaceae
Gram (-)
rods-some encapsulated
catalase (+), oxidase (-), many strains produce pink to red pigments, IMVC
(- + D +), glucose may or may not be fermented with gas production,
lactose not fermented
5)
optimum 25 to 30℃
6)
7)
8)
9)
10)
11)
optimum around 7
soil and water
S. marcescans
some psychrotrophic and cause surface discoloration of meat and fish
spoil meat, poultry, eggs, seafood; also cause lipolytic degradation
same as Klebsiella
2-30
Shigella
1)
2)
3)
4)
Enterobacteriaceae
Gram (-)
short rods
acid but not gas from carbohydrates, oxidase (-), catalase (±), nonmotile,
inhibited by KCN, H2S not produced, IMVC (D + - -), aerobic
5)
optimum 37℃
6)
7)
8)
9)
optimum 6.4 to 7.8
intestinal tract and polluted water
S. dysenteriae – bacillary dysentery
all species produce dysentery and are undesirable in foods: refrigeration
usually prevents growth
10) cause dysentery when transmitted by water and food
11) use gram-negative broth followed by selective agars (low=MacConkey or
Tergitol 7 Agar; intermediate=Xylose-Lactose-Desoxycholate (XLD);
high=Salmonella-Shigella Agar or Hektoen Enteric Agar); confirm by
biochemical tests and serology
Sporolactobacillus
1)
2)
3)
4)
Bacillaceae
Gram (+)
rods-single, pair or short chains with endospores
microaerophilic, catalase (-), fermentative lactic metabolism, motile by
peritrichous flagella, needs sugar in medium
5)
15 to 40℃ with optimum of 30 to 35℃
6)
7)
8)
9)
10)
11)
pH 4.0 is limit
isolated from grains, plants and soil
S. inulinus
similar to Lactobacillus spp. except sporeformation similar to Bacillus spp.
potential role in food-spoilage
still being researched
2-31
Sporosatcina
1)
2)
3)
4)
Bacillaceae
Gram(+)
cocci in tetrads or packets with endospores
strict aerobes respiratory, motile or nonmotile, need complex media for
growth, catalase (-)
5)
optimum 22 to 30℃, no growth at 37℃
6)
7)
8)
range 6.4 to 9.4, optimum sporulation 6.8 to 7.0 but optimum growth at 8.8
soil
S. uteae
9)
Sporaformer, spores withstand 85℃ for 10 min
10) uncertain
11) similar to Bacillus species
Streptococcus
1)
2)
3)
4)
Streptococcaceae
Gram (+)
cocci in chains & pairs
catalase (-), homofermentative, non-pigmented, D-Lactic acid, facultative
anaerobes, usually nonmotile, complex nutritional requirements
5)
optimum 37℃; minimum & maximum vary with species
6)
7)
varies with species but generally 4 to 9.6
foods, beverages, animal body (nasopharynx, intestinal tract, etc.)
8)
Pyogenic
Viridans
Enterococcus
Lactococcus
10℃
-
-
+
+
45℃
-
+
+
-
-
-
+
+
-
pH 9.6
6.5 % NaCl
S. agalactiae
S. pyogenes
S. thermophilus
2-32
S. faecium
S. faecalis
S. lactis
S. cremoris
9)
must have fermentable carbohydrate, colonies remain small & not
pigmented, catalase (-) because no cytochromes, high tolerance to acid
10) S. agalactiae – Mastitis in cows
S. pyogenes – Strep throat, scarlet fever
S. thermophilus – Swiss & Italian cheeses, yogurt & thermophilic
S. faecalis-indictors of fecal contamination, thermoduric, grows 5 to 50℃,
proteolytic, produces acid in pickles and sauerkraut
S. faecium – common in plants, thermoduric
S. cremoris & S. lactis – starter bacteria (cottage cheese, Cheddar cheese,
sour cream, etc.), slimy & ropy milk (long chain formation)
S. lactis – sour raw milk at 10-37℃
11) use selective media for lactics or acid-producers (Lactic Agar, Trypticase
Soy Agar with Bromcresol purple, etc.)
Biochemical tests: gram reaction; catalase test; fermentation of sugars;
tolerance to pH, temperature and salt
Staphylococcus
1)
2)
3)
4)
Micrococcaceae
Gram(+)
cocci – pairs or grapelike clusters (solid media)
catalase (+); facultative anaerobe; nonmotile; require amino acids, thiamine
and nicotinic acid; when grown anaerobically require uracil and
fermentable carbohydrate
absence of oxygen
Glucose
Lactic acid
presence of oxygen
Glucose
Acetic acid + CO2
Grow in 15% NaCl or 40% bile & tolerate sodium azide, tellurite, mercuric
chloride
5)
range 6.5 to 46℃, optimum 35 to 40℃
6)
7)
range 4.2 to 9.3, optimum 7 to 7.5
skin and mucous membranes
2-33
8)
Coagulase
S. aureus
S. epidermidis
S. saprophyticus
9)
Mannitol-Acid
Anaerobically
+
-
+
-
α-toxin
+
-
enterotoxin = heat resistant (200-320℃ for 8 to 20 minutes) usually
pigmented yellow to orange.
