Iturinic Lipopeptide Diversity in the Bacillus subtilis Species Group – Important Antifungals for Plant Disease Biocontrol Applications

Abstract

Iturins and closely related lipopeptides constitute a family of antifungal compounds known as iturinic lipopeptides that are produced by species in the Bacillus subtilis group. The compounds that comprise the family are: iturin, bacillomycin D, bacillomycin F, bacillomycin L, mycosubtilin, and mojavensin. These lipopeptides are prominent in many Bacillus strains that have been commercialized as biological control agents against fungal plant pathogens and as plant growth promoters. The compounds are cyclic heptapeptides with a variable length alkyl sidechain, which confers surface activity properties resulting in an affinity for fungal membranes. Above a certain concentration, enough molecules enter the fungal cell membrane to create a pore in the cell wall, which leads to loss of cell contents and cell death. This study identified 330 iturinic lipopeptide clusters in publicly available genomes from the B. subtilis species group. The clusters were subsequently assigned into distinguishable types on the basis of their unique amino acid sequences and then verified by HPLC MS/MS analysis. The results show some lipopeptides are only produced by one species, whereas certain others can produce up to three. In addition, four species previously not known to produce iturinic lipopeptides were identified. The distribution of these compounds among the B. subtilis group species suggests that they play an important role in their speciation and evolution.

Phylogenetic distribution of secondary metabolites in the Bacillus subtilis species complex

“…Mycosubtilin group detected in B. atrophaeus and few B. subtilis (mostly in subspecies spizizenii), bacillomycin in 3 of B. inaquosorum, whereas iturin A, bacillomycin D and bacillomycin F was spread across different B. velezensis and B. amyloliquefaciens isolates, confirming previouslyproposed species and strain level presence of iturinic lipopeptides(11). Initial examination of results also found BGCs to be split by the origin in B. velezensis Hx05; for ease of analysis, this strain was therefore dropped.…”

Structural and Functional Insights into Iturin W, a Novel Lipopeptide Produced by the Deep-Sea Bacterium Bacillus sp. Strain wsm-1

“…The iturinic lipopeptides also contain lipopeptides bacillomycin D, bacillomycin F, bacillomycin L, mycosubtilin, and mojavensin, which are mainly different in the amino acid sequences of the heptapeptides (3,12). In addition, these lipopeptides often contain a number of structural homologs with identical amino acid sequence of heptapeptide and different fatty acid chain (C14, C15 or C16), while the differences of biological activities among these lipopeptide homologs are seldom investigated (13,14).…”

Lipopéptidos producidos por agentes de control biológico del género Bacillus: revisión de herramientas analíticas utilizadas para su estudio

“…La identificación de lipopéptidos utilizando HPLC-ESI-MS/MS puede hacerse utilizando estándares de lipopéptidos mediante una comparación entre los valores m/z. Sin embargo, lo realmente útil de utilizar este sistema, es que permite hacer la identificación de lipopéptidos sin el uso de estándares (Dunlap et al, 2019). Esto se logra porque con el sistema HPLC-ESI-MS/MS es posible obtener simultáneamente la masa primaria (MS 1 ) de un compuesto -generalmente el compuesto intacto en forma de ión-y su masa secundaria (MS 2 ), generada a partir de la fragmentación del compuesto.…”