Microorganisms: Bacteria, Archaea, Fungi, Protists, Viruses

Rhizobium

Involved in nitrogen fixation in symbiosis with plants.

Azotobacter

A free-living nitrogen-fixing bacterium in soil.

Escherichia coli (E. coli)

Used in nitrate reduction and glycolysis pathways; also a facultative anaerobe.

Paracoccus denitrificans

Involved in denitrification (reduces nitrate to nitrogen gas).

Shewanella

Transfers electrons extracellularly to metals.

Acidithiobacillus ferrooxidans

Iron-oxidizing bacterium, oxidizes iron using oxygen as an electron acceptor.

Nitrosomonas

Converts ammonia to nitrite in nitrification.

Nitrobacter

Converts nitrite to nitrate in nitrification.

Bacillus

Naturally competent bacterium for horizontal gene transfer.

Streptococcus

Naturally competent bacterium for transformation.

Neisseria

A gram-negative bacterium known for natural competence in gene transfer.

Haemophilus

Another naturally competent gram-negative bacterium.

Actinomyces odontolyticus

Supports ultrasmall bacteria in human mouth.

Candidatus Saccharibacteria

An obligate parasite of Actinomyces odontolyticus.

Agrobacterium tumefaciens

Causes crown gall disease in plants; has a tumor-inducing plasmid (Ti).

Methanogens

Generate methane gas and live in extreme environments.

Candida auris

A multidrug-resistant yeast.

Various Mycorrhizal fungi

Symbiotic fungi that assist plant roots in nutrient absorption.

Rusts, Powdery Mildews, and Smuts

Pathogenic fungi that cause plant diseases.

Diatoms

Photosynthetic protists with silica-based cell walls.

Dinoflagellates

Photosynthetic protists involved in algal blooms.

Green algae

Photosynthetic protists involved in primary plastid evolution.

Red algae

Another group involved in plastid evolution.

Hydrogenosome-bearing protists

Have specialized organelles for anaerobic energy metabolism.

Bacteriophages

Viruses that infect bacteria.

SARS-CoV-2

The virus responsible for COVID-19.

Influenza virus

Demonstrated in viral budding and replication processes.

Phages in Phage Therapy

Used to treat bacterial infections resistant to antibiotics.