Many beta hemolytic coagulase (+) = pathogenic
produces coagulase, hemolysins, lipases, deoxyribonuclesases, catalase,
protease, enterotoxins
10) grow in wide variety of foods
pathogenic – disease in all parts of body
cause food intoxication – ingestion of enterotoxin
11) (a) aerobic plate count on Baird-parker Agar (egg yolk, lithium chloride &
tellurite) → tellurium which produces black, shiny, round colonies
surrounded by clear zones) – 35℃ for 24h
(b) coagulase test (+)
catalase test (+)
anaerobic use of mannitol & glucose (+)
lysostaphin sensitive (+)
thermostable nuclease (+)
© most Probable Number (MPN) = if less than 100 S. aureus /g
suspected – 3 tubes trypticase soy broth with 10% NaCl – 35℃
for 48h – streak on Baird-Parker agar & do above biochemicals
(d) enterotoxins (A, B, C, D, E) – microslide diffusion test (see FDA
Bacteriological Analytical Manual)
2-34
Streptomyces
1)
2)
3)
4)
Streptomycetaceae
Gram (+)
branched mycelium with slender coenocytic hyphae
aerobic, oxidative, produce pigments (white, gray, yellow, red, blue, green)
5)
optimum 25 to 35℃
6)
7)
8)
9)
10)
11)
pH 6.5 to 8.0
soil and human oral cavity
species usually not identified
used for antibiotic production
cause musty and earthy taste in fresh meat & poultry
isolate on plate count agar, then observe morphology and biochemistry
Vibrio
1)
2)
3)
4)
Vibrionaceae
Gram(-)
short, straight or curved rods, occasionally S or spiral shaped
oxidase (+), respiratory & fermentative metabolism, motile by one polar
flagellum or nonmotile, facultative anaerobes, non pigmented or yellow,
some need 3% salt, catalase(+)
5)
18 to 37℃ optimum
6)
7)
8)
6.0 to 9.0
water and alimentary canal
V. cholerae – cholera
V. parahaemolyticus – food poisoning
9) associated with fish; leading food poisoning in Japan because of raw fish
consumption; readily killed by heat
10) food poisoning, especially from raw fish
11) use glucose salt teepol broth and incubate at 37℃ for 18h; then streak onto
thiosulfate citrate bile salts sucrose agar; confirm by biochemical and
serological tests
2-35
Xanthomonas
1) Pseudomonadaceae
2) Gram(-)
3) single, straight rods
4) respiratory metabolism, never fermentative, catalase(+), oxidase(- or weak),
strict aerobes, complex minimal growth requirements (methionine,
glutamic acid, nicotinic acid, etc.) motile by one polar flagellum, yellow
pigment
5)
7 to 30℃
6)
7)
8)
9)
10)
5 to 10 with optimum around 7
plants
usually not identified
yellow pigment contains brominated derivatives of aryl octanes
plant pathogen that spoils vegetables by various blights and rots, also used
for xanthan production which has application as a stabilizer
11) same as for Pseudomonas
Yersinia
1)
2)
3)
4)
Enterobacteriaceae
Gram(-)
ovoid or rods
oxidase (-), catalase (+), lactose not fermented, no gas or H2S formed,
nonmotile at 37℃ but motile below 37℃ with peritrichous flagella,
IMVC (D + - -), KCN not tolerated
5)
-2 to 45℃ with optimum at 30 to 37℃
6)
7)
8)
optimum around 7
soil and water
Y. enterocolitica – food-borne illness
Y. pseudotuberculosis – food-borne illness
Y. pestis – plague in humans and rodents
2-36
Zoogloea
1)
2)
3)
4)
Pseudomonodaceae
gram(-)
curved, plump rods
motile with single flagellum, from flocs and films in late stages of growth
in liquids, in gelatinous media form zoogloeae “tree-like” morphology,
aerobic but grow anaerobically in present of nitrate, oxidase(+), proteolytic
on gelatin, urease(+)
5)
optimum 28 to 37℃
6)
7)
8)
9)
10)
11)
optimum 7 to 7.5
water, wastewater
usually not given
flocculent
used in wastewater treatment in activated sludge and trickling filters
enrichment media inoculated with activated sludge
2-37
2. Important Molds and Yeasts in Food
A. Mold
1. morphology
* hyphae mycelium----- vegetative & fertile
septa vs. non-septa
“perfect fungi”-----both sexual & asexual reproduction,
eg, Oomycetes or Zygomycetes---nonseptat
Ascomycetes or Basidiomycetes---septat
“fungi imperfecti”----only asexual reproduction
*asexual spores
(1)conidia 分生孢子
(2)arthrospore 關節孢子 (3)sporangiospore 囊孢子
*sexual spores
(1)oospore 卵孢子
(2)zygospore 接合孢子
2. Physiological characteristics
Aw, temp. mesophile, psychrotrophic, nutrient
2-38
(3)ascospore 子囊孢子
3. Important Mold
(A) Enumeration
(1) Plating method:
(a) Acidified medium (pH3.5)
(b)Antibiotic-added medium (chloramphenicol and / or chlortetracycline)
.dichloran: inhibit spreading
.sodium thiosulfate
.sodium tetrathionate reduce effect of heavy metal toxicity.
