microbial diversity- bacteria

bacterial taxonomy

phenotypic:

  • Cell morphology

  • Metabolic activity

  • Staining

  • Pathogenicity

  • Nutritional needs

molecular taxonomy

genotypic:

  • DNA based – G-C content

  • 16S rRNA sequencing for prokaryotes (bacteria and archaea)

  • 18S rRNA sequencing for eukaryotes

  • Metagenomics of whole sample (microbiome)

  • No reliance on culture

functional diversity: presence or absence of genes involved in specific functional mechanisms

physiological → metabolism and biochemistry

morphological → appearance

ecological → organisms relationship with its environment and other organisms occupying the same niche

microbial habitats

microbes are everywhere and many have adapted to a specific environment and now require those conditions to survive

temp: -5 to 120 degrees C

  • thermophiles

  • psychrophiles

salinity:

  • halophiles

pH:

  • acidophiles

  • alkaliphiles

pressure:

  • barophiles

populations can also vary with diff niches of the same environment:

soil types- pH, water and organic content

fresh water- zones, flow rates, oxygen levels, pH

marine environment- pressure, light levels, oxygen levels

DIVERSITY OF BACTERIA

bacterial phyla

-largest taxon of prokaryote domain

55 bacterial phyla with cultured representatives listed in LPSN

  • many more have Candidatus status

More identified based on 16S rRNA sequencing

  • From heterogenous samples

Increasing

Almost all (90%) of those characterised are from only 4 phyla

  • Proteobacteria, Acinetobacteria, Firmicutes and

Bacteroides