Identification of a diguanylate cyclase expressed in the presence of plants and its application for discovering candidate gene products involved in plant colonization by Pantoea sp. YR343.

Microbial colonization of plant roots is a highly complex process that requires the coordination and regulation of many gene networks, yet the identities and functions of many of these gene products have yet to be discovered. Pantoea sp. YR343, a gamma-proteobacterium isolated from the rhizosphere of Populus deltoides, forms robust biofilms along the root surfaces of Populus and possesses plant growth-promoting characteristics. In this work, we identified three diguanylate cyclases in the plant-associated microbe Pantoea sp. YR343 that are expressed in the presence of plant roots. One of these diguanylate cyclases, DGC2884, localizes to discrete sites in the cells and its overexpression results in reduced motility and increased EPS production and biofilm formation. We performed a genetic screen by expressing this diguanylate cyclase from an inducible promoter in order to identify candidate gene products that may be involved in root colonization by Pantoea sp. YR343. Further, we demonstrate the importance of other domains in DGC2884 to its activity, which in combination with the genes identified by transposon mutagenesis, may yield insights into the mechanisms of plant association as well as the activity and regulation of homologous enzymes in medically and agriculturally relevant microbes.

Disparate outer membrane exclusionary properties underlie intrinsic resistance to hydrophobic substances in Pseudomonas spp. isolated from surface waters under triclosan selection.

Representative members of surface water microbiota were obtained from three unrelated municipal sites in Oklahoma by direct plating under selection by the hydrophobic biocide triclosan. Multiple methods were employed to determine if intrinsic triclosan resistance reflected resistance to hydrophobic molecules by virtue of outer membrane impermeability. While all but one organism isolated in the absence of triclosan were able to initiate growth on MacConkey agar, only one was able to initiate significant growth with triclosan present. In contrast, all bacteria selected with triclosan were identified as Pseudomonas spp. using 16S RNA gene sequencing and exhibited growth comparable to Pseudomonas aeruginosa controls in the presence of hydrophobic antibacterial agents to include triclosan. Two representative bacteria isolated in the absence of triclosan allowed for greater outer membrane association with the fluorescent hydrophobic probe 1-N-phenylnapthylamine than did two triclosan-resistant isolates. Compound 48/80 disruption of outer membrane impermeability properties for hydrophobic substances either partially or fully sensitized nine of twelve intrinsically resistant isolates to triclosan. These data suggest that outer membrane exclusion underlies intrinsic resistance to triclosan in some, but not all Pseudomonas spp. isolated by selection from municipal surface waters and implicates the involvement of concomitant triclosan resistance mechanisms.

Hand eczema among Hong Kong nurses: a self-report questionnaire survey conducted in a regional hospital.

BACKGROUND: Hand eczema is common in the nursing profession, and has been reported widely in various parts of the world. OBJECTIVES: The aim of this study was to determine the prevalence and severity of hand eczema among nurses working in a regional hospital in Hong Kong, as well as its psychosocial impact and any possible associated risk factors. PATIENTS/MATERIALS/METHODS: The study took the form of a self-report questionnaire survey; 1240 nurses in a regional hospital were asked to participate in the survey by completing the questionnaire and returning it anonymously within 2 weeks. RESULTS: Seven hundred and twenty-four nurses returned the questionnaire (a response rate of 59%). The prevalence of hand eczema among the respondents was 22.1% (160/724). More than 90% had moderate to severe hand eczema. Itchiness and dryness were the most common symptoms. Occupational work, housework, mood, social activities and sleep were particularly affected. Multinomial logistic regressions showed that a personal or family history of atopy and a hand washing frequency of >20 times per day were independent risk factors for hand eczema. CONCLUSIONS: Hand eczema is common and severe among Hong Kong nurses. The results of this study suggest that hand eczema is an important problem for nurses and that preventive measures should be emphasized.