Streptococcus pyogenes, copyright NIAID.

Belongs within: Lactobacillales.

Streptococcus is a genus of aerobic or facultatively anaerobic Gram-positive bacteria that form pairs or chains of cocci, with the cells sometimes being elongated in the direction of the chain (Gray 1990).

Published 23 December 2008

Streptococcus is one of the most familiar bacterial genera. There was a time when the name was used to refer to almost any spherical, Gram-positive bacterium that grew in a chain-shaped colony, but the old Streptococcus calved off a few genera in the mid-1980s, most notably Enterococcus and Lactococcus. One of the most significant features distinguishing Streptococcus from the latter two genera is that Streptococcus secretes a protective capsule of slimy polysaccharides. In pathogenic species, this capsule apparently mimics the host’s connective tissue, allowing the bacterium to pass unnoticed by the host’s immune system.

The best-known members of the genus include Streptococcus pneumoniae and S. pyogenes. Streptococcus pneumoniae causes (unsurprisingly) pneumonia. Streptococcus pyogenes causes… well, almost anything that you’d care to mention, really. It’s most commonly associated with “strep throat”, but it can also cause such dreadful conditions as scarlet fever, toxic shock syndrome and ye olde puerperal fever that caused the death of so many new mothers before Oliver Wendell Holmes suggested in 1843 that getting doctors to wash their hands before delivering a baby was perhaps not such a bad idea. The most infamous (though thankfully, one of the rarest) condition caused by S. pyogenes is necrotising fasciitis—the dreaded flesh-eating bacterium. Yes, it does exist. No, it is not just something invented by B-grade horror movies.

Not all members of Streptococcus are pathogens. Streptococcus thermophilus, for instance, is used in the production of yoghurt. Unfortunately, though all too typically for bacteria, the non-pathogenic taxa have generally been ignored in favour of their more attention-seeking cousins.

Systematics of Streptococcus
| i. s.: S. apisBB99
| S. cremorisGHP92
| S. faecalisG90
| S. milleriPHK96
|--S. pleomorphusTTH03
`--+--+--S. gallolyticusTTH03
| | |--S. g. ssp. gallolyticusJC08
| | `--S. g. ssp. pasteurianus (Poyart et al.) Schlegel et al. 2003 [=S. pasteurianus Poyart et al. 2002]JC08
| |--+--S. macedonicus Tsakalidou et al. 1998TTH03, MF02
| | `--S. waius Flint et al. 1999TTH03, MF02
| `--+--+--S. bovisTTH03
| | `--S. equinusTTH03
| `--S. infantariusTTH03
| |--S. i. ssp. infantariusTTH03
| `--S. i. ssp. coli [incl. S. lutetiensis Poyart, Quesne & Trieu-Cuot 2002]TTH03
`--+--S. alactolyticusTTH03
`--+--S. orisrattiTTH03
|--+--+--+--S. cricetiTTH03
| | | `--S. thoraltensisBD03
| | `--+--S. downeiTTH03
| | `--S. sobrinusTTH03
| `--+--+--S. mutansTTH03
| | `--S. rattiTTH03
| `--+--S. ferusTTH03
| `--+--S. macacae Beighton, Hayday et al. 1984BD03
| `--S. ovisBD03
`--+--+--+--S. salivariusTTH03
| | `--+--S. thermophilusBD03
| | `--S. vestibularisBD03
| `--+--+--S. acidominimusTTH03
| | `--S. suisTTH03
| `--+--S. parasanguinisTTH03
| `--+--+--S. gordonii Kilian, Mikkelsen & Henrichsen 1989TTH03
| | `--+--S. intermediusTTH03
| | `--+--S. anginosusTTH03
| | `--S. constellatusTTH03
| `--+--S. cristatusTTH03
| `--+--S. sanguinisTTH03
| `--+--+--S. infantisTTH03
| | `--S. perorisTTH03
| `--+--S. oralisTTH03
| `--+--S. mitisTTH03
| `--S. pneumoniaeTTH03 [=Diplococcus pneumoniaePHK96]
`--+--+--S. hyovaginalisTTH03
| `--S. pluranimaliumTTH03
`--+--S. hyointestinalisTTH03
`--+--S. urinalisTTH03
`--+--S. uberisTTH03
|--+--S. equiTTH03
| | |--S. e. ssp. equiTTH03
| | `--S. e. ssp. zooepidemicusTTH03
| `--+--S. canisTTH03
| `--S. pyogenesTTH03
`--+--+--S. iniaeTTH03
| `--S. parauberisTTH03
`--+--S. porcinusTTH03
`--+--S. agalactiaeTTH03
|--S. dysgalactiaeTTH03
| |--S. d. ssp. dysgalactiaeKM03
| `--S. d. ssp. equisimilis Vandamne, Pot et al. 1996KM03
`--S. phocae Skaar, Gaustad et al. 1994TTH03

