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Dr John Fuerst BSc. (Hons) PhD (Qld) M.Lit.St(Qld) Senior Lecturer in Microbial Ecology and Systematics Tel: (61 7) 3365 4643 Fax: (61 7) 3365 4620 Email:fuerst@biosci.uq.edu.au |
My research interests are in the area of microbial evolution and the molecular cell biology of bacteria, and concentrate on the cell biology, phylogenetics and ecology of the planctomycetes:
Molecular phylogenetics and cell biology of Gemmata obscuriglobus and other planctomycetes in relation to the origin of eukaryotes
Gemmata obscuriglobus is of great significance to the study of evolution because it possesses a membrane-bounded nucleoid, a feature previously known only in eukaryotes. These organisms may provide an understanding into how the first eukaryote nucleus evolved and in what type of organism that evolution occurred. We have recently discovered that cells of both species ofPirellula possess a large nucleoid-containing cellular compartment , the 'pirellulosome', surrounded by only a single membrane. These organisms are members of the planctomycetes, a unique phylum within the Domain Bacteria. The phylogenetic position of this group of Bacteria is uncertain, but it may be quite ancient within the Bacteria.
Our research involves two major areas. First, we are investigating the ultrastructure of the membrane-bounded nuclear region in G. obscuriglobus by relatively artefact-free methods such as freeze-fracture and cryosubstitution, combined with 3-D reconstruction from serial sections. We know from this work that the nuclear region is bounded by two membranes, as is the eukaryotic nucleus, and that the region contains the cell's genomic DNA. We are also developing methods for isolation of nuclear bodies and examining the possible correlations of nuclear body structure with function by use of autoradiography for investigating localization of RNA and protein synthesis, and in situ hybridization for localizing 16S ribosomal RNA.
Secondly, we are attempting to solve the problem of evolutionary relationships of the planctomycetes (for example whether they are a relatively ancient group within the Domain Bacteria) and how closely they are related to the Chlamydia) using sequence data from ancient conserved proteins such as elongation factor (EF-Tu). In a microbial genomics approach, we are also performing random sequencing of clone libraries from Gemmata obscuriglobus and Pirellula marina as a means to discovery of genes of cell biological and evolutionary relevance.
We are also interested in determining whether the nuclear body of planctomycete cells is homologous or analogous to the nucleus of eukaryotes, and whether new mechanisms involving transport of RNA and protein across the nuclear membranes may have evolved in these organisms. Such mechanisms may illuminate the possible ways by which the eukaryote nucleus originally evolved.
Electron micrograph of thin-sectioned cell of cryosubstituted Gemmata obscuriblobus showing membrane-bounded nuclear body (arrow). Click to view.
Molecular diversity of planctomycetes
Studies by a number of research groups have shown that bacteria with a morphology characteristic of planctomycetes or with planctomycete-specific 16S rRNA sequences are widely distributed within a variety of unusual and important habitats such as sewage treatment sludge, cattle manure, the meromictic saline Ekho Lake in Antarctica, alkaline chalk mines, acid bog water (Schlesner, H. 1994. System. Appl. Microbiol. 17, 135-145), soil from Mt. Coot-tha in Brisbane, Australia (Liesack, W. & Stackebrandt, E. 1992. J. Bacteriol. 174, 5072-5078) and in `marine snow', organic aggregates found in seawater (De Long, E. F., Franks, D. G. & Alldredge, A. I. 1993. Limnol. Oceanogr. 38, 924-934), in addition to classical habitats for planctomycetes such as eutrophic freshwater ponds. We have determined that post-larval prawns commonly used in aquaculture (Penaeus monodon) harbour planctomycete bacteria similar to Pirellula marina. 16S rRNA gene sequencing of our isolates has been performed to confirm their phylogenetic relationship to planctomycetes (Fuerst et al., 1997; Appl. Env. Microbiol. 63:254-262 ).
We are isolating new strains of planctomycetes in culture from Australian habitats including soil and freshwater, exploring their potential physiological diversity via enrichment culture, and using molecular ecology approaches to attempt to demonstrate the phylogenetic affinities of uncultured morphotypes such as the freshwater stalked rosette-former Planctomyces bekefii.
Membrane-bounded nuclear structures in sponge symbionts and other bacteria-like cells:
We have recently found evidence for membrane-bounded nuclear regions in cells of bacteria-like symbionts occurring in the 'mesohyl' of marine sponge tissue. Several morphotypes have been found, and some of these display regular subunit structure in their cell walls consistent with membership of the Domain Archaea. The nuclear region in several of these morphotypes is bounded by a single membrane in a similar way to that found in the pirellulosome of Pirellula marina (see above). The membrane-bounded region includes all the cell DNA in at least one of these morphotypes (Fuerst et al., 1998:FEMS Microbiol. Lett. 166: 29-34). The morphotypes have been found in several sponge genera including Stromatospongia, Astrosclera, Jaspis, Pseudoceratina and Axinyssa.
Laboratory Members
Selected Research Publications
Other Professional
interests and Affiliations
Research Collaborators include:
Richard Webb: Webpage
Prof Mike Jetten: Webpage
Dr Marc Strous: Webpage