Microbiology Exam 3: Nutrients and Microbial Growth

Define "Inoculum

When microbes are introduced into a medium to initiate growth

Define "culture

Act of cultivating microorganisms or the
microorganisms that are cultivated

Define "growth

-Refers to microbial multiplication
-Increase in number, i.e. bacterial division, not individual size

Define "culture medium

Nutrient material prepared for growth of microorganisms in lab

Define "pure culture

Culture containing cells of only one species

What are two areas where growth may occur?

1) Colony
2) Biofilm

Define "biofilm

Collection of surface microbes living in a simple complex community

What are the two broad factors for microbial growth?

1) Physical - Environmental
2) Chemical - Nutritional

What is another name for a physical factor affecting microbial growth? What four subfactors would be included in this?

Environmental Factors"
1) Temperature*
2) pH*
3) Light*
4) Osmosis*
*Think like homeostasis factors for plants

Why is (some forms) of oxygen toxic to certain bacteria?

-For the same reason it is a final electron acceptor: high electron affinity
-Oxidation can easily occur between it and other compounds

What are three deadly forms of Oxygen for some bacteria?

Hydroxyl Radical
Superoxide radicals
Singlet oxygen

What are superoxide radicals? Where are they found?

-Highly reactive metabolic products
-Found in cytoplasm

What neutralizes superoxide radicals?

An enzyme: superoxide dismutase (SOD)
2O2- + 2H+ = H2O2 + O2

If a bacteria has a peroxidase, what two products does it produce when peroxide is poured on it?

2H2O2 = 2H2O + O2
Water and atmospheric oxygen

Hydrolase and catalase are typically present in what kind of bacteria? What is the significance of this?

-Aerobic bacteria

What is singlet oxygen?

-Singlet oxygen is toxic, molecular oxygen
-It contains electrons that have been boosted to a higher energy state during ETC

What are hydrogen peroxide and peroxide anion?

-A form of toxic oxygen
-Active component of many antimicrobial agents

What neutralizes hydrogen peroxide?

Catalase : H2O2 + NADH + H = 2H2O
Peroxidase: H2O2 + H + NADH = 2H2O + NAD+

How are vitamins E and C helpful for reducing damage of toxic oxygen?

They are antioxidants: provide donor e- to oxygen.

*Why is temperature important to microbial growth? What is the affect on certain molecules?

Lipids: too high of heat and they become too fluid, too low and they are too rigid.
Proteins: Too high of a temperature and they denature; too low and they can't undergo hydrogen bonding

What is "minimum growth temperature?" Name two compounds it has effects on.

-Lowest temperature at which species will grow
-Will create slowest rate of metabolism
Effects fats and protein macros and organelles.

What is "optimum growth factor?

Temperatures at which microbes grow the best

What happens to proteins at high and low temperatures?

Low: Hydrogen bonding does not occur to create peptides, polypeptides, helices or ultimately proteins
High: Denaturation, i.e. breaking of Hydrogen bonds between more complex structures of protein

What happens to lipids at both high and low temperatures? What lipid is this most pertinent to?

Low: lipids become fragile, stiff and unable to adapt
High: too fluid, membrane protection compromised and cell dessication/lysis

What are the four categories of temperature-based microorganisms?

1) Psychrophiles
2) Mesophiles
3) Thermophiles
4) Hyperthermophiles

What temperatures do psychrophiles grow at?

Low: -5 to 20 degrees Celsius

What is the optimum growth temperature for thermophiles?

Higher temperatures: 42-80 Celsius

What is the optimum growth temperature for hyperthermophiles?

Highest temperatures: 65-105 Celsius

What is the optimum growth temperature for mesophiles? What is the significance of this?

-Moderate: 20-40 Celsius
-They are the most common human pathogens, whose mean temperatures are 37 Celsius

What is a classic example of a more heat-tolerant genus mesophile? Where are they most found?

