Bacteriology-8 Factor That Influence Bacteria Lives

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Factor that influence

bacteria lives

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Factors that influence

bacteria lives

Water

Temperature Acidity (pH)

Salinity

Oxygen Food supply (Nutrition)

Light

Chemicals

A. Abiotik

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Water availability

Water is solvent for biomolecules, and itsavailability is critical for cellular growth

The availability of water depends upon itspresence in the atmosphere (relative humidity) or

its presence in solution or a substance (wateractivity, (Aw)

Awpure (100%).

Microorganisms live over a range of Awfrom 1.0 to

0.7. The Awof human blood is 0.99; seawater =0.98; maple syrup = 0.90; Great Salt Lake = 0.75.Water activities in agricultural soils range between0.9 and 1.0.

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Temperature

Temperature is a major environmental

factor controlling microbial growth. The

cardinal temperaturesare the minimum,

optimum, and maximum temperatures at

which each organism grows.

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Microorganisms can be grouped by the

temperature ranges they require.

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Low or High pH

The acidity or alkalinity of an

environment can greatly affect microbial

growth.

Organisms that grow best at low pH are

called acidophiles; those that grow best

at high pH are called alkaliphiles.

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Growth of thermophilic cyanobacteria in Grand

Prismatic Spring, Yellowstone

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Some organisms have evolved to grow

best at low or high pH, but most

organisms grow best between pH 6 and

8. The internal pH of a cell must stay

relatively close to neutral even though the

external pH is highly acidic or basic.

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pH profiles for some prokaryotes

Organism Minimum pH Optimum pH Maximum pH

Thiobacillus thiooxidans 0.5 2.0-2.8 4.0-6.0Sulfolobus acidocaldarius 1.0 2.0-3.0 5.0

Bacillus acidocaldarius 2.0 4.0 6.0

Zymomonas lindneri 3.5 5.5-6.0 7.5

Lactobacillus acidophilus 4.0-4.6 5.8-6.6 6.8Staphylococcus aureus 4.2 7.0-7.5 9.3

Escherichia coli 4.4 6.0-7.0 9.0

Clostridium sporogenes 5.0-5.8 6.0-7.6 8.5-9.0

Erwinia caratovora 5.6 7.1 9.3Pseudomonas aeruginosa 5.6 6.6-7.0 8.0

Thiobacillus novellus 5.7 7.0 9.0

Streptococcus pneumoniae 6.5 7.8 8.3

Nitrobactersp 6.6 7.6-8.6 10.0

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Salinity

Some microorganisms (halophiles)

have evolved to grow best at reduced

water potential, and some (extreme

halophiles) even require high levels of

salts for growth.

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Oxygen

Aerobesrequire oxygen to live,

whereas anaerobesdo not and may even

be killed by oxygen.

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Microaerophilesare aerobes that can

use oxygen only when it is present at

levels reduced from that in air.

Facultativeorganisms can live with or

without oxygen. Aerotolerant anaerobescan tolerate oxygen and grow in its

presence even though they cannot use it.

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Growth of thermophilic cyanobacteria in Grand

Prismatic Spring, Yellowstone

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Toxic Forms of Oxygen

Several toxic forms of oxygen can be

formed in the cell as the result of

respiration, but enzymes are present that

can neutralize most of them. Hydrogen

peroxide is one of those forms that can

be neutralized by catalase.

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Several toxic forms of oxygen can be

formed in the cell as the result ofrespiration, but enzymes are present that

can neutralize most of them. Hydrogen

peroxide is one of those forms that can beneutralized by catalase.

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Anaerobic growth chambers

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Nutrition

Bacteria feed by secreting enzymes

which break down their food source into

smaller molecules that can be absorbed

by the bacteria.

This is called

extra-cellular

digestion.

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Miscellaneous conditions Radiation (solar, UV, gamma)

Can all damage cells; bacteria have pigments toabsorb energy and protect themselves.

Endospores are radiation resistant.

Deinococcus radiodurans: extremely radiationresistant

Extremely efficient DNA repair, protection against

dessication damage to DNA.

Barophiles/barotolerant: microbes from deep sea Baro- means pressure. Actually require high

pressure as found in their environment.

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ParasitesLive on or in larger organisms

and feed off them. If they causedisease they are called pathogens.

SaprophytesConsume dead matter.

These bacteria are scavengersand decomposers.

Mutualism

Both mutualistic partner species benefit fromthe relationship. One example is that ofcellulose-digesting protozoa/bacteria living inthe guts of many herbivores

B. Biotik

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Nitrogen cycle

Plants and animals need nitrogen to makeprotein but they cant use the nitrogen inthe air because they cannot break open

the N2 molecules.

Nitrogen fixing bacteria in the roots of

plants like clover, convert nitrogen gasfrom the air into nitrates which can beused by plants as a source of nitrogen

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Nitrogen cycle

Animals get there nitrogen by eating plants oranimal protein.

Dead animal and plant protein, and animal urineis broken down by decomposers. The nitrogenchanges back to nitrates.

Some bacteria in the soil can change nitratesback into nitrogen gas, these are denitrifyingbacteria.

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Nitrogen Cycle

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Decomposers

Nitrogen fixing

bacteriaDenitrifying

bacteria

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Saprophyte

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Helpful and harmful:

Naturally helpful: Many bacteria and fungi are decomposers

breaking down dead tissue (e.g. in compost

heaps).

These micro-organisms release nutrients that

plants can absorb. They form important parts of

the nitrogen and carbon cycle.

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Carbon cycle

Carbon is released from dead matter by

decomposers into the atmosphere as

carbon dioxide gas, which is absorbed by

plants as they manufacture food.

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Herbivores and gut bacteria

Herbivores cannot

produce cellulose-

digesting enzymes. Bacteria which can do

this are found in the

alimentary tract of

herbivores. These bacteria receive

food and shelter, and

aid plant digestion.

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Summary

Parasitism Mutualism

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Species A

Species B

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