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Genome-wide transposon mutagenesis in pathogenic Leptospira species

Australian Bacterial Pathogenesis Program, Department of Microbiology, Monash University, Clayton, VIC 3800, Australia.
Infection and immunity (Impact Factor: 4.16). 01/2009; 77(2):810-6. DOI: 10.1128/IAI.01293-08
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ABSTRACT Leptospira interrogans is the most common cause of leptospirosis in humans and animals. Genetic analysis of L. interrogans has been severely hindered by a lack of tools for genetic manipulation. Recently we developed the mariner-based transposon Himar1 to generate the first defined mutants in L. interrogans. In this study, a total of 929 independent transposon mutants were obtained and the location of insertion determined. Of these mutants, 721 were located in the protein coding regions of 551 different genes. While sequence analysis of transposon insertion sites indicated that transposition occurred in an essentially random fashion in the genome, 25 unique transposon mutants were found to exhibit insertions into genes encoding 16S or 23S rRNAs, suggesting these genes are insertional hot spots in the L. interrogans genome. In contrast, loci containing notionally essential genes involved in lipopolysaccharide and heme biosynthesis showed few transposon insertions. The effect of gene disruption on the virulence of a selected set of defined mutants was investigated using the hamster model of leptospirosis. Two attenuated mutants with disruptions in hypothetical genes were identified, thus validating the use of transposon mutagenesis for the identification of novel virulence factors in L. interrogans. This library provides a valuable resource for the study of gene function in L. interrogans. Combined with the genome sequences of L. interrogans, this provides an opportunity to investigate genes that contribute to pathogenesis and will provide a better understanding of the biology of L. interrogans.

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    • "The results of phage display showed LipL32 to interact with chloride channel accessory 2, glycoprotein VI, scavenger receptor expressed by endothelial cell isoform I, coronin 2A, laminin alpha 5, collagen XX and prostaglandin receptor EP1 of the host cells (Chaemchuen et al., 2011). Though large number of studies provided strong evidence for LipL32 in the role of pathogenesis, the unexpected results of Murray et al. (2009a, b) revealed by transposon mutagenesis studies in Leptospira interrogans denied the fact of LipL32 in pathogenesis. These concluding results arises several questions on the role of this abundant gene which is nearly 40 000 copies per cell. "
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