Bacterial Diversity

1
Bacterial Diversity

• Objective
• To be able to describe the main features of
  bacterial cells and to understand the different
  nutritional and metabolic types.
• References
• Gray N.F. Biology of Wastewater Treatment
• Madigan M.T., Martinko J.M., Parker J.
• Brock - Biology of Microorganisms
• Stanier R.Y. General Microbiology
• Lecture Outline
• Bacterial Cell Structure
• Characteristics of Bacteria

2
Introduction

• What are they?
• Prokaryotic organisms
• Bacteria (eubacteria), Archaea (archaebacteria)
• Importance in Environmental Engineering
• Biodegradation
• Nutrient Cycling
• Pathogens in Contaminated Waters

3
Cell Structure

• Size
• smallest living organisms, 1?m.
• Shape
• typically cocci or rods (bacilli), spiral,
  stalked, filamentous.
• multicellular swarms (gliding myxobacteria,
  myxococcus)
• DNA
• single strand, supercoiled, no nuclear membrane.
• Extranuclear DNA or Plasmids.
• Reproduction
• Asexual Binary fission, Conjugation via Pili.

4
Cell Structure

• Cell Wall
• Two types, Gram Positive, Gram Negative
• Both have Peptidoglycan
• Gram Negatives also have Lipopolysaccharide (LPS)
• Archaea
• similar to Gve, have pseudopeptidoglycan

5
Cell Structure

• Flagellum
• May be present - Motile
• Polar or peritricious
• Driven by Proton motive Force (PMF)
• Chemotaxis - tumble frequency increases.
• Cytoplasm
• complex subcellular organelles usually absent.
• vesicular and lamellar structures (mesosomes)
  form by invagination of cytoplasmic membrane
  (e.g. N-fixing, Nitrifying, and Phototrophic
  bacteria).
• cytoplasmic membrane essential (maintains PMF).
• Ribosomes - Protein synthesis
• Enzymes - metabolism
• Granules (Inclusions)
• Gas Vesicles (buoyancy, e.g. cyanobacteria)

6
Characteristics

• Extreme environments
• Barophiles, halophiles,
• Temperature
• Thermophiles 55 - 65C e.g. Thermus aquaticus
• Mesophiles 30 - 40C e.g. Escherichia coli
• Psychrophiles 5 - 15C e.g. Flavobacterium sp.
• pH
• most environments are at pH 5 - 9.
• Neutrophiles pH6 - pH8 e.g. most
• Acidophiles lt pH2 e.g. Thiobacillus ferrooxidans
• Alkaliphiles gt pH10 e.g. Bacillus sp.

7
Characteristics

• Oxygen Requirements
• Aerobic
• Microaerophilic
• Facultative (aerobe)
• Anaerobic (strict)
• Growth Requirements - Organic substrates
• Heterotrophic (Chemoorganotrophs)
• Pseudomonas, Bacillus, Zoogloea, etc.
• Key role in Nutrient Cycling
• Biodegradation of Organic Detritus
• Soluble low molecular weight substrates e.g.
  acetate, methanol, sugars.
• Polymers degraded by extracellular hydrolytic
  Enzymes.

8
Metabolism

• Growth Requirements - Inorganic substrates
• Autotrophic (Chemolithotrophic, Phototrophic)
• Nitrosomonas, Nitrobacter, Methanococcus,
  Chlorobium, etc.
• Reduced forms of sulphur H2S, S0, S2O32-, SO3-
• Reduced forms of nitrogen NH3
• Hydrogen H2
• Iron Fe2
• Growth Requirements - Light
• Photosynthetic (phototrophic)
• light and CO2
• oxygenic blue-green (cyanobacteria)
• anoxygenic green-sulphur (Chlorobium sp.)

9
Metabolism

• Substrate Concentration
• Bacteria have high affinity, low Ks for
  substrates.
• 
  ? growth rate
• 
  
  KS substrate affinity
• 
  
  S substrate concentration
• better competitors in low substrate environments
  such as in water treatment.
• Capability
• Can metabolise toxic chemicals Cyanide, THMs,
  etc.
• Cell physically robust.