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Bacteria Survival Endospore- •a thick celled structure that forms inside the cell•they are the major cause of food poisoning•they can withstand boiling, freezing, and extremely dry conditions•it encloses all the nuclear materials and some cytoplasm

•allows the bacteria to survive for many years

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Bacillus subtilisEndospore-the black section in the middle

highly resistant structurescan withstand radiation, UV light, and boiling at 120oC for 15 minutes.

Bacteria Survival

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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 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

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

Leuconostoc cremoris – used in the production of buttermilk and

sour cream

Lactobacillus casei – found in human intestines and mouth to improve digestion

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 *All of these require– Recovery methods which minimize– Storage microbial damage.

Other important roles cont’d• Biogeochemistry

– 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: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

N2

Nitrogen - fixationAmmonia (NH3)

Nitrate ion (NO3-)

PseudmonasN2

Nitrite ion (NO2-)

NitrobacterNitrate ion (NO3

- )

Ammonium ion (NH4+)

NitrosomonasNitrite ion (NO2

- )

Amino acids (–NH2)Microbial ammonification

Ammonia (NH3)

Proteins and waste productsMicrobial decomposition

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

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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

What are some common pathogens?

• Pathogenic E. coli (like O157:H7)– Found in ground beef, contaminated fruits

and vegetables

• Salmonella– Found in raw meats, poultry, eggs, sprouts,

fruit and vegetables

• Listeria– Found in deli foods, lunch meats, smoked

fish and vegetables

E. coli O157:H7

Salmonella

Listeria

Examples of PathogensSalmonella

Staphylococcus aureus

Campylobacter jejuni

E. coli O157:H7

What shape are these bacteria?

Cocci, bacilli, or spiral?

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

• 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

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Controlling Microbe3 ways to control

bacteria:1) Canning- the process of sealing food in airtight cans or jars after killing bacteria

•endospores are killed during this process2) 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 MicrobeAntiseptic vs. DisinfectantsAntiseptic- 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