*Type species of generic name indicated


[BD03] Baele, M., L. A. Devriese, M. Vancanneyt, M., Vaneechoutte, C. Snauwaert, J. Swings & F. Haesebrouck. 2003. Emended description of Streptococcus ferus isolated from pigs and rats. International Journal of Systematic and Evolutionary Microbiology 53: 143–146.

[BB99] Ball, B. V., & W. A. Bruce. 1999. Varroa jacobsoni as a vetor of honey bee pathogens. In: Needham, G. R., R. Mitchell, D. J. Horn & W. C. Welbourn (eds) Acarology IX vol. 2. Symposia pp. 297–301. Ohio Biological Survey: Columbus (Ohio).

[GHP92] Gottschal, J. C., W. Harder & R. A. Prins. 1992. Principles of enrichment, isolation, cultivation, and preservation of bacteria. In: Balows, A., H. G. Trüper, M. Dworkin, W. Harder & K.-H. Schleifer (eds) The Prokaryotes: A handbook on the biology of bacteria: Ecophysiology, isolation, identification, applications 2nd ed. vol. 1 pp. 149–196. Springer-Verlag: New York.

[G90] Gray, T. R. G. 1990. Soil bacteria. In: Dindal, D. L. (ed.) Soil Biology Guide pp. 15–31. John Wiley & Sones: New York.

[JC08] Judicial Commission of the International Committee on Systematics of Prokaryotes. 2008. Status of strains that contravene Rules 27 (3) and 30 of the International Code of Nomenclature of Bacteria. Opinion 81. International Journal of Systematic and Evolutionary Microbiology 58: 1755–1763.

[KM03] Kawata, K., T. Minakami, Y. Mori, M. Katsumi, Y. Kataoka, A. Ezawa, N. Kikuchi & T. Takahashi. 2003. rDNA sequence analyses of Streptococcus dysgalactiae subsp. equisimilis isolates from pigs. International Journal of Systematic and Evolutionary Microbiology 53: 1941–1946.

[MF02] Manachini, P. L., S. H. Flint, L. J. H. Ward, W. Kelly, M. G. Fortina, C. Parini & D. Mora. 2002. Comparison between Streptococcus macedonicus and Streptococcus waius strains and reclassification of Streptococcus waius (Flint et al. 1999) as Streptococcus macedonicus (Tsakalidou et al. 1998). International Journal of Systematic and Evolutionary Microbiology 52: 945–951.

[PHK96] Prescott, L. M., J. P. Harley & D. A. Klein. 1996. Microbiology 3rd ed. Wm. C. Brown Publishers: Dubuque (Iowa).

[TTH03] Täpp, J., M. Thollesson & B. Herrmann. 2003. Phylogenetic relationships and genotyping of the genus Streptococcus by sequence determination of the RNase P RNA gene, rnpB. International Journal of Systematic and Evolutionary Microbiology 53: 1861–1871.


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