Structural Characterization and Multiomics Analysis Reveal Extensive Diversity and Global Distribution of Kurstakin Lipopeptides

Bacillus species,
particularly those investigated
as biocontrol agents, are known to produce a cocktail of bioactive
lipopeptides that act synergistically to shape the ecological function
of these beneficial microbes. However, while certain families of lipopeptides
are well-characterized, others remain elusive. Herein, we describe
the characterization of the kurstakins, a family of lipopeptides associated
with promising biocontrol properties but that lack adequate characterization.
Metabolomic analyses of a semipurified Bacillus cereus EM195W extract fraction revealed the presence of approximately 50
cyclic- and linear-peptide analogs. Deeper analyses revealed that
the chemical diversity stems from the diverse lipid tails, including
linear, iso-, and anteiso-lipid
tails ranging from C8–C18, along with
several hydroxylated lipid tails. Isolation and complete structural
analysis of two new analogs represented the first kurstakin analogs
characterized by NMR and provided the first experimental analyses
for deducing their absolute configuration. Finally, analysis of publicly
available genomic and MS data provided insights into the true chemical
diversity and distribution of the kurstakins. These results expand
our understanding of this family of compounds, opening the door for
determining their ecological functions and the role they play in the
broader activity of biocontrol agents.