Microbial Weeds in Hypersaline Habitats: The Enigma of the Weed-Like Haloferax Mediterranei

FEMS Microbiol Lett. 2014 Oct;359(2):134-42. doi: 10.1111/1574-6968.12571. Epub 2014 Aug 28.


Heterotrophic prokaryotic communities that inhabit saltern crystallizer ponds are typically dominated by two species, the archaeon Haloquadratum walsbyi and the bacterium Salinibacter ruber, regardless of location. These organisms behave as 'microbial weeds' as defined by Cray et al. (Microb Biotechnol 6: 453-492, 2013) that possess the biological traits required to dominate the microbiology of these open habitats. Here, we discuss the enigma of the less abundant Haloferax mediterranei, an archaeon that grows faster than any other, comparable extreme halophile. It has a wide window for salt tolerance, can grow on simple as well as on complex substrates and degrade polymeric substances, has different modes of anaerobic growth, can accumulate storage polymers, produces gas vesicles, and excretes halocins capable of killing other Archaea. Therefore, Hfx. mediterranei is apparently more qualified as a 'microbial weed' than Haloquadratum and Salinibacter. However, the former differs because it produces carotenoid pigments only in the lower salinity range and lacks energy-generating retinal-based, light-driven ion pumps such as bacteriorhodopsin and halorhodopsin. We discuss these observations in relation to microbial weed biology in, and the open-habitat ecology of, hypersaline systems.

Keywords: Archaea; Haloferax; Haloquadratum; Salinibacter; halophilic.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anaerobiosis
  • Ecosystem*
  • Halobacteriales / growth & development
  • Halobacteriales / physiology
  • Haloferax mediterranei / growth & development
  • Haloferax mediterranei / physiology*
  • Salinity*
  • Salt Tolerance
  • Water Microbiology*