Micro: Bacterial Growth and Metabolism

Question 1

The growth rate of a particular organism depends on what 4 factors?

Answer 1

availability of nutrients, environmental pH, salinity and temperature

Question 2

What are prototrophs?

Answer 2

bacteria that can synthesize all essential metabolites

Question 3

What are auxotrophs?

Answer 3

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

Question 4

True or false, most bacteria are inhibited by acidic pH

Answer 4

True

Question 5

True of false, high salinity is a common inhibitor of bacterial growth

Answer 5

True

Question 6

Human pathogens are classified as __________ because they grow optimally between ____ Celsius and ___ Celsius.

Answer 6

Mesophiles; 30-37 Celsius

Question 7

Bacteria that grow in extreme cold are called:

Answer 7

psychrophiles

Question 8

Bacteria that can grow in extreme heat are called:

Answer 8

thermophiles

Question 9

What necessary bacterial nutrient stands out because of its importance to growth and virulence?

Answer 9

Iron

Question 10

How do bacteria counter iron limitation by the host (sequestration of free Fe)?

Answer 10

By secreting siderophores which chelate Fe and are then actively transported into the bacterial cell

Question 11

Most bacteria take between ____ and ____ minutes to replicate.

Answer 11

30-60 minutes

Question 12

The ____ phase of bacterial cell propagation is the period following initial inoculation in which essentially no growth occurs.

Answer 12

Lag phase

Question 13

Why is there essentially no growth of bacteria during the lag phase?

Answer 13

The bacteria are adapting to the new nutrient environment, reprogramming gene expression to meet new standards.

Question 14

Following the lag phase, bacterial growth enters the ______ phase, wherein bacteria begin to replicate and establish constant, optimal doubling times.

Answer 14

exponential (log) phase

Question 15

During which phase of the bacterial growth curve are the bacteria most sensitive to antibiotic therapy and why?

Answer 15

Log phase, because the bacteria experience maximal DNA and protein synthesis.

Question 16

During which phase of the cell growth curve is the best time to gram stain organisms?

Answer 16

log phase

Question 17

What are two consequences of log growth that are dependent on the environment to prevent halting bacterial growth?

Answer 17

depletion of nutrients and accumulation of wastes

Question 18

When the nutrients in a culture’s environment are outstripped by demands and waste products accumulate beyond healthy levels, this area of the bacterial growth curve has been reached.

Answer 18

Stationary phase. The rate of cell division becomes equal to the rate of cell death.

Question 19

Why is gram staining not ideal during the stationary phase of the bacterial cell growth curve?

Answer 19

Bacteria may begin sporulation (if spore formers) due to the austere environment. The nature of the spore will inhibit or reduce efficacy of gram staining.

Question 20

As the nutrients deplete and waste increases, the rate of cell death exceeds the rate of cell division and the culture enters the ____ “death” phase.

Answer 20

Decline phase.

Question 21

Individual, free-living bacteria are also referred to as

Answer 21

planktonic bacteria

Question 22

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

Answer 22

Biofilm

Question 23

It is estimated that 80% of infections result in the organization of bacteria into this structure that is a source of recurrent infections and treatment failures:

Answer 23

Biofilm

Question 24

The nature of a biofilm impairs _______ access to the residing bacteria, is anti-_________, and because of its ______ nature, often requires the removal of a infected implanted medical devices.

Answer 24

antibiotic access
anti-phagocytic
adherent nature

Question 25

In aerobes or facultative anaerobes , respiration occurs where?

Answer 25

Internal face of cytoplasmic membrane

Question 26

How many ATPs are produced in oxidative respiration in aerobic bacteria?

Answer 26

34

Question 27

Strict (or obligate) anaerobes use _________, another form of anaerobic respiration, to generate energy and metabolites.

Answer 27

Fermentation

Question 28

In the absence of oxygen, anaerobic respiration can occur, in which an ______ or ___________ compound other than oxygen serves as the final electron acceptor.

Answer 28

Organic or inorganic compound

Question 29

During fermentation, _______ is converted to various organic end products (e.g. acetic acid, butyric acid or lactic acid), CO2, or Hydrogen and electrons are directly transferred to ________ acceptors.

Answer 29

pyruvate; organic acceptors

Question 30

Is fermentation an efficient way to generate energy?

Answer 30

No.

Question 31

Which is faster, aerobic or anaerobic growth for facultative anaerobes?

Answer 31

Aerobic

Question 32

Strict aerobes produce 3 enzymes to diffuse the damage caused by the production of superoxide and hydrogen peroxide. Name them.

Answer 32

superoxide dismutase (SOD), catalase, and peroxidase

Question 33

What are the two enzymes always produced by facultative anaerobes to diffuse the damage caused by superoxide and hydrogen peroxide?

Answer 33

SOD and peroxidase

Question 34

Strict anaerobes lack this enzyme and are therefore killed in the presence of oxygen due to the accumulation of superoxide anions.

Answer 34

Superoxide dismutase (SOD)

Question 35

The presence or absence of catalase has this consequence for bacteria:

Answer 35

Patients with chronic granulomatous disease (CGD) lack NADPH oxidase in their neutrophils. Consequently, the neutrophils fail to produce an oxidative "burst". This allows catalase positive cells such as staphylococci to overcome the basal levels of peroxide and survive, causing recurrent infections.

Question 36

Bacteria must synthesize _____ acid (a source of nucleotides and methionine) rather than use environmental sources.

Answer 36

Folic acid

Question 37

These two antimicrobials exploit the bacterial pathway for synthesizing folic acid to kill microbes.

Answer 37

sulfonamides and trimethoprim

Question 38

Obligate intracellular bacteria are dependent on host cell ______ ________ and ______, and cannot be grown on synthetic media.

Answer 38

nucleotide cofactors; ATP

Question 39

________ is the mechanism of disease development.

Answer 39

Pathogenesis

Question 40

_______ is a term expressing degrees of pathogenicity.

Answer 40

Virulence

Question 41

________ is the presence and multiplication of microorganisms without tissue invasion or damage.

Answer 41

Colonization

Question 42

______ is colonization that generally leads to disease.

Answer 42

Infection

Question 43

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

Answer 43

Epidemic

Question 44

_______ ______ is any number of products produced and often secreted by pathogens to invade and cause disease in a host and evade host defenses.

Answer 44

Virulence factor