Chapter 5: Environmental Influences Flashcards by Lock Nim

Organisms growing outside normal growth conditions.

Extremophiles

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What are “normal” growth conditions:

Sea level (1 atm)
Temperature 20-40 C
Neutral pH
0.9% salt, and ample nutrients

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The main criterion that a microbe’s environmental habitat is based on.

The tolerance of that organism’s proteins and macromolecular structures

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Do bacteria regulate temp?

No. They match their immediate environment.

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Each organism has an _______ temperature, as well as _______ and _______ temperatures that define its growth limits.

Optimum; minimum; maximum

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Microbes that grow at higher temps typically achieve….

Higher rates of growth

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The growth rate doubles for every…

10 degrees Celsius rise in temp.

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The typical temp growth range usually spans an organism’s optimal growth temp by…

30-40 degrees

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Live in 0-20 degrees

Psychrophiles

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Live in 15-45 degrees

Mesophiles

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Live in 40-80 degrees

Thermophiles

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Live in 65-121 degrees

Hyperthermophiles

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Heat-shock response is the result of…

Rapid temperature change during growth activities

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What does the heat shock response activate and what do these produce?

Activates - stress response genes

Produces - chaperones and enzymes that change membrane lipid composition

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What kind of organisms have the heat shock response?

All organisms do

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Barophiles or piezophiles are adapted to…

Grow at very high pressures

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_______ organisms grow well over the range of 1-50 MPa, but their growth falls off thereafter

Barotolerant

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Many barophiles are also-

Psychrophiles

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Water activity

A measure of how much water is available for use

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Water activity is measured as…

The ratio of the soln’s vapor pressure relative to that of pure water

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Most bacteria require water activity levels of

Greater than 0.91

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Fungi can tolerate water activity levels of

Greater than 0.86

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A measure of the number of solute molecules in a solution

Osmolarity

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Osmolarity is ________ related to water activity

Inversely

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Aquaporins

Membrane-channel proteins that allow water to traverse the membrane much faster than by diffusion

Aquaporins help protect from

Osmotic stress

Microbes' 2 mechs to minimize osmotic stress:

1. In hypertonic media they protect internal water by synthesizing or importing compatible solutes (eg proline or K+) 2. In hypotonic media, pressure-sensitive or mechanosensitive channels can leak solutes out of the cell

Require high salt conc

Halophiles

Salt conc for halophiles

2-4 M NaCl

To achieve a low internal conc of Na+ halophilic microbes...

Use special ion pumps to excrete sodium and replace it with other cations, such as K+

All enzyme activities exhibit______________ with regard to pH

Optima, minima, and maxima

Do bacteria regulate internal pH?

Yes

______ _______ pass through membranes and disrupt ____ homeostasis, thus killing cells

Weak acids; pH

3 classes of organisms differentiated by the pH of their growth range:

1. Neutralophiles 2. Acidophiles 3. Alkaliphiles

______ _____ lakes have high salt conc and pH values as high as pH 11

Saline soda

Saline soda lakes contain

Alkalophiles such as the archaeon Halobacterium salinarium and cyanobacterium Spirulina (flamingos)

Most alkaliphiles use a ______ motive force in addition to a ______ motive force to do much of the work in the cell.

Sodium; proton -also rely heavily on Na/H antiporters to bring protons into the cell

When cells are placed in pH conditions below the optimum....

Protons can enter the cell and lower internal pH to lethal levels

Microbes can prevent the unwanted influx of protons by..

exchanging extracellular K+ for intracellular H+ when the internal pH becomes too low

Under extremely alkaline conditions, cells use...

Na/H antiporter to bring protons into the cell in exchange for Na

Many microbes posses an emergency global response system called

Acid tolerance or acid resistance

TEA

Terminal electron acceptor

TEA in aerobic respiration

oxygen

Oxygen is toxic to cells that lack

enzymes capable of efficiently destroying the reactive oxygen species (ROC)

Only grow in oxygen

Strict aerobes

Grow in oxygen while retaining a fermentation-based metabolism

Aerotolerant anaerobes

Facultative anaerobes

Can live with or without oxygen

Grow only at lower O2 levels

Microaerophiles

3 oxygen removing techniques

1. Special reducing agents (thioglycolate) or enzyme systems (oxyrase) can be added to ordinary liquid media 2. An anaerobe jar 3. An anaerobic chamber with glove ports

Starvation response

Enzymes are produced to increase the efficiency of nutrient gathering and tk protect cell macromolecules Usually triggered by accumulation of small signal molecules like cAMP

Eutrophication

the sudden infusion of large quantities of a formerly limiting nutrient

Ways humans have caused nutrient pollution:

1. Runoff from agricultural fields, urban lawns, and golf courses 2. Untreated or partially treated domestic sewage

Killing or removal of pathogens from inanimate objects

Disinfection

Sterilization

Killing of all living organisms

Killing or removal of pathogens from the surface of living tissues

Antisepsis

Reducing the microbial population to "safe" levels

Sanitation

Decimal reduction time

The length of time it takes an agent or a condition to kill 90% of the population

Steam autoclave

121 C at 15 psi for 20 minutes

LTLT

Low temp/ long time pasteurization (63 C for 30 min)

HTST

High temp/ short time pasteurization (72 C for 15 sec)

Pasteurization kills

Coxiella burnetii, the cause of Q fever

Temp for food preservation

4-8

Long term storage of cultures:

1. -70 in glycerol | 2. Lyophilization or freeze-drying

Filters that can remove microbial cells

Micropore filters (0.2 um)

Force air through HEPA filters removing >99.9% of airborne particulate material 0.3 um in size or larger

Laminar air flow biological safety cabinets

Used for surface sterilization for has poor penetrating power

Ultraviolet light

Used to irradiate foods and other heat-sensitive items. Has high penetrating power.

Gamma rays, e- beams, and x-rays

Factors influencing the efficacy of a given chemical agent:

1. The presence of organic matter 2. Kinds of organisms present 3. Corrosiveness 4. Stability, odor, and surface tension

Phenol coefficient test

Compares the effectiveness of disinfectants

Commercial disinfectants and antiseptics

- ethanol - iodine - chlorine - ethylene oxide

Mechanisms of resistance to disinfectants:

1. Altering fatty acid synthesis protein normally targeted by triclosan 2. Producing membrane-spanning, multidrug efflux pumps 3. Forming multispecies biofilms, which offer collaborative protection

The use of one microbe to control the growth of another

Biocontrol

Aims to treat infectious diseases with a virus targeted to the pathogen

Phage therapy