Taxonomy of Microorganisms

Taxonomy of Microorganisms The taxonomic classification scheme for bacteria is found in Bergey’s Manual of systematic Bacteriology. In Bergey’s Manual, bacteria are divided into four divisions(according to the characteristics of the cell wall), three divisions consists of eubacterial cells and the fourth division consists of the archea.Each division is subdivided into sections according to such characteristics as Gram stain reaction, cell shape, cell arrangements, oxygen requirements, motility and nutritional and metabolic properties. Each section contains several genera as follows:
Name of the section:	Inportant genera	Habitat	Gram Reaction	Special features:
Spirochetes	Triponema, Borrelia Leptospira	Aquatic; animal parasites	-	Helical morphology, motility by axial filaments
Aerobic/microaerophilic motile, helical/vibrioid-Gram negative bacteria.	Spirillum Azospirillum Campylobacter Bdwellovibrio	Soil and aquatic environments, human intestinal tract and oral cavity.	-	Helical morphology, motility by flagella, no axial filaments; vibrioids do not have a complete turn. Includes nitrogen fixing bacteria and some pathogens.
Nonmotile or rarely motile) Gram negative curved bacteria.	Spirosoma Meniscus	Aquatic and sedimentary environments	-	Un common; mostly aquatic non pathogenic.
Gram negative aerobic rods and cocci	Pseudomonas Burkholderia Legionella, Neisseria, Brucella, Bordetella, Francisella, Rhizobium, Agrobacterium.	Soil, Water; animal parasites	-	Organisms of medical, industrial and environmental importance.
Facultative anaerobic Gram negative rods	Escherichia, Salmonella, Klebsiella, Yersinia, Vibrio, Enterobacter, Hemophilus, Pasteurella.	Soil, Plants, Water;animal respiratory and intestinal tracts.	-	Many important pathogens.
Anaerobic Gram negative straight, curved or helical rods.	Bacteroides, Fusobacterium	Animals and insects.	-	Obligate anaerobes, mostly onf the intestinal tract.
Dissimilatory sulfate reducing or sulfur reducing bacteria.	Desulfovibrio	Anaerobic sediments.	-	Reduce oxidized forms of sulfur to H2S.
Anaerobic Gram negative cocci	Veillonella	Mostly animal intestinal tracts	-	Nonmotile anaerobes.
Rickettsias and Chlamydias	Rickettsia, Coxiella, Ehrilichia, Chlamydia	Parasites of arthropods and animals	-	Obligate intracellular pathogens.
Mycoplasmas	Mycoplasma	Parasites of animals, plants and insects.	-	Pleomoprphic; lack cell walls, Some are pathogenic.
Gram Positive cocci	Staphylococcus Streptococcus, Lactococcus, Enterococcus,	Soils, skin and mucos membrane of animals	+	Some important pathogens and industrial organisms.
Endospore forming rods and cocci	Bacillus Clostridium	Soil, animal intestinal tract	+	Anaerobic/aerobic facultative anaerobes
Regular nonsporing, Gram positive rods	Lactobacillus Listeria	Dairy products, genital and orakl cavities, animal feces.	+	Some important pathogens (Listeria) and industrial organisms
Irregular nonsporing Gram positive rods	Corneybacterim Propionibacterium	Human pathogens; soil organisms.	+	Pleomorphic morphology
Mycobacteria	Mycobacterium	Soil; plants and animals	+	Acid fast, pathogenic bacteria.
Nocardioforms	Nocardia	Soil and animals	+	Form branched filaments, reproduce by fragmentation, acid fast.
Budding and/or appendaged bacteria.	Hyphomicrobium Caulobacter	Mostly aquatic	-	Posses prosthecae, some are stalked and reproduce by budding.
Sheathed bacteria	Sphaerotilus	Mostly aquatic	-	Cells encased in a hollow sheath.
Nonphotosynthetic, non-fruiting, gliding bacteria.	Cytophaga Beggiatoa	Aquatic	-	Cytophaga degrade cellulose. Beggiatoa oxidizes H2S
Gliding fruiting bacteria	Myxococcus	Dung, soil	-	Cell aggregate to form a fruiting body.
Aerobic chemoautotrophic bacteria.	Nitrosomonas, Nitrobacter, Thiobacillus.	Soil	-	Nitrifying and sulfur oxidizing bacteria.
Archaea	Methanobacterium Halobacterium Sulfolobus	Extreme environments.	+/-	Not related to other bacterial groups; no peptidoglycan in cell walls.
Anoxygenic Photosynthetic bacteria.	Chromatium Rhodospirillum Chlorobium.	Anaerobic sediments	+	Includes green and purple sulfur and non sulfur bacteria.
Oxygenic Photosynthetic bacteria (Cyanobacteria)	Chroococcus Anabaena	Aquatic	-	Produce oxygen during photosynthesis, fixes atmospheric nitrogen.
Actinomyces	Streptomyces, Frankia, Micromonospora	Soil; water.	+	Branching filaments with reproducing conidiospores.
Based on : Bergey?s Manual of Systematic Bacteriology, vol. 2., Holt et al., 1986: Williams and Wilkins, Baltimore, USA.
Taxonomy of Viruses The International Committee for taxonomy of Viruses (ICTV) has been grouping viruses into families based on: (1) Nucleic acid type (ex: single/double stranded DNA/RNA viruses), (2) Strategy of replication (ex: retovirus), (3) Morphology (ex: helical viruses), (4) Disease caused (ex: Influenza virus), (5) Host range (ex Tobacco Mosaic Virus) etc. The suffix-virus in used as genus name and family names ends in viridae (ex: Retroviridae). In general, the ICTV has not yet established higher taxa. A viral species is a group of viruses sharing same genetic information and ecological niche. Special epithets are designated by descriptive common names such as human immunodeficiency virus (HIV) with sub species (if any) designated by a number (HIV1).