Microbial Physiology of Extremophiles

Dr D J Gilmour

My laboratory is concerned with the physiology of micro-organisms which live in extreme environments. Extreme environments are usually defined as habitats which show a low species diversity, but not necessarily a low biomass, since the extremophile organisms found in these environments can often grow to high cell densities.

My long-standing interest is in algae and bacteria growing at high salinities. In particular the unicellular green alga, Dunaliella, which can grow in salinities from 0.1 to 5.0 M NaCl by using glycerol as a compatible solute. Recent work in my laboratory has concentrated on glycerol leakage from Dunaliella cells and our long term aim is to develop a commercial system of glycerol production from Dunaliella.

In addition to the salinity work we are also looking at the response of both algae and bacteria to pH stress. The bioenergetic problems that are associated with growth at the extremes of pH are considerable and it has been suggested that some bacteria growing at pH values of 10 or more may be exceptions to Mitchell’s chemiosmotic theory. This is a fascinating field for future work.

Figure Legend - An extremely salty lake in Western Australia showing a bloom of Dunaliella. The red colour is due to beta-carotene, which is produced commercially using Dunaliella and sold in tablet form as a vitamin supplement.

Selected Publications

Analysis of protein solvent interactions in glucose dehydrogenase from the extreme halophile Haloferax mediterranei. Britton KL, Baker PJ, Fisher M, Ruzheinikov S, Gilmour DJ, Bonete MJ, Ferrer J, Pire C, Esclapez J, Rice DW. Proc Natl Acad Sci U S A. 2006 Mar 28;103(13):4846-51.

A mutant of Dunaliella parva CCAP 19/9 leaking large amounts of glycerol into the medium. B.C. Hard and D.J. Gilmour. J. Appl. Phycol. (1991) 3, 367-372.

Mechanisms for controlling balance between light input and utilisation in the salt tolerant alga Dunaliella C9AA. D. Rees, C.B. Lee, D.J. Gilmour and P. Horton. Photosyn. Res. (1992) 32,181-191.

Regulation of cell volume in the salt tolerant bacterium Halomonas elongata. E. Miguelez and D.J. Gilmour. Lett. Appl. Microbiol. (1994) 19, 363-365.

The effect of NaCl on the growth of a Halomonas species: accumulation and utilization of compatible solutes. S.P. Cummings and D.J. Gilmour. Microbiology (1995) 141, 1413-1418.

The uptake of organic compounds by Dunaliella parva CCAP 19/9. B.C. Hard and D.J. Gilmour. Eur. J. Phycol. (1996) 31, 217-224.