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Numerous small untranslated RNAs (sRNAs) have been identified in Escherichia coli in recent years, and their roles are gradually being defined. However, few of these sRNAs appear to be conserved in Vibrio cholerae, and both identification and characterization of sRNAs in V. cholerae remain at a preliminary stage. We have characterized one of the few sRNAs conserved between E. coli and V. cholerae: RyhB. Sequence conservation is limited to the central region of the gene, and RyhB in V. cholerae is significantly larger than in E. coli. As in E. coli, V. cholerae RyhB is regulated by the iron-dependent repressor Fur, and it interacts with the RNAbinding protein Hfq. The regulons controlled by RyhB in V. cholerae and E. coli appear to differ, although some overlap is evident. Analysis of gene expression in V. cholerae in the absence of RyhB suggests that the role of this sRNA is not limited to control of iron utilization. Quantitation of RyhB expression in the suckling mouse intestine suggests that iron availability is not limiting in this environment, and RyhB is not required for colonization of this mammalian host by V. cholerae.In the past few years, it has become increasingly clear that small untranslated RNAs (sRNAs) regulate many diverse cellular processes. In Escherichia coli, sRNAs have already been shown to modulate sigma factor production, iron utilization, acid resistance, porin expression, and the response to oxidative stress, and functions still need to be defined for a majority of its more than 50 sRNAs (reviewed in reference 2). The modes of action of sRNAs have also been shown to be diverse. In general, sRNA-based regulation is thought to depend upon base pairing between short regions of complementary sequence in the sRNA and its target mRNA(s), although sRNAs that interact with proteins (e.g., CsrB and 6S RNA) have also been described (32,40). Pairing between an sRNA and an mRNA can promote or inhibit mRNA translation or increase or decrease mRNA stability, depending upon the RNAs involved (7,21,22,27). The location of the target sequence within an mRNA probably influences the events that follow binding to an sRNA; still, it is not fully understood how sRNA binding has such a range of consequences.Many of the sRNAs that interact with mRNAs also interact with the RNA-binding protein Hfq. Hfq has homology to eukaryotic Sm proteins and appears to function as an RNA chaperone (12,25,43). Hfq interacts with both sRNAs and mRNAs and can foster formation of sRNA:mRNA complexes. mRNAbinding sRNAs generally have reduced stability in strains lacking Hfq, and their regulatory roles are typically impaired in an hfq strain background (12,25,36). We recently reported that Vibrio cholerae lacking hfq is severely attenuated in its ability to colonize the small intestines of suckling mice and thus is largely avirulent in this commonly used model host for study of cholera pathogenesis (8). This finding suggested that one or more sRNAs might be critical for V. cholerae virulence. Lenz et al. subsequently identified fo...

While remaining a major problem in hospitals, Staphylococcus aureus is now spreading in communities. Strain MW2 (USA400 lineage) and other community methicillin-resistant S. aureus strains most commonly cause skin infections with abscess formation. Multidrug resistance (MDR) efflux pumps contribute to antimicrobial resistance but may also contribute to bacterial survival by removal of environmental toxins. In S. aureus, NorA, NorB, NorC, and Tet38 are chromosomally encoded efflux pumps whose overexpression can confer MDR to quinolones and other compounds (Nor pumps) or tetracyclines alone (Tet38), but the natural substrates of these pumps are not known. To determine the role of these efflux pumps in a natural environment in the absence of antibiotics, we used strain MW2 in a mouse subcutaneous abscess model and compared pump gene expression as determined by reverse transcription-PCR in the abscesses and in vitro. norB and tet38 were selectively upregulated in vivo more than 171-and 24-fold, respectively, whereas norA and norC were downregulated. These changes were associated with an increase in expression of mgrA, which encodes a transcriptional regulator known to affect pump gene expression. In competition experiments using equal inocula of a norB or tet38 mutant and parent strain MW2, each mutant exhibited growth defects of about two-to threefold in vivo. In complementation experiments, a single-copy insertion of norB (but not a single-copy insertion of tet38) in the attB site within geh restored the growth fitness of the norB mutant in vivo. Our findings indicate that some MDR pumps, like NorB, can facilitate bacterial survival when they are overexpressed in a staphylococcal abscess and may contribute to the relative resistance of abscesses to antimicrobial therapy, thus linking bacterial fitness and resistance in vivo.

Annual wild soybean (Glycine soja Sieb. et Zucc.) is believed to be a potential gene source for future soybean improvement in coping with the world climate change for food security. To evaluate the wild soybean genetic diversity and differentiation, we analyzed allelic profiles at 60 simple-sequence repeat (SSR) loci and variation of eight morph-biological traits of a representative sample with 196 accessions from the natural growing area in China. For comparison, a representative sample with 200 landraces of Chinese cultivated soybean was included in this study. The SSR loci produced 1,067 alleles (17.8 per locus) with a mean gene diversity of 0.857 in the wild sample, which indicated the genetic diversity of G. soja was much higher than that of its cultivated counterpart (total 826 alleles, 13.7 per locus, mean gene diversity 0.727). After domestication, the genetic diversity of the cultigens decreased, with its 65.5% alleles inherited from the wild soybean, while 34.5% alleles newly emerged. AMOVA analysis showed that significant variance did exist among Northeast China, Huang-Huai-Hai Valleys and Southern China subpopulations. UPGMA cluster analysis indicated very significant association between the geographic grouping and genetic clustering, which demonstrated the geographic differentiation of the wild population had its relevant genetic bases. In comparison with the other two subpopulations, the Southern China subpopulation showed the highest allelic richness, diversity index and largest number of specific-present alleles, which suggests Southern China should be the major center of diversity for annual wild soybean.