Journal of Bacteriology, July 2000, p. 3913-3919, Vol. 182, No. 14
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

andBIOMERIT Research Centre, Department of Microbiology, National University of Ireland, Cork, Cork, Ireland
Received 10 January 2000/Accepted 24 April 2000
The GacS-GacA two-component signal transduction system, which is
highly conserved in gram-negative bacteria, is required for the
production of exoenzymes and secondary metabolites in
Pseudomonas spp. Screening of a Pseudomonas
fluorescens F113 gene bank led to the isolation of a previously
undefined locus which could restore secondary metabolite production to
both gacS and gacA mutants of F113. Sequence
analysis of this locus demonstrated that it did not contain any obvious
Pseudomonas protein-coding open reading frames or
homologues within available databases. Northern analysis indicated that
the locus encodes an RNA (PrrB RNA) which is able to phenotypically
complement gacS and gacA mutants and is itself regulated by the GacS-GacA two-component signal transduction system. Primer extension analysis of the 132-base transcript identified the
transcription start site located downstream of a
70
promoter sequence from positions
10 to
35. Inactivation of the
prrB gene in F113 resulted in a significant reduction of
2,4-diacetylphloroglucinol (Phl) and hydrogen cyanide (HCN) production,
while increased metabolite production was observed when
prrB was overexpressed. The prrB gene sequence
contains a number of imperfect repeats of the consensus sequence
5'-AGGA-3', and sequence analysis predicted a complex secondary
structure featuring multiple putative stem-loops with the consensus
sequences predominantly positioned at the single-stranded regions at
the ends of the stem-loops. This structure is similar to the CsrB and
RsmB regulatory RNAs in Escherichia coli and Erwinia carotovora, respectively. Results suggest that a regulatory RNA molecule is involved in GacA-GacS-mediated regulation of Phl and HCN
production in P. fluorescens F113.
Present address: Cork Cancer Research Centre, Mercy Hospital, Cork, Ireland.
Present address: Department of Food Technology, National
University of Ireland, Cork, Cork, Ireland.
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