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Chapter 11
The Prokaryotes: Domains
Bacteria and Archaea
Part 2
The Nonproteobacteria GramNegative Bacteria
• Not closely related to the gram-negative
proteobacteria
• Several physiological and morphologically
distinctive photosynthesizing bacteria
• Phyla Cyanobacteria, Chlorobi (green sulfur
bacteria) & Choloroflexi (green nonsulfur
bacteria)
The Nonproteobacteria GramNegative Bacteria
Photosynthetic Bacteria
Photosynthetic Bacteria
• Phyla Cyanobacteria, Chlorobi, Chloroflexi,
photosynthetic purple sulfur bacteria (proteobacteria), and purple nonsulfur
bacteria (-proteobacteria)
• Photoautotrophs and chemoheterotrophs
• Photosynthetic purple and green sulfur
bacteria are generally anaerobic and usually
found in deep sediments of lakes and ponds
Cyanobacteria
• Oxygenic (oxygen-producing) photosynthetic
bacteria
– Produce O2 from H2O using light energy
• Characteristic blue-green (cyan) pigmentation
• Gliding motility or gas vacuoles
• Fix nitrogen (into ammonium) from
atmosphere in specialized cells called
heterocysts
• Morphologically varied (Unicellular to
colonial form)
Cyanobacteria
Figure 11.12a-c
Purple and Green Photosynthetic Bacteria
• Anoxygenic photosynthesis (does not
produce O2)
– carry out photosynthesis to make carbohydrates
– Possess chlorophyll
Oxygenic
2H2O + CO2
light
(CH2O) + H2O + O2
Anoxygenic (purple sulfur and green sulfur bacteria)
2H2S + CO2
light
(CH2O) + H2O + 2S0
Phylum Chlamydiae
• Do not contain peptidoglycan in cell walls
– Chlamydia: intracellular parasite; a unique
developmental cycle (elementary body is the
infective agent); gram-negative coccoid
– Transmitted via interpersonal contact or by
airborne respiratory routes
• C. trachomatis
• C. pneumoniae
• C. psittaci
Trachoma, STD, urethritis
Mild form of pneumoniae
Causes psittacosis (ornithosis)
In Bergey's Manual, Volume 5
Figure 11.22a
In Bergey's Manual, Volume 5
Figure 11.22b
Phylum Spirochaetes
• Coiled morphology; outer sheath; axial filaments
(endoflagella) for motility
– many are found in oral cavity
• Borrelia
Relapsing fever and Lyme disease
• Leptospira leptospirosis
• Treponema syphilis (T. pallidum)
Figure 11.23
Phylum Bacteroidetes
• Anaerobic Bacteria
– Bacteroides: nonmotile; in mouth (gingival
crevice) and large intestine; also recovered
frequently from deep tissue infections
– Cytophaga: degrade cellulose and chitin in
soil; gliding motility
Phylum Fusobacteria
• Often pleomorphic,
may be spindleshaped
– Fusobacterium:
found in mouth
(gingival crevice);
may be involved in
dental diseases
Figure 11.24
Gram-Positive Bacteria
• Two groups:
– high G + C ratios (above 50%)
e.g. Phylum Actinobacteria (mycobacteria,
corynebacteria,and actinomycetes)
– low G + C ratios (below 50%)
e.g. Phylum Firmicutes (common soil bacteria,
lactic acid producing bacteria, and several
human pathogens)
Phylum Firmicutes
• Low G + C
• Gram-positive
Order Clostridiales
• Clostridium
– Form endospores
– Obligate anaerobes
• C. botulinum Botulism
• C. tetani
Tetanus
• C. perfringens Gas gangrene
Food diarrhea
• C. difficile
Severe diarrhea
• Epulopiscium
– Giant prokaryote; symbiotic
in the gut of surgeonfish
Figure 11.14 & 15
Order Bacillales
• Important genera of grampositive rods and cocci
