Puwainaphycins (PUWs) and minutissamides (MINs) are structurally analogous cyclic lipopeptides possessing cytotoxic activity. Both types of compound exhibit high structural variability, particularly in the fatty acid (FA) moiety. Although a biosynthetic gene cluster responsible for synthesis of several PUW variants has been proposed in a cyanobacterial strain, the genetic background for MINs remains unexplored. Herein, we report PUW/MIN biosynthetic gene clusters and structural variants from six cyanobacterial strains. Comparison of biosynthetic gene clusters indicates a common origin of the PUW/MIN hybrid nonribosomal peptide synthetase and polyketide synthase. Surprisingly, the biosynthetic gene clusters encode two alternative biosynthetic starter modules, and analysis of structural variants suggests that initiation by each of the starter modules results in lipopeptides of differing lengths and FA substitutions. Among additional modifications of the FA chain, chlorination of minutissamide D was explained by the presence of a putative halogenase gene in the PUW/MIN gene cluster of Anabaena minutissima strain UTEX B 1613. We detected PUW variants bearing an acetyl substitution in Symplocastrum muelleri strain NIVA-CYA 644, consistent with an O-acetyltransferase gene in its biosynthetic gene cluster. The major lipopeptide variants did not exhibit any significant antibacterial activity, and only the PUW F variant was moderately active against yeast, consistent with previously published data suggesting that PUWs/MINs interact preferentially with eukaryotic plasma membranes.IMPORTANCE Herein, we deciphered the most important biosynthetic traits of a prominent group of bioactive lipopeptides. We reveal evidence for initiation of biosynthesis by two alternative starter units hardwired directly in the same gene cluster, eventually resulting in the production of a remarkable range of lipopeptide variants. We identified several unusual tailoring genes potentially involved in modifying the fatty acid chain. Careful characterization of these biosynthetic gene clusters and their diverse products could provide important insight into lipopeptide biosynthesis in prokaryotes. Some of the variants identified exhibit cytotoxic and antifungal properties, and some are associated with a toxigenic biofilm-forming strain. The findings may prove valuable to researchers in the fields of natural product discovery and toxicology.

• Klíčová slova
• biosynthesis, cyanobacteria, fatty acyl-AMP ligase, lipopeptides, nonribosomal peptide synthetase,
• MeSH
• Anabaena genetika   MeSH
• antifungální látky MeSH
• antiinfekční látky MeSH
• bakteriální geny genetika   MeSH
• bakteriální proteiny genetika   MeSH
• cyklické peptidy biosyntéza   chemie   genetika   MeSH
• lipopeptidy biosyntéza   chemie   genetika   farmakologie   MeSH
• multigenová rodina MeSH
• peptidsynthasy genetika   MeSH
• polyketidsynthasy genetika   MeSH
• sinice genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antifungální látky MeSH
• antiinfekční látky MeSH
• bakteriální proteiny MeSH
• cyklické peptidy MeSH
• lipopeptidy MeSH
• non-ribosomal peptide synthase MeSH Prohlížeč
• peptidsynthasy MeSH
• polyketidsynthasy MeSH

A highly divergent 16S rRNA gene was found in one of the five ribosomal operons present in a species complex currently circumscribed as Scytonema hyalinum (Nostocales, Cyanobacteria) using clone libraries. If 16S rRNA sequence macroheterogeneity among ribosomal operons due to insertions, deletions or truncation is excluded, the sequence heterogeneity observed in S. hyalinum was the highest observed in any prokaryotic species thus far (7.3-9.0%). The secondary structure of the 16S rRNA molecules encoded by the two divergent operons was nearly identical, indicating possible functionality. The 23S rRNA gene was examined for a few strains in this complex, and it was also found to be highly divergent from the gene in Type 2 operons (8.7%), and likewise had nearly identical secondary structure between the Type 1 and Type 2 operons. Furthermore, the 16S-23S ITS showed marked differences consistent between operons among numerous strains. Both operons have promoter sequences that satisfy consensus requirements for functional prokaryotic transcription initiation. Horizontal gene transfer from another unknown heterocytous cyanobacterium is considered the most likely explanation for the origin of this molecule, but does not explain the ultimate origin of this sequence, which is very divergent from all 16S rRNA sequences found thus far in cyanobacteria. The divergent sequence is highly conserved among numerous strains of S. hyalinum, suggesting adaptive advantage and selective constraint of the divergent sequence.

• MeSH
• bakteriální RNA chemie   genetika   MeSH
• DNA bakterií genetika   izolace a purifikace   MeSH
• fylogeneze MeSH
• konformace nukleové kyseliny MeSH
• operon * MeSH
• promotorové oblasti (genetika) MeSH
• ribozomy metabolismus   MeSH
• RNA ribozomální 16S chemie   genetika   MeSH
• sinice klasifikace   genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• bakteriální RNA MeSH
• DNA bakterií MeSH
• RNA ribozomální 16S MeSH