Thermophiles Flashcards
What are thermophiles and examples
They’re considered to live in the upper rang that a group of organisms would live in.
Geobacillus is gram positive and its used for sterilization tests. Its common food spoilage organisms that grows in extreme temps
Thermococcus and pyrobus: these organisms are inactivated and are frozen so they stop dividing and they only start regrowing if you get to boiling temperatures, these aren’t very common.
What do S-layers do
S-layers play a role for the primitive precursor form of cell envelopes
Definition of a thermophile
A thermophile is an organism capable of living at (or near) the maximum temperature for its taxonomic group.
For microbes, any species growing above 55 oC is thermophilic.
Eukaryotic microbes only grow up to 62oC (very few) – so majority are prokaryotes
Classification of thermophile microbes
Above 80oC, all Thermophiles are Archaea except for Thermotoga and Aquifex. Above 90 degrees, they are all called hyperthermophiles and are all archaea
Whats the structure of thermotoga
The structure on the outer side of the shell gives a balloon extension of both shells which creates large spaces that have a limited access to the outside.
The layer is the membrane in which the S-layer sits, two proteins in the structure, one is porin.
The organism has about two thousand genes, they’re small and contain 24% of the chromosome.
Thermatoga produces hydrogen during metabolism as a producer of hydrogen.
Whats the aquifex
Water former, has a small genome, 16% of archaea origin. This allows them to adapt to extreme temperatures. By product of metabolism, creates water from respiration.
The metabolic sources of thermophiles
Most hyperthermophilic Archaea obtain their energy by using elemental sulphur (So) as their electron acceptor - found in hot springs
The ability to use O2 as an electron acceptor above 90 oC is very limited.
What is the importance of lipids in thermophiles
Every aspect of the cell is important.
Membrane lipid composition is a major factor in determining temperature growth range.
At high temperature, the lipids are in liquid crystalline state and the membranes are disordered.
Because these transitions are limited and defined by the chemistry of the lipid, theres a maximum temperature range thats determined by the lipids that the organism produces
What are bacterial lipids generally like and what happens as temperature increases
Fluidity of the membrane is due to fatty acid chain composition.
Chemistry is important for their features - the synthesis of the fatty acids is done by the normal chemical pathways.
As temperature increases:
a) 1. a) fatty acid chain length increases
2. b) decrease in unsaturation
c) increase in the ratio of iso- to ante iso-branching
The packing of these fatty acids determine how in the membrane, the fatty acids relatively to each other can pack -determines how stable the structure is
What are the lipid adaptations in thermophiles
In bacterial thermophiles long chains and iso-branched fatty acids are found - no unsaturated fatty acids (i.e. no double bonds).
In archaeal thermophiles, ether-linked lipids with hydrocarbon chains of fixed length of either 20 or 40 carbons are found
Chains of 40 chains are the longest chains - two basic types
Tetraether membranes maintain their integrity above 80 degrees found in all hyperthermophiles.
Hyperthermophilic archaea introduce cyclisation of the acyl chains at high temperature
The failure of bacteria to grow above 80 degrees is due to the lack of tetraether lipids
What are thermophile archaeal ether lipids
Two basic types:
1. Diether, forms a bilayer membrane
2. Tetraether which forms a monolayer membrane
There are major differences between the two structures
Proteins in thermophiles and the analogous protein from mesophiles and their comparisons
Tungsten containing enzymes play thought to play a role in primary metabolic pathways of some hyperthermophiles.
The analogous enzymes in mesophiles use molybdenum.
Molybedenum has 42 proteins while tungsten has a higher molecular weight and a higher contrast and is used in electron microscopy as a stain but tungsten is much more often found
Why is tungsten found more often
In the ocean, a lot of studies have been done- the molecular is 0.64pp and tungsten is 0004pp so tungsten is rarer in the ocean than molybdenum
In ocean water molybedenum is normally found in molybednum disophit- found to be relatively insoluble.
Bioavailability of this molecule is lower than the actual concentration would make it. At the same condition the tungsten is negatively charged and more bioavailable - so although its rarer, its more bioavailable
How are proteins more stable in thermophiles and how was this discovered
Was discovered by doing comparisons of the amino acid sequence and 3D structure of homologous hyprethrmophilic and mesophilic proteins
What did studies on citrate synthase by Mike Dansons group show
Thermophilic enzymes had shorter surface loops, had a reduction in internal cavities (looked more compact due to loss), had an increase in internal packing (supports thermal stability).
All of these made the enzyme more compact and rigid, increasing the thermostability but reducing the catalytic efficiency
These rules are not universal - may not be a close relationship between conformational flexibility and catalytic function
