Lecture Set 3 : Part 4 Flashcards
what are cardinal temperatures?
-3 temperatures at which an organism can grow
-minimum, optimum, maximum
-not an even distribution (optimum is typically closer to the maximum)
why are cardinal temperatures important?
-temperature affects chemical reaction rates in the cell
-higher temperatures will result in faster reactions (optimum and maximum temps are usually very close)
what can happen to cells at too low of temperatures?
-membrane gelling (loses its fluidity)
-transport processes slow (growth cannot occur)
what can happen to cells at too high of temperatures?
-protein denaturation (shape loss)
-cytoplasmic membrane collapses (thermal lysis)
what are the different temperature classes of microorganisms?
-psychrophiles
-psychrotolerant (psychotroph)
-mesophiles
-thermophiles
-hyperthermophiles
what are psychrophiles?
-cold loving
-optimum less than or equal to 15
-maximum is less than 20
-minimum is less than or equal to 0 (not dead, but not growing)
-only found in permanently cold environments
-can be killed at moderate temperatures (20 or greater)
what in the environment allows psychrophiles to grow below 0?
-solid ice has tiny pockets where solutes have lowered the freezing point of liquid water
what are examples of places where psychrophiles could live?
-antarctic sea ice
-frozen lakes
what is an example of a psychrophile with a very low optima?
-polaromonas
-optimum growth at 4 degrees
what do the psychrophiles themselves have that allows them to grow in the cold?
-enzymes that function optimally at low temperatures and may denature at moderate temperatures
-modified lipids in the membrane
-high number of unsaturated fatty acid phospholipids (double bond (kink))
-these fatty acids remain semi-fluid at lower temperatures (prevents membrane gelling)
what are psychrotrophs (psychrotolerant)?
-above psychrophiles but below mesophiles
-optimum is 20-40
-maximum is around 45
-minimum is 0 (grow very slowly)
-more widely distributed than psychrophiles
-the bacteria that spoil food in your fridge
what are mesophiles?
-organisms with a midrange optimum
-those found in soils and lakes (optima = 30)
-warm blooded animals (optima = 37)
-most pathogens are mesophiles (why they can grow in the human body)
what is a direct mesophile example? what are its 3 cardinal temperatures?
-E.coli
-minumum = 8
-maximum = 48
-optimum = 39
what are thermophiles?
-heat loving
-optimum between 45-80
-found in hot springs, surface soils and compost, hot water tanks
what is a direct example of a thermophile? what is this organism used for?
-thermus aqauticus
-used as a source of heat stable enzymes for the polymerase chain reaction (Taq DNA polymerase)
what are hyperthermophiles?
-extreme heat loving
-2 groupings
-either have an optimum above 80 or above 100
-found in boiling hot springs and deep ocean hydrothermal vents
what is a direct example of a hyperthermophile?
-Methanopyrus kandleri
-archaea
-temp range is from 80-122
-is not present in our environments (autoclave is 121)
what are the upper limits for life?
-only prokaryotes can grow above 65
-no eukaryotes can grow at these temps
-chemoorganotrophs or chemolithotrophs can be supported well in these environments
-no phototrophy above 73
-labratory experiments with biomolecules suggest that lifes upper limit is 140-150 (no specific organism)
why do thermophiles provide such interest?
-thermophiles and hyperthermophiles produce enzymes widely used in the microbiology industry
-ex: Taq DNA polymerase is used for in vitro DNA synthesis reactions
-ex: produce heat stable hydrolytic enzymes such as proteases, cellulases, and lipases (more stable and have higher activity typically than mesophile enzymes of the same type)
how do hyperthermophiles fit into the evolution of microbes?
-may be the closest descendants of ancient microbes
-hyperthermophillic archaea and bacteria are found on the deepest and shortest branches of the phylogenetic tree
-oxidation of H2 is common to many hyperthermophiles which suggests that it may have been the first energy-yielding metabolism
how does the metabolism of thermophiles work?
-thermophillic phototrophy only exists until 73
-thermophillic chemoorganotrophy exists until 110 (no organic molecules past this)
-thermophillic chemolithotrophy exists until 95 when using inorganic molecules such as S or Fe2+ (above 110 only H2 exists (up to 122))
