Lecture 12: Extremophiles and Bacterial Growth Conditions

Extremophiles

Organisms thriving in extreme environmental conditions.

Growth Rate

Slope of line during exponential growth phase.

Growth Yield

Height of line in stationary growth phase.

Mesophiles

Bacteria thriving at 37°C, optimal for growth.

Thermophiles

Bacteria with optimal growth between 50°C-80°C.

- proteins fold properly at high temp

-membranes with long, straight-chain fatty acids (low fluidity)

Hyperthermophiles

Bacteria thriving at temperatures 80°C-113°C.

"Hypersaline"

- Extremely cold

Psychrophiles

Bacteria with optimal growth at 4°C-10°C.

- low temp

- membrane fatty acids have extensive unsaturation or branching (more fluid)

Obligate Aerobe

organism that requires a constant supply of oxygen in order to live

faculative halophiles

Organisms that do not require high salt concentrations but can tolerate salt concentrations at 2 percent

Aerotolarant anaerobes

can tolerate the presence of oxygen but can't use it for growth

strict anaerobes

die in the least bit of oxygen

Microaerophiles

Aerobes that require Oxygen levels from 2-10% and have a limited ability to detoxify Hydrogen Peroxide and Superoxide Radicals

Halophiles

Organisms thriving in high salt concentrations.

- Ponds > 2m NaCl

Red color due to Archaea Halobacterium are extreme halophile

Osmotic Stress

Pressure from solute concentration affecting cell function.

Desiccation

Extreme dryness limits bacterial growth and function.

- water squeezes out of the cell

- Atacama desert Chile

-Low water concentration limits protein function and causes chromosomes to shear into fragments (lethal)

Radiation

Ultraviolet and ionizing radiation damage DNA.

- powerful mutagen- forms thymine-thymine dimmers in DNA

-ionizes most common molecules in the cell (water) to attack the largest molecule

Deinococcus radiodurans

• isolated from an irradiated can of meat

• extremely radiation-resistant

• tolerance - 5,000,000 rad

• Human tolerance - 100 rad

• multiple chromosomes/cell (4-10)

• nucleoid compacted into a torus

Deinococcus is also very desiccation resistant. Why?

1. Can quickly and efficiently repair DNA

2. Has proteins that acts as antioxidants that provide a shield

3. Has a tightly packed genome structure that protects DNA from damage

Pressure

High pressure conditions affecting DNA replication.

Superoxide Dismutase (SodA)

enzyme that detoxifies radicals

Catalase (KatF)

Enzyme converting hydrogen peroxide to water.

Deinococcus radiodurans

Radiation-resistant bacterium with multiple chromosomes.

Autoclave

Device using high pressure and temperature for sterilization for endospores

Halotolerance Curves

Graphs showing bacterial growth in varying salt concentrations.

- similar to desiccation

- Jellies (sugar), Brines (salt), curing (salt).

Endospores

Dormant, resistant structures formed by some bacteria.

- need very high heat

Limiting Bacteria growth

1. Rise temp (Cooking/pasteurizing)

-From dsDNA to melted ssDNA

- Damage protein structure

- disrupts membranes

2. Lower temp (fridge)

Nutrient Limitation

Insufficient nutrients hindering bacterial growth.

Thermostable Proteins

Proteins that maintain structure at high temperatures.

Membrane Fluidity

Degree of lipid mobility in cellular membranes.

Thymine Dimers

DNA damage caused by ultraviolet light.

Hydrogen Peroxide

Reactive oxygen species damaging cellular components.

Oxygen Radicals

Reactive molecules generated during aerobic respiration.

Desiccation Resistance

Ability to survive extreme dryness.

Barophiles

Organisms thriving under high pressure conditions.

Antibiotics

Substances targeting bacterial growth without harming humans.

Functional Proteins

Proteins maintaining activity under specific conditions.

Chromosome Melting

Denaturation of DNA at high temperatures.

Cell Wall

Structure providing shape and protection to bacteria.

Hydrothermal Vents

Underwater openings supporting unique microbial life.

-life around "black smoker"

- animals feed on microbial biomass growing near the smoker

- steep temp gradient in rock

Microbial Biomass

Total mass of microorganisms in a given area.

Nucleoid

Compact structure of bacterial chromosome.

Oxygen Tolerance

Ability of bacteria to survive in oxygen presence.

Oxygen Damage

- Superoxide (Radical O-) reacts with and damages all macromolecules it encounters

- DNA (largest) common target

- Difficult to repair

- halt DNA replication

GasPak

Anaerobic chamber for growing oxygen-sensitive bacteria.

Psychrophile Adaptations

Membrane adaptations for low-temperature survival.

Halobacterium

Extreme halophile known for red pigmentation.

Sodium Hypochlorite

Chemical compound used as a disinfectant.

Heavy Metals

Toxic elements affecting protein function.

Cold Temp

1. causes the membrane to shatter

2. proteins inflexible leading to denaturation

3. slow metabolism to crawl

Phenolics

Chemical compounds disrupting cellular membranes.

Protein Denaturants

-alcohols (ethanol, isopropanol)

-halogens (iodine)

Poisons (inactivate proteins)

heavy metals (silver, mercury, arsenic)

membrane disruptors

phenolics (Lysol)

detergents (soap)

Antibiotics

Specifically, target structures or reactions required for bacterial but not human growth