Journal
MOLECULAR MICROBIOLOGY
Volume 69, Issue 4, Pages 794-808Publisher
WILEY
DOI: 10.1111/j.1365-2958.2008.06299.x
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Funding
- CDC
- Association of Public Health Laboratories
- NIAID [1T32AI055429, A1070666, A1042308]
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Conjugal DNA transfer in Mycobacterium smegmatis occurs by a mechanism distinct from plasmidmediated DNA transfer. Previously, we had shown that the secretory apparatus, ESX-1, negatively regulated DNA transfer from the donor strain; ESX-1 donor mutants are hyper-conjugative. Here, we describe a genome-wide transposon mutagenesis screen to isolate recipient mutants. Surprisingly, we find that a majority of insertions map within the esx-1 locus, which encodes the secretory apparatus. Thus, in contrast to its role in donor function, ESX-1 Is essential for recipient function; recipient ESX-1 mutants are hypo-conjugative. In addition to esx-1 genes, our screen identifies novel non-esx-1 loci in the M. smegmatis genome that are required for both DNA transfer and ESX-1 activity. DNA transfer therefore provides a simple molecular genetic assay to characterize ESX-1, which, in Mycobacterium tuberculosis, is necessary for full virulence. These findings reinforce the functional intertwining of DNA transfer and ESX-1 secretion, first described in the M. smegmatis donor. Moreover, our observation that ESX-1 has such diametrically opposed effects on transfer in the donor and recipient, forces us to consider how proteins secreted by the ESX-1 apparatus can function so as to modulate two seemingly disparate processes, M. smegmatis DNA transfer and M. tuberculosis virulence.
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