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XI International Congress of Bacteriology and Applied Microbiology 2005
In July 2005 I attended the XI International Congress of Bacteriology and Applied Microbiology at the Joint Meeting of the 3 Divisions of the International Union of Microbiological Societies 2005. The conference was held over four days in San Francisco, California, USA. The conference brought together microbiologists ranging from Virologists to Mycologists with the Bacteriology congress providing a variety of interesting and diverse sessions.
My interest in bacterial gene regulation, in particular the control of plant cell wall degrading exoenzyme, antibiotic and pigment production in Serratia, prompted me to attend sessions focused on regulation of pathogenic processes. Some sessions and talks of particular interest are discussed below.
Two-component systems are known to be very important regulatory systems in bacteria, where they control numerous cellular processes. In this session, Igor Zhulin introduced the interesting idea that one component systems may in fact be more widespread, diverse and evolutionarily older than their two component counterparts. One-component systems contain both the sensor and output domains (as also found in two-component systems) fused in one protein, where the “signal transduction” occurs within the protein. Evolution of two-component systems via domain shuffling has allowed the transduction of extracellular signals into the cell where they can exert an intracellular response.
Horizontal gene transfer (HGT) in the environment is known to provide increased genetic diversity and aid in the increase of antibiotic resistance – relevant to biocontrol strategies. However, estimates of the frequency of HGT is often debated and limited by techniques that rely on cultivating bacteria. A particularly fascinating talk by S. Sørensen, from Denmark, revealed an inventive strategy that utilised flourescence activated cell sorting (FACS) to detect GFP expression in recipient cells following conjugation of an IncP plasmid from E. coli or Pseudomonas sp. donors. GFP expression occurred only in recipient bacteria due to the presence of a repressor protein in the donor strains. Recipients could be quantified and also phylogenetic information garnered by sequencing the 16S rDNA. Using this technique they demonstrated that conjugation frequencies in the Rhizosphere were commonly underestimated by 100-1000-fold and that the taxonomic variability of recipients was much greater than previously known.
The importance of small regulatory RNA’s in the control of numerous phenotypes was the focus of one session. Here, Deiter Haas discussed the complex regulatory circuit that controls secondary metabolite production in the biocontrol strain Pseudomonas fluorescens CHA0. This system involves at least two small proteins (RsmA and RsmE) that repress target mRNA’s posttranscriptionally in the absence of three small RNA’s (RsmX, RsmY and RsmZ). Furthermore, this system is controlled by a GacAS two-component system in response to an extracellular signal. Bonnie Bassler demonstrated that a similar GacAS/Rsm system was involved in the already complex small RNA containing quorum sensing system of Vibrio cholerae. Discovery and understanding of these “new” regulatory modes requires novel genetic and bioinformatic approaches and is often hindered by redundancy in the systems.
To be able to understand bacterial pathogenesis or symbiosis it is essential to have a good knowledge of the regulatory mechanisms employed under different environmental conditions. This conference covered a range topics including bacterial strategies of gene regulation (only a few of which were discussed here), highlighting the diverse ways that microbial communities can adjust their behaviours.
Finally, the wonderful surrounds of San Francisco and the Bay area enabled a few conference participants the opportunity to visit the Golden Gate Bridge, Nappa Valley and the stunning Yosemite National Park. I am extremely grateful to the BSPP for the travel fund that supported my trip to IUMS 2005.
Peter Fineran University of Cambridge
