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. Importance in Environmental Engineering
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 Shape DNA Reproduction
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 Archaea
Two types, Gram Positive, Gram Negative
Both have Peptidoglycan
Gram Negatives also have Lipopolysaccharide (LPS)
Archaea
similar to G+ve, have pseudopeptidoglycan

5. Cell Structure Flagellum Cytoplasm 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 Temperature pH
Barophiles, halophiles,
Temperature
Thermophiles C e.g. Thermus aquaticus
Mesophiles C e.g. Escherichia coli
Psychrophiles C e.g. Flavobacterium sp. pH
most environments are at pH
Neutrophiles pH6 - pH8 e.g. most
Acidophiles < pH2 e.g. Thiobacillus ferrooxidans
Alkaliphiles > pH10 e.g. Bacillus sp.

7. Growth Requirements - Organic substrates
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. Growth Requirements - Inorganic substrates
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. Substrate Concentration
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, THM’s, etc.
Cell physically robust.