Week 5: Environmental influences on growth - Oxygen and temp

Question 1

Psychrophile, psychrotolerant, mesophils, thermophilsa nd hyperthermophile

Answer 1

Psychrophile: optimum growth < 15 C

Psychrotolerant: 0-35 C

Mesophile: 15-45 C

Thermophile: 45-80C

hyperthermophile: growth above 80 C

Question 2

acidphile, neutrophils and alkaliphile

Answer 2

cidophile; groth below pH 5

neutrophile; between 5-8

alkaliphile: above 8

Question 3

obligate anaerobe, aerotolerant, facultative anerobe, microaerophilea and obligate aerobe

Answer 3

obligate strict aerobes: cant grow without O2 mycobacterium spp (tuberbulosis)

obligate anerobes: killed by oxygen Clostridium

Facultative: perfer to grow with oxygen but can also grow in absence by relying on femrnetation or anerobic resp (anerobic growth yeilds less energy so still perfer aerobic) E. clo or S. aureus

• aerotolerant: indifferent, dont use oxygen bc fermentation metabolism but ont care about oxygen lactic acid bacteria - steptococcus
  microaerophiles: require a minimum conc of oxygen about 1-10% - well below the 21% atm campylobacter

Question 4

what types of organisms are clostridium

Answer 4

obliate anerobces found in body

• gram pos, rod shaped
• form endospores allowing them to survive in presence of oxygen
• cause majro ifnections, C diff, C tetani, C perfringes (infection starts in dead tissue not suplpied ith oxygen)

Question 5

what is the great oxygenation event?

Answer 5

• oxygen revolution causing mass extinction
• most organisms could not survive the powerful oxidative properties of ROS - hihgly unstable ions and mol from partial reduction of oxygen
• can damage virtually any macromolecule or structure with which they come in contact

Question 6

what is a thioglycolate tube?

Answer 6

• Starts with autoclaved thioglycolate medium w/ low % agar to allow motile bacteria to move thru medium
• Thioglycolate has strong reducing properties and autoclaving flushes out most oxygen
• Tubed inoculated and incubated at an appropriate temp

Overtime oxygen slowly diffuses throughout the thioglycolate tube culture from top - bacterial density inc in area where ox conc is best suit for growth of that organism

Question 7

use of oxygen for aerobic respiration

Answer 7

• electron transport chain generation the PMF
• O2 serves as the terminal electron acceptro for aerobic respiration

Question 8

dealing with ROS

Answer 8

• enzymes gorwing in presence of ROS need enzyme to detoxify (superoxide dismutase conv O2 => H2O2) - catalase or peroxidase detofiy bc H2O2 is also toxic
• Catalase produces oxygen: H₂O₂ -> 2H₂O + O₂
• Peroxidase: H₂O₂ -> 2H₂O + NAD+

*can do catalase test to detect gram +ive cocci - will see bubbles bc O2

Question 9

how are anaerobes cultured in the lab?

Answer 9

• can use anerobic jar: chemicals in gas pack react with oxygen and remove it by converting it to water (can use for anerobies but not super anerobic)
• Candle jar: not as great, flame consumes the oxygen, not 100% removal so not a fully anerobic environment (cant be super sensitive to oxygen)
• for those v sensitive to oxygen use a glove box: everything anerobic inside bc airlock chamber

Question 10

ex of mesophiles. psychorphiles. thermophiles and hyperthermophiles

Answer 10

Mesophiles: human associated bacteria

psychroiles: bacillus psychrophlius

Thermophiles: thermus aquaticus

Hyperthermophiles: pyrococcus (archaeon) and thermotoga (bacterium)

Question 11

what is the arrhenius effect

Answer 11

• increasing temperatures increases the rates of cellualr enzymativ reactions (until optiumum is reached)

Question 12

what happens below and above the growth range

Answer 12

below minimum: membrane solidifies: nutrient transport, enzyme activity drops

above maxiumum: membrane mroe fluid, thermal lysis, enzymes denature

Question 13

whatdoes icnreasing temperature do

Answer 13

causes spontaneous chemcial changes - increases mutations

• why hyperthermophiles have higher rates of mutations

Question 14

how to bacteria adapt to high temp environments?

Answer 14

• saturases to remodel the memrbane and alter the biosynthesis of lipid mem (syn saturated instead of unsat FA)

*take away double bonds so more stirahgt and pack tighter to stiffen memrbane and coutneract fluidity

• heat shock proteins (if one critical protein denatures the cell will die)

*can be chaerone to help fold properly, form protective shell around the protein to hold in 3D conformation

*hyperthermophiles often archea- have ether linkages not ester which are mroe stable

Question 15

how do bacteria adapt to cold environments?

Answer 15

• desaturases go into membrane and introduce bonds into fatty acid chains (inc dobule bonds so more kinky and inc fluidity)
• cryoprotectants likeglycerol prevent formation of ice rystals
• cold shock protiens are induced when proteins are in danger of loss of available water (expressed wtih much higher rates in psychrophiles)

Question 16

archaeal membranes

Answer 16

• form tetraether monolayers in hyperthermophiles
• thermostability of ether linkage vs ester linkage
• noramlyl fatty acid tail is attached to glycerol via ester link - in areach can attach to eachother to membrane memrbane more stable

*if u anchor tails to eachother at middle of membrane then movement is considerably reduced