Bacterial Growth and Metabolism

Question 1

bacteria replicate by ___

Answer 1

binary fission

Question 2

what is binary fission?

Answer 2

one cell divides to yield 2 daughter cells

Question 3

the growth rate of a particular organism depends on:

Answer 3

availability of nutrients, environmental pH, salinity, and temperature

Question 4

what are prototrophs?

Answer 4

bacteria that can synthesize all essential metabolites

Question 5

what are autotrophs?

Answer 5

bacteria with acquired mutations that require them to obtain certain essential metabolites from the environment

Question 6

most bacteria are inhibited by ___ pH and ___ salt

Answer 6

low (acid); high

Question 7

why are human pathogens classified as mesophiles?

Answer 7

grow optimally bw 30-37C

Question 8

other bacteria can grow in extreme cold of heat. what are these called?

Answer 8

psychrophiles and thermophiles

Question 9

what nutrient stands out as one that greatly impacts the rate of cell division?

Answer 9

iron, important to growth and virulence

Question 10

why is sequestration of free iron in blood and other body fluids by transferrin and lactoferrin (iron-binding proteins) significant?

Answer 10

defense against infection

Question 11

Bacterial growth in a liquid (“broth”) culture can be measured by ___

Answer 11

growing aliquots of the culture on agar medium as the aliquots are taken at various times after broth inoculation

Question 12

bacterial growth can also be followed by measuring the ___ of a liquid culture over time

Answer 12

turbidity; as the bacteria multiply, they cloud the broth which can be visibly seen and measured using a spectrophotometer

Question 13

the bacterial growth curve includes what phases?

Answer 13

lag, exponential, stationary, decline/death phase

Question 14

what is happening in the lag phase?

Answer 14

essentially no growth occurs; bacteria are adapting to new nutrient environment, reprogramming gene expression to meet new needs

Question 15

what is happening in the exponential phase?

Answer 15

establish constant, optimal doubling times; bacteria experience maximal DNA and protein synthesis and are most acutely sensitive to antibiotic therapy; also best time to Gram stain organisms
- exponential growth leads to depletion of nutrients and accumulation of wastes. Metabolism is therefore greatly reduced and rate of cell division becomes equal to rate of cell death

Question 16

what is happening in the stationary phase?

Answer 16

no net increase in number of viable cells (bacteria become somewhat refractive to antibiotic therapy and Gram positive spore
formers initiate sporulation)

Question 17

what is happening in the decline phase?

Answer 17

nutrients deplete and waste increases, the rate of cell death exceeds the rate of cell division

Question 18

what is a biofilm?

Answer 18

bacteria in a biofilm are encased in a protective carbohydrate matrix that is adhesive and only formed after a series of events requiring motility and adhesion of planktonic bacteria

Question 19

why are biofilms significant?

Answer 19

bc of their prevalence, but also bc they are a source of recurrent infections and treatment failures; impairs antibiotic access to the residing bacteria, is anti-phagocytic, and bc of its adherent nature, often requires the removal of an infected implanted valve

Question 20

what is the purpose of metabolism?

Answer 20

provide the energy and building blocks a cell needs to survive and replicate

Question 21

describe oxidative respiration of aerobes and facultative anaerobes?

Answer 21

In the presence of oxygen, aerobes and facultative anaerobes funnel pyruvate through the citric acid cycle and oxygen serves as the final electron acceptor; produces 34 ATP

Question 22

oxid. respiration occurs where?

Answer 22

internal face of cytoplasmic membrane

Question 23

describe anaerobic respiration

Answer 23

In the absence of oxygen, an organic or inorganic compound other than oxygen serves as the final electron acceptor

Question 24

is fermentation an efficient way of generating energy?

Answer 24

no

Question 25

what is the major drawback of oxidative respiration?

Answer 25

produces hydrogen peroxide and superoxide anions (toxic to cell)

Question 26

what enzymes do strict aerobes produce to diffuse the damage caused by production of ROS?

Answer 26

superoxide dismutase, catalase, and peroxidase

Question 27

what enzymes do facultative anaerobes produce to diffuse the damage caused by production of ROS?

Answer 27

superoxide dismutase and peroxidase; will not always have catalase

Question 28

what enzymes do strict anaerobes produce to diffuse the damage caused by production of ROS?

Answer 28

catalase and peroxidase, lack superoxide dismutase so die in presence of O2 due to accumulation of superoxide anions

Question 29

why must bacteria synthesize folic acid?

Answer 29

source of nucleotides and methionine

Question 30

obligate intracellular pathogens are dependent on the host cell for ____

Answer 30

nucleotide cofactors and ATP

Question 31

can obligate intracellular pathogens be grown on synthetic medium in a lab?

Answer 31

no

Question 32

how can normal flora (commensals) cause disease?

Answer 32

1) when spread to a normally sterile site
2) when they overgrow their typical niche as a potential pathogen
3) the host becomes immunocompromised

Question 33

define pathogenesis

Answer 33

mechanism of disease development

Question 34

define virulence

Answer 34

term expressing degrees of pathogenicity

Question 35

define colonization

Answer 35

presence and multiplication of micro-organisms without tissue invasion or damage

Question 36

define infection

Answer 36

colonization that generally leads to disease.

Question 37

define epidemic

Answer 37

a disease that rapidly affects many people in a fixed period of time

Question 38

define virulence factor

Answer 38

any number of products produced and often secreted by pathogens that allow the pathogen to invade and cause disease in a host and evade host defenses