Microbial Growth and Ecology

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Unit 2, SJRState, Kempke, Micro

What are three physical factors affecting bacterial growth?

Temperature, pH, and Osmotic pressure

Psychrophiles thrive at which temperatures?

≤15

Mesophiles thrive at which temperatures?

25-40 C

Thermophiles thrive at which temperatures?

≥40

Psychrotrophs thrive at which temperatures?

0-30 C

An example of a psychrotroph is:

Pseudomonas

Most bacteria thrive at in a narrow pH range near __________.

Neutrality

Acidophiles thrive at which pH?

<5

Alkaliphiles thrive at which pH?

>9

Neutrophiles thrive at which pH?

5.4-8.0

An example of an acidophile is:

H. pylori

An example of a mesophiles is:

E. coli, Salmonella

Most human pathogens are:

Mesophiles

Hyperthermophiles thrive at which temperatures?

>80

An example of a hyperthermophile is:

T. acidophilum

An example of a hypoacidophile is:

T. acidophilum

Define facultative:

can adapt to

Osmotic pressures have to do with which compound?

NaCl

Define facultative halophile:

an organism that can adapt to higher salt concentrations

Halophiles thrive in which environment:

salt

An example of a facultative halophile is:

S. aureus

Which of the properties can be used to differentiate bacteria?

Halophile or not

Do the cells of halophiles shrink when placed in an osmotic solution?

No

Define plasmolysis:

shrinkage of the cell membrane due to high osmolarity

Define obligate halophile:

must have salt to live

What type of agar is best suited for S. aureus?

Mannitol

What is the carbon source for autotrophs?

CO2

An example of a photo-autotroph is:

photosynthesizing bacteria

What is the energy source of chemo-heterotrophs and chemo-autotrophs?

Glucose

What is the carbon source of heterotrophs?

Organic Compounds/Glucose

What is the energy source of photo-heterotrophs and photo-autotrophs?

Light

Most bacteria have which energy/carbon source combination?

Chemo-heterotroph

Most humans have which energy/carbon source combination?

Chemo-heterotroph

T or F Carbon is a chemical requirement for growth

T

T or F Sodium is a chemical requirement for growth

F

T or F Nitrogen is a chemical requirement for growth

T

T or F Hydrogen is a chemical requirement for growth

F

T or F Oxygen is a chemical requirement for growth

T

T or F Sulfur and Phosphorus can be chemical requirements for growth

T

What is a component of proteins, nucleic acids, coenzymes, and cell walls?

Nitrogen

Nitrogen accounts for 12-15% of ___________ of a bacterial cell

Dry weight

Bacteria obtain Nitrogen from inorganic/organic/both sources?

Both

Define Nitrogen fixation

the conversion of Nitrogen to a usable form

What is an important component of amino acids?

Sulfur

What type of sulfur is used directly by bacteria?

Inorganic sulfate

What is an important component of nucleic acids and phospholipids?

Phosphorus

What type of phosphorus is used directly by bacteria?

Inorganic phosphate

Normal molecular oxygen that has been boosted into a higher energy state:

singlet oxygen

Toxic to cellular components, need SOD to neutralize it:

Superoxide free radical

Toxic to cells, need catalase to neutralize it:

Hydrogen peroxide

No known enzymatic system to deal with this, but has a very short half-life:

Hydroxyl radical

In obligate aerobes oxygen is:

required

In facultative aerobes oxygen is:

not required

In micoraerophiles oxygen is:

required but at levels lower than in atmosphere

In obligate anaerobes oxygen is:

toxic

Enzymes used by obligate aerobes:

SOD+, Catalase +

Enzymes used by facultative aerobes:

SOD+, Catalase +

Enzymes used by micoraerophiles:

SOD-, Catalase -

Enzymes used by obligate anaerobes:

SOD-, Catalase -

An example of an obligate aerobe:

Bacillus

An example of a facultative aerobe:

E. coli

An example of a microaerophile:

Helicobacter

An example of an obligate anaerobe:

Clostridium

A complex polysaccharide derived from red algae:

Agar

Can Agar be degraded by microorganisms?

No

At what temp does Agar liquefy?

100C

At what temp should a water bath be for Agar?

50C

The highest incubation temperature for Agar:

near 100C

A medium whose exact chemical composition is known is called a:

chemically defined medium

Chemically defined mediums are good for organisms that require:

many growth factors

Define fastidious organism:

An organism that has complex nutritional requirements

An example of a fastidious organism:

N. gonorrhoeae

You should culture fastidious organisms on which type of medium?

Chemically defined

In what type of media are the requirements for energy, carbon, nitrogen, and sulfur primarily provided by protein?

Complex media

Define peptone

small, soluble protein fragments that can be digested by most bacteria

A nutrient broth is an example of what type of media?

Complex

What is a nutrient broth called if you add agar to it?

