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MICR 2430 > TOPIC 5: Chemical and Environmental Influence on Microbial Growth > Flashcards

TOPIC 5: Chemical and Environmental Influence on Microbial Growth Flashcards

1
Q

what happens to microbe growth at high temperatures?

A

microbes die, as enzymes start to denature

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2
Q

what happens to microbial growth at low temperatures?

A

rates fail because of the decrease in membrane fluidity and enzymatic activity

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3
Q

what type of bacteria are most bacteria?

A

mesophiles

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4
Q

what are the growth temperatures for psychrophiles, mesophiles, thermophiles, and hyperthermophiles?

A

0-20
15-45
40-70
65-105

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5
Q

describe psychrophiles

A

optimal growth temp: below 15C

produce enzymes that function optimally at cold temperatures (flexible structures, less intermolecular and intramolecular bonds)

cyroprotectants (trehalose) or anti-freeze proteins are imported/synthesized to prevent ice formation in the cytoplasm

cytoplasmic membrane has a higher concentration of unsaturated fatty acids to maintain membrane fluidity

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6
Q

describe an adaption to the cell membrane to help bacteria grow at a low temperature

A

unsaturated membrane lipids pack less tightly, maintains fluidity at low temperatures because of double bonds (kinks)

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7
Q

what are thermophiles/hyperthermophiles?

A

live in high temperatures
have stable enzymes/proteins that resist unfolding (denaturation) at high temperature

membrane rich in saturated fatty acids (to make less fluid)

more intramolecular interactions to prevent degredation

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8
Q

what kind of linkage is used in hyperthermophillic archaea

A

ether, as ether binds are more stable and resistant to hydrolysis than ester bonds. The -OH groups can be phosphoryltated to form the archaea monolayer

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9
Q

what is the difference between pyrococcus furiosus (hyperthermophile) and clostridium symbiosum (mesophile)

A

p. furiosus has more ionic interactions to keep protein stable at higher temperatures

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10
Q

what types of bacteria live at different pressures?

A

barophiles - high pressues
barotolerant - grow up to a certain pressure, but die at higher pressures
barosensitive - organisms die as pressure increases

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11
Q

describe barophiles

A

most are also psychrophiles (average temperature at the ocean floor is 2C)

membrane at high pressure is less fluid - have polyunsaturated phospholipids to maintain membrane fluidity

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12
Q

how do non-halophiles avoid osmotic stress in hypertonic solutions?

A

avoiding plasmolysis
import/snythesis of compatible solutes (proline, glutamate)
water particles move out of cell. Cell membrane shrinks and detaches from cell wall (plasmolysis)

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13
Q

how do non-halophiles avoid osmotic stress in hypotonic solutions?

A

avoid osmotic lysis
stop import and synthesis of compatible solutes
mechanosensitive membrane channels open allowing solutes to diffuse out of cytoplasm
water particles move into cell, cell wall counteracts osmotic pressure to prevent lysis and swelling

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14
Q

what are halophiles?

A

grow at 3-10% NaCl
adapted to low environmental water activity (aw ~ 1/osmolarity)
maintain a high concentration of organic and non-organic solutes in cytoplasm (ex. glycine betaine, ectoine, dimethylsulfonlopropionate, sucrose, trehalose) to prevent dehydration

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15
Q

describe extreme halophiles

A

distinct group of archaea
absolute requirement for high [NaCl] (15-30%)
adaption for K+ import to balance salt concentration and prevent dehydration
proteins have more Asp and Glu on surface
grow in salt lakes, salt ponds, and marine salterns
can give lakes a pink colour to prevent UV damage from sun

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16
Q

why don’t halophiles have a high concentration of Na+?

A

sodium motif force needs to be maintained for energy requiring processes such as transport

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17
Q

why do extreme halophiles have higher concentration of Asp and Glu?

A

they are acidic (negative charge)
interact with K+ ions in the cell
bring water molecules in to hydrate the proteins

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18
Q

what types of bacteria live at different pHs?

A

acidophiles (1-5)
neutophiles (6-8)
alkaliphiles (9-14)

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19
Q

what can the environmental pH affect?

A

energy generation by the proton motif force

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20
Q

how have microbes adapted to live at extreme pH conditions?

A

maintain a neutral cytoplasm even at high external pH

acidic conditions: microbes pump protons out or produce enzymes that catalyze reactions that consume protons

basic conditions: pump protons into cells or produce enzymes that catalyze the production of acids

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21
Q

what types of microbes can grow at different [O2]?

