B. subtilis GS67 Protects C. elegans from Gram-Positive Pathogens via Fengycin-Mediated Microbial Antagonism

Abstract

Studies on Caenorhabditis elegans have provided detailed insight into host-pathogen interactions. Usually, the E. coli strain OP50 is used as food source for laboratory studies, but recent work has shown that a variety of bacteria have dramatic effects on C. elegans physiology, including immune responses. However, the mechanisms by which different bacteria impact worm resistance to pathogens are poorly understood. Although pathogen-specific immune priming is often discussed as a mechanism underlying such observations, interspecies microbial antagonism might represent an alternative mode of action. Here, we use several natural Bacillus strains to study their effects on nematode survival upon pathogen challenge. We show that B. subtilis GS67 persists in the C. elegans intestine and increases worm resistance to Gram-positive pathogens, suggesting that direct inhibition of pathogens might be the primary protective mechanism. Indeed, chemical and genetic analyses identified the lipopeptide fengycin as the major inhibitory molecule produced by B. subtilis GS67. Specifically, a fengycin-defective mutant of B. subtilis GS67 lost inhibitory activity against pathogens and was unable to protect C. elegans from infections. Furthermore, we found that purified fengycin cures infected worms in a dose-dependent manner, indicating that it acts as an antibiotic. Our results reveal a molecular mechanism for commensal-mediated C. elegans protection and highlight the importance of interspecies microbial antagonism for the outcome of animal-pathogen interactions. Furthermore, our work strengthens C. elegans as an in vivo model to reveal protective mechanisms of commensal bacteria, including those relevant to mammalian hosts.

Succession and dynamics of Pristionchus nematodes and their microbiome during decomposition of Oryctes borbonicus on La Réunion Island

“…While we keep more detailed analysis of individual genera and species for future studies investigating the interactions between nematodes and bacteria, we would like to point out that the family Enterobacteriaceae includes Escherichia coli , which is the most widely used food source of P. pacificus and C. elegans . Other bacterial families such as Bacillaceae , for which interactions with P. pacificus and C. elegans have been studied (Sinha et al ., ; Iatsenko et al ., ; Iatsenko et al ., ), were not found in high abundance.…”

“…Other bacterial families such as Bacillaceae, for which interactions with P. pacificus and C. elegans have been studied (Sinha et al, 2012;Iatsenko et al, 2014;Iatsenko et al, 2013), were not found in high abundance.…”

Characterization of Lipopeptide Biosurfactants Produced by Bacillus licheniformis MB01 from Marine Sediments

“…ESI/MS was applied to determine the molecular structures of all three main lipopeptides (Surfactins, iturins, and fengycins) (Pecci et al, 2010; Iatsenko et al, 2014). As one of the most important members of the lipopeptides family, the molecular structure of surfactins has the following characteristics: (1) a fatty acid chain linked with a seven-amino acids-peptide via its β-hydroxy; (2) the C-terminal amino acid residues of peptide that turns to cyclic compound; (3) positions 3 and 6 of N-terminal side of the peptide are Leu, position 5 is Asp, and position 2, 4, and 7 are non-determinate, generally Val, Leu or Ile (Horowitz and Griffin, 1991; Jacques, 2011).…”

C. elegans and its bacterial diet as a model for systems-level understanding of host–microbiota interactions

“…For instance, C. elegans fed B. subtilis GS67 (GS67) showed strong resistance to the pathogenic effects of B. thuringiensis DB27 (DB27) [36]. GS67 can inhibits growth of DB27 directly and also reduce the colonization of DB27 in C. elegans intestine.…”