Nutrient Agar

T or F Nutrient broth and Nutrient Agar are the same thing?

F

T or F Many bacteria have never been grown successfully on laboratory media?

T

Two examples of bacteria that have never been grown successfully in the lab?

M. leprae and T. pallidum

Which types of bacteria have not been grown successfully on laboratory media?

Obligate intracellular

What do capnophiles require for growth?

Higher concentrations of CO2

This media inhibits the growth of one type of bacteria while permitting the growth of another.

Selective media

This media does not inhibit one type of bacteria over another but allows different bacteria to display different characteristics

Differential media

An example of a differential media is

blood agar

An example of a selective and differential media at the same time is:

Mannitol

Mannitol is selective for

halophiles

A differential medium that differentiates lipase producing bacteria

Spirit Blue Agar

This selective and differential media is selective to gram negative coliforms:

EMB

This selective and differential media is used to differentiate lactose vs. sucrose fermentation:

EMB

Which bacteria is negative on Spirit blue (non-lipase producing)?

E.coli

Which bacteria is positive on Spirit blue (lipase-producing)?

Serrata

Is Mannitol selective, differential, or both?

Both

Mannitol is selective for:

Staph

Mannitol is differential for:

Mannitol fermenters

An example of a non-Mannitol fermenter:

S. epidermidis

An example of a Mannitol fermenter is:

S. aureus

Is Spirit Blue Agar selective, differential, or both?

Differential

Spirit Blue is differential for:

lipase producing bacteria

An example of a lipase producing bacteria:

Serratia

An example of a non-lipase producing bacteria:

E. coli

Is EMB selective, differential, or both?

Both

EMB is selective for:

gram - microbes

EMB is differential for:

lactose vs. sucrose fermentation

Lactose fermenters form _____ colonies on EMB.

Colored

Non-lactose fermenters form ______ colonies on EMB.

Non-colored

Is MacConkey Agar selective, differential, or both?

Both

MacConkey is selective for:

gram - enterics

MacConkey is differential for:

lactose vs. non-lactose fermenting

What in MacConkey agar inhibits the growth of gram + bacteria?

Crystal violet and bile salts

What is the pH indicator in MacConkey?

Neutral Red

Strong lactic acid colonies form what on MacConkey?

A pink halo

If a bacterium produces lactic acid what color is it on MacConkey?

Pink

An example of a lactic acid producer via MacConkey:

E. coli

This type of culture is designed to increase very small numbers of desired organisms to detectable amounts.

Enrichment Cultures

An example of substances to be tested using enrichment cultures include:

soil or fecal samples, drinking water txt facilities

An increase in bacterial numbers is called:

growth

A simple splitting of a parent cell into two daughter cells is called:

binary fission

When a cell forms a small initial outgrowth that enlarges until its size approaches that of the parent cell, and then separates is called:

budding

The time required for a bacterial cell to divide is called:

generation time

What is the relative generation time for most bacteria?

30 - 60 minutes

Do pathogens generally have a short or long doubling time?

Short

Which pathogen has a generation time of 10 - 30 days?

M. leprae

Bacteria in a free-floating state are said to be:

planktonic

The phase in which there is little to no cell division and the microbial population is undergoing intense metabolic activity:

Lag

The phase in which exponential growth occurs and cellular reproduction is most active:

Log

The phase in which the number of deaths equals the number of new cells:

Stationary

The phase in which the number of deaths exceeds the number of new cells:

Death

Microbes are most sensitive to antibiotics during which phase?

Log

Bacterial growth can be measured either ___________ or __________.

Directly/Indirectly

Tell whether the following is an indirect or direct measure: Serial dilution and standard plate counts.

Direct

Tell whether the following is an indirect or direct measure: Direct microscopic counts.

Direct

Tell whether the following is an indirect or direct measure: Most probable number.

Direct

Tell whether the following is an indirect or direct measure: Filtration.

Direct

Tell whether the following is an indirect or direct measure: Turbidity

Indirect

Tell whether the following is an indirect or direct measure: Spectrophotometry

Indirect

Tell whether the following is an indirect or direct measure: Metabolic Activity

Indirect

Tell whether the following is an indirect or direct measure: Dry Weight

Indirect

How many colonies fall constitute a "countable" range?

30-300

What measures the number of viable cells?

Plate counts

What is done to ensure that colony counts are in a countable range?

Serial dilution

A series of small dilutions is called

Serial dilution

Which type of count requires no incubation time?

Direct Microscopic Count

Which type of count requires the use of a microscope and slides?

Direct Microscopic Count

Which type of count incorporates statistical estimating?

MPN

Which type of count is used when microbes will not grow on solid media?

MPN

Which type of count is used when the quantity of bacteria is extremely small?

Filtration

Which type of count estimates bacterial numbers by measuring a population's metabolic activity?

Metabolic Activity

Obligate Anaerobe:

Clostridium

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