Article

The mosaic structure of the mcyABC operon in Microcystis

University of Oslo, Department of Molecular Biosciences, 0316 Oslo, Norway.
Microbiology (Impact Factor: 2.84). 08/2008; 154(Pt 7):1886-99. DOI: 10.1099/mic.0.2007/015875-0
Source: PubMed

ABSTRACT An extensive study of the mcyABC genes and regions flanking the mcy gene cluster was performed in naturally occurring Microcystis strains. Lack of methylation in strains producing only desmethyl(7)-microcystin was found to be associated with point mutations in substrate-binding sequence motifs of the N-methyltransferase (NMT) domain in McyA. Multiple recombination events giving rise to 'phylogenetic mosaics' were detected within the NMT-domain-encoding mcyA sequences and the adenylation (A) domain sequences of mcyB and mcyC. Recombination leading to exchanges between the mcyB and mcyC regions encoding A domains in modules McyB1 and McyC was also detected. A previously reported replacement of the A domain in McyB1 was found to involve the region between the conserved motifs A3 and A8/A9. In all microcystin-producing strains the mcy gene cluster was flanked by the genes uma1 and dnaN. Clear indications of recombination, an insertion element and footprints of IS elements were found in the dnaN-mcyJ intergenic region. Among the non-microcystin producers, uma1 and dnaN were linked in some, but not all strains. Most non-producing strains lacked all mcy genes, while one strain possessed a partially deleted mcy operon. Our results show that frequent horizontal gene transfer events in addition to point mutations and insertions/deletions contribute to variation in the mcy gene cluster.

