Dynamics of a bacterial DNA uptake machinery

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Competence is a developmental state in which various species of bacteria can take up DNA from their environment and incorporate the DNA into their chromosome via homologous recombination (HR), leading to horizontal gene transfer. We have found that several DNA recombination proteins (that confer important roles during DNA repair in growing cells) accumulate in a differential manner at a single or both cell poles in competent Bacillus subtilis cells, where the DNA uptake machinery assembles. Different Rec proteins are recruited, dependent on whether plasmid or chromosomal DNA or phage DNA is added. The central player in HR, RecA, assembles at the uptake complex, and forms filamentous structures (threads) that appear to guide incoming DNA to the chromosome. In contrast to recombination proteins, the uptake complex is highly static and stable. We will identify all components of the competence complex and analyse changes occurring in the composition dependent on the addition of different kinds of DNA. We will elucidate how the machinery assembles at a specific subcellular location and how Rec proteins gain novel functional specificity, dependent on what type of DNA is added to the cells. We will study the functional interaction of Rec proteins with the Com machinery and determine how the unprecedented robustness of the uptake complex is achieved at a molecular level.