The molecular basis of microbial adaptation
Horizontal gene transfer system in Acinetobacter baylyi
Microbial life has been detected in virtually every environment on earth ranging from hydrothermal vents, salt-saturated alkaline ponds, acidic hot springs, antarctic ice, dry dessert soils, the upper atmosphere, and in animal and plant hosts. To exploit such different environments, microorganisms must have evolved phenotypic traits allowing survival under very different environmental conditions. Data obtained in studies of molecular microbial ecology and genome analyses provide growing evidence that horizontal gene transfer is a major force for bacterial adaptation to changing environments.
Despite the important impact of DNA transfer in evolution, information on the structure and function of DNA translocators is limited. Acinetobacter baylyi (former Acinetobacter sp. BD413) is very well known for its extraordinary trait to take up large amounts of free DNA even from members of other domains of life (e.g. horizontal gene transfer). To understand the mechanism of natural transformation and elucidate structure of the DNA translocator we combined modern molecular, physiological, biochemical, immunological, and electron microscopical methods. These studies led to the identification the first set of subunits of the A. baylyi transformation machinery. Interestingly several of the proteins are very similar to components implicated in the biogenesis of type IV pili, dynamic structures which are essential for host cell adhesion and motility on solid surfaces of pathogenic bacteria and raised the question of an implication of the Acinetobacter pili in DNA translocation. This question has been answered clearly, since we showed that the Acinetobacter pili are not linked to DNA transport. Our molecular, biochemical, and electron microscopical studies have culminated in the first model of the A. baylyi DNA translocator. Further studies are underway to identify novel genes of the DNA translocator, analyze their function and interactions and to understand the broad substrate specificity of the A. baylyi DNA translocator.
The DNA translocator of A. baylyi.
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