Identification of an rsh gene from a novosphingobium sp. necessary for quorum-sensing signal accumulation

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Title: Identification of an rsh gene from a novosphingobium sp. necessary for quorum-sensing signal accumulation
Author: Gan, Han Ming; Buckley, Larry; Szegedi, Erno; Hudson, André O.; Savka, Michael A.
Abstract: The stringent response is a mechanism by which bacteria adapt to environmental stresses and nutritional deficiencies through the synthesis and hydrolysis of (p)ppGpp by RelA/SpoT enzymes. Alphaproteobacteria and plants contain a single Rsh enzyme (named for RelA/SpoT homolog) that is bifunctional. Here we report the identification of a new species of bacteria belonging to the genus Novosphingobium and characterization of an rsh mutation in this plant tumor-associated isolate. Isolate Rr 2-17, from a grapevine crown gall tumor, is a member of the Novosphingobium genus that produces the N-acyl-homoserine lactone (AHL) quorum-sensing (QS) signals. A Tn5 mutant, Hx 699, deficient in AHL production was found to have an insertion in an rsh gene. The Rsh protein showed significant percent sequence identity to Rsh proteins of alphaproteobacteria. The Novosphingobium sp. rsh gene (rshNsp) complemented the multiple amino acid requirements of the Escherichia coli relA spoT double mutant by restoring the growth on selection media. Besides QS signal production, the rsh mutation also affects soluble polysaccharide production and cell aggregation. Genetic complementation of the Hx 699 mutant with the rshNsp gene restored these phenotypes. This is the first discovery of a functional rsh gene in a member of the Novosphingobium genus.
Description: April 2009 article from the journal of bacteriology. Please see http://journals.asm.org/ for more information.
Record URI: http://hdl.handle.net/1850/10235
Date: 2009-04

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