Microbiology EXAM 2

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What are the components a bacteria must synthesize for a new cell?

* peptidoglycan
* metabolites, cofactors, ions needed for metabolism

Bacteria must do what two things before dividing?

1) synthesis components

2) grow in size

T/F: bacteria grow exponentially. the number of cells doubles with each binary fission

True

define generation time

time it takes for a cell to grow and divide into two cells

explain the equation

Nn=N0 x 2^n

Nn= the number of cells at any generation

N0= initial number of cells

n= number of generations

List the phases of bacterial growth

1) lag phase

2) exponential phase

3) stationary phase

4) death phase

What happens during the lag phase?

the cell is altering the metabolism to adapt to the new environment

what happens during the exponential/log phase?

growth rate reaches a constant maximum value, log is taken of the linear scale

what happens during the stationary phase?

the population consumes available nutrients and critical waste products collect

replication rate = cell death rate

what happens during the death phase?

cells often undergo morphological changes or lyses during this phase

\*endospores persist and wait for trigger to come out of endospore form

What is a biofilm?

* a thin, slimy layer encasing bacteria that adheres to a surface
* can consist of a single species or by multiple

how do biofilms benefit the bacteria?

* they allow easier access to horizontal gene transfer
* able to share nutrients
* sheltered from environmental factors

What is Quorum sensing?

* when bacteria secrete an inducer to attract other bacterial cells
* coordinates metabolism in response to stimuli
* change gene expression to produce metabolites that are only beneficial at high cell density

why does tooth decay happen?

plaque (a biofilm of bacteria) grows on teeth

the bacteria produces acids that eat away at the enamel into the pulp.

treatment is root canal

What are the physical growth requirements for bacteria?

temperature

pH

osmotic pressure

what growth requirement affects the RATE of microbial growth?

physical requirements

what are the chemical growth requirements for bacteria?

essential nutrients (C, N, S, P, and trace elements)

oxygen

what enzyme is produced by bacteria that neutralizes O2-? what about peroxide anions (O2 2-)?

superoxide dismutase

(this is possessed by all aerobic organisms)

catalase and peroxidase

what are obligate aerobes? how do they get energy?

only grow where oxygen is highest

respiration only

what are microaerophiles? how do they get energy?

grow best at lower oxygen levels

respiration only

what are facultative anaerobes? how do they get energy?

can grow without oxygen, but prefer to have it

both respiration and fermentation

what is an aerotolerant anaerobe? how does it get energy?

oxygen has no effect on growth rate

fermentation only

what is an obligate anaerobe? how does it get energy?

they grow with no oxygen

fermentation only

what neurtralizing enzymes must obligate aerobes contain?

catalase and SOD

Do microaerophiles contain neutralizing enzymes for oxygen?

slides don’t say so, rather they produce lethal amounts of toxic oxygen at a normal amount

what neutralizing enzymes do facultative anaerobes possess?

catalase and SOD

what neutralizing enzymes do aerotolerant anaerobes possess?

SOD only

what neutralizing enzymes do obligate anaerobes possess?

none

what are the cardinal temperatures?

the minimum, optimum, and maximum growth temperatures for a given bacteria

match the type of bacteria to preferred environment:

A:

mesophiles

hyperthermophiles

psychrophiles

psychotrophs

thermophiles

B:

Polar regions, deep sea

hot springs

refrigerator

animal pathogens

volcanic hot springs, deep sea vents

psychrophiles= polar regions, deep sea

psychrotrophs= fridge

mesophiles= animal pathogens

thermophiles= hot springs

hyperthermophiles= volcanic hot springs, deep sea vents

what do we call bacteria that grow at a low pH?

acidophiles

what pH do molds and yeast prefer?

5-6 pH

what is the pH level most organisms prefer to live in?

6\.5-7.5 pH

what do hypertonic environments cause?

plasmolysis (high plasmolytic pressure)

osmolarity definition

measure of the number of solute molecules in a solution

what are extreme/obligate halophiles?

require high osmotic pressure (high salt)

what are facultative halophiles?

tolerate high osmotic pressure (salty environment)

what is a fomite?

an object or material that are likely to carry infection such as clothes, utensils, and furinture

definition of sepsis

bacterial contamination

definition of asepsis

absence of significant bacterial contamination

what is sterilization?

destruction of all living cells, spores, and viruses

what is commercial sterilization?

destruction of *Clostridium botulinum* endospores in canned goods

does not result in sterilization

what is disinfection?

destroys vegetative pathogens

not sterilization

what is the difference between disinfectant and antiseptic?

disinfectant: inert surfaces/substances

antiseptic: living tissue

what is sanitization?

reducing microbial counts to safe public health levels

not sterilization

what is a -cidal agent?

lethal effects

bacteriocidal agents kill bacteria

what is a -static agent?

slows or stops metabolism of bacteria, but not lethal

inhibits bacterial growth

death curves are plotted _____________

logarithmically

what is the decimal reduction time? (D-value)

length of time it takes an agent to kill 90% of the population

what are external factors that influence the speed at which lethal damage accumulates?

* population size
* types of cells
* duration of exposure to the lethal agent
* environment (in organic material or higher temp for example)

How do microbial control agents work?