Download full-text

Full-text

Available from: Ave Tooming-Klunderud, Sep 02, 2015
0 Followers
 · 
118 Views
 · 
116 Downloads
  • Source
    • "In other Planktothrix-dominated European lakes, the presence of at least one of the five demethylated MCs was also recorded (Barco et al. 2004; Welker et al. 2004a; Kurmayer et al. 2005; Briand et al. 2005; Welker and Erhard 2007; Bauman and Jüttner 2008; Tooming-Klunderud et al. 2008; Rohrlack et al. 2009; Rounge et al. 2009). Four of the microcystins (m/z 981, 1,024, 1,031, 1,045) were identified in field samples and in the P. agardhii isolates from Viry-Chãtillon’s lake in France (Yépremian et al. 2007). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Planktothtrix agardhii (Oscillatoriales) is a filamentous cyanobacterium, which frequently forms blooms in shallow, polymictic and eutrophicated waters. This species is also a rich source of unique linear and cyclic peptides. In the current study, the profile of the peptides in samples from the P. agardhii-dominated Siemianówka Dam Reservoir (SDR) (northeast Poland) was analyzed for four subsequent years (2009–2012). The LC–MS/MS analyses revealed the presence of 33 peptides. Twelve of the most abundant ones, including five microcystins, five anabaenopeptins, one aeruginosin and one planktocyclin, were present in all field samples collected during the study. The detection of different peptides in two P. agardhii isolates indicated that the SDR population was composed of several chemotypes, characterized by different peptide patterns. The total concentration of microcystins (MCs) positively correlated with the biomass of P. agardhii. Between subsequent years, the changes in the ratio of the total MCs concentration to the biomass of P. agardhii were noticed, but they were less than threefold. This is the first study on the production of different classes of non-ribosomal peptides by freshwater cyanobacteria in Poland. Electronic supplementary material The online version of this article (doi:10.1007/s00203-014-1008-9) contains supplementary material, which is available to authorized users.
    Archives of Microbiology 06/2014; 196(10). DOI:10.1007/s00203-014-1008-9 · 1.86 Impact Factor
  • Source
    • "Positive selection acting on the adenylation domains of McyB1 and McyC was reported as the possible cause of the large number of microcystin variants produced by cyanobacteria [24]. Deletion of the entire N-methyltransferase domain of mcyA in Anabaena or point mutations in this gene in Microcystis were associated with the absence of N-methylation in the microcystins produced by these strains [23,26]. Furthermore, recombination in the same region (mcyA1) was related to the synthesis of microcystins containing 2-amino-2-butenoic acid (Dhb) in some strains of the genus Planktothrix[25]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Background Many important toxins and antibiotics are produced by non-ribosomal biosynthetic pathways. Microcystins are a chemically diverse family of potent peptide toxins and the end-products of a hybrid NRPS and PKS secondary metabolic pathway. They are produced by a variety of cyanobacteria and are responsible for the poisoning of humans as well as the deaths of wild and domestic animals around the world. The chemical diversity of the microcystin family is attributed to a number of genetic events that have resulted in the diversification of the pathway for microcystin assembly. Results Here, we show that independent evolutionary events affecting the substrate specificity of the microcystin biosynthetic pathway have resulted in convergence on a rare [D-Leu1] microcystin-LR chemical variant. We detected this rare microcystin variant from strains of the distantly related genera Microcystis, Nostoc, and Phormidium. Phylogenetic analysis performed using sequences of the catalytic domains within the mcy gene cluster demonstrated a clear recombination pattern in the adenylation domain phylogenetic tree. We found evidence for conversion of the gene encoding the McyA2 adenylation domain in strains of the genera Nostoc and Phormidium. However, point mutations affecting the substrate-binding sequence motifs of the McyA2 adenylation domain were associated with the change in substrate specificity in two strains of Microcystis. In addition to the main [D-Leu1] microcystin-LR variant, these two strains produced a new microcystin that was identified as [Met1] microcystin-LR. Conclusions Phylogenetic analysis demonstrated that both point mutations and gene conversion result in functional mcy gene clusters that produce the same rare [D-Leu1] variant of microcystin in strains of the genera Microcystis, Nostoc, and Phormidium. Engineering pathways to produce recombinant non-ribosomal peptides could provide new natural products or increase the activity of known compounds. Our results suggest that the replacement of entire adenylation domains could be a more successful strategy to obtain higher specificity in the modification of the non-ribosomal peptides than point mutations.
    BMC Evolutionary Biology 04/2013; 13(1):86. DOI:10.1186/1471-2148-13-86 · 3.41 Impact Factor
  • Source
    • "Intriguingly, this region almost precisely corresponds to the amino acid recognition pocket previously identified in structural studies (Conti et al., 1997). These features provide direct insights into the evolution of NRPS systems, suggesting a scenario in which new NRPS functionality can already arise by recombinatorial exchange of only short DNA stretches covering the specificity region, in addition to the previously observed exchanges of entire modules (Rounge et al., 2008), A domains (Fewer et al., 2007; Ishida et al., 2009), or multiple regions (Tooming-Klunderud et al., 2008). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Hormaomycin produced by Streptomyces griseoflavus is a structurally highly modified depsipeptide that contains several unique building blocks with cyclopropyl, nitro, and chlorine moieties. Within the genus Streptomyces, it acts as a bacterial hormone that induces morphological differentiation and the production of bioactive secondary metabolites. In addition, hormaomycin is an extremely potent narrow-spectrum antibiotic. In this study, we shed light on hormaomycin biosynthesis by a combination of feeding studies, isolation of the biosynthetic nonribosomal peptide synthetase (NRPS) gene cluster, and in vivo and in vitro functional analysis of enzymes. In addition, several nonnatural hormaomycin congeners were generated by feeding-induced metabolic rerouting. The NRPS contains numerous highly repetitive regions that suggest an evolutionary scenario for this unusual bacterial hormone, providing new opportunities for evolution-inspired metabolic engineering of novel nonribosomal peptides.
    Chemistry & biology 03/2011; 18(3):381-91. DOI:10.1016/j.chembiol.2010.12.018 · 6.59 Impact Factor
Show more