-Thermoduric mesophiles
-Survive the canning and pasteurization process

What is the disease causing agent for leprosy? Alternate name for the disease?

-Mycobacterium leprae
-Hansen's disease

What 3 areas does the leprosy bacteria cultivate? Why?

Mycobacterium leprae" cultivates in the following:
1) Extremities
2) Face
3) Groin
ML does best in cooler areas of the human body

What is the growth rate of the leprosy bacterium?


What animal is used to cultivate the leprosy bacteria?

Mycobacerium leprae is cultivated in armadillos because it prefers cold enironments for slow growth
-Armadillos are poikolothermic

What are mesophilic bacteria that prefer the lower end of the moderate temperature range?

1) Mycobacterium leprae
2) Treponema species

Does treponema species have a medium for growth?

No, but they are cultivated in living rabbit testicles

What are the three types of pH-dependent growth categories for bacteria? What are the majority of human pathogens?

Neutrophiles - most human pathogens (obviously)

What is the optimum pH range for neutrophiles?

6.5 - 7.5

What is the optimum pH range for acidophiles?

1 - 5.5

What are common acidophiles? In what kind of medium are they grown?

Grown in environment of salt and sugar

What is an example of a type of acidophile bacteria?

Thiobacillus ferroxidans: a rod-shaped bacteria that is able to produce sulfide gas from hydrogen sulfide.

What kind of energy respiration does thiobacillus use? What does it produce?

Anaerobic respiration
Energy + H2SO4- = H+ + SO4-
Hydrogen gas

What kind of environment does thiobacillus grow in? What kind of bacteria does this make it?

pH of 0 - 2
This makes it an "obligate acidophile.

What kinds of pH-dependency are most fungi? Why are they unique

They are acidophiles
They are unique in that they are able to form a H+/acidic environment around their outer membrane

What are the three important acidophiles to know?

1) Thiobacillus ferroxidans
2) Helicobacter pylori
3) Candida

Why are cells and bacteria sensitive to Hydrogen?

Hydrogen interferes with hydrogen bonding, i.e. nucleic acids and proteins

*What is an obligate acidophile?

A bacteria that dies if its environmental pH goes to 7.0 or above.

*What and where is the role of the thiobacillus ferroxidans?

Sulfur recycling in the environmental chemical cycle, particularly within mining

What causes women's yeast infections? Teleology?

A non-growth of candida, a symbiotic yeast

What is the mechanism of a yeast infection?

-Normal microflora ferments sugars and then generates acidic products
-Prevents outgrowth of yeast
-Normal cultures die, others non-native bacteria colonizes

How is h. pylori unique to other acidophiles?

-It contains a urease enzyme
HCO3 + Urease Enzyme = CO2 + NH3
This reaction creates:
-ECF acidic environment
-ICF neutral environment

What kind of pH-bacteria is vibrio cholera? Prefered pH?

8.5 - 14

Where is vibrio cholerae typically found? What kind of pH environment?

Soils and lakes
8.5 -14 pH

Osmosis is the ___ movement of solvent molecules across a _____________ membrane.

Selectively permeable membrane

What is the difference in osmosis between living and non-living structures?

-In living systems, solvents can only be water.
-Water travels to drier areas


Collapse of a walled cell's cytoplasm due to a lack of water
Hint: The "plasma" membrane is "lysing


The rupturing of a cell due to excess internal pressure brought on by high water absorption
Hint: "the cytosol is lysing

Staphylococcus aureus is a _____ ________ and can tolerate up to ___% ____

salt tolerant and can tolerate environments with 20% salt

Staphylococcus aureus causes what 3 kinds of symptoms?

1) Pimples
2) Sties
3) Boils

Within what part of the body is staphylococcus aureus present?

Nasal cavity

What are the 6 key CHEMICAL growth factors of bacteria?

1) Water
2) Trace elements
3) Building elements
4) Growth factors
5) Carbon and Energy together
6) Oxygen

What function does water play in bacterial growth?

