question

• Temperature
• Pressure
• Osmolarity
• pH
• Oxygen

answer

Environmental factors that affect microbial growth

question

minimum temperature

answer

cellular processes slow; cytoplasmic membranes stiffen; harder to transport in and out of cell

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maximum temperature

answer

- proteins start to denature

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• 0°C–20°C

• 20°C–45°C

• 40°C–80°C

• 65°C–113°C

answer

psychrophiles

mesophiles

thermophiles

extreme thermophiles

question

Chlamydomonas- “snow algae”

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• Psychrophiles- found in constantly cold environments

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• Molecular adaptations of psychrophiles:

answer

• Membranes have high content of unsaturated fatty acids – semi-fluid at low temperatures

• Proteins are more flexible compared to mesophiles or thermophiles

question

• Cryoprotectants

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can be used to preserve microbial cultures at low temperatures

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• 10% DMSO (Dimethylsulfoxide) & 10% glycerol

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are commonly used in laboratories to preserve microbial cultures for long time in freezers

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mesophiles

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• Found in warm-blooded animals & many terrestrial & aquatic environments.

• Examples- most organisms you are familiar with such as Escherichia coli (found in the human intestine)

question

• Soils subjected to full sunlight

• Fermenting materials (compost)

• Hot springs

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places thermophiles are found

question

• Thermus aquaticus

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a common hot spring thermophile. The heat stable DNA polymerase from this bacterium is mass-produced and used in laboratories to replicate DNA in a test tube

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molecular adaptations of thermophiles

answer

• Membranes have a high content of saturated fatty acids – stable & functional at high temperatures

• Enzymes are heat stable - proteins are more rigid compared to mesophiles or psychrophiles

question

heat shock response

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• Occurs at high end of temperature range
• “Emergency” proteins produced
• Help keep proteins from denaturing
• Induced by many stressful conditions

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barophiles

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• Adapted to high pressures
• Up to 1,000 atm

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• Barotolerant organisms

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• Grow at high, but not very high pressure

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• Barosensitive organisms

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• Die at high pressure
• Most “typical” bacteria, all mammals

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high; lower

low; high

answer

• Water moves from areas of ____ water concentration to areas of _____ water concentration.

• Water moves from areas of ____ solute concentration to areas of ____ solute concentration.

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hypotonic

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____ environment, water will move into cell

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hypertonic; plasmolysis

answer

____ environment, water will move out of the cell and the cell will die of _____

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TRUE

answer

no physical barrier that prevents cell from losing too much water if cell is in hypertonic environment. T/F

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cell wall

answer

physical barrier that keeps cell at equilibrium in hypotonic environments for prokaryotes

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1. Pumping inorganic ions (K+) into the cell

2. Making or concentrating an organic solute (glycerol) in the cell.

answer

• Some cells can increase solute concentration in cell to prevent too much water loss by:

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osmophile

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organism that grows in high solute concentrations (hypertonic environments)

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halophiles

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grow best in high salt habitats

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3%

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__% salt concentration in ocean

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extreme halophiles

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require high levels (15% to 30%) of salts for growth

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– Halobacterium salinarium

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(requires 25% salt) lives in very salty lakes – HUGE amount of salt

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halotolerant

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can survive at higher salt concentrations but grow best in absence of salt

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– Staphylococcus aureus

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organism that's halotolerant

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hydrogen

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pH relative to ____ ion

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weak

answer

• ___ acids can pass through membranes very easily

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Thiobacillus

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produces sulfuric acid

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acidophiles

answer

• Fungi as a whole are usually mostly

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• Sulfolobus

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double extremophile – thermophilic and acidophilic

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alkaline

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Many species of Bacillus live in very ____ soils

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Proteases & lipases

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• _____ made by alkaliphiles are mass-produced & used in household detergents.

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Spirulina

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• – flamingos eat and become pink

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• Oxic environment

• Anoxic environment

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O2 is present

no O2 present

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• Facultative aerobes

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use O2 in respiration but can also grow in anoxic environments
• Ex. E. coli in large intestine

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• Obligate aerobe -

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use O2 in respiration & require oxic environments for growth. Grow at atmospheric O2 levels (21%)

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• Microaerophile -

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use O2 in respiration but require low O2 concentrations, 2-10%, (microoxic environments) to grow – use candle jar to grow
• Ex. Streptococcus pneumonia

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• Aerotolerant anaerobes -

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do not use O2 to generate energy but can survive in the presence of it

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• Obligate anaerobes

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can only grow in anoxic environments; may die if even minute amount of O2 is present

question

reducing agent

answer

• A ______ such as thioglycolate can be added to a medium to test an organism's requirement for O2

question

aerobes

answer

Culture medium must be oxygenated by shaking or bubbling air into the medium for these microorganisms

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Catalase, peroxidase, superoxide dismutase, superoxide reductase

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Enzymes made by cells can neutralize toxic forms of oxygen.

question

• Autoclave –

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sterilizes using steam and pressure; Kills all bacteria (sterilizes)

question

• “Cold sterilization” –

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uses gases such as ethylene oxide in machine similar to autoclave

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• UV hood –

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air is blown outward through a filter from the back and from edges of the hood so that the area inside the hood remains sterile once the UV light is turned off.

question

ionizing radiation

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• Causes breaks in DNA; breaks hydrogen bonds & disulfide bridges in proteins; used widely in medicine

question

depth and membrane

answer

2 types of filters used for filtration

question

depth filters

answer

ibrous sheets or mats made from a random array of overlapping paper, asbestos, or borosilicate

• Traps large particles from liquids & air

question

membrane filters

answer

• Thin sheets of polymers (cellulose); contain tiny holes of known size

• Act like sieves, trap particles on membrane surface; Ex - antibiotics

question

• Nucleation track (nucleopore)

answer

filters used for concentrating a liquid sample for view on the scanning electron microscope.

question

• Disinfectants

answer

Used to reduce microbial numbers on nonliving materia
• Bleach (chlorine), ethanol

question

• Antiseptics

answer

• Used to reduce microbial numbers on living tissues
• Betadyne (iodine), H2O2 (hydrogen peroxide)

question

antibiotics

answer

• Naturally occurring antimicrobial substances produced by microorganisms; selectively kills microbes; typically safe to be ingested (disinfectants and antiseptics are not)

question

penicillin

answer

• Many derivatives
• Blocks cell wall synthesis
• Growing bacteria lyse
– Slow-growing bacteria take longer to die

question

1

answer

less than __ % clinically useful antibiotics because of poor uptake or toxicity

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probiotics

answer

• “Good” bacteria – ingest and they will take up space in digestive system so pathogens won’t have a place to live there
• Displace pathogens from tissues

question

bacteriophage

answer

• Viruses that infect bacteria
• Do not harm eukaryotes

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