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The primary sigma factor of Staphylococcus aureus, [[sigma].sup.SA], regulates the transcription of many genes, including several essential genes, in this bacterium via specific recognition of exponential growth phase promoters. In this study, we report the existence of a novel staphylococcal phage G1-derived growth inhibitory polypeptide, referred to as G1ORF67, that interacts with [[sigma].sup.SA] both in vivo and in vitro and regulates its activity. Delineation of the minimal domain of [[sigma].sup.SA] that is required for its interaction with G1ORF67 as amino acids 294 to 360 near the carboxy terminus suggests that the G1 phage-encoded anti-[sigma] factor may occlude the -35 element recognition domain of [[sigma].sup.SA]. AS would be predicted by this hypothesis, the G1ORF67 polypeptide abolished both RNA polymerase core-dependent binding of [[sigma].sup.SA] to DNA and [[sigma].sup.SA]-dependent transcription in vitro. While G1ORF67 profoundly inhibits transcription when expressed in S. aureus cells in mode of action studies, our finding that G1ORF67 was unable to inhibit transcription when expressed in Escherichia coli concurs with its inability to inhibit transcription by the E. coli holoenzyme in vitro. These features demonstrate the selectivity of G1ORF67 for S. aureus RNA polymerase. We predict that G1ORF67 is one of the central polypeptides in the phage G1 strategy to appropriate host RNA polymerase and redirect it to phage reproduction.

Disruption of xylanase-encoding genes on the xylanolytic system of wild-type Streptomyces lividans using vectors that integrate into respective genes shows that it decreases the growth rate and xylanase activities. Disruption of xlnA did not affect xlnB and xlnC expression while xlnB and xlnC disruptions did not affect xlnA expression but affected the expressions of each other. XlnB or xlnC hydrolytic product fractions influence xlnB and xlnC expressions in the disrupted strain while the small xylo-oligosaccharides do not affect the expressions.

The cloning of the gene pabB encoding the aminase activity of p-aminobenzoate (PABA) synthase in Lactococcus lactis subsp. lactis in pIJ41 was undertaken. These genes are usually expressed in Streptomyces lividans strains, which are inefficient in PABA biosynthesis. The 1.2 kb deletion in the region between the aph promoter and the cloning site in the PIJ41 was associated with the expression of the gene. The localization of the pabB complementing gene in the 1.9 kb segment was induced by the subcloning of the pBR322 and the expression of the cloned L. lactis DNA fragment in Escherichia Coli AB3295.