Identification of a divergent botulinum neurotoxin like gene cluster in Furfurilactobacillus

Abstract

Botulinum neurotoxins (BoNTs) are among the most potent biological toxins and are traditionally associated with Clostridium species. However, recent discoveries have identified BoNT-like proteins in diverse bacterial genera, revealing an expanding family of neurotoxins with unique evolutionary and functional traits. In this study, we report the identification of a novel BoNT-like gene cluster in Furfurilactobacillus sp. OKN36, encoding a toxin we tentatively designate as "Furfuritoxin". Sequence and structural analyses indicate that Furfuritoxin shares key domains with clostridial neurotoxins, including a light chain zinc metalloprotease domain and heavy chain translocase and binding domains, while exhibiting significant sequence divergence. Phylogenetic analysis places Furfuritoxin within a divergent lineage alongside previously reported BoNT/Wo, suggesting a shared ancestral relationship. Gene neighborhood analysis reveals features shared with other BoNT gene clusters including ORFX-related genes and conjugation-associated elements, indicating horizontal gene transfer may have facilitated its distribution. This study adds to the growing family of BoNT-like toxins, providing insights into their evolution and diversity.