Genetic and functional analysis of the DKxanthene biosynthetic gene cluster from Myxococcusstipitatus DSM 14675

Abstract

Myxobacteria are gram-negative soil bacteria that are well known for the production of diverse bioactive secondary metabolites [1-4]. DKxanthenes are a class of yellow pigments produced by myxobacteria belonging to the genera Myxococcus and Stigmatella (Fig. 1) [5, 6]. Myxococcus xanthus displays phase variations between yellow-and tan-phase cells [7]. DKxanthenes are produced by yellow-phase cells but not by tan-phase cells [8]. DKxanthenes are required for developmental sporulation in M. xanthus. Mutant cells of M. xanthus defective in DKxanthene biosynthesis produce severely reduced amounts of heat-resistant viable spores [5]. It has been suggested that tan-phase cells are the progenitors of spores and yellow-phase cells provide factors that tan-phase cells need to produce viable spores [9]. Later, DKxanthene was suggested as one of the factors needed by tan-phase cells for the maturation of spores in M. xanthus [5]. The majority of secondary metabolites isolated from myxobacteria are biosynthesized by polyketide synthases (PKSs) and/or non-ribosomal peptide synthases (NRPSs) [10]. DKxanthenes are also biosynthesized by PKSs and NRPSs. The structure of DKxanthenes from M. xanthus was elucidated and their biosynthetic gene clusters were identified in M. xanthus DK1622 and Stigmatella aurantiaca DW4/3-1 [5, 6]. The organization of the two biosynthetic gene clusters identified in M. xanthus DK1622 and S. aurantiaca DW4/3-1 was similar but not identical. Both clusters have core PKS and NRPS genes for the production of the DKxanthene backbone structure. However, S. aurantiaca has additional PKS genes, dkxQR and dkxT. The organization of the associated genes was also different (Fig. 2) [6]. A total of 13 DKxanthene derivatives were identified from M. xanthus DK1622, whereas S. aurantiaca DW4/3-1 was reported to produce five derivatives among them [6]. M. stipitatus is another species of the genus Myxococcus. M. stipitatus forms multicellular fruiting bodies consisting

Transcriptomic analysis of the Myxococcus xanthus FruA regulon, and comparative developmental transcriptomic analysis of two fruiting body forming species, Myxococcus xanthus and Myxococcus stipitatus

“…Although the M. stipitatus genome has been sequenced completely, little to nothing has been experimentally determined regarding the genetic and molecular mechanisms of fruiting body formation in M. stipitatus [ 44 ]. Indeed, publications about this organism are essentially limited to its use as a source for the identification and characterization of diverse natural products [ 45 – 47 ]. Here, we use RNAseq to compare the developmental transcriptomes of M. xanthus and M. stipitatus.…”

Interactions of Different Streptomyces Species and Myxococcus xanthus Affect Myxococcus Development and Induce the Production of DK-Xanthenes

“…The production of 13 yellow pigment derivatives of DK-xanthenes, encoded by a 47 kb cluster, by M. xanthus DK1050, was described as being crucial for M. xanthus [49]. The production of four new DK-xanthenes in M. xanthus has been described in a comparative study of DK-xanthenes from Myxococcus stipitatus DSM145675 and M. xanthus DK1622, and the antifungal activity of DK-xanthenes isolated from both species has also been shown [42]. Interestingly, upregulation of the expression of 10 DK-xanthene genes has recently been described in M. xanthus predation on Sinorhizobium meliloti [50].…”

“…The analysis of the molecules produced in this interaction revealed that peaks P1, P2, and P3, obtained from minute 3.8 to 5.8, corresponded to different DK-xanthenes, with DK-xanthene 574 being the most abundant compound [41,42]. Since DK-xanthenes are known to have antifungal activity [41,42], the antifungal activity of the controls (M. xanthus and S. peucetius) and the M. xanthus/S. peucetius coculture was checked through a bioassay using S. cerevisiae W303 as the sensitive strain.…”

“…Analysis of the organic extracts (ethyl acetate acidified) indicated that several compounds had been induced (Figure 6A). The analysis of the molecules produced in this interaction revealed that peaks P1, P2, and P3, obtained from minute 3.8 to 5.8, corresponded to different DK-xanthenes, with DK-xanthene 574 being the most abundant compound [41,42]. Since DK-xanthenes are known to have antifungal activity [41,42], the antifungal activity of the controls (M. xanthus and S. peucetius) and the M. xanthus/S.…”

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“…In detail, the antibacterial activity of althiomycin was demonstrated by Fujimoto, H. et al [24], whereas myxothiazol A strongly inhibits the growth of gram-positive bacteria and filamentous fungi by acting on the cytochrome bc1 complex [25,26]. Similarly, DKxanthene-518 was revealed to possess antioxidant activity (although the mechanism is unknown) [27] and inhibit the growth of fungi A. niger, C. albicans from the extract of strain M. stipitatus DSM 14675 [28], while the electron inhibitor myxalamide has inhibitory properties against bacteria, yeast, and fungi. Besides, myxochelin A was demonstrated with the antioxidant, antibacterial, and antiproliferative effects on K-562 white blood cells at the IC50 concentration of 1.9 μM and inhibited the invasion of mouse colon carcinoma 26-L5 cells at a non-cytotoxic concentration [29,30].…”