• Bacillus
– Rod-shaped bacteria that
form endospores
– Common in soils
• B. anthracis: Anthrax
• B. thuringiensis: Microbial
insect pathogen
• B. cereus: Occasional
food poisoning
Figure 11.16b
Order Bacillales
• Staphylococcus
– Cocci in clusters
• S. aureus: facultative anaerobes; can tolerate high
osmotic pressure and low moisture; produce many toxins
(e.g. enterotoxin); toxic shock syndrome, food poisoning
Figure 1.17
Order Lactobacillales
• Generally aerotolerant anaerobes, lack an
electron-transport chain
• Lactobacillus
– produce lactic acid (industrial and commercial
application); found in vagina, intestinal tract, and
oral cavity
• Enterococcus
– facultative anaerobes; found in GI tract, vagina, and
oral cavity; leading cause of nosocomial infection
Order Lactobacillales
– E. faecalis & E. faecium: infect surgical
wounds & urinary tract
• Listeria: facultative anaerobes
– L. monocytogenes: contaminate food (dairy
products); can grow in refrigeration
temperature
• Streptococcus
– Usually cocci in chains; human pathogens
– Have hemolytic activity (alpha hemolysis,
beta hemolysis, and no hemolysis)
Order Lactobacillales
– S. pyogenes: scarlet
fever, pharyngitis,
impetigo, and
rheumatic fever
– S. mutans: dental
carries
– S. pneumoniae:
most common
cause of pneumonia
Figure 11.18
Order Mycoplasmatales
• Wall-less and highly
pleomorphic
• Very small (0.1 - 0.25
µm)
• Degenerative evolution
– M. pneumoniae:
common form of mild
pneumonia
– Spiroplasma: plant
pathogens and common
parasites of plantfeeding insects
Figure 11.19a, b
Actinobacteria
• High G + C
• Gram-positive; highly pleomorphic; tend to
be filamentous; very common inhabitants in
soil
Phylum Actinobacteria
• Mycobacterium
– Aerobic, acid-fast (contains mycolic acids
which forms waxy, water resistant layer in cell
wall); slow grower (may take weeks for visible
colonies to appear)
– Found in soil and water; occasional pathogens
– Human pathogens
• M. tuberculosis
• M. leprae
Tuberculosis
Leprosy
Phylum Actinobacteria
• Nocardia
– Aerobic; filamentous morphology
– Reproduction by forming rudimentary
filaments which fragment into short rods
– Cell wall resemble mycobacteria; often acidfast
• N. asteroides
Mycetoma and occasionally cause a
chronic, difficult-to-treat pulmonary
infection
Phylum Actinobacteria
• Corynebacterium
– Tend to be pleomorphic; morphology varies
with the age of the cells
• C. diphtheriae
Diphtheria
• Propionibacterium
– Form propionic acid; fermentation of Swiss
cheese
• P. acnes
Common on human skin, cause acne
• Frankia
– Form nitrogen-fixing nodule in alder tree roots
Phylum Actinobacteria
• Gardenella
– Gram-variable; highly pleomorphic
– Cause of one of the most common forms of
vaginitis
• Actinomyces
– Facultative anaerobe; filamentous morphology
– Found in the mouth and throat of humans and
animals
• A. israelii
actinomycosis
Phylum Actinobacteria
• Streptomyces
– One of the most commonly isolated bacteria from
soil; responsible for the musty odor of soil
– Strict aerobes; filamentous bacteria
– Produce most of our commercial antibiotics
Figure 11.20b
Microbial Diversity
• Bacteria size
range
– Thiomargarita
(750 µm) to
nanobacteria
(0.02 µm) in
rocks
Figure 11.26
Microbial Diversity
• PCR indicates up to 10,000 bacteria/gm of soil.