A

aerobic –> high oxygen
microaerophilic –> low oxygen
anaerobic –> no oxygen
facultative/areotolerant anaerobes –> grow anywhere

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22
Q

why is oxygen needed in the cell>

A

for the electron transport chain during oxidative phosphorylation
O2 is the final electron acceptor

O2 + 4H+ + 4e- –> 2H2O

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23
Q

what can form due to the incomplete reduction of oxygen gas?

A

oxygen radicals
only 1e- is taken, not two
causes cancer and aging

O2 + e- –> O2-

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24
Q

what enzymes detoxify oxygen radicals?

A

superoxide dismutase:
2O2- + 2H+ –> H2O2 + O2

enzyme catalase
2H2O2 –> 2H20 + O2

peroxidase
H2O2 + 2H+ –> 2H2O

note: H2O2 is less reactive than ROS but still not good

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25
describe obligate anaerobes
do not produce superoxide dismutase or catalase cannot survive with O2 due to radical formation
26
describe microaerophiles
prefer lower [O2] so ROS don't accumulate inefficient O2 reduction by ETC/inefficient O2 radical detoxification
27
how to grow anaerobic microorganisms?
sealed container with no O2 catalyst in lid convers O2 to H2O GasPak envelope generates H2 and CO2 systems with an air lock, glove port, and chamber to pump in N2
28
why do we car about controlling microbial growth?
treat bacterial infections food preservation prevent disease transmission microbiological experiments
29
what does sterile mean?
no microorganisms present
30
what does it mean to disinfect?
remove infectious agents, non-pathogenic bacteria still present
31
what are the three physical methods to control bacterial growth
heat, radiation, filtration
32
describe how MOIST heat can control bacterial growth
a) steam - denatures proteins, >100C, can kill bacterial endospores in a relatively short period of time b) autoclave - 121C for 20 minutes c) pasteurization (not sterile) - 72C, 15 seconds, kill bacteria in milk that causes disease, reduce number of microorganisms, prevent spoilage for a certain period of time
33
how can DRY heat control bacterial growth
kills by oxidation ex. flaming an inoculating loop
34
describe how RADIATION can control bacterial growth
ultraviolet light, X-rays, gamma rays - damages DNA and/or proteins
35
why isn't radiation as commonly used?
need much more radiation to kill bacteria compared to humans (3600 grays vs 10 grays) radiation is very expensive consumers do not like radiation sterilization
36
how can FILTRATION control bacterial growth?
membranes with 0.2 micrometer pore size use pressure to pass water through holes can use syringe filters or bottle top filters
37
how would you sterilize: glucose plastic metal loop TSA
filter sterilize (autoclave would caramelize the sugar) radiation dry heat autoclave
38
what are the chemical ways of controlling microbial growth?
biocides/disinfectants antibiotics
39
what are biocides
non-specific - do not target specific cellular structures in microorganisms normal household products (do not need prescription) will kill humans too
40
what are antibiotics?
kill only bacteria target specific cellular structures, usually specific to certain types of bacteria used to treat diseases/infections in humans and animals (medicinal)
41
how can you tell that the bacteria produced in the lab is antibiotic or cytotoxic?
when you do ESKAPE tests the only inhibit SOME bacteria (antibiotic, not biocyde)
42
what is the active ingredient in clorox? how does it kill microorganisms?
sodium hypochloride (NaOCl) oxidizing agent - inactivates proteins and lipids
43
what is the active ingredient in tincure iodine? how does it kill microorganisms?
iodine (I2) modifies proteins (tyrosine amino acid) and acts as an oxidizing agent (catalyzes oxidation reactions)
44
what is the active ingredient in germX and alcohol prep pads? how does it kill microorganisms?
ethanol ethanol dissolves lipid membranes and denatures proteins (organic solvent)
45
what is the active ingredient in WetOnes wipes? how does it kill microorganisms?
benzethonium chloride (a quaternary ammonium compound) positive charge on the nitrogen interacts with phospholipids and disrupts cytoplasmic membrane
46
what is the active ingredient in listerine? how does it kill microorganisms?
thymol (phenol) organic compound that kills by denaturing proteins
47
what is the active ingredient in soap? how does it kill microorganisms?
detergent dissolves cytoplasmic membrane mechanical removal of microorganisms
48
