Microorganisms

Chris A Hayward, University of Queensland, Brisbane, Australia

Published online: April 2006

DOI: 10.1038/npg.els.0004244

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
    book 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.
    book 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.
    book 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.
    book Perry JJ, Staley JT and Lory S (2002) Microbial Life. Sunderland, MA: Sinauer Associates, Inc.
    book Schlegel HG (1993) General Microbiology, 7th edn. Cambridge, UK: Cambridge University Press.
    book 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.
    book 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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Article Title: Microorganisms
 
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]