Halomonas

All the organisms in the genus Halomonas are Gram-negative rods. They are extremophiles in that they are able to tolerate (and in some cases require) medium or high concentrations of salt for growth (at least 0.2M NaCl). Members of this genus vary from moderate halophiles such as Halomonas elongata to extreme halophiles such as Halobacterium salinarum. The word "halophile" means "salt-loving" in Greek. Halophiles are common in aquatic environments such as the Dead Sea, where halophillic bacteria tint the sediments bright colors. Many other salt lakes and inland seas, usually found in arid regions, have similarly high salt concentrations and are inhabited by halophiles. Halomonas species are also found in hypersaline Antarctic lakes beneath the ice-sheets - these are tough bugs! Halomonas sp, phase contrast microscopy, cells 1 µm wide, 5-20 µm long:

Among the adaptations that halophiles employ to survive in such environments are proteins designed to function in high ionic strength solution and maintaining high concentrations of inert substances ("compatible solutes") within their cytoplasm to reduce osmotic pressure.

Halomonas species are capable of anaerobic growth with glucose (in the absence of nitrate) and have membranes containing fatty acids ester-linked to glycerol.  This is in contrast to most other halophilic bacteria such as Halococcus and Halobacterium, where the fatty acids are ether-linked to glycerol.  Members of the Halomonas genus are either non-pigmented or yellow pigmented, and polarly or laterally flagellated and motile. Some are capable of carrying out denitrification, reducing nitrate to nitrogen and gaining energy in the process.

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