Microbiology Part 6

pH

The natural environment varies with respect to H+ ion concentrration

Acidophiles

Grow optimally at low pH values (1-3 pH)

Neutralophiles

Grow optimally at near-neutral pH values

Alkaliphiles

Grow optimally at alkaline pH values (8-11)

Increases

What direction does temperature go with an increase in reaction rates

Enzymes

What denatures when temperatures increase too much?

Water activity

Measure of free water availability for biological functions, Aw = product/water

0.9

What water activity are most bacteria inhibited below?

Water diffuses across their lipid bilayer

Why do bacteria need high water activity?

Cidal agent

Agents which kill cells in bacteria

Static agents

Agents which inhibit the growth of cells without killing them

Bactericidal, bacteriostatic

What is the killing of bacteria called? the inhibition of growth?

Sterilization

The complete destruction or elimination of all viable organisms, no degrees of this

Incineration

Sterilization that burns organisms and physically destroys them

Incineration, boiling, and autoclaving

What are the three ways to use heat to sterilize?

Autoclaving

Steam under pressure or pressure cooker to sterilize

Dry heat, irradiation, filtration, and chemicals

Four other ways to sterilize an object?

Expensive and time consuming

Why is sterilization not used for everything?

Physical and chemical agents

What two agents can control microbial growth?

Pasteurization

The use of mild heat to reduce the number of microorganisms in a product or food

Heat, low temp, and drying

What are three ways food can be perserved?

Antibiotics

Antimicrobial agents produced by microorganisms that kill or inhibit other microorganisms