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Characterization of Mycobacterium smegmatis Expressing the Mycobacterium tuberculosis Fatty Acid Synthase I (fas1) Gene. Oren Zimhony, 2004.Unlike most other bacteria, mycobacteria make fatty acids with the multidomain enzyme eukaryote-like fatty acid synthase I (FASI) . Previous studies have demonstrated that the tuberculosis drug pyrazinamide and 5-chloro-pyrazinamide target FASI activity . Biochemical studies have revealed that in addition to C16:0, Mycobacterium tuberculosis FASI synthesizes C26:0 fatty acid, while the Mycobacterium smegmatis enzyme makes C24:0 fatty acid . In order to express M . tuberculosis FASI in a rapidly growing Mycobacterium and to characterize the M . tuberculosis FASI in vivo, we constructed an M . smegmatis  fas1
strain which contained the M . tuberculosis fas1 homologue . The
M . smegmatis
fas1
(attB::M . tuberculosis fas1) strain grew more slowly
than the parental M . smegmatis strain and was more susceptible
to 5-chloro-pyrazinamide . Surprisingly, while the M . smegmatis
fas1
(attB::M . tuberculosis fas1) strain produced C26:0,
it predominantly produced C24:0 . These results suggest
that the fatty acid elongation that produces C24:0 or C26:0
in vivo is due to a complex interaction among FASI, FabH, and FASII
and possibly other systems and is not solely due to FASI elongation,
as previously suggested by in vitro studies .
XopC and XopJ, Two Novel Type III Effector Proteins from Xanthomonas campestris pv . vesicatoria. Laurent Noël, 2003.Pathogenicity of the gram-negative plant pathogen Xanthomonas campestris pv. vesicatoria depends on a type III secretion (TTS) system which translocates bacterial effector proteins into the plant cell . Previous transcriptome analysis identified a genome-wide regulon of putative virulence genes that are coexpressed with the TTS system . In this study, we characterized two of these genes, xopC and xopJ . Both genes encode Xanthomonas outer proteins (Xops) that were shown to be secreted by the TTS system . In addition, type III-dependent translocation of both proteins into the plant cell was demonstrated using the AvrBs3 effector domain as a reporter . XopJ belongs to the AvrRxv/YopJ family of effector proteins from plant and animal pathogenic bacteria . By contrast, XopC does not share significant homology to proteins in the database . Sequence analysis revealed that the xopC locus contains several features that are reminiscent of pathogenicity islands . Interestingly, the xopC region is flanked by 62-bp inverted repeats that are also associated with members of the Xanthomonas avrBs3 effector family . Besides xopC, a second gene of the locus, designated hpaJ, was shown to be coexpressed with the TTS system. hpaJ encodes a protein with similarity to transglycosylases and to the Pseudomonas syringae pv . maculicola protein HopPmaG . HpaJ secretion and translocation by the X . campestris pv . vesicatoria TTS system was not detectable, which is consistent with its predicted Sec signal and a putative function as transglycosylase in the bacterial periplasm .
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