Extremophiles Flashcards
Extremophiles are all prokaryotes (bacteria & archaea). What are:
Thermophiles Psychrophiles Acidophiles Alkaliphile Halophiles
Heat, cold, acidic, alkaline, salty
How are thermophiles adapted to their environments? (2)
What are thermophilic enzymes used for?
What are some examples?
Proteins- more prolines which are less susceptible to unfolding - more compact
Heat stable cytoplasmic membranes (rich saturated FAs)
Biotechnology as very stable e.g Taq polymerase in PCR, and for washing clothes at high temp
Thermus- metabolises aspirin
Archaeoglobales- strict anaerobe & oxidises iron (e- donor) & respires with nitrate (e- acceptor)
What is the optimum temperature for a psychrophilic?
What temp has metabolic activity been detected?
Where are bacteria found? How can they be detected?
What characteristics help them survive? (3)
Below 15C, max is below 20C
-20C
Liquid water in brine veins between ice crystals- fluorescence (with its DNA being fluorescently labelled)
Cytoplasmic membrane high content of unsaturated FAs (semi fluid state so don’t freeze)
Seasonal dormancy
Proteins have more alpha helices than beta sheets- more flexible in cold
How do acidophiles survive? (1)
What pH do Picrophilus grow at and die?
How are some acidic environments created?
What do acidophiles have to cope with in these environments? What does this mean about diversity?
Stable cytoplasmic membrane with high concentration of H+
Grow 0.7, dye pH>4 (lyse cells)
Mining activity- contamination ground & surface waters, particularly FeS2 is oxidised to sulfuric acid leading to Acid Mine Drainage (AMD) causing water pH < 3
Need to cope with toxic metals like arsenic, iron, copper etc- diversity of prokaryotes in AMD is lower than other extreme environments
Where are alkaliphiles found?
Alcalilimnicola is a haloalkaliphilic bacteria- what can it metabolise?
What is significant about the diversity in extreme environments? What can they be useful for studying?
How can prokaryotes survive in high concentrations of toxin environments?
In high salt & carbonate environments (haloalkaphile is high pH and high salt)
Arsenic
Significantly lower. Astrobiology & origins of life.
Resistance (energy in form of ATP) or metabolism (produce ATP for cell growth)
What are the states of arsenate, arsenite, elemental, arsine?
Why is arsenate toxic?
How is arsenite toxic?
What are the past uses of arsenic? (4)
What are the sources of arsenic contamination?
+5, +3, 0 (not common or toxic), -3
Analogue of phosphate so enters cells via phosphate transport system & replaces phosphate & inactive proteins/processes
100x more toxic- enter cells by diffusion (cell membrane) or enter glycerol transport system. Inactivates proteins by bind to -SH groups
Homicidal agent- killed aristocrats, nobles & husbands
Pigments- paintings
Medicine- treat tumours, leukaemia (still used), anaemia, warts/herpres etc before realised toxic
Pesticide & wood preservatave- copper arsenate
Anthropogenic (mining), natural (hydrothermal vents), drinking water
Which forms of arsenic do microbes oxidise & reduce for respiration/resistance?
What does resistance genes to aresnic require? Where are the genes found?
As5+ enters cell via phosphate transform system. What are the steps after?
If As3+ enters cell via glycerol transport system, what are the steps after?
As3+ oxidation to 5+ is respiration, reduction of 5+ to 3+ is respiration and resistance (need ATP)
Needs ATP. Found in chromosomes and plasmids in prokaryotes, found also in eukaryotes but are homologs of prokaryotic ones
- Reduced to As3+ by ArsC (arsenate reductase)
- As3+ pumped through membrane pore ArsB using ATP (hydrolysed by arsA ATPase)
- Directly pumped out by ArsA ArsB pump
Aerobic arsenite oxidisers found in different environments as they lower pH, what are they? What’s the equation?
Whats the equation for anerobic arsenite oxidisers? What is different about the free energy?
Where have they been isolated from?
What are the 2 types of arsenite oxidisers?
Where is arsenite oxidase present in NT26 gram negative? What and where is the oxygen reduced to?
Gold mines, sweage, contaminated soil, sediments, lake water, geothermal vents
2H3AsO3 + O2 -> HAsO4 (2-) + H2AsO4 (-) + 3H+
H2AsO3 (-) + NO3- ->H2AsO4(-) + NO2- Half the free energy produced.
Mono lake california (haloalkalphile) and As contaminated soil
Chemolithoautotrophs (use CO2 as carbon source for oxidation of arsenite)
Heterotrophs (need organic matter for arsenite oxidation)
Periplasm
Water in the cytoplasmic membrane
Different organisms use different donors for arsenic respirations.
What is the equation for acetate? what are the donors/acceptors?
How would you find arsenic respirers?
Where is arsenate reductase in gram negative bacteria? What is reduced & what is oxidised?
2HAsO4 (2-) + 2H2AsO4(-) + 5H+ + CH3COO- -> 4H3AsO3 + 2HCO3-
H2AsO4- is donor and Ch3COO- is acceptor
Figure out the free energy available from a reaction & then find the organisms from the right environment
Periplasm (reduces As5+ to As3+ linked to electron transfer chain)
Acetate oxidised to CO2 in cytoplasm- generates ATP for cell growth