Reactant in many reactions:
-Many enzymes and nutrients dissolve in H2O

How is water specifically important to the tuberculosis bacteria? What is it good for?

Mycobacterium tuberculae can retain water within its cell walls:
-This allows MT to withstand dry conditions.

(Endo)spores are able to _________ in order to survive unfavorable conditions


What are the important trace elements and what is their other categorical name?

1) Cobalt
2) Copper
3) Zinc
4) Magnesium
5) Manganase
6) Iron
7) Selenium
Mostly metals

What type of water contains the most trace elements?

Tap water

What is the function of trace elements?

A.k.a micronutrients function as a cofactor for enzymatic reactions

What does glass contain?

It contains the micronutrient/trace element selenium

Nitrogen has a huge part in ___________. What does Nitrogen help build?

In ANABOLISM, Nitrogen helps build:
1) NAG and NAM (glucosamine and muremic acid)
2) Nucleic acid
3) Proteins
4) Amine subgroups

What are amine subgroups used for?

Amino acids


Shriveling of a bacterial cytoplasm due to being in a hypertonic solution

What role does phosphorous play in bacterial cells?

1) Phospholipid membranes
3) ATP
4) Some proteins

What role does sulfur play in bacterial cells?

1) Sulfur-containing amino acid synthesis
2) Vitamins

To what 3 vitamins is sulfur an important component?


What is growth factor and why is it needed?

-What: Growth factors are organic compounds required by the cell
-Why: They are essential because they are (precursor) components that the cell cannot synthesize autonomously.

What are three organic growth factor molecules?

1) Amino acids
2) Purines and pyrimidines
3) Vitamins

Why do bacteria need purines and pyrimidines?

These organic growth factor molecules are needed for nucleic acid synthesis

Why do bacteria need vitamins?

These organic growth factor molecules are needed as enzyme cofactors in biosynthesis and chemical reactions.

What macromolecule does mycoplasma genus need that is different from all other bacteria?

Cholesterol, because this bacteria has no PG Layer.

What is the role of riboflavin in bacterial cells?

Riboflavin function as a precursor of FAD
Also these...
1) Function of heme
2) Flavin, important integral protein in ETC

Carbon is an important component for bacterial growth. What are the two types and what kinds of organisms derive them?

1) Inorganic - autotrophs as CO2
2) Organic - hetertrophs as macromolecules

Carbon and Energy: What are the two subcategories of autotrophs?


Carbon and Energy: What are two types of heterotrophs?

1) Photoheterotrophs
2) Chemoautotrophs

What uses both organic and inorganic sources of Carbon for nourishment and growth?


What do all trophs require for sustainment?

H+ ions and e- for ATP production

What are the 2 functions of iron in bacterial growth?

1) Produces H+ from ETC as an integral protein.
2) H+ used for reactions to digest toxic forms of oxygen
-Metals are a catalyst for these reactions

What does it mean to be facultative or obligate?

Facultative: Capable of but not restricted to a particular function or mode of life
-E.g., facultative anaerobe
Obligate: Restricted to a particular function.
-E.g., obligate phototrophs

What is the main obligate aerobe bacterial genus? Presence of SOD and catalse?

Pseudomona aeroginosa
Abundance of the enzymes

What broad species are obligate aerobes?

But all algae, most fungi and protozoa and many prokaryotes.

What is a microaerophile? What is the prime example of it?

-Bacteria that require oxygen levels of 2% to 10%
-H. pylori

H. Pylori
1) Does it contain SOD or catalse?
2) In addition, how does it use oxygen>

1) Yes, but in very limited amounts
2) Microaerophile, it requires atm. of 2-10% O2.

What are the two most common facultative anaerobes?

1) E. coli
2) Yeast (a fungus)

What is the relationship between oxygen level and growth for a facultative anaerobe?

