Salt lakes are highly productive ecosystems with a natural biodiversity we are just starting to explore. Some are used commercially for salt manufacture eg. Lake Tyrrell, Victoria (picture left) and for biotechnology. Dunaliella salina, a green alga, is cultivated for beta-carotene, a widely used antioxidant and food colouring agent. Nationally, this is an important industry, as Australia produces 95% of the world's supply of beta-carotene. There is a great potential to use salt lakes for the production of useful compounds other than beta-carotene, but first the organisms that grow in them need to be thoroughly understood, and genetic methods developed to be able to manipulate them. My work on the dominant archaea in salt lakes is a step towards this goal.

DIVERSITY, GENOMICS AND EVOLUTION

Haloarchaea belong to the family Halobacteriaceae (Phylum Euryarchaeota, Domain Archaea). The family currently possesses about 26 recognised genera,and increasing every year. These organisms are also called halobacteria or extremely halophilic Archaea. The most famous of the family are the Square Haloarchaea of Walsby (SHOW group organisms), pictured below. These cells are like thin tiles, approx. 1.7 x 0.2 µm, and normally have gas vesicles to regulate their buoyancy in the water column. First discovered by A. Walsby in 1980, they often represent the dominant cell type, ranging from 40-80% of the total cell population. Despite growing very well in nature, they were not able to be grown in culture until 2004. David Burns [website] first grew them in my laboratory in 2002 (B.Sc. hons, thesis), and the work was formally published on 21 August 2004. Being able to grow these organisms was a major step towards understanding their ecology, characteristics and evolution, and to be able to study their genetics and biotechnological potential. From diversity and cultivation studies I have moved into genomic sequencing in order to understand their genetic makeup and evolution in precise detail. more on the SHOW group.

HALOVIRUSES

Viruses of haloarchaea (haloviruses) outnumber cells 10-fold and are significant modulators of the cell population, infecting and lysing host cells. They may be useful to control particular species of haloarchaea (the same idea as 'phage therapy' in human medicine). For example, salt manufacture may be improved by suppressing certain cell types in crystallizer ponds. They are biologically interesting because they are adapted to high salt and must be able to replicate in archaeal cells. The transcription and translation systems in Archaea are primitive/simpler versions of those in eukaryotes, and their membrane lipids are fundamentally different from those in Bacteria or Eukarya. The types of viruses and their interactions with host cells will tell us a great deal about the selective pressures on cell populations in hypersaline environments, and their role in lateral gene transfer. They are also likely to provide useful genetic tools for manipulating haloarchaea. Over several years, I and my students have isolated a number of novel haloviruses (HF1, HF2, His1, His2, SH1) from australian salt lakes, and and have been studying their characteristics and genomes. All are novel, and many have unusual morphologies (e.g. the lemon-shaped His1), or uncommon replication strategies (eg. protein-primed polymerases). The 3D structure of one of our halovirus isolates, SH1, has recently been published in PNAS, and has wonderful surface spikes (for cell attachment) and a previously unknown surface geometry (T=28 dextro).

Why put a picture of Flamingos here? Well, they are an elegant bird, they display haloarchaeal colours, they often frequent hypersaline lakes, and maybe they carry haloarchaea with them on their travels...
[Photo: MDS]

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What I'm listening to, in Deutsch of course!: Peter Fox (a very cool guy): Haus am See; Die Toten Hosen ( famous german punk rock band), Steh auf, and Willkommen in Deutschland.