what is the active ingredient in dettol (antibacterial soap)? how does it kill microorganisms?
triclosan triclosan inhibits lipid synthesis enzymes in bacteria and fungi banned in the US to prevent the growth of antibiotic resistant bacteria
49
where do antibiotics come from?
isolated from microorganisms chemical derivatives of natural antibiotics soil microbes may produce antibiotics to kill their competition
50
what are the mechanisms of antibiotics?
inhibit cell wall synthesis inhibit protein synthesis affect nucleic acid synthesis or integrity disrupt cell membrane inhibit synthesis of an essential metabolite
51
how does penicillin work?
COMPETATIVE INHIBITOR inhibits peptidoglycan synthesis by inhibiting activity of penicillin binding protein, inhibiting transpeptidation disrupting peptidoglycan causes the cell to keep growing and burst B-lactam ring resembles D-Ala-D-Ala dipeptide catalyzes the reaction of D,D-transpeptidase, with released D-alanine, weakening peptidoglycan
52
how does vancomycin work?
binds to substrate (D-ala-D-ala) on NAM, preventing transpeptidation reaction same effect as B-lactam antibiotics, but does not bind to penicillin binding protein
53
how do various antibiotic inhibit protein synthesis
streptomycin --> binds to A site, causes mistranslation chloramphenicol --> binds to P site tetracyclin --> binds to A site, inhibits tRNA binding Erythromycin --> binds to P site
54
why do antibiotics that inhibit protein synthesis not affect human ribosomes?
human ribosomes are sufficiently different from prokaryotic ribosomes
55
how do quinolones affect nucleic acid synthesis
binds to DNA gyrase (catalyzes DNA supercoiling) causing gyrase-DNA covalent complex to be stick at this stage prevents DNA polymerase from accessing origin of replication DNA synthesis inhibited
56
what does the free radical of metronidazole do?
causes DNA breaks treats anaerobic bacteria, which donates electrons to prodrug, forming the radical that causes the DNA breaks used to treat tooth decay, highly specific reacts with biomolecules that are essential for cell growth
57
how does rifampin work?
binds to RNA polymerase and inhibits gene transcription
58
how does actinomycin D work?
binds to DNA so DNA polymerase, RNA polymerase, and other DNA binding proteins cannot access DNA, interfering with replication and transcription peptide antibiotic
59
how do polymyxins and antimicrobial peptides disrupt cell membranes?
gamicidin forms a channel through the cytoplasmic membrane, allowing the free diffusion of cations better at treating gram negative bacteria, as they have lipopolysacharides and can diffused through outer cell membrane
60
how do enzyme inhibitors (ex. sulfanilamide) work?
looks similar to PABA, which is required for the synthesis of folic acid, an essential vitamin sulfanilamide binds to an enzyme required to synthesize folic acid competitive inhibitor
61
how can bacteria resist penicillin?
produces an enzyme that modifies antibiotic B-lactamase cuts B-lactam ring in half, producing penicilloic acid
62
how does bacteria resist chloramphenicol?
adds a CH3 group so it cannot bind to and inhibit ribosomes produces chloramphenicol 3-acetate
63
how do gene mutations propagate antibiotic resistance?
single amino acid change in bacterial ribosome may be sufficient to prevent macrolide antibiotic from disrupting its function
64
how can bacteria pump antibiotic out of the cell?
ArcAB utilizes the proton motif force to pump antibiotics out of the cell through TolC use antiport/proton motif force to pump out bacteria concentration of antibiotics in cytoplasm too low to inhibit bacterial growth
65
why are slow growing bacteri (eg mycobacterium tuberculosis generally more resistant to antibiotics?
thick outer membrane, preventing influx of antibiotic into cell needs to be metabolically active for antibiotics to target cell growth and fission (does not divide as often when slow growing)
66
what is a normal dose of antibiotics compared to a dose to treat TB?
normal: 1 antibiotic for 2 weeks TB: 4 antibiotics for 6 months
67
why are biofilms more resistant to antibiotics?
not actively growing matrix makes it hard to get into cell eg. teeth - streptococcus mutans lungs - CF, pseudomonas aeruginosa hospital equipments - catethers
68
describe antibiotic misuse
agriculture - livestock - used to give antibiotics to animals to prevent sickness improper prescription of antibiotics - not testing beforehand, antibiotics do not affect viruses patients not finishing antibiotic dose prescribed

MICR 2430 (5 decks)

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