MICR221 Lecture 6 - Bacterial Persistence and Surviving An Environmental Influx

Question 1

what is the only environment bacteria cant grow in?

Answer 1

bacteria can grow in any environment except space

Question 2

is the gut aerobic or anaerobic?

Answer 2

anaerobic

Question 3

is the soil and sky aerobic or anaerobic?

Answer 3

both are aerobic

Question 4

what is one of the most important chemical and abiotic factors?

Answer 4

oxygen

Question 5

what is an abiotic factor?

Answer 5

a non-living part of an ecosystem that shapes its environment

Question 6

what is the percentage of oxygen in the atmosphere?

Answer 6

21%

Question 7

what environments do aerobes prefer?

Answer 7

oxic environments

Question 8

what are oxic environments?

Answer 8

environments that contain free molecular oxygen

Question 9

what is the relationship between micro-aerobes and oxygen?

Answer 9

micro-aerobes require trace (little) oxygen of between 2-10%

Question 10

what percentage of oxygen do micro-aerobes require?

Answer 10

2-10%

Question 11

what environment do micro-aerophiles prefer?

Answer 11

hypoxic environments

Question 12

what is hypoxia?

Answer 12

gradual depletion of oxygen leading to a stationary phase that is slowed by growth and persistent phenotypes

Question 13

what percentage of oxygen do anaerobes require?

Answer 13

strictly 0%

Question 14

what environment do anaerobes prefer?

Answer 14

anoxic environments

Question 15

what are anoxic environments?

Answer 15

environments with no oxygen

Question 16

what is the relationship between facultative anaerobes and oxia?

Answer 16

facultative anaerobes change their metabolism under oxia

Question 17

what is a facultative anaerobe?

Answer 17

an organism which can survive in the presence of oxygen by using oxygen in aerobic respiration, but can also survive without oxygen via fermentation or anaerobic respiration

Question 18

what are host-associated environments?

Answer 18

internal or bacteria-dense anaerobic environments

Question 19

what is relationship with oxygen levels and increasing depth in soils/oceans

Answer 19

in soils and oceans oxygen levels decrease with increasing depth

Question 20

what is eutrophication?

Answer 20

the high local activity of aerobes leading to oxygen minimum zones

Question 21

what are higher eukaryotes?

Answer 21

inflexible organisms that are unable to adapt to conditions that are threatening (e.g no oxygen results in death and there is no fluctuation around this, humans are an example of this). They are obligate heterotrophs therefore they use sugars, a.a’s and fats (fixed organic sources) as substrates. They are also obligate aerobes as oxygen is required for respiration

Question 22

what are 3 fixed organic sources?

Answer 22

sugars
amino acids
fats

Question 23

what is the relationship between higher eukaryotes and fermentation?

Answer 23

fermentation is done transiently and the products of fermentation must be recycled

Question 24

what are bacteria?

Answer 24

extremely flexible organisms that can adapt under ideal conditions. They are diverse organic and inorganic e- donors. Bacteria are facultative anaerobes as they accept both oxygen and anaerobic e-.

Question 25

what is the mode of energy generation for bacteria?

Answer 25

fermentation is the terminal and sustained mode of energy generation

Question 26

what is the relationship between E coli and substrates for energy generation?

Answer 26

E coli has numerous substrates for energy generation and use > 6 alternatives to oxygen for respiration (flexible)

Question 27

why is E coli considered flexible?

Answer 27

because it can use > 6 alternatives to oxygen for respiration and they can survive on trace gases if no nutrients are available allowing flexibility for ATP generation during environmental changes

Question 28

what is the relationship between digestive enzymes of bacteria and where they are located?

Answer 28

bacteria have diverse digestive enzymes for breaking down several polymers that are typically bound in or associate with the cell surface to prevent loses to competition

Question 29

what do the digestive enzymes of bacteria release?

Answer 29

release monomers or shorter oligomers that conserved pathways can use (glucose, amino acids and fatty acids)

Question 30

what occurs if there is no food available for bacteria?

Answer 30

bacteria become persistent

Question 31

what is bacterial persistence?

Answer 31

persistence is when growth is slow or not at all but the bacteria are still metabolically active (not true dormancy)

Question 32

what is most likely the normal state of bacteria?

Answer 32

persistence

Question 33

what are the 2 strategies used to colonise diverse environments?

Answer 33

R-type strategy

K-type strategy

Question 34

what are R-type strategists?

Answer 34

fast growing (Td= minutes) that results in a dynamic persistence of a small subpopulation. Food is used wastefully. “Bust and boom” is a last ditch strategy used

Question 35

what is an example of bacteria that is a R-type strategist?

Answer 35

E coli

Question 36

what are K-type strategists?

Answer 36

slow growing (Td= days) that the bulk of the population persists and stress is survived for months-years with less drastic metabolic changes

Question 37

when are current antibiotics only effective?

Answer 37

only effective when a bacteria is growing in the exponential/log growth phase

Question 38

what do starvation responses induce in some antibiotics?

Answer 38

starvation responses induce protective responses

Question 39

what can recover bacterial growth activity?

Answer 39

adding nutrients

Question 40

what is an example of a bacteria that is a K-type strategist?

Answer 40

M. tuberculosis

Question 41

what is antibiotic resistance?

Answer 41

the heritable genetic changes that allow bacteria to grow even with the presence of antibiotics

Question 42

what is antibiotic persistence?

Answer 42

the non-heritable physiological changes that allow the survival of a few slow or non-growing cells

Question 43

why does antibiotic persistence lead to antibiotic resistance?

Answer 43

the inability of antibiotics to kill non-growing cells makes treatment times longer allowing persistence to lead to resistance

Question 44

what does environmental persistence result from?

Answer 44

results from the response to fluctuating food and nutrient supplies and targets different population-level strategists (R/K)

Question 45

what does antibiotic persistence result from?

Answer 45

results from the response an environmental catastrophe
e.g antibiotic killing and targets similar to population-level strategies. The subpopulation of cells is randomly pre-adapted giving less time to respond. Similar genetic mechanisms govern entry into persistence

Question 46

what do all forms of persistence cause?

Answer 46

a shift in energy metabolism that permits survival without growth

Question 47

what are the 3 ways bacteria enter a persistent state?

Answer 47

stringent response
SOS response
toxin-antitoxin systems

Question 48

what is the stringent response of bacteria entering a persistent state?

Answer 48

the global shift to the expression of survival functions. This is mediated by the molecule (p)ppGpp that stops expensive biosynthetic processes

Question 49

what is the SOS response of bacteria entering a persistent state?

Answer 49

the stress induced response to repair DNA damage. This is both a stress and survival response mediated by protein RecA

Question 50

what is the toxin-antitoxin systems response of bacteria entering a persistent state?

Answer 50

toxin-antitoxin systems are a balancing act with diverse cellular functions where the disruption of antitoxin leads to growth inhibited by toxin

Question 51

what are biofims?

Answer 51

a slimy matrix of various bacteria produced polymers

Question 52

what is the result of a local depletion of oxygen/nutrients?

Answer 52

leads to persister cell formation and physical protection from the environment combined with antibiotic persistence