Exercise 14: Effects of Environmental Condition

Every microorganism has a specific requirement of what five factors?

-temperature

-osmotic pressure

-pH

-UV-radiation

-oxygen

Microorganisms have a set of temperatures at which they can grow. What are these temperatures called?

Cardinal temperatures

What are the three cardinal temperatures?

-minimum

-optimum

-maximum

Which two cardinal temperatures are closet together?

Optimum and maximum

What did we use in lab to evaluate/determine optimum growth in our growth media? What bacteria was this used for?

determined by amount of turbidity; E. coli and Geobacillus stearothermophilus

The production of what pigment by what bacteria is affected by temperature?

prodigiosin; Serratia marcescens

What is prodigiosin?

a pigment; a secondary metabolite produced by S. marcescens

What temperature is prodigiosin produced at? And not produced at?

25 degrees C; 37 degrees C

Bacteria have adapted to live in a variety of pH environements. What are they?

-acidophiles

-neutrophiles

-alkaphiles

Acidophiles=

acidic; low pH

Neutrophiles=

neutral; neutral pH

Alkaphiles=

basic; high pH

Many organisms have developed a tolerance to osmotic pressure. What are the four main osmotic pressure environments?

-nonhalophile

-halotolerant

-halophile

-extreme halophile

Nonhalophiles=

hate salt; will die in the presence of sat

Halotolerant=

prefers non salty environments but can handle some salt

Halophile=

love salt; these organisms are found in oceans

Extreme halophile=

needs salt to live; will die without salt

What is an example of a nonhalophile?

E. coli

What is an example of a halotolerant?

S. auerus

What is an example of a halophile?

Vibrio fischeri

What is an example of a extreme halophile?

Halobacterium salinarum

UV irradiation (260nm) is absorbed by ____. What does this cause and what happens?

cellular DNA; may be inactivated--->kills the bacteria

UV irradiation causes what to form? Which type specifically?

pyrimidine dimers; especially thymine dimers

UV irradation leads to:

DNA damage; prevents replication

UV irradiation can be used for:

used in the industry to disinfect surfaces

Oxygen tolerance refers to:

the presence or absence of oxygen

Microbes can fall under four categories when it comes to oxygen tolerance. What are they?

-obligate (strict) aerobe

-obligate (strict anaerobe

-facultative anaerobe and aerotolerant anaerobes

-microaerophile

Obligate (strict) aerobe need:

oxygen

Obligate (strict) anaerobe need:

the absence of oxygen

Microorganisms that can tolerate both conditions are called:

facultative anaerobe and aerotolerant anaerobes

Microaerophile need:

oxygen at lower than atmospheric concentrations

What is used to examine the oxidation-reduction potential of microorganisms?

fluid thioglycollate broth

What does fluid thioglycollate have? What does it do?

has thiglycolate which reduces the amount of oxygen present and a small amount of agar to create an oxygen gradient in the tube

The top of the tube is more? The bottom of the tube is more?

Aerobic=top

anaerobic= bottom

What is added to the tube to indicate presence of oxygen?

resazurin