(2) microscopic methods: enumerate mold filaments in canned fruit &
vegetables.
(3) Indirect methods
(B) Role of fungi in food
. Spoilage
. Health hazards
. fermentation
(C) Molds important in foods
(1) Zygomycetes 接合菌綱，完全菌〈具有性世代及無性世代〉
，菌
絲無隔膜，生長快速。
.Mucor -糖化菌，Starch→單糖
Rhizopus -類似 Mucor，有 Rhizoid，亦為糖化菌ㄧ種
R.stolonifer: bread mold
R.oligosporus: Tempeh
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Thamnidium 一枝黴，長期冷藏肉之表面之黑點,
T. elegans: ”whiskers” of beef in cooler
(2)Ascomycetes 子囊菌綱
.Byssochlamys
Some spores heat resistant → survive heating processing
growth in reduced O2 → produce pectic enzyme → soft texture of canned
& fruits → spoilage
(B. fulva)
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.Claviceps
C. purpurea produce alkaloid toxin(ergot) on cereals→ hallucinations(幻覺) “St.
Anthodny’s fire”
.Neurospora 營養需求低，遺傳及生化研究工具
(3)Deuteromycetes 不完全菌綱，只有無性世代
. Alternaria 互生子菌屬
黑色孢子
plant pathogens
spoilage of tomato in the field
A.alternate produce mycotoxins (alternarin)
.Aspergillus 麴黴
A. niger: black conidia,citric acid.
A. flaus & A.parasiticus: yellow-green
conidia aflatoxin
A. candidus: white conidia
A. ochraceus: yellow-brown conidia, dry
food, ochratoxin.
A. oryzae: sake,soy sause,miso production.
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.Botrytis 蠶絲菌屬
如樹枝狀分支
灰色
fruit & vegetable spoilages
.Cladosporium
分枝黴菌
分隔，由之產生厚膜孢子
C. herbarum:”black spot” on beef, cheese
C. cladosorioides: grains, flour, vegetable
.Fusarium 鐮刀黴菌屬
plant pathogens
F.moniliforme:gibberellic acid
一種植物生長激素
F.oxysporium
F.roseum
F.tricintcum
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Zearalenone
(mycotoxin)
.Geotrichum
yeastlike,white
G. candidum: machinery mold.
.Penicillum 青黴菌屬
P.chrysogenum: produce gluconic acid,
protease, penicillin.
P.camemberti: Camembert cheese
P.cyclopium: penicillic acid (mycotoxin)
P.viridicatum: citrinin ochratoxin
P.expansum: patulin (apple)
.
Trichoderma
T. roseum:cellulolytic
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Yeasts
有性生殖-接合生殖
無性生殖-分裂，出芽生殖
菌落多為黃色，少數褐、灰，(粉)紅
(1) Ascomycetes :有性生殖及無性生殖均有
.Debaryomyces
D. hanasenii: highsalt tolerance.(18~21%salt)
film forming yeast in brine
slime on salted meats
spoilage of orange juice, yogurt,cheese,wine,…
.Hanseniaspora
.inositol & pantothenate: growth factor.
can be used to assay for these compounds.
.Hansenula
.assimilate nitrate.
,pseudomycelium or true mycelium may be formed.
.Kluyveromyces
can use lactose
whey→alcohol by Kluveromyces
.Pichia
.film forming yeast on liquid media or brine.
.budding & from pseudomycelium.
.Saccharymyces
.sugar fermentation ,not use lactose & nitrate.
S. cerevisiae & S. uvarum
S. rouxii: osmophilic yeast,soy sauce.
S. bailii: xerotolerant
S. bisporus: xerophilic
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