Microbial Diversity and Pathogenicity: Bacteria, Archaea, and Viruses

Hadobacteria

Extremophiles; Deinococcus resists radiation, T. aquaticus used in PCR.

Hyperthermophilic

Live in very hot environments.

Firmicutes

Endospore-forming, low GC Gram+. Includes Mycoplasma.

Actinobacteria

Filamentous, make antibiotics (high GC Gram+).

Cyanobacteria

Photosynthetic; origin of chloroplasts.

Spirochetes

Corkscrew motion; Lyme & syphilis.

Chlamydia

Tiny obligate parasites, steal ATP.

Proteobacteria

Largest group, includes E. coli, Salmonella.

Crenarchaeotes

Thermo/acidophilic.

Euryarchaeotes

Methanogens; anaerobes in guts.

Biofilms

Communities of microorganisms; protect against stress.

Microbiome

All microbes in an organism; affects digestion, immunity.

Nitrogen cycle

Bacteria fix nitrogen → essential for plants.

Koch's Postulates

Steps linking microbes to disease.

Toxigenicity

Ability to produce toxins.

Endotoxins

Released when cell dies (Gram-).

Exotoxins

Secreted while alive (more toxic).

Virus

Infectious particle with DNA/RNA & protein coat; not living.

Retrovirus

RNA → DNA via reverse transcriptase (e.g., HIV).