1. Bacterial response to environment
Rapid response crucial for survival
Simultaneous transcription and translation
Coordinate regulation in operons and regulons
Global genetic control through modulons
Bacteria respond
Change from aerobic to anaerobic
Presence/absence of glucose
Amount of nutrients in general
Presence of specific nutrients
Population size

2. Quorum Sensing Bacteria monitor their own population size
Pathogenesis: do not produce important molecules too soon to tip off the immune system.
Light production: a few bacteria make feeble glow, but ATP cost per cell remains high.
Bacteria form spores when in high numbers, avoid competition between each other.
System requirements
A signaling molecule that increases in concentration as the population increases; LMW
A receptor; activation of a set of genes

3. Chemotaxis and other taxes
Movement in response to environmental stimulus
Positive chemotaxis, attraction towards nutrients
Negative: away from harmful chemicals
Aerotaxis: motility in response to oxygen
Phototaxis: motility to certain wavelengths of light
Magnetotaxis: response to magnetic fields
Taxis is movement
Includes swimming through liquid using flagella
Swarming over surfaces with flagella
Gliding motility, requiring a surface to move over

4. Flagellar structures www.scu.edu/SCU/Departments/ BIOL/Flagella.jpg
img.sparknotes.com/.../monera/ gifs/flagella.gif

5. Runs and Tumbles: bacteria find their way

6. Motility summarized
Flagella: protein appendages for swimming through liquid or across wet surfaces.
Axial filament: a bundle of internal flagella
Between cell membrane and outer membrane in spirochetes
Filament rotates, bacterium corkscrews through medium
Gliding
No visible structures, requires solid surface
Slime usually involved.

7. Axial filaments

8. Gliding Motility Movement on a solid surface.
Cells produce, move in slime trails.
Cells glide in groups, singly, and
can reverse directions.
Unrelated organism glide:
myxobacteria, flavobacteria,
cyanobacteria;
Recent data support polysaccharide synthesis, extrusion model.

9. Starvation Responses Bacteria frequently on verge of starvation
Rapid utilization of nutrients by community keeps nutrient supply low
Normal life typical of stationary phase
Bacteria monitor nutritional status and adjust through global genetic mechanisms
Types of responses
Lower metabolic rates, smaller size (incr surface:volume)
Release of extracellular enzymes, scavenging molecules
Production of resting cells, spores
Induction of low Km uptake systems

10. Type of molecule affects transport
Small molecules can pass through a lipid bilayer
Water; otherwise, no osmosis
Gases such as O2 and CO2
Lipid molecules can
Dissolve in lipid bilayer, pass through membrane
Many antibiotics, drugs are lipid soluble
Larger, hydrophilic molecules cannot
Ions, sugars, amino acids cannot pass through lipids
Transport proteins required

11. Extracellular molecules
Enzymes
Polymers cannot enter cells
Proteins, starch, cellulose all valuable nutrients
Enzymes produced and released from the cell
LMW products taken up; nutrients gathered exceed energy costs.
Low molecular weight aids
Siderophores, hemolysins collect iron
Antibiotics may slow the growth of competition when nutrients are in short supply

12. Sporulation Resting cells
Cells respond to low nutrients by sporulation or slowing down metabolic rate, decr size.
Some cells change shape, develop thick coat
Endospores form within cells; very resistant.
Spores in bacteria generally are for survival
Not reproduction
A spore structure protects cells against drying, heat, etc. until better nutrient conditions return
An inactive cell can’t protect itself well

13. Endospore formation
Genetic cascade producing alternative sigma factors.

14. Responses of microbes to other environmental stresses
Compatible solutes: small neutral molecules accumulated in cytoplasm when external environment is hypertonic.
Heat shock proteins and other stress proteins
Bacteria express additional genes that code for protective proteins.