Dataset Information

Seawater-regulated genes for two-component systems and outer membrane proteins in myxococcus.

ABSTRACT: When salt-tolerant Myxococcus cells are moved to a seawater environment, they change their growth, morphology, and developmental behavior. Outer membrane proteins and signal transduction pathways may play important roles in this shift. Chip hybridization targeting the genes predicted to encode 226 two-component signal transduction pathways and 74 outer membrane proteins of M. xanthus DK1622 revealed that the expression of 55 corresponding genes in the salt-tolerant strain M. fulvus HW-1 was significantly modified (most were downregulated) by the presence of seawater. Sequencing revealed that these seawater-regulated genes are highly homologous in both strains, suggesting that they have similar roles in the lifestyle of Myxococcus. Seven of the genes that had been reported in M. xanthus DK1622 are involved in different cellular processes, such as fruiting body development, sporulation, or motility. The outer membrane (Om) gene Om031 had the most significant change in expression (downregulated) in response to seawater, while the two-component system (Tc) gene Tc105 had the greatest increase in expression. Their homologues MXAN3106 and MXAN4042 were knocked out in DK1622 to analyze their functions in response to changes in salinity. In addition to having increased salt tolerance, sporulation of the MXAN3106 mutant was enhanced compared to that of DK1622, whereas mutating gene MXAN4042 produced contrary results. The results indicated that the genes that are involved in the cellular processes that are significantly changed in response to salinity may also be involved the salt tolerance of Myxococcus cells. Regulating the expression levels of these multifunctional genes may allow cells to quickly and efficiently respond to changing conditions in coastal environments.

SUBMITTER: Pan HW

PROVIDER: S-EPMC2655515 | biostudies-literature | 2009 Apr

REPOSITORIES: biostudies-literature

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Seawater-regulated genes for two-component systems and outer membrane proteins in myxococcus.

Pan Hong-wei HW Liu Hong H Liu Ting T Li Cheng-yun CY Li Zhi-feng ZF Cai Ke K Zhang Cui-ying CY Zhang Yong Y Hu Wei W Wu Zhi-hong ZH Li Yue-zhong YZ

Journal of bacteriology 20090116 7

When salt-tolerant Myxococcus cells are moved to a seawater environment, they change their growth, morphology, and developmental behavior. Outer membrane proteins and signal transduction pathways may play important roles in this shift. Chip hybridization targeting the genes predicted to encode 226 two-component signal transduction pathways and 74 outer membrane proteins of M. xanthus DK1622 revealed that the expression of 55 corresponding genes in the salt-tolerant strain M. fulvus HW-1 was sign ...[more]

PMID: 19151139

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Project description:BackgroundThe diffusion of antibiotics through the outer membrane is primarily affected by the porin super family, changes contribute to antibiotic resistance. Recently we demonstrated that the CpxAR two-component signaling system alters the expression of an uncharacterized porin OmpC(KP), to mediate antimicrobial resistance in K. pneumoniae.Principal findingsIn this study, functional characterization of the putative porin OmpC(KP) (denoted kpnO) with respect to antimicrobial susceptibility and virulence was evaluated by generating an isogenic mutant, ΔkpnO in a clinical isolate of K. pneumoniae. Estimation of uronic acid content confirmed that ΔkpnO produced ∼2.0 fold lesser capsular polysaccharide than the wild-type. The ΔkpnO displayed higher sensitivity to hyper osmotic and bile conditions. Disruption of kpnO increased the susceptibility of K. pneumoniae to oxidative and nitrostative stress by ∼1.6 fold and >7 fold respectively. The loss of the Klebsiella porin led to an increase in the minimum inhibitory concentration of tetracycline (3-fold), nalidixic acid (4-fold), tobramycin (4-fold), streptomycin (10-fold), and spectinomycin (10-fold), which could be restored following complementation. The single deletion of kpnO reduced the survival of the pathogen by 50% when exposed to disinfectants. In Caenorhabditis elegans model, the kpnO mutant exhibited significantly (P<0.01) lower virulence. To dissect the role of PhoBR signaling system in regulating the expression of the kpnO, a phoB(KP) isogenic mutant was constructed. The phoB(KP) mutant exhibited impaired gastrointestinal stress response and decreased antimicrobial susceptibility. The mRNA levels of kpnO were found to be 4-fold less in phoB(KP) mutant compared to wild type. A regulatory role of PhoB(KP) for the expression of kpnO was further supported by the specific binding of PhoB(KP) to the putative promoter of kpnO.Conclusions and significanceLoss of PhoBR regulated porin KpnO resulted in increased antimicrobial resistance, increased susceptibility to gastrointestinal stress, and reduced virulence in K. pneumoniae NTUH-K2044.

Project description:Myxococcus xanthus serves as a model organism for development and complex signal transduction. Regulation of developmental aggregation and sporulation is controlled, in part, by the Che3 chemosensory system. The Che3 pathway consists of homologs to two methyl-accepting chemotaxis proteins (MCPs), CheA, CheW, CheB, and CheR but not CheY. Instead, the output for Che3 is the NtrC homolog CrdA, which functions to regulate developmental gene expression. In this paper we have identified an additional kinase, CrdS, which directly regulates the phosphorylation state of CrdA. Both epistasis and in vitro phosphotransfer assays indicate that CrdS functions as part of the Che3 pathway and, in addition to CheA3, serves to regulate CrdA phosphorylation in M. xanthus. We provide kinetic data for CrdS autophosphorylation and demonstrate specificity for phosphotransfer from CrdS to CrdA. We further demonstrate that CheA3 destabilizes phosphorylated CrdA (CrdA~P), indicating that CheA3 likely acts as a phosphatase. Both CrdS and CheA3 control developmental progression by regulating the phosphorylation state of CrdA~P in the cell. These results support a model in which a classical two-component system and a chemosensory system act synergistically to control the activity of the response regulator CrdA. IMPORTANCE While phosphorylation-mediated signal transduction is well understood in prototypical chemotaxis and two-component systems (TCS), chemosensory regulation of alternative cellular functions (ACF) has not been clearly defined. The Che3 system in Myxococcus xanthus is a member of the ACF class of chemosensory systems and regulates development via the transcription factor CrdA (chemosensory regulator of development) (K. Wuichet and I. B. Zhulin, Sci. Signal. 3:ra50, 2010; J. R. Kirby and D. R. Zusman, Proc. Natl. Acad. Sci. U. S. A. 100:2008-2013, 2003). We have identified and characterized a homolog of NtrB, designated CrdS, capable of specifically phosphorylating the NtrC homolog CrdA in M. xanthus. Additionally, we demonstrate that the CrdSA two-component system is negatively regulated by CheA3, the central processor within the Che3 system of M. xanthus. To our knowledge, this study provides the first example of an ACF chemosensory system regulating a prototypical two-component system and extends our understanding of complex regulation of developmental signaling pathways.

Dataset Information

Seawater-regulated genes for two-component systems and outer membrane proteins in myxococcus.

Publications

Seawater-regulated genes for two-component systems and outer membrane proteins in myxococcus.

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