perfringens[32, 44]. Obana et al. [45] showed that VR-RNA regulates

the stability of colA mRNA by cleaving the transcript. The processed shorter colA transcript was more stable than the longer intact colA transcript. It is possible that among other factors, downregulation of vrr in mTOR target 13124R (−158) may have contributed to a decrease in the level of transcription of genes. The vrr in NCTRR was upregulated twofold. virX is another regulatory gene that, even in the absence of the VirR/VirS regulatory system, activates the transcription of the pfoA, plc and colA genes, and its overexpression results in the increased expression of toxin genes [44, 46]. qRT-PCR results showed that the expression of this gene increased at least 2.2 times in NCTRR and decreased by −3.0 in 13124R. Another regulatory gene whose expression was altered in the Tanespimycin purchase mutants was revR, which was downregulated in 13124R and upregulated in NCTRR. revR is a response regulator that STI571 alters the transcription

of 100 genes, including those for potential virulence factors, which also are regulated by (VirR/VirS), and those for cell wall metabolism [47]. Hiscox et al. [47] found that a revR mutant of C. perfringens 13 was filamented. Gram staining of the wild types and mutants of ATCC 13124 and NCTR showed that cells of both mutants were filamented and longer than those of the wild types. Microarray and qRT-PCR analysis (Table 1) showed that some putative membrane protein genes were differentially expressed in the mutants and wild types of both strains. The amino acid sequences of the toxin OSBPL9 genes and the regulatory genes (virR/virS) in the mutants

and wild types of both strains were identical, except that there were two silent mutations in virR/virS in NCTRR, so the expression of toxin genes and their regulators was not the result of gene mutation. The sequence of vrr was identical in the mutants and wild types of both strains, and the sequence of revR in ATCC 13124 and 13124R was also identical. Obana and Nakamura [48] also detected other regulatory genes, CPE_1446-CPE_1447, which appear to regulate the transcription of plc, pfoA, nanI and nagHIJK at transcription level. Microarray analysis showed that CPE_1447 was downregulated in NCTRR, but this gene was not detected in the microarray data from ATCC 13124. qRT-PCR confirmed that nanI was downregulated and sialidase was decreased in NCTRR; however, the role of CPE_1447 in the regulation of this gene is not clear. Another global regulatory protein, CodY, has been shown to regulate expression of many genes in Bacillus subtilis and Clostridium difficile[49, 50]. It appears to repress genes whose products are not needed during growth in high nutrient medium. qRT-PCR showed that CodY was upregulated (6.9 times) in NCTRR and downregulated (−1.89 times) in 13124R.

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