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

2. Microbes can live in diverse environments

3. 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

4. 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)

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

6. 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)

7. 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.

8. All species have growth optima and limits

9. How we figure out growth optima

10. 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

11. We have names for different optima

12. 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

13. 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

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

15. General mechanisms for acclimating to stress
Gene expression

16. Example transporters: used for acclimation to pH

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

18. Vex I. Adaptations to high temperatures (thermophiles)

19. Vex III. High pressure
1000 atm!

20. Pressure and temperature stress are related

21.  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

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

23. Vex IV. Osmolarity

24. Vex III. Adaptation to high Na+: halophiles

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