* remove from surfaces, liquids, or gases
* slow metabolism
* damage membranes
* damage proteins/inhibit enzymes
* damage to nucleic acids
* radicals/oxidizers attack and cause damage to everything

what are the two categories that microbial control methods fall under?

physical or chemical

what are physical control methods used for?

used to sterilize and or control growth

* temperature
* water
* mechanical
* radiation

what are chemical control methods used for?

\

used to control growth

few achieve sterility

* \

how does dry heat sterilize?

kills by oxidation

* flaming
* incineration
* hot-air sterilization

how does moist heat sterilize?

kills by denaturing proteins (breaks H bonds)

* boiling steam (max 100 degrees C)
* raise the temperature by putting steam under pressure

what is the autoclave?

steams under pressure

121 degrees C at 15 psi for 15 min

kills all organisms and endospores

what is pasteurization?

mild heating to eliminate pathogenic microbes while preserving food quality. thermoduric (heat-resistant) bacteria survive

what is high-temp short-time pasteurization?

72 degrees C for 15 sec.

low temps exert a bacterio-_____ effect. what is the difference between refrigeration and freezing?

bacteriostatic

fridge: inhibits metabolism

freezer: stops metabolism, kills microbes

what is the process of desiccation?

the removal of water needed for microbial growth

what is lyphilization?

rapid freeze → vacuum (water lost by sublimation)

what influences the efficiency of chemical disinfectants?

* presence of organic matter
* kinds of organisms present
* corrosiveness
* stability, odor, and surface tension

catabolism vs. anabolism

catabolism is when you release energy by breaking down large molecules into smaller ones

anabolism is when energy is used by small molecules being assembled into larger ones

The way an organism generates energy determines what?

the environment it is able to live in

All organisms need ____ __and__ ____

energy and carbon

chemotrophs utilize the energy stored in what?

chemical bonds

what is a oxidation-reduction reaction?

redox rxn where when an electron is lost, it is oxidized. when an electron is gained it is reduced.

(OIL RIG)

what are electron carriers?

molecules used to shuttle electrons from one reaction to another

example: NADH, FADH2

Redox reactions extract energy from nutrient molecules by ___________ organic compounds

oxidizing

choose one:

organic molecules are highly (reduced/oxidized)

reduced (they have many hydrogens)

what is atp?

adenosine triphosphate

what are the 3 phosphorylation mechanism used to generate ATP? and which uses the electron transport chain?

1) substrate-level phosphorylation

2) oxidative phosphorylation (uses ETC)

3) photo-phosphorylation (uses ETC)

what is the input and output of steps 1 and 2 of glycolysis/Embden-Meyerhof-Parnas pathway?

Step 1) input= glucose, output= 2 G3P

Step 2) input= 2 G3P, output= 2 pyruvate

what are two alternative pathways to glycolysis?

Entner-Doudoroff Pathway or Pentose Phosphate Pathway

what happens to pyruvate in fermentation?

electrons are put back on

what happens to pyruvate in respiration?

electrons are transferred to the electron transport system

What is the primary purpose of Fermentation?

Regenerate NAD+ for the continuation of glycolysis

ATP is generated ONLY during what process?

glycolysis!!!

Lactic acid fermentation examples

food spoilage and food production

* *streptococcus, lactobacillus*

Alcohol fermentation examples

yeasts: *Saccharomyces*

beer: waste products are ethyl alcohol and CO2 waste products

what are key events that happen before entering the TCA cycle?

1) pyruvate is broken down into acetyl-CoA and CO2

2) production of NADH

what are key events in the TCA cycle?

1) acetyl-CoA enters the cycle

2) reactions couple energy-yielding events (CO2 release) to energy-storing events (NADH formation)

Glucose (6 Cs) → glycolysis → 2 _____ → 2 ____→ TCA cycle which releases 4 ____ , 2 _______, FADH2 and NADH

2 pyruvate

2 acetyl CoA

4 CO2

2 ATP

At each step along the metabolic pathway, energetic electrons were stored as what?

stored as NADH and FADH2

explain where the ATP comes from during respiration in a bacterial cell

occurs on the cell wall and in cytoplasm


1. 2 ATP from glycolysis
2. 2 ATP from TCA cycle
3. 10 NADH + 2 FADH2 from oxidation of glucose can generate 34 ATP through the ETC

38 ATP total!

Energy from __________ generates proton motive force

redox reactions

what is the final ETS carrier??

cytochrome oxidase

what are the enzymes in the ETS called?

oxidoreductases

______________ is used to drive ATP synthesis

proton motive force

what makes up the proton motive force?

charge difference and H+ concentration

what is the final electron acceptor?

oxygen!!!

anaerobic respiration: the use of _______ electron acceptors

inorganic

what is the final electron acceptor in anaerobic respiration?

an inorganic substance

what is the electron acceptor for denitrifiers?

NO3-

what is the electron acceptor for the sulfur cycle?

SO4 2-

what is the electron acceptor for methanogens?

CO3 2-

what must happen to fats and proteins before the Krebs/TCA cycle?

must be broken down

what metabolizes fats?

lipases to glycerols and fatty acids

(aka beta-oxidation)

what must proteins do before entering the TCA cycle?

deamination, decarboxylation, and desulferization