Lipopeptide production in Pseudomonas sp. strain DSS73 is regulated by components of sugar beet seed exudate via the Gac two-component regulatory system.
Pseudomonas sp. strain DSS73 isolated from the sugar beet rhizosphere produces the cyclic lipopeptide amphisin, which inhibits the growth of plant-pathogenic fungi. By Tn5::luxAB mutagenesis, we obtained two nonproducing mutant strains, DSS73-15C2 and DSS73-12H8. The gene interrupted by the transposon in strain DSS73-15C2 (amsY) encoded a protein with homology to peptide synthetases that was designated amphisin synthetase. DSS73-12H8 carried the transposon in a regulatory gene encoding a protein with homology to the sensor kinase GacS. Growth of strain DSS73-15C2 (amsY) was impaired during the transition to stationary phase in a minimal medium amended with an exudate of sugar beet seeds. This growth phenotype could be complemented by purified amphisin. Seed exudate further induced expression of bioluminescence from the amsY::luxAB reporter during the transition to stationary phase. This agreed with an increase in amphisin production by the DSS73 wild-type strain during early stationary phase. Amphisin synthesis in DSS73 was strictly dependent on GacS, and even induction by seed exudate depended on a functional gacS locus. Hence, a signal triggering the GacS/GacA two-component system appeared to be present in the seed exudate.
Section of Genetics and Microbiology, Department of Ecology, Royal Veterinary and Agricultural University, DK-1871 Frederiksberg C, Denmark.
Birgit
B
Koch
Tommy H
TH
Nielsen
Dan
D
Sørensen
Jens Bo
JB
Andersen
Carsten
C
Christophersen
Søren
S
Molin
Michael
M
Givskov
Jan
J
Sørensen
Ole
O
Nybroe
D001426:Bacterial Proteins / Q000378:metabolism; D027461:Beta vulgaris / Q000737:chemistry*; D004251:DNA Transposable Elements / Q000235:genetics; D016296:Mutagenesis; D010453:Peptide Synthases / Q000096:biosynthesis / Q000378:metabolism; D010456:Peptides, Cyclic / Q000378:metabolism*; D010641:Phenotype; D010936:Plant Extracts / Q000494:pharmacology; D011549:Pseudomonas / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D012639:Seeds / Q000737:chemistry*; D014157:Transcription Factors / Q000378:metabolism
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; C091100:GacA protein, Bacteria; D010456:Peptides, Cyclic; D010936:Plant Extracts; D014157:Transcription Factors; C438267:amphisin; C074165:lemA protein, bacterial; D010453:Peptide Synthases