Deciphering regulatory mechanisms for secondary metabolite production in the myxobacterium Sorangium cellulosum So ce56

Abstract

SummarySorangium cellulosum strains produce approximately 50% of the biologically active secondary metabolites known from myxobacteria. These metabolites include several compounds of biotechnological importance such as the epothilones and chivosazols, which, respectively, stabilize the tubulin and actin skeletons of eukaryotic cells. S. cellulosum is characterized by its slow growth rate, and natural products are typically produced in low yield. In this study, biomagnetic bead separation of promoter-binding proteins and subsequent inactivation experiments were employed to identify the chivosazol regulator, ChiR, as a positive regulator of chivosazol biosynthesis in the genome-sequenced strain So ce56. Overexpression of chiR under the control of T7A1 promoter in a merodiploid mutant resulted in fivefold overproduction of chivosazol in a kinetic shake flask experiment, and 2.5-fold overproduction by fermentation. Using quantitative reverse transcription PCR and gel shift experiments employing heterologously expressed ChiR, we have shown that transcription of the chivosazol biosynthetic genes (chiA-chiF) is directly controlled by this protein. In addition, we have demonstrated that ChiR serves as a pleiotropic regulator in S. cellulosum, because mutant strains lack the ability to develop into regular fruiting bodies.

Complete genome sequence of the myxobacterium Sorangium cellulosum

“…The genus Sorangium produces B50% of all known myxobacterial metabolites. Sequencing of this model Sorangium therefore opens the way to understanding the molecular details of the regulatory processes governing cell differentiation and secondary metabolism in other S. cellulosum strains, as demonstrated recently for chivosazol biosynthesis 38 . Such information should in future facilitate increased exploitation of the metabolic potential of the more than 1,800 Sorangium strains available from the German Collection of Microorganisms and Cell Cultures, including the epothilone producer S. cellulosum So ce90.…”

Identification of Additional Players in the Alternative Biosynthesis Pathway to Isovaleryl‐CoA in the Myxobacterium Myxococcus xanthus

“…This phenotype could be complemented to wild-type levels by the addition of IVA or DMAA. However, as an insertion into any gene of the aibR--mvaS operon would most likely exhibit polar effects and thus directly influence expression of mvaS, we complemented the Dbkd/ mvaS (DK5624) and Dbkd/MXAN_4265 (HB015) double mutants genetically by addition of a copy of mvaS under control of the constitutive T7A1-promotor; [27] this resulted in strains HB019 (Dbkd, mvaS::kan, mvaS + ) and HB020 (Dbkd, MXAN_ 4265::kan, mvaS + ). Whereas the fatty acid profile of HB019 was similar to the wild-type cells as expected, no complementation was observed for HB020 (Table 4).…”

Discovery of the Autonomously Replicating Plasmid pMF1 from Myxococcus fulvus and Development of a Gene Cloning System in Myxococcus xanthus

“…In the past few decades, genetic studies of myxobacteria were performed mainly with the model species Myxococcus xanthus using transduction (7, 23) and the more efficient electroporation protocols (19). Besides these studies, Sorangium strains were also studied using conjugation protocols (13,14,22,31,33). Sorangium is a special cellulose degrader among the 17 myxobacterial genera (34, 50) and produces almost one-half of the known secondary metabolites produced by myxobacteria (8).…”