Role of IS5- and ISL3-like insertion sequences in the dissemination of catabolic genes

BOSCH, R.; CHRISTIE-OLEZA, J.; MARTÍN-CARDONA, C.; LANFRANCONI, M.P.; CORTÉS, P.; LALUCAT, J.; NOGALES, B.

Viena (AUSTRIA)

Simposio; 11th International Symposium on Microbial Ecology; 2006

Transposable elements are commonly found in bacteria and are known to contribute to the spread of genes. Catabolic genes are not an exception since very similar catabolic gene clusters are widely distributed among bacteria, presumably implying common origins and a broad dissemination in nature. Thus, it has been suggested that transposition might be the mechanism whereby catabolic clusters were spread in nature and, in fact, the sequencing of entire catabolic units has revealed the presence of a great diversity of flanking transposable elements. As example, IS5- and ISL3-like insertion sequences (IS) were detected in close proximity to the nah catabolic genes of Pseudomonas stutzeri AN10, a naphthalene degrading bacteria profusely studied in our laboratory. Interestingly, two copies of this IS5-like IS were flanking the nahW gene (salicylate hydroxylase encoding gene) of strain AN10 forming a composite transposon-like structure. We have analyzed, using gene hybridization and PCR amplification techniques, the relation between the presence of these two families of IS concomitantly with several hydrocarbon degrading genes (alkB, nahAc, nahW, nahH, catA) in more than 250 hydrocarbon degrading environmental isolates. Furthermore, we have introduced a kanamycin resistance gene into the nahW transposon-like structure of strain AN10 and, using P. stutzeri as experimental model, we have studied its capability of mobilization. Our results show that i) the presence of IS5- and ISL3-like ISs is correlated with the presence of hydrocarbon degrading genes, and ii) the presence of IS5-like sequences in the model genome facilitates the dissemination of non-self mobile IS5-constituted composite transposon-like structures.