Big bacteria

Citation
Hn. Schulz et Bb. Jorgensen, Big bacteria, ANN R MICRO, 55, 2001, pp. 105-137
Citations number
102
Language
INGLESE
art.tipo
Review
Categorie Soggetti
Microbiology
Journal title
ANNUAL REVIEW OF MICROBIOLOGY
ISSN journal
0066-4227 → ACNP
Volume
55
Year of publication
2001
Pages
105 - 137
Database
ISI
SICI code
0066-4227(2001)55:<105:BB>2.0.ZU;2-5
Abstract
A small number of prokaryotic species have a unique physiology or ecology r elated to their development of unusually large size. The biomass of bacteri a varies over more than 10 orders of magnitude, from the 0.2 mum wide nanob acteria to the largest cells of the colorless sulfur bacteria, Thiomargarit a namibiensis, with a diameter of 750 mum. All bacteria, including those th at swim around in the environment, obtain their food molecules by molecular diffusion. Only the fastest and largest swimmers known, Thiovulum majus, a re able to significantly increase their food supply by motility and by acti vely creating an advective flow through the entire population. Diffusion li mitation generally restricts the maximal size of prokaryotic cells and prov ides a selective advantage for mum-sized cells at the normally low substrat e concentrations in the environment. The largest heterotrophic bacteria, th e 80 x 600 mum large Epulopiscium sp. from the gut of tropical fish, are pr esumably living in a very nutrient-rich medium. Many large bacteria contain numerous inclusions in the cells that reduce the volume of active cytoplas m. The most striking examples of competitive advantage from large cell size are found among the colorless sulfur bacteria that oxidize hydrogen sulfid e to sulfate with oxygen or nitrate. The several-cm-long filamentous specie s can penetrate up through the ca 500-mum-thick diffusive boundary layer an d may thereby reach into water containing their electron acceptor, oxygen o r nitrate. By their ability to store vast quantities of both nitrate and el emental sulfur in the cells, these bacteria have become independent of the coexistence of their substrates. In fact, a close relative, T. namibiensis, can probably respire in the sulfidic mud for several months before again f illing up their large vacuoles with nitrate.