Search

Proteins MiaA and MiaB catalyze sequential isopentenylation and methylthiolation, respectively, of adenosine residue in 37th position of tRNA XXA . The mia mutations were recently shown by us to affect secondary metabolism and morphology of Streptomyces. However, it remained unknown as to whether both or one of the aforementioned modifications is critical for colony development and antibiotic production. Here, we addressed this issue through analysis of Streptomyces albus J1074 strains carrying double miaAmiaB knockout or extra copy of miaB gene. The double mutant differed from wild-type and miaA-minus strains in severity of morphological defects, growth dynamics, and secondary metabolism. Introduction of extra copy of miaB gene into miaA mutant restored aerial mycelium formation to the latter on certain solid media. Hence, miaB gene might be involved in tRNA thiomethylation in the absence of miaA; either MiaA- or MiaB-mediated modification appears to be enough to support normal metabolic and morphological processes in Streptomyces.

Analysis of the draft sequence of the genome of teicoplanin producer Actinoplanes teichomyceticus (NRRL-B16726) led to identification of several genes encoding AraC-family regulators that resemble AdpA, master regulator of transcription in Streptomyces. We elucidated possible regulatory functions of one of the identified genes, adpA19(at), most similar to archetypal adpA from model Streptomyces species, in a series of expression experiments. Introduction of adpA19 at under control of its own promoter on moderate copy number vector pKC1139 into NRRL-B16726 had no influence on antibiotic production and sporulation. Introduction of adpA19 at into Streptomyces coelicolor M145 and several S. ghanaensis strains had major influence on antibiotic production by these bacteria. Finally, adpA19 at expression in a set of soil actinomycete isolates led to induction of synthesis of antibiotic compounds. Our data point to pleiotropic regulatory role of adpA19(at), warranting its use as a tool to manipulate secondary metabolome of actinomycetes.

The cell wall of the model actinomycete Streptomyces coelicolor M145 has recently been shown to contain the novel glycopolymer teichulosonic acid. The major building block of this polymer is 2-keto-3-deoxy-D-glycero-D-galacto-nononic acid (Kdn), suggesting initial clues about the genetic control of biosynthesis of this cell wall component. Here, through genome mining and gene knockouts, we demonstrate that the sco4879-sco4882 genomic region of S. coelicolor M145 is necessary for biosynthesis of teichulosonic acid. Specifically, mutants carrying individual knockouts of sco4879, sco4880 and sco4881 genes do not produce Kdn-containing glycopolymer and instead accumulate the minor cell wall component poly(diglycosyl 1-phosphate). Our studies provide evidence that this region is at least partly responsible for biosynthesis of Kdn, whereas flanking genes might control the other steps of teichulosonic acid formation.