Many bacteria have not been identified or
characterized because they:
– Haven't been able to culture (need to develop special
media/nutrients and cultivation condition)
– Are part of complex food chains requiring the
products of other bacteria
– Need to be cultured to understand their metabolism
and ecological role
Chapter Review
• Prokaryotic organisms are classified into 2
domains: Archaea & Bacteria based on
rRNA sequences
– Each domain is further subdivided into phylum,
class, order, family, genus, and species
• Domain Bacteria
– Relatively few species cause disease in humans,
animals, plants or any other organisms
– Essential part of life on Earth
Domain Bacteria
• Phylum: Proteobacteria (gram-negative
bacteria)
1) Alpha- (α-) proteobacteria
– Includes most of the proteobacteria that are
capable of growth at very low levels of
nutrients; nitrogen –fixing bacteria & several
plant & human pathogens
– Some bacteria with unusual morphology such
as prosthecae
– Prosthecae: a stalk or bud protruding from a
prokaryotic cell
Domain Bacteria
2) Beta- (-) proteobacteria
– Often use nutrient substances that diffuse away
from areas of anaerobic decomposition of
organic matter
– Considerable overlap between the α- & proteobacteria, especially among the nitrifying
bacteria; some human pathogens in this group
– Spirillum helical shaped bacteria, but use
flagella for motility (not axial filament)
Domain Bacteria
3) Gamma- (-) proteobacteria
– Constitute the largest subgroup of proteobacteria;
many are human & plant pathogens (e.g. Order
Pseudomonadales, Legionellales, Vibrionales,
Enterobacteriales, & Pasteurellales)
4) Delta (-) proteobacteria
– Include some bacteria that are predators of other
bacteria and important contributors to the sulfur
cycle (e.g. Bdellovibrio, Desulfovibrio, and
Myxococcus)
– Myxococcus form fruiting bodies under low
nutrients condition
Domain Bacteria
5) Epsilon- (-) proteobacteria
– Slender gram-negative rods that are helical or
vibrioid (e.g. Campylobacter & Helicobacter)
– Vibrioid: helical bacteria that do not have a
complete turn
• Gram-negative Nonproteobacteria
– Include several photosynthetic bacteria: Phyla
cyanobacteria, green sulfur bacteria, & green
nonsulfur bacteria (Table 11.2)
Domain Bacteria
– Purple sulfur (α-proteobacteria) & purple
nonsulfur (-proteobacteria) also included in this
section
– Cyanobacteria carry out oxygenic (oxygenproducing) photosynthesis and fix nitrogen gas
(in specialized cell called heterocyst) from the
atmosphere into ammonium
– Green & purple photosynthetic bacteria carry out
anoxygenic photosynthesis (generally anaerobic)
Domain Bacteria
• Gram-positive bacteria
– 2 groups based on G + C ratio
1) Firmicutes (low G + C ratio)
– Includes important endospore forming bacteria
(e.g. Bacillus & Clostridium), medically
important bacteria (e.g. Staphylococcus,
Enterococcus, & Streptococcus), industrially
important bacteria (e.g. Lactobacillus), and
wall-less Mycoplasma
Domain Bacteria
2) Actinobacteria (high G + C ratio)
– Highly pleomorphic, but tend to be fimalentous
– Common inhabitants in soil
– e.g. acid-fast group (e.g. Mycobacterium &
Nocardia), and antibiotic producing Streptomyces.
• Assorted Phyla
– Chlamydiae: no peptidoglycan in cell wall;
intracellular parasite (human pathogen); has unique
developmental cycle (elementary body =
infectious)
Domain Bacteria
– Spirochaetes: coiled morphology; motility by
axial filament; many found in human oral
cavity & in environment; some human
pathogens
– Bacterioidetes: several genera of anaerobic
bacteria
– Fusobacteria: anaerobic bacteria, spindleshaped (often pleomorphic); can cause dental
diseases
Domain Archaea
• Cell wall lacks peptidoglycan; a few lack cell
wall
• Frequent inhabitants of exceptional extreme
environment (heat, cold, acidity, & pressure)
• 3 major groups:
– Extreme halophiles: survive in very high
concentrations of salt; found in Great Salt Lake,
solar evaporating ponds, salinas, & Dead Sea
Domain Archaea
– Extreme thermophiles: thrive in high
temperature (above 70 oC) or sulfur rich
environment; found in acidic, sulfur rich hot
springs or deep ocean hydrothermal vents
– Methanogens: obligately anaerobic methane
producing bacteria; found in human intestines
and used in sewage-treatment processes
• Microbial Diversity
– Various sizes: nanobacteria (0.02 – 0.03 μm) to
giant bacteria (750 μm)
Microbial Diversity
• Many bacteria in the environment have not
been identified or characterized due to:
– Lack of culture method
– Some bacteria are part of complex food chains
and can only grow in the presence other
microbes that provide specific growth
requirements
• PCR can be used to reveal the presence of
bacteria that cannot be cultured in the
laboratory
Chapter Review
• Know these terms: prosthecae, vibrioid, and
oxygenic
• Know different groups of proteobacteria (and
some examples) given in the chapter review
section
• Know the names of different photosynthesizing
bacteria and their mode of photosynthesis
Chapter Review
• Know characteristics of 2 groups of grampositive bacteria and some of the examples
listed in the chapter review
• Know characteristics of Arhaea, and its 3
major groups (characteristics and where
they are found) given in the chapter review
• Know why many bacteria have not been
classified and identified (2 main reasons) &
use of PCR to detect them without culturing
them