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The specialized secretory apparatus ESX‐1 is essential for DNA transfer in Mycobacterium smegmatis
Author(s) -
Coros Abbie,
Callahan Brian,
Battaglioli Eric,
Derbyshire Keith M.
Publication year - 2008
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2008.06299.x
Subject(s) - mycobacterium smegmatis , biology , mutant , dna , mutagenesis , genetics , plasmid , transposon mutagenesis , gene , virulence , transfer dna , genome , secretion , transposable element , mycobacterium tuberculosis , biochemistry , tuberculosis , transgene , agrobacterium tumefaciens , medicine , pathology
Summary Conjugal DNA transfer in Mycobacterium smegmatis occurs by a mechanism distinct from plasmid‐mediated 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.