Microbial Growth and Biochemistry of the Genome

Biofilm

• complex multicellular community of microorganisms embedded i self produced extracellular matrix attached to biotic or abiotic surfaces

Plaktonic Lifestyle

• free floating microbial cells that live in an aquatic environment

Sessile Lifestyle

• planktonic cells can attach to a surface

EPS - exopolysaccharide 

• hydrated gel composed primarily of polysaccharides and containing other macromolecules such as proteins, nucleic acids, and lipids 

Why are cells in the biofilm less susceptible to antibiotics? 

• cells in deep layers are metabolically inactive and may be less susceptible to the action of antibiotics 

• increased production of membrane-embedded proteins that effectively extrude antibiotics out of bacterial cells

• EPS slows the diffusion of antibiotics and antiseptics preventing them from reaching cell

Biofilm Formation Steps

1. reversible attachment of plankton 

2. First colonizer become irreversibly attached 

3. growth and cell division 

4. production of EPS and formation of water channels 

5. attachment of secondary colonizers and dispersion of microbes to new sites

What environmental factors effect microbial growth

• oxygen 

• pH

• temperature

• pressure 

• radiation 

Obligate anerobes

• killed in the presence of O2

Facultative Anaerobes

• thrive in the presence of O2

• can grow in its absence via fermentation and anaerobic respiration

Aerotolerant anaerobes

• indifferent to the presence of oxygen

• usually perform fermentation

• NOT harmed by presence of oxygen

Microaerophiles

• require minimum level of oxygen to grow

• 1-10%

Thioglycolate

• strong reducing properties and autoclaving flushes out most of the oxygen 

Aerobe

• growns in the presence of atmospheric oxygen 

Obligate aerobe

• requires O2

O2

• easily reduced to toxic reactive oxygen species 

  • superoxide radical 

  • hydrogen peroxide

  • hydroxyl radical 

What protective enzymes do aerobes produce?

• superoxide dismutase (SOD)

• catalase

• peroxidase 

Which cells would have more access to oxygen and nutrients in the biofilm?

• cells located at the surface 

Catalyst Test

• detects presence of the enzyme catalase by noting whether bubblers are released when hydrogen peroxide is added to a sample culture

Microbe pH

• microbes maintain an internal pH neutrality regardless of the environmental pH

Acidic Tolerance Response

• proteins show increased negative surface charge that stabilizes them in low pH

• pumps eject H+ ions out of cells

• changes in comp. of membrane reflect the need to maintain membrane fluidity at low pH

What are the different stabilize protein structure

• H bond

• proline

• interaction with chaperones 

Stablize membrane

• increase saturated lipids

• more branched lipids 

Stabilize DNA

• histone-like-proteins 

Psychrophiles

• bacteria that grow at very low temperatures

Mesophiles

• bacteria that grow at moderate temperatures

• most human bacteria

Theromophiles

• bacteria that grow at higher temperatures 

• 40-80 degrees 

Hyperthermophiles

• bacteria grow at extremely high temperatures 

2O2 +2H —> O2 +H2O2 needs what enxyme?

• superoxide dismutase 

2H2O2 —→ 2H2O + O2 needs what enzyme?

• catalase

H2O2 + NADH + H —> 2H2O + NAD needs what enzyme 

• peroxidase