Microorganisms

Abstract

An organism that is too small to be seen with the naked eye requiring the use of a light or electron microscope. They consist of single cells or cell clusters; also including the viruses that are microscopic but not cellular. Cellular microorganisms include the prokaryotes (Bacteria and Archaea) and some unicellular plant‐like and animal‐like eukaryotes and some fungi. Many can be cultivated in artificial medium using special techniques.

Keywords: prokaryote; mutualism; pathogenesis; stromatolite; ribosome

Figure 1.

The three‐domain tree of life based on small‐subunit rRNA sequences.

Figure 2.

Pairs of optical photomicrographs (transmitted light) showing living cyanobacteria (a,c,e,g) from mat‐building stromatolitic communities of Baja, Mexico, for comparison with their Precambrian morphological counterparts (b,d,f,h). (a) Lyngbya aestuarii Leibm. ex Gomont, Oscillatoriaceae, encompassed by a cylindrical mucilagenous sheath (at arrow). (b) Palaeolyngbya helva German, a similarly ensheathed (at arrows) oscillatoriacean, shown in an acid‐resistant residue of carbonaceous siltstone from the ∼950‐Ma‐old Lakhanda Formation of the Khabarovsk region of Siberia, Russia. (c) Spirulina subsalsa Oerst. ex Gomont, Oscillatoriaceae. (d) Heliconema turukhania German, a Spirulina‐like oscillatoriacean shown in an acid‐resistant residue of carbonaceous siltstone from the ∼850‐Ma‐old Miroedikha Formation of the Turukhansk region of Siberia, Russia. (e) Gloeocapsa cf. repestris Kütz., Chroococcaceae, a four‐celled colony having a thick distinct encompassing sheath (at arrow). (f) Gloeodiniopsis uralicus Krylov & Sergeev, a similarly sheath‐enclosed (at arrow) four‐celled colonial chroococcacean shown in a petrographic thin section of bedded chert from the ∼1500‐Ma‐old Satka Formation of southern Bashkiria, Russia. (g) Entophysalis cf. granulosa Kütz., Entophysalidaceae. (h) Entophysalis belcherensis Hofmann, an Entophysalis‐like colonial entophysalidacean from stromatolitic chert of the ∼2150‐Ma‐old Belcher Group of Northwest Territories, Canada.

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Further Reading

Douglas AE (1996) Microorganisms in symbiosis: adaptation and specialization. In: Roberts DMcL, Sharp P, Alderson G and Collins MA (eds) Evolution of Microbial Life. Proceedings of the 54th Symposium of the Society for General Microbiology, University of Warwick, pp. 225–242. Cambridge, UK: Cambridge University Press.

Hugenholtz P, Goebel BM and Pace NR (1998) Impact of culture‐independent studies on the emerging phylogenetic view of bacterial diversity. Journal of Bacteriology 180: 4765–4774.

Kuo A and Garrity GM (2001) Exploiting Microbial Diversity. In: Staley JT and Reysenbach A‐L (eds) Biodiversity of Microbial Life, Chap. 15. New York: John Wiley & Sons, Inc.

Madigan MT, Martinko JM and Parker J (2003) Brock Biology of Microorganisms, 10th edn. Upper Saddle River, NJ: Prentice‐Hall.

Pace NR (1996) New perspectives on the natural microbial world: molecular microbial ecology. ASM News 62: 463–470.

Perry JJ, Staley JT and Lory S (2002) Microbial Life. Sunderland, MA: Sinauer Associates, Inc.

Schlegel HG (1993) General Microbiology, 7th edn. Cambridge, UK: Cambridge University Press.

Schopf JW (1996) Are the oldest fossils cyanobacteria?. In: Roberts DMcL, Sharpe P, Alderson G and Collins MA (eds) Evolution of Microbial Life. Proceedings of the 54th Symposium of the Society for General Microbiology, University of Warwick, pp. 23–61. Cambridge, UK: Cambridge University Press.

Staley JT and Reysenbach A‐L (2002) Biodiversity of Microbial Life. New York, NY: Wiley‐Liss.

Williams DM and Embley TM (1996) Microbial diversity: domains and kingdoms. Annual Review of Ecology and Systematics 27: 569–595.

Young JM (2001) Implications of alternative classifications and horizontal gene transfer for bacterial taxonomy. International Journal of Systematic and Evolutionary Microbiology 51: 945–953.

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How to Cite close
Hayward, Chris A(Apr 2006) Microorganisms. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0004244]