Microbiology for Environmental Microbiology for Environmental

Health OfficersHealth Officers

EHL0033 Prokaryotes (1)

Key WordsKey WordsProkaryotic Outer membrane Eubacteria (Bacteria) Periplasmic spaceArchaebacteria (Archaea) Oxidative phosphorylationEukaryotic Spheroplast/protoplast Plasmid Flagella Chromosome ChemotaxisRibosome Axial filament Peptidoglycan (murein, mucopeptide) Periplasmic binding protein Gram stain PermeasesGram negative Storage Granules Gram positive Pili (fimbriae) Cell envelope Capsule (slime layer, glycocalyx)Cell membrane Endospore (spore) Cell wall

Metabolic Relationships to Oxygen

• Prokaryotic metabolism also varies with respect to oxygen

• Obligate aerobes• Facultative anaerobes• Obligate Anaerobes

Nitrogen Metabolism

• Production of amino acids and nucleic acids

• Cyanobacteria• nitrogen fixation

• Self –sufficient, almost!

Anabaena

A biofilm. The yellow mass in this colorized SEM is dental plaque, a biofilm that forms on tooth surfaces.

Archea --- “extremophiles”

• Thermophiles• Halophiles• methanogens

Prokaryotes play crucial roles in the biosphere

If humans were to disappear from the planet tomorrow, life on Earth would go on for most other species. But prokaryotes are so important to the biosphere that if they were to disappear, the prospects for any other life surviving would be dim.

Mutualism: bacterial “headlights.” The glowing oval below the eye of the flashlight fish (Photoblepharon palpebratus) is an organ harboring bioluminescent bacteria. The fish uses the light to attract prey and to signal potential mates. The bacteria receive nutrients from the fish.

Prokaryotes’ impacts on humans

• Harmful– Illness

• Beneficial– Essential tools in agriculture and industry

Pathogenic Prokaryotes

Exo and Endotoxins

• Poisons

• Exotoxins are proteins secreted by prokaryotes

• Endotoxins are lipopolysaccharidecomponents of the outer membrane of gram–negative bacteria

Bioremediation