Low/no O2 = Low growth
High O2 = High growth rate

What is the relationship between O2 requirement and ATP usage?

The more O2 used, the more ATP required for the organism

What is aerotolerant? Catalase/SOD presence?

-Bacteria that do not use aerobic metabolism
-Can tolerate toxic oxygen b/c of enzymes that detoxify oxygen's poisonous forms

What is a prime example of an aerotolerant bacteria?

1) Streptococcus pyogenes
2) Lactobacillus
Both are fermenters of lactic acids

Why would it make sense that helicobacter pylori is a microaerophile?

It lives in the stomach where atmospheric Oxygen levels are very low.

Aerotolerant bacteria are also __________.

Fermenters (Fart left TT)

What is an obligate anaerobe? Example? Catalase or SOD presence?

-Can only be anaerobic respirators
-No catalase or SOD presence

What does clostridium ferment?


What two characteristics characterize the media?

Physical states
Chemical compositions

What 3 states can a physical media exist in? Give an example of all three.

Solid - Nutrient agar or test tube
Semisolid - " "
Liquid - Broth in a test tube
Both defined and complex media can be in these 3 forms.

What are the two types of chemical media? Definitions of both?

Defined - One in which the exact chemical composition is known
Complex - Exact composition is unknown

What is a complex media consist of?

1) Nutrients: yeast, beef, soy, or proteins
2) Protein: Derived from casein
3) Vitamins

What does a defined medium consist of?

1) Nutrients: glucose and salts
2) Optional: vitamins and amino acids

What are peptones? What are they used for?

-These are enzymatic digests of animal proteins.
-Used as a nutrient souce of Carbon, Nitrogen, and Energy for bacterial growth in media.

In what kind of media is a buffer required? Why?

-Complex media; amino acids make a very acidic medium

What is an advantage of using a defined or complex media?

-Organisms that require a relatively large number of growth factors are termed fastidious. Such organisms may be used as
living assays for the presence of growth factors. They require specific media.
-Complex media are able to support a wide variety of ba

What is an example of a bacteria that is highly adaptive versus one that is fastidious?

-E. coli (pic'd) is a highly versatile bacteria.
-Neisseria gonorrhea is very fastidious.

Gonorrhea is a very particular bacteria. What does it generally require for growth?

Wide variety of vitamins and amino that are not needed for other bacteria

How is gonorrhea grown? Mechanisms?

-Thayer Martin Media (TM)
-3 antibiotic agents that kill off everything but the diplococci gram- bacteria.

How is Rickettesia's grown?

In chicken embryos

What media does fungi grow best on? Characteristics of this media?

-Sabouraud's Media (SAB)
-More salt and sugar content and lower pH.

What do the Thayer Martin and Sabouraud's Media have in common?

They are both selective: their scope of bacterial growth is narrow.

What is a Blood Agar Medium? What is it used for?

Animal blood, mainly sheep.
-Detection of hemolysis, a partial destruction of red blood cells.

What is Beta hemolysis on the Blood Agar Medium?

-Streptococcus pyogenes (left) completely uses red blood cells
-Produces a clear zone termed Beta-hemolysis

What is Alpha hemolysis on the Blood Agar Medium?

-Streptococcus pneumoniae (middle) partially uses red blood cells
-Produces a discoloration termed alphahemolysis

Contrasting media: Agar is a _________ media, having a (low/high?) bacterial growth range.

defined, low

Does agar provide nutrients? What (else) does it provide? What kind of media does this make it?

-No, it only provides a derivative of cellulose which only few bacteria can (partially) digest.
-It is a selective media

What is Agar and from what is it derived?

-It is a complex polysaccharide
-Derived from the cell walls of certain red algae

Agar: Why is having a complex polysaccharide an advantage for a growth medium?

If most microbes cannot digest agar, i.e. it remains solid even when bacteria and fungi are growing on them.

Agar: It dissolves in water at ___C. Why is this an advantage?

