The lipopeptides mycosubtilin and surfactin enhance spreading of Bacillus subtilis strains by their surface-active properties
The colonizing behaviour and the pellicle formation of Bacillus subtilis strains producing different families of lipopeptides were evaluated under several cultural conditions. The pattern of lipopeptides produced determined the architecture of the colony on a swarming medium as well as the flotation and the thickness of the pellicle formed at the air/liquid interface. The overproduction of mycosubtilin, a lipopeptide of the iturin family, led to increased spreading but had no effect on pellicle formation. A physico-chemical approach was developed to gain an insight into the mode of action of the biosurfactants facilitating the colonization. A relationship between surface tension of the culture medium and spreading of a lipopeptide non-producing strain, B. subtilis 168, was established. Goniometry was used to highlight the modification of the in situ wettability in the area where spreading was enhanced. On a solid medium, co-cultures of a surfactin producing with other strains showed a diffusion ring of the surfactin around the colony. This ring characterized by a higher wettability favoured the propagation of other colonies.
KeywordsBacillus subtilis Spreading Swarming Surfactin Mycosubtilin Surface tension Wettability
This work received financial supports from the Université des Sciences et Technologies de Lille, the Région Nord-Pas-de-Calais and the Fonds Européen pour le Développement de la Recherche. We are particularly grateful to Dr Christine Faille (INRA, Villeneuve d’Ascq, France) for allowing and explaining the use of the goniometer. P. Fickers was a recipient of a Post-Doc grant from the Université des Sciences et Technologies de Lille.
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