Around 25% of vegetable food is lost worldwide because of infectious plant diseases, including microbe-induced decay of harvested crops. In wet seasons and under humid storage conditions, potato tubers are readily infected and decomposed by anaerobic bacteria (Clostridium puniceum). We found that these anaerobic plant pathogens harbor a gene locus (type II polyketide synthase) to produce unusual polyketide metabolites (clostrubins) with dual functions. The clostrubins, which act as antibiotics against other microbial plant pathogens, enable the anaerobic bacteria to survive an oxygen-rich plant environment.

Metabolic profiling and genome mining revealed that anaerobic bacteria have the potential to produce acyloin natural products. In addition to sattazolin A and B, three new sattazolin congeners and a novel acyloin named clostrocyloin were isolated from three strains of Clostridium beijerinckii, a bacterium used for industrial solvent production. Bioactivity profiling showed that the sattazolin derivatives possess antimicrobial activities against mycobacteria and pseudomonads with only low cytotoxicity. Clostrocyloin was found to be mainly active against fungi. The thiamine diphosphate (ThDP)dependent sattazolin-producing synthase was identified in silico and characterized both in vivo and in in vitro enzyme assays. A related acyloin synthase from the clostrocyloin producer was shown to be responsible for the production of the acyloin core of clostrocyloin. The biotransformation experiments provided first insights into the substrate scope of the clostrocyloin synthase and revealed biosynthetic intermediates.

A novel antimycobacterial natural product, clostroindolin, was discovered from the anaerobic bacterium Clostridium beijerinckii.

Anaerobic bacteria have only recentlyb een recognizeda sasource of antibiotics;y et, the metabolic potential of Negativicutes (Gram-negative stainingF irmicutes) such as the oak-associated Dendrosporobacter quercicolus has remained unknown. Genome mining of D. quercicolus and phylogenetic analyses revealed ag ene cluster for at ype II polyketide synthase (PKS)c omplex that belongs to the most ancestral enzyme systems of this type. Metabolic profiling, NMR analyses,a nd stable-isotope labeling led to the discovery of an ew family of anthraquinone-type polyphenols, the dendrubins, which are diversified by acylation, methylation,a nd dimerization. Dendrubin Aa nd Bw ere identified as stronga ntibiotics againstarange of clinically relevant,h uman-pathogenic mycobacteria.