Open AccessThe alternative σ factor HrpL negatively modulates the flagellar system in the phytopathogenic bacterium Erwinia amylovora under hrp ‐inducing conditions
Author(s) -
Cesbron Sophie,
Paulin JeanPierre,
Tharaud Michel,
Barny MarieAnne,
Brisset MarieNoëlle
Publication year - 2006
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2006.00172.x
Subject(s) - flagellin , virulence , biology , sigma factor , microbiology and biotechnology , type three secretion system , flagellum , erwinia , bacteria , mutant , virulence factor , motility , secretion , regulator , escherichia coli , genetics , gene , biochemistry , rna polymerase
In this work we present evidence of an opposite regulation in the phytopathogenic bacteria Erwinia amylovora between the virulence‐associated Type III secretion system (TTSS) and the flagellar system. Using loss‐of‐function mutants we show that motility enhanced the virulence of wild‐type bacteria relative to a nonmotile mutant when sprayed on apple seedlings with unwounded leaves. Then we demonstrated through analyses of motility, flagellin export and visualization of flagellar filament that HrpL, the positive key regulator of the TTSS, also down‐regulates the flagellar system. Such a dual regulation mediated by an alternative σ factor of the TTSS appears to be a level of regulation between virulence and motility not yet described among Proteobacteria.