Extremophiles

what is the difference between extremofiles and extremotolerant cells

extremofiles grow best in extreme environments, Extremotolerant cells can tolerate extremes but grow best under normal conditions

what is a mesofile

prefer normal conditions and won’t grow under extreme conditions

what is the difference between extremofiles and extremotolerant cells

extremofiles grow best in extreme environments, Extremotolerant cells can tolerate extremes but grow best under normal conditions

what is a mesofile

prefer normal conditions and won’t grow under extreme conditions

what is water activity

Pure water: Aw = 1.00

higher solute concentrations = lower Aw

water moves from a higher water activity to low water activity

what is an isotonic solution

when the concentration of solutes in the solution is the same as the concentration inside the cell

what is a hypertonic solution

when the concentration of solutes in the solution is higher than inside the cell

what is a hypotonic solution

when the concentration of solute in a solution is lower than inside the cell

what term describes microbes which can grow over a range of water activities

xerotolerant or xerophiles

how do most microbes respond to increases in osmolarity

accumulating compatible solutes

what are compatible solutes

molecules which can be accumulated inside the cells to high concentrations without interfering with cellular metabolism

what are the functions of compatible solutes

1. reduce internal water activity to control osmosis

2. stabilise cell structures and maintain shape and function even in low water activity environments

what is a halophile

A special class of Osmophile which specifically live in high salt environments

what is the ideal concentration of salt for halophiles and extreme halophiles

more than 0.2M, 2-8M for extreme halophiles

how do you halophiles cope with high levels of salt

use potassium as a compatible solute to balance water activity and stop osmosis pulling the water out of the cell. all other cell components must be adapted to high levels of potassium

what are the different classes of microbes for different pHs

Acidophiles - 0-5.5

Neutrophiles - 5.5-8

Alkalophiles - 8-11.5

how do pH tolerance cells cope

• have pumps to keep internal proton levels right

• have membranes and/or cell walls with altered permeability

• accumulate or get rid of cations like K+ to alter the movement of positively charged protons

• proteins which cope with pH changes or stabilise other proteins

What does poikilothermic mean?

Cant regulate temperature, so it varies with the environment around them

At which temperatures can thermophiles and hypothermophiles live at

43-80°C, 67-106°C

What are low temperature living microbes called? What temperature do they live at?

psychrophiles, <15°C, will not grow above 20 °C

How do psychrophiles survive low temperatures?

• Low-temp adapted proteins have fewer inter-chain interactions to increase flexibility

• Adjust their long chain fatty acids in the membrane - Shorter, unsaturated fatty acids have fewer interactions holding them together, and the unsaturated “bends” in the carbon chains prevent the molecules packing too closely, making these membranes more fluid

• Produce anti-freeze proteins to reduce the freezing point of water and stop ice crystals from growing around them and killing them

What is the optimum temp for mesothermic microbes?

20-45 °C

What problems do thermophiles have to overcome?

• Increased fluidity of membranes so significantly less control over what moves across it

• Denaturation of proteins - bonds holding amino acids break

How do thermophiles deal with such high heat?

• More disulphide bonds within the protein structure (forms covalent bridges)

• may make ‘chaperone’ proteins which help hold/stabilise other proteins

• Use DNA stabilising proteins

• archaeal ether lipids are more heat restart than bacterial ones

• To prevent membranes becoming too fluid shorter, unsaturated lipids are replaced with longer, saturated lipids

How is aerobic respiration more efficient than aerobic?

Aerobic - 1 glucose molecule makes 30 ATP molecules

Anaerobic - 1 glucose molecule makes 2 ATP molecules

What is an ROS?

Reactive Oxyegn Species - can chemically modify molecules which they come into contact with eg superoxide, hydrogen peroxide and hydroxyl radicals

How do aerobic microbes deal with ROSs?

The enzyme superoxide dismutase (SOD) converts superoxide to H2O2

Catalase and peroxidase enzymes convert H2O2 to water

Antioxidant molecules are used to absorb the effects of hydroxyl radicals

What are the different classes of microbes depending on oxygen requirements?

Obligate aerobes – MUST have O2 for growth

Facultative anaerobes – do not require O2 for growth, but do grow better with it

Aerotolerant anaerobes – ignore O2 and grow equally well whether it is present or not

Obligate anaerobes – strict anaerobes which do not tolerate O2 and die in its presence

Microaerophiles – are damaged by the normal atmospheric level of O2 (20%) but require lower levels (2 to 10%) for growth

What is the Great Oxygenation Event?

photosynthetic microbes evolved and began to release O2 into the atmosphere, which likely killed off huge number of organisms which weren’t resistant to ROSs

What are the classes of microbes depending on amount of pressure?

Barotolerant - can tolerate high pressure

Barophillic - will grow around 700atm, but not below 500atm

What issues does high pressure cause for microbes?

• Compresses lipid membranes (lower fluidity) - shorter, less saturated membranes can help this

• Reduces protein flexibility and ∴ affects enzymes, slowing reaction rates

How to barophillic organisms cope under normal pressure?

Structures which are adapted to ‘pushing back’ against higher pressure deform when that pressure is removed

What are the two potential strategies for repairing Double Stranded Breaks cause by ionising radiation

Non-homologous End Joining (NHEJ) attempts to directly join blunt DNA ends.

This process is fast, but can induce mutations as nucleotides are added or removed to get the strands to anneal before bonding them, and if many fragments are present it may join them in the wrong order

Homology Directed Repair uses a section of identical, undamaged DNA as a repair template.  

This is much more effective and gives fewer mutations, but is more complex and slow

How do some microbes resist radiation?

Cannot prevent DNA breaking, so excel at healing broken DNA

Antioxidant molecule prevent/repair oxidised proteins, lipids etc

What is the most radiation resistant organism?

Deincoccus radiodurans

How does D.radiodurans resist against radiation?

• DNA condensed into a small volume - smaller target for radiation

• DNA is help in a rigid shape by proteins - end of DNA won’t float away when broken

• High levels of Mn (antioxidant)

• Contains 5+ copies of its genome for repair templates

What are the advantages of using enzymes in industry?

• Cheaper and easier than industrial systems

• Avoid by-products of chemical reactions

• Safer (replace chemicals that could be dangerous in food, few harsh solvents needed)

• Easy to distribute

• Extremophilkic enzymes are resilient and ∴ easy to use at industrial scales

when did life evolve?

Archaean Eon (~3.8 billion years ago)

What occurred during the archaean eon?

Temps dropped for 200-300°C to 0-100°C

20-30atm dropped to 0.2-1 atm

No O2 or ozone layer - higher UV radiation

100ppm hydrogen cyanide gas

What is the Panspermia theory?

Life evolved through your the universe and can travel between parents on stellar debris