Physiology of Halophilic archaea isolated from ancient salt deposits

Halophilic archaea (halobacteria) have been isolated from two ancient salt deposits in Britain: namely Winsford Salt Mine in Cheshire and Boulby Potash Mine in Cleveland. These deposits are both over 200 million years old.;Most strains of halobacteria, both from salt-mine and surface environments, could utilise trehalose and glycerol, many can utilise amino acids, but none could utilise glycine betaine. During aerobic growth on glucose, glycerol and trehalose, all halobacteria produce acetic acid together with smaller amounts of other acids such as propionic, butyric, iso-butyric, iso-valeric and pyruvic acids. Acid was not produced during growth on proline. Most strains of halobacteria can grow anaerobically utilising TMAO or DMSO. Some strains can grow using NO3 or fumarate. Most strains were able to grow fermentatively in complex growth medium, and a few strains could grow by fermentation of glucose or trehalose.;CO2 fixation by both salt-mine and surface halobacteria was shown to be highest under aerobic conditions. Incubation under light or dark conditions had no significant effect. 13C-NMR studies indicated that the major CO2 fixation occurring was via pyruvate carboxylase or PEP carboxylase into oxaloacetate, and also into carbonyl phosphate for synthesis of arginine. Enzyme assays confirmed the presence of pyruvate carboxylase.;Some strains of halobacteria, isolated from salt deposits, have the ability to emulsify and degrade crude oil. Surface strains showed only weak or no emulsification of crude oil. Crude oil may represent a carbon source, which is available to halobacteria within the salt deposits.;The salt-mine strains of halobacteria thus did not differ from the surface strains of halobacteria in the range of carbon sources they could use, the modes of anaerobic growth or the pathways of CO2 fixation, although no surface strains were shown to degrade crude oil. Therefore it is likely that the salt-mine strains of halobacteria have not grown actively within the salt deposits since their formation, but have either been present in a state of "suspended animation" or are more recent contaminants.