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Query: UMLS:C0149958 (complex partial seizures)
 2,563 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Escherichia coli group 1 capsules are important virulence determinants, yet little is known about the transcriptional organization or regulation of their biosynthetic (cps) operons. Transcription of the prototype serotype K30 cluster is modulated by the JUMPStart-RfaH antitermination mechanism, with the cps promoter being localized to a region immediately upstream of the JUMPStart sequence. A putative stem-loop structure located within the K30 cps cluster separates conserved genes with products that are required for surface expression of capsule from serotype-specific genes encoding enzymes for polymer repeat-unit synthesis and polymerization. This putative stem-loop structure significantly reduces transcription in a termination-probe vector and may contribute to differential expression of the cps genes. Previous work indicated that increased amounts of group 1 capsular polysaccharide synthesis resulted from the overexpression of the Rcs (regulator of capsule synthesis) proteins. However, neither overexpression of the transcriptional activator RcsB nor an rcsB::aadA chromosomal insertion altered the level of transcription measured by cps::lacZ fusions. In the group 1 strains examined, an RcsAB box was found immediately upstream of galF, a gene involved in the production of sugar nucleotide precursors. Overexpression of RcsB was found to result in a threefold increase in transcription of a galF::lacZ chromosomal fusion. Moreover, overexpression of GalF gave rise to a two- to threefold increase in cell-free as well as cell-associated capsule, without affecting cps::lacZ activity. These results indicate that transcription of the E. coli group 1 capsule cluster itself is not regulated by the Rcs system and may, in fact, be constitutive. However, the Rcs system can potentially influence levels of capsular polysaccharide production by increasing galF transcription and influencing the available pool of biosynthetic precursors.
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PMID:Transcriptional organization and regulation of the Escherichia coli K30 group 1 capsule biosynthesis (cps) gene cluster. 1258 58

Vibrio parahaemolyticus, a biofouling marine bacterium and human pathogen, undergoes phase variation displaying translucent (TR) and opaque (OP) colony morphologies. Prior studies demonstrated that OP colonies produce more capsular polysaccharide (CPS) than TR colonies and that opacity is controlled by the Vibrio harveyi LuxR-type transcriptional activator OpaR. CPS has also been shown to be regulated by the scrABC signaling pathway, which involves a GGDEF-EAL motif-containing sensory protein. The present study identifies cps genes and examines their regulation. Transposon insertions in the cps locus, which contains 11 genes, abolished opacity. Such mutants failed to produce CPS and were defective in pellicle formation in microtiter wells and in a biofilm attachment assay. Reporter fusions to cpsA, the first gene in the locus, showed approximately 10-fold-enhanced transcription in the OP (opaR+) strain compared to a TR (deltaopaR) strain. Two additional transcriptional regulators were discovered. One potential activator, CpsR, participates in the scrABC GGDEF-EAL-signaling pathway; CpsR was required for the increased cps expression observed in scrA deltaopaR strains. CpsR, which contains a conserved module found in members of the AAA+ superfamily of ATP-interacting proteins, is homologous to Vibrio cholerae VpsR; however, unlike VpsR, CpsR was not essential for cps expression. CpsS, the second newly identified regulator, contains a CsgD-type DNA-binding domain and appears to act as a repressor. Mutants with cpsS defects have greatly elevated cps transcription; their high level of cpsA expression was CpsR dependent in TR strains and primarily OpaR dependent in OP strains. Thus, a network of positive and negative regulators modulates CPS production in V. parahaemolyticus.
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PMID:Multiple regulators control capsular polysaccharide production in Vibrio parahaemolyticus. 1294 95

K. pneumoniae is the predominant pathogen isolated from liver abscesses of diabetic patients in Asian countries. Although elevated blood glucose levels cause various immune problems, its effects on K. pneumoniae virulence are unknown. This study investigated the regulation of capsular polysaccharide (CPS) biosynthesis, a major determinant for K. pneumoniae virulence, in response to exogenous glucose. We found that K. pneumoniae produce more CPS in glucose-rich medium via reduction in cyclic AMP (cAMP) levels. Individual deletion of cyaA or crp, which respectively encode adenylate cyclase and cAMP receptor protein in K. pneumoniae, markedly increased CPS production, while deletion of cpdA, which encodes cAMP phosphodiesterase, decreased CPS production. These results indicate that K. pneumoniae CPS biosynthesis is controlled by the cAMP-dependent carbon catabolite repression (CCR). To investigate the underlying mechanism, quantitative real-time PCR and promoter-reporter assays were used to verify that the transcription of CPS biosynthesis genes, which are organized into 3 transcription units (orf1-2, orf3-15, and orf16-17), were activated by the deletion of crp. Sequence analysis revealed putative CRP binding sites located on P(orf3-15) and P(orf16-17), suggesting direct CRP-cAMP regulation on the promoters. These results were then confirmed by electrophoretic mobility shift assay. In addition, we found putative CRP binding sites located in the promoter region of rcsA, which encodes a cps transcriptional activator, demonstrating a direct repression of CRP-cAMP and P(rcsA). The deletion of rcsA in mutation of crp partially reduced CPS biosynthesis and the transcription of orf1-2 but not of orf3-15 or orf16-17. These results suggest that RcsA participates in the CRP-cAMP regulation of orf1-2 transcription and influences CPS biosynthesis. Finally, the effect of glucose and CCR proteins on CPS biosynthesis also reflects bacterial resistance to serum killing. We here provide evidence that K. pneumoniae increases CPS biosynthesis for successful infection in response to exogenous glucose via cAMP-dependent CCR.
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PMID:Role of the cAMP-dependent carbon catabolite repression in capsular polysaccharide biosynthesis in Klebsiella pneumoniae. 2340 39