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Mutational Analysis of the fruA Promoter Region Demonstrates that C-Box and 5-Base-Pair Elements Are Important for Expression of an Essential Developmental Gene of Myxococcus xanthus. D. Srinivasan, 2004.Myxococcus xanthus uses extracellular signals during development to regulate gene expression . C-signaling regulates the expression of many genes induced after 6 h into development . FruA is a protein that is necessary for cells to respond to C-signaling, but expression of the fruA gene does not depend on C-signaling . Yet the fruA promoter region has a C box and a 5-bp element, similar to the promoter regions of several C-signal-dependent genes, where these sequences are crucial . Here, we show that the C box and 5-bp elements are important for expression of fruA, demonstrating for the first time that these sequences play a role in the expression of a gene that does not depend on C-signaling and is required for M . xanthus development . The N-Acetyltransferase RimJ Responds to Environmental Stimuli To Repress pap Fimbrial Transcription in Escherichia coli. Christine A. White-Ziegler, 2002.In uropathogenic Escherichia coli, P pili (Pap) facilitate binding to host epithelial cells and subsequent colonization . Whereas P pili can be produced at 37°C, the expression of these fimbriae is suppressed at 23°C . Previously, insertion mutations in rimJ, a gene encoding the N-terminal acetyltransferase of ribosomal protein S5, were shown to disrupt this thermoregulatory response, allowing papBA transcription at low temperature . In this study, we created an in-frame deletion of rimJ . This deletion relieved the repressive effects not only of low temperature but also of rich (Luria-Bertani [LB]) medium and glucose on papBA transcription, indicating that RimJ modulates papBA transcription in response to multiple environmental stimuli . papI transcription was also shown to be regulated by RimJ . papBA transcription is also controlled by a phase variation mechanism . We demonstrated that the regulators necessary to establish a phase ON state—PapI, PapB, Dam, Lrp, and cyclic AMP-CAP-are still required for papBA transcription in a rimJ mutant strain . rimJ mutations increase the rate at which bacteria transition into the phase ON state, indicating that RimJ inhibits the phase OFF  ON transition . A
 rimJ hns651 mutant is viable on LB medium but not on minimal medium . This synthetic lethality, along with transcriptional analyses, indicates that RimJ and H-NS work through separate pathways to control papBA transcription . Mutations in rimJ do not greatly influence the transcription of the fan, daa, or fim operon, suggesting that RimJ may be a pap-specific regulator . Overexpression of rimJ under conditions repressive for papBA transcription complements the
rimJ mutation but has little effect on transcription under activating conditions, indicating that the ability of RimJ to regulate transcription is environmentally controlled .
A Food-Grade Approach for Functional Analysis and Modification of Native Plasmids in Lactococcus lactis. Paul D. Cotter, 2003.While plasmids from lactic acid bacteria possess many traits that are of industrial value, their exploitation is often frustrated by an inability to conduct food-grade engineering of native plasmids or to readily screen for their transfer . Here we describe a system that uses a RepA+ temperature-sensitive helper plasmid and a RepA- cloning vector to overcome these problems while maintaining the food-grade status of the native plasmid . This strategy was used to precisely delete ltnA1 alone, or in conjunction with ltnA2 (encoding the structural proteins of the lantibiotic lacticin 3147), from the native 60.2-kb plasmid pMRC01 and to select for the transfer of pMRC01 between Lactococcus lactis strains .
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