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Bacteria Survival
Endospore•a thick celled structure that forms inside
the cell
•they are the major cause of food poisoning
•allows the bacteria to survive for many years
•they can withstand
boiling, freezing, and
extremely dry conditions
•it encloses all the
nuclear materials
and some cytoplasm
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Bacteria Survival
Bacillus subtilis
Endospore-the black section in the middle
highly resistant structures
can withstand radiation, UV light, and
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boiling at 120oC for 15 minutes.
Microbe Survival – Food sources
parasites – microbe that feed on living things
saprophytes – use dead materials for food
(exclusively)
decomposers – get food from breaking down
dead matter into simple chemicals
important- because they send minerals
and other materials back into the soil so
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other organisms can use them
Beneficial Microbe
“What is soil, becomes grass,
becomes a cow, becomes you
and me and then becomes soil
again. Without microbes, the
whole ecosystem would
collapse”
Importance of Microbes
• Life is microbial! (to the first
approximation)
– Micro-organisms colonise every
environment on earth
– >80% of life’s history was
bacterial
– You have more bacterial cells than
human cells
– Microbes play a key role in the
biosphere
– Pathogenic microbes globally are
the most important cause of
human disease and death
Are all Microbe pathogens?
• No, most are harmless
• Some are even helpful
– Examples of helpful bacteria:
• Lactobacillus: makes cheese, yogurt, &
buttermilk and produces vitamins in your
intestine
• Leuconostoc: makes pickles & sauerkraut
• Pediococcus: makes pepperoni, salami, &
summer sausage
The Importance of MOs
• Most microbes are not harmful!
In fact, a large number have beneficial effects
• Human health (historical)
• Environmental recycling
• Industrial applications
• Mining, Agriculture
• Human health (contemporary)
• Biotechnology
• Food/beverage commodities
• primary producers
Microbes and Agriculture
• Certain soil bacteria live symbiotically in
the roots of legumes (Rhizobium)
• Convert N2 to NH3 provides amine for aa’s
• Mycorrhizal fungi and enhanced plant
vigor
• Also, bacteria in rumens of cattle, sheep
benefit these animals in breakdown of
cellulose
Importance of microbes in
food production
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Bread
Beer & Wine
Yogurt
Pickles
Sauerkraut
Cheeses
Kim-chi
Production of vitamins, amino acids, flavors
A Closer Look – Helpful Bacteria
Pediococcus
- used in
production of fermented meats
Lactobacillus casei – found in
human intestines and mouth to improve
digestion
Leuconostoc cremoris –
used in the production of buttermilk and
sour cream
Lactobacillus bulgaricus –
used in the production of yogurt
Mineral and energy related
industries involving MOs
• Natural gas (methane) is a product of
bacterial action
– Will be discussed in Archaebacteria section
– Anaerobic, methanogens
• Crude oil is subject to microbial ATTACK.
In fact crude oil is a product of microbial
planktonic algae zooplankton
– Drilling
– Recovery
– Storage
*All of these require
methods which minimize
microbial damage.
