Effect of lipopeptides of antagonistic strains of Bacillus subtilis on the morphology and ultrastructure of the cucurbit fungal pathogen Podosphaera fusca.
OBJECTIVE
To analyse the morphological and ultrastructural effects of lipopeptides of cell-free liquid cultures from the antagonistic Bacillus subtilis strains, UMAF6614 and UMAF6639, on the cucurbit powdery mildew fungus, Podosphaera fusca, conidial germination.


RESULTS
Butanolic extracts from cell-free supernatants of B. subtilis cultures were tested for their ability to arrest P. fusca conidial germination using the zucchini cotyledon disc method. Previously, the occurrence of lipopeptide antibiotics fengycin, iturin/bacillomycin and surfactin in the extracts was verified by diverse chromatographic approaches. Conidial germination was strongly reduced by antifungal extracts obtained from liquid cultures of both B. subtilis strains. Scanning electron microscopy analysis showed morphological damage in conidia characterized by the presence of large depressions and loss of turgidness. Transmission electron microscopy analysis revealed severe modifications in the plasma membrane and disorganization of the P. fusca cell cytoplasm.


CONCLUSIONS
The lipopeptides produced by the two strains of B. subtilis are able to reduce cucurbit powdery mildew disease by arresting conidial germination, which seems to result from the induction of important cytological alterations.


CONCLUSIONS
We elucidated the mechanisms employed by these antagonistic strains of B. subtilis to suppress cucurbit powdery mildew disease and delineate the ultrastructural damages responsible for their suppressive effect.
Romero
D
D
Departamento de Microbiología, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain.
de Vicente
A
A
Olmos
J L
JL
Dávila
J C
JC
Pérez-García
A
A
D000898:Antibiosis / Q000502:physiology*; D000935:Antifungal Agents / Q000494:pharmacology; D001203:Ascomycota / Q000187:drug effects* / Q000254:growth & development / Q000648:ultrastructure; D001412:Bacillus subtilis / Q000145:classification / Q000378:metabolism* / Q000502:physiology; D001426:Bacterial Proteins / Q000494:pharmacology*; D017077:Culture Media, Conditioned / Q000494:pharmacology; D008074:Lipoproteins / Q000494:pharmacology*; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D010572:Pest Control, Biological / Q000379:methods; D013172:Spores, Fungal / Q000187:drug effects / Q000254:growth & development / Q000648:ultrastructure
D000935:Antifungal Agents; D001426:Bacterial Proteins; D017077:Culture Media, Conditioned; D008074:Lipoproteins