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.

SK

S

S max