Other important roles cont’d
• Biogeochemistry
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oil production/degradation
soil genesis
harvest gold
reduce sulfur in oil
• Chemical production
– Food additives, citric acid, lactic acid, xanthan gum, MSG
– Chemicals, alcohols, glycerol, dextran, biocontrol agents,
proteases, antioxidants
MOs can produce natural
proteins
• Insulin-lowers blood sugar
• Interferon-an anti-viral substance
• Factor VIII-substance for clotting blood;
missing in hemophiliacs
• Streptokinin -a substance used to dissolve
blood clots in coronary arteries
• Beta endorphins-pain suppressors
impact of microorganisms on human affairs:
Fermentation
Microbes and Agriculture
• Nitrogen fixation
1. association between plants (legumes) and
bacteria
2. reduce need for fertilizer
• Rumen microbes in cattle and sheep allow them to
breakdown/digest grass and hay
• Nutrient cycling (C, N, and S)
• Plant and animal diseases
1. Microorganisms and Food
– prevent microbial spoilage of food and food
borne disease
– Manufacturing of foods
2. Microorganisms, energy and environment
– Natural gas (methane)
– Ethanol (biofuel)
– Bioremediation
3. Microbes and the future
– Biotechnology-genetic engineering
The Alphaproteobacteria
• Nitrogen-fixing
bacteria
– Rhizobium
• Fix nitrogen in the
roots of plants
Figure 27.5, step 5
The Nitrogen Cycle
Figure 27.4
Nitrogen Cycle
Proteins and waste products
Microbial ammonification
Amino acids (–NH2)
Ammonium ion (NH4
Nitrite ion (NO2
-)
Nitrate ion (NO3
N2
-)
Nitrogen - fixation
Microbial decomposition
+)
Nitrosomonas
Nitrobacter
Pseudmonas
Ammonia (NH3)
Nitrite ion (NO2- )
Nitrate ion (NO3- )
N2
Ammonia (NH3)
Amino acids
The Sulfur Cycle
Figure 27.7
Decomposition by Microbes
• Bioremediation
– Use of microbes to
detoxify or degrade
pollutants; enhanced by
nitrogen and
phosphorus fertilizer
• Bioaugmentation
– Addition of specific
microbes to degrade of
pollutant
• Composting
– Arranging organic
waste to promote
microbial degradation
Figure 27.9
Decomposition by Microbes
Figure 27.10
Harmful Bacteria
• some bacteria cause diseases
•Animals can pass diseases to humans
Communicable Disease –
Disease passed from one organism to another
This can happen in several ways:
•Air
•Touching clothing, food, silverware, or toothbrush
•Drinking water that contains bacteria
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What are some common pathogens?
• Pathogenic E. coli
(like O157:H7)
E. coli
O157:H7
– Found in ground beef, contaminated fruits
and vegetables
• Salmonella
Salmonella
– Found in raw meats, poultry, eggs, sprouts,
fruit and vegetables
• Listeria
– Found in deli foods, lunch meats, smoked
fish and vegetables
Listeria
Examples of Pathogens
Salmonella
Staphylococcus
aureus
E. coli O157:H7
What shape are
these bacteria?
Cocci, bacilli, or
spiral?
Campylobacter
jejuni
Infection and Disease
 Infection
the entry of a microbe into the host.
 Disease
infection followed by the appearance of
signs and symptoms.
 Pathogen
an infectious or disease agent.
 Saprobe
a microbe that lives on dead or
decaying organic matter.
 Opportunistic pathogen
is a microbe that cause disease in immunocompromised
hosts
or when the normal microbiota is altered.
Medically-important Endospore-forming
Bacteria
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Bacillus anthracis causes anthrax
Bacillus cereus causes food poisoning
Clostridium tetani causes tetanus
Clostridium botulinum causes botulism
Clostridium perfringens causes food poisoning and
gas gangrene
• Clostridium difficile causes antibiotic-induced
diarrhea and pseudomembranous colitis
Koch’s Postulates (1884)
1. Suspect pathogenic organism
should be present in all cases of
the disease and absent from
healthy animals
2. Suspect organism should be
grown in pure culture
3. Cells from a pure culture of
suspect organism should cause
disease in healthy animal
4. Organism should be reisolated
and shown to be same as the
original
Controlling Microbe
3 ways to control bacteria:
1) Canning- the process of sealing food in
airtight cans or jars after killing bacteria
•endospores are killed during this process
2) Pasteurization- process of heating milk
to kill harmful bacteria
3) Dehydration- removing water from food
•Bacteria can’t grow when H2O is removed
•example: uncooked noodles & cold cereal
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Controlling Microbe
Antiseptic vs. Disinfectants
Antiseptic- chemicals that kill
bacteria on living things
•means – “against infection”
Examples: iodine, hydrogen peroxide,
alcohol, soap, mouthwash
Disinfectants- stronger chemicals that
destroy bacteria on objects or nonliving
things
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