Lecture 4: extremes of temperature Flashcards
the majority of organisms an temperature ranges
majority can only tolerate a narrow range of temperatures
cryophiles (psychrophiles)
low temperature optima for growth
what do we find at -18 DC
himalayan midge active at -18 DC and some single celled organisms
mesophiles
mid-range temperature optima (humans)
thermophiles
high temperature optima
extremeophiles grow best at a __ range of extreme conditions
narrow
temperature of most of the oceans
are at approx 5DC and ocean depths are at 1-2 C
–> COLD
cold areas on earth
- oceans
- poles (rarely exceed 0DC)
ice is rarely completely ____
frozen
- inclusions of liquid water are common
- channels of brine pockets present
- condensed microscopic halophilic environments
lots of organisms can survive cold organisms but can they ___
GROW
Fragilaria sublinearis
- diatom
- eukaryotic algae
- grows on underside of ice flow (stable) and photosynthesises on the light filtering through
- stick together
- gives ice flow a brown colour
- temp optimum = 7-12 DC
- but will grow at 1-2DC
Fragilaria sublinearis adaptations for survival
- stick together
- high light harvesting capacity (limited light through ice)
- lipid structure which allow them to function at low temp (polyunsaturated fatty acids)
- cryoprotectants (prevents freezing)
- osmoprotectants
Melosira arctica
- filamentous diatom
- which can form large growths on the underside of ice floes
- low CO2, low light environments, small temp range
2 filamentous diatoms (eukaryotic algae) found under ice sheets
- Melosira arctica
- Fragilaria sublinearis
massive ___ have been found under sea ice
algal blooms
– due to new tech (access is difficult drill through 1/2m of ice) ?? or due to Climate change???
studying diatoms: ____ approaches allow us to study their adaptions
- genomic approaches allow us to study their adaptions
- culture it in lab
- unusual no. of light harvesting complex genes
‘Red snow’
- eukaryotic algae
- Chlamydomonas nivalis
- photosynthetic
- common in snow fields
- summer you get melt water pools, but in winter u get red snow
- survive when frozen, thrive in pools??? –> assumption
- extreme temp = resistant spores with photo protective red pigment == RED
Chlamydomonas nivalis =
– global spread?
north america, New zealand, australia, europe –> LOW CO2 environments
red snow name
Chlamydomonas nivalis
Chlamydomonas nivalis physiology
- pink form = resting form? JUST surviving?
- Williams et al 2003 used gas exchange to measure photosynthesis in dense algae blooms
- GAS EXCHANGE OCCURS IN RED SNOW
problems organisms face at low temperatures
- lipid membranes become semi-crystalline and lose integrity at low temperatures (e- transport point, structure)
- enzyme activity becomes v slow
- ice crystal formation can disrupt cell structure
organisms which exist at low temperatures produce membranes which are rich in __ fatty acids
unsaturated (double bonds in chain)
membranes at low and high temp
- at low = semi crystalline become brittle
- middle = gel
- at high = blow up
appearance of saturated and unsaturated fatty acids
unsaturated = kink. stops them packing together so well
- sat = tougher, stick together at high temp
