Impact of rhizosphere factors on cyclic lipopeptide signature  from the plant beneficial strain Bacillus amyloliquefaciens S499.
Cyclic lipopeptides (cLPs) of the surfactin, iturin and fengycin families synthesized by plant-associated Bacilli represent an important class of antibiotics as they may be tightly involved in the protective effect of selected strains against phytopathogens. However, their production by Bacillus cells developing on roots under rhizosphere conditions is still poorly understood. In this work, we combined electrospray and imaging mass spectrometry-based approaches to determine the detailed pattern of surfactins, iturins and fengycins produced in planta by Bacillus amyloliquefaciens S499. Very different production rates were observed for the three cLPs families. Whereas surfactin accumulated in significant amounts, much lower quantities of iturins and fengycins were detected in the environment of colonized roots in comparison with laboratory medium. In addition, the surfactin pattern produced by strain S499 evolving on roots is enriched in homologues with long fatty acid chains (C15) compared with the chains typically secreted under in vitro conditions. Additional experiments revealed that lipopeptide production by root-associated S499 cells is qualitatively and quantitatively dictated by the specific nutritional context of the rhizosphere (exudates enriched in organic acids, oxygen limitation) but also by the formation of biofilm-related structures around root hairs. As surfactins, iturins and fengycins retain specific functions and bioactivities, the biological relevance of their differential production observed in planta is discussed in the context of biocontrol of plant diseases.
Walloon Center for Industrial Biology, University of Liège/Gembloux Agro-Bio Tech, Gembloux, Belgium.
Venant
V
Nihorimbere
Hélène
H
Cawoy
Alexandre
A
Seyer
Alain
A
Brunelle
Philippe
P
Thonart
Marc
M
Ongena
D001407:Bacillus / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D018441:Biofilms; D005227:Fatty Acids; D055666:Lipopeptides / Q000032:analysis / Q000378:metabolism*; D010935:Plant Diseases / Q000382:microbiology; D018517:Plant Roots / Q000382:microbiology; D010944:Plants / Q000382:microbiology; D058441:Rhizosphere
D005227:Fatty Acids; D055666:Lipopeptides; C049972:fengycin