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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
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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
Introduction • What are they? • Prokaryotic organisms • Bacteria (eubacteria), Archaea (archaebacteria) • Importance in Environmental Engineering • Biodegradation • Nutrient Cycling • Pathogens in Contaminated Waters
Cell Structure • Size • smallest living organisms, 1m. • 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.
Cell Structure • Cell Wall • Two types, Gram Positive, Gram Negative • Both have Peptidoglycan • Gram Negatives also have Lipopolysaccharide (LPS) • Archaea • similar to G+ve, have pseudopeptidoglycan
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)
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 < pH2 e.g. Thiobacillus ferrooxidans • Alkaliphiles > pH10 e.g. Bacillus sp.
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.
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.)
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.
