The specialized secretory apparatus ESX-1 is essential for DNA transfer in Mycobacterium smegmatis.
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.
The Microscopy and Imaging Center, Texas A&M University, 2257 TAMU, College Station, TX 77843, USA.
Abbie
A
Coros
Brian
B
Callahan
Eric
E
Battaglioli
Keith M
KM
Derbyshire
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D001692:Biological Transport / Q000235:genetics; D003227:Conjugation, Genetic; D004247:DNA / Q000378:metabolism*; D005798:Genes, Bacterial; D016254:Mutagenesis, Insertional; D020102:Mycobacterium smegmatis / Q000235:genetics* / Q000378:metabolism* / Q000472:pathogenicity; D009876:Operon
D001426:Bacterial Proteins; D004247:DNA