Investigation of secondary metabolism in the industrial butanol hyper-producer Clostridium saccharoperbutylacetonicum N1-4

Abstract

Clostridium saccharoperbutylacetonicum N1-4 (Csa) is a historically significant anaerobic bacterium which can perform saccharolytic fermentations to produce acetone, butanol, and ethanol (ABE). Recent genomic analyses have highlighted this organism’s potential to produce polyketide and nonribosomal peptide secondary metabolites, but little is known regarding the identity and function of these metabolites. This study provides a detailed bioinformatic analysis of seven biosynthetic gene clusters (BGCs) present in the Csa genome that are predicted to produce polyketides/nonribosomal peptides. An RNA-seq-based untargeted transcriptomic approach revealed that five of seven BGCs were expressed during ABE fermentation. Additional characterization of a highly expressed nonribosomal peptide synthetase gene led to the discovery of its associated metabolite and its biosynthetic pathway. Transcriptomic analysis suggested an association of this nonribosomal peptide synthetase gene with butanol tolerance, which was supported by butanol challenge assays.

Sporulation in solventogenic and acetogenic clostridia

“…Polyketides have been studied in C. acetobutylicum and C. saccharoperbutylacetonicum . In C. saccharoperbutylacetonicum, polyketides involved in sporulation initiation, solvent formation, and tolerance were detected (Kosaka et al 2007 ; Li et al 2020a ). In C. acetobutylicum , three polyketides were detected, and the structures of two of them, clostrienose and clostrienoic acid, were solved (Herman et al 2017 ).…”

Chain release mechanisms in polyketide and non-ribosomal peptide biosynthesis

“…Examples of primary alcohol-containing natural products produced by four-electron R domains include myxochelin A, 156,157 myxalamid A (44), 146,171 lyngbyatoxin, 172 and, recently, a dipeptide produced by the industrially important Clostridium saccharoperbutylacetonicum N1-4. 173 Myxochelin A is related to the aldehyde myxochelin B described in the previous section. Myxochelin A is formed if a second reduction reaction occurs before aldehyde transamination can occur.…”

Induced Production, Synthesis, and Immunomodulatory Action of Clostrisulfone, a Diarylsulfone from Clostridium acetobutylicum

“…However, in most cases the gene clusters are silent and need to be activated by means of particular stimuli. Several genetic and chemical approaches to triggering biosynthesis [5] have been applied to clostridia, [3a, 6] A range of antibiotics, such as closthioamides, [3a, 7] clostrubins, [8] clostrindoline, [9] antibacterial acyloins, [10] and a new lipopeptide [11] have been isolated from various clostridia. Mining the genome sequence of C. acetobutylicum [12] pointed to a high biosynthetic potential [4] .…”