It dissolves at 100C
If one wanted to, you could dissolve nutrients into it and they will remain intact.*
*Yes, you can add nutrients to Agar.

Agar: What are 2 advantages of it solidifying at __C?

-40 C
-Sterile nutrients can be added
-Can be poured over most bacterial cells without harming them (Pour plate isolation)

Agar: What two nutrients can be added to it?

1) Blood
2) Vitamins

Agar: Since SOLID agar does not melt below ___C, what kind of bacteria can it grow?

100 C

Special Medium: An anaerobic growth medium is a.k.a. a ________ medium because it creates ___ from _2 and _2 gas.

An anaerobic growth medium is a.k.a. a reducing medium because it creates H2O from H2 and O2 gas.

Special Med.: What is the purpose of sodium thioglycollate in the gas pak?

It absorbs all dissolved oxygen, making anaerobic conditions.

Special Med.: What is done to sodium before inoculation in a gas pak? Why?

-Heat is added to sodium thioglycollate
-Drives absorbed oxygen from thioglycollate immediately before such a medium is inoculated.

Gas Pak: What reaction is carried out? What is the catalyst?

2H2 + O2 = 2H2O
Catalyst: Palladium (above)

Slant tube: Made from what? What is its purpose?

Agar dried in a TT at an angle
Large aerobic area at top, anaerobic area on bottom.

What is a MacConkey Agar?

Differential and selective media

What is MacConkey Agar selective?

Selective: Gram-negative and Bacilli

How is MacConkey Agar differential?

Differentiates bacteria based on lactose fermentation

What are capnophiles? Example?

Bacteria that require elevated carbon dioxide levels.
Gonorrhea neisseria

What is generation time?

Time required for a single cell to grow and divide

What are the two rates of growth?

Transport Media Summary

Hospital personnel use special transport media to carry clinical specimens of feces, urine, saliva, sputum, blood, and other
bodily fluids in such a way as to ensure that people are not infected and that the specimens are not contaminated. Speed in

What is a purine on its own?

A colorless crystalline compound with basic properties, forming uric acid on oxidation.

What is pyrimidine on its own?

A colorless crystalline compound with basic properties.

What specificially does pyrimidine form?

Nucleobases thymine and cytosine.

What specifically does purine form?

Nucleobases adenine and guanine

Extra Credit
What are phenols?

compounds derived from phenol molecules
that have been chemically modified by the addition of halogens or organic functional groups

What is denaturation?

Denaturation is when a protein or nucleic acid loses its functional structure

How does decon work as an antimicrobial agent?

Denaturation of proteins

How do heavy metal ions act as antimicrobial agents?

They combine with sulfur atoms in molecules of cysteine, an amino acid, in order to denature.

What are the main heavy metal ions that are used in antimicrobial activity?

1) Arsenic
2) Zinc
3) Mercury
4) Silver
5) Copper

What is cord factor and what does it do?

It is a virulence factor that...
1) Creates biofilm that...
2) Aggregates like bacteria on to biofilm, that then...
3) Prevents macrophage engulfment

What is the scientific name of cord factor?

Trehalose dimycolate?

Where are exo- and endotoxins found, respectively?

Exo: Gram negative and positive bacteria
Endo: Gram negative

What two things can a glycocalyx be?

1) Slime layer
2) Capsule

What are two examples of a complex but synergistic relationship?

1) E. coli in the gut
2) Biofilms with bacteria - many different species accumulate here

Where are biofilms observed in industry? What benefits do they serve in industry?

-Pipes, drains and cooling towers (water related infrastructure)

Where are biofilms observed in nature?

Slime on rocks

Give 4 examples of where are biofilms observed in health?

1) Prostatitis
2) Kidney infection
3) Cystic fibrosis
4) Artificial medical device implants

What 2 things were used to clean up the Exxon mobile spill?

(1) Bioremediation with the bacteria pseudomonas and (2) inorganic salts