Microorganisms and the limits of life ….Vexing situations for microbes and how they deal with it. Pyrodictium abyssii 100-110oC Hydrothermal vents

Microbes can live in diverse environments

Practical applications: Listeria monocytogenes Gram-positive Habitat: Soil, water, humans, animals When ingested: Meningitis, bacteremia (microbes in your blood), food poisioning, miscarraige 25% mortality rate if you get the disease Virulence is low Lots of cells to cause infection Immunocompromised individuals

How Listeria invades the body Often in or on food, unless pasteurized or sterilized Pathogenesis genes: Lysteriocin O (breaks apart phagosomes), Act A (controls host tubulin)

Stress resistance makes L. monocytogenes hard to control Psychrotolerant Acid tolerant Salt tolerant Facultative aerobe

You will need to read the assigned listeria paper To learn about physiological response to environment: To learn how microbiologists study this with genomics (Thursday’s lecture)

Learning outcomes Be able to define the known limits of life and explain how several parameters (temperature, pH, etc) impact microbes Be able to explain how microbes alter their phospholipids, proteins, nucleic acids, and transporters in order to become physiologically acclimated to these changes Be able to describe some of the adaptations allowing extremophiles to thrive in harsh environments Be able to explain how microbiologists study acclimation and adaptation to environmental stresses.

All species have growth optima and limits

How we figure out growth optima

Normal growth conditions and abnormal terminology Sea-level temperature 20–40oC neutral pH 0.9% salt ample nutrients phile vs tolerant (optimal versus permissive) E.g. thermophile versus thermotolerant Mesophile

We have names for different optima

Species can acclimate and adapt to abnormal conditions Acclimation – (also called adaptation) Physiological change in response to environmental change Adaptation – (verb) Evolution that is primarily driven by natural selection Adaptation – (noun) Trait that evolved because of natural selection Phenotypic plasticity – having an adaptation that enables acclimation

Adaptation versus acclimation Adaptation (noun) High temperature – turn on sigma 32 Sigma 32 – allows you to turn on the right genes when you need them. Start consuming PHB reserves in absence of food The genes required to make PHB Cold - Put more unsaturated fatty acids in membrane The genes required to make alternative fatty acids and regulators to do it at the right time

Effect of stressors on cellular components Protein Lipids Nucleic acids Too hot Too cold High pH Low pH High salinity Low salinity

General mechanisms for acclimating to stress Gene expression

Example transporters: used for acclimation to pH

Vex I. Acclimation to high temperatures Heat-shock response Protein issues: Chaperones Membrane issues: phospholipids DNA/RNA issues: DNA binding proteins

Vex I. Adaptations to high temperatures (thermophiles)

Vex III. High pressure 1000 atm!

Pressure and temperature stress are related

 Compare and contrast the adaptations of psychrophiles and hyperthermophiles and barophiles.  To what extent might adaptation to one extreme condition automatically increase the performance of an extremophile in a new condition? Describe adaptations to cold Describe adaptations to pressure Compare and contrast

Vex II. Adaptation to low temperature (psychrophiles) More flexible proteins (move faster) more unsaturated FA antifreeze proteins Ice nucleation

Vex IV. Osmolarity

Vex III. Adaptation to high Na+: halophiles

Describe an adaptation that allows microbes to resist several different environmental assaults.