Nostoc edaphicum CCNP1411 from the Baltic Sea-A New Producer of Nostocyclopeptides.

Anna Fidor,Robert Gromadka,Hanna Mazur-Marzec,Michał Grabski,Jan Gawor,Grzegorz Węgrzyn

doi:10.3390/md18090442

Abstract

Nostocyclopeptides (Ncps) constitute a small class of nonribosomal peptides, exclusively produced by cyanobacteria of the genus Nostoc. The peptides inhibit the organic anion transporters, OATP1B3 and OATP1B1, and prevent the transport of the toxic microcystins and nodularin into hepatocytes. So far, only three structural analogues, Ncp-A1, Ncp-A2 and Ncp-M1, and their linear forms were identified in Nostoc strains as naturally produced cyanometabolites. In the current work, the whole genome sequence of the new Ncps producer, N. edaphicum CCNP1411 from the Baltic Sea, has been determined. The genome consists of the circular chromosome (7,733,505 bps) and five circular plasmids (from 44.5 kb to 264.8 kb). The nostocyclopeptide biosynthetic gene cluster (located between positions 7,609,981–7,643,289 bps of the chromosome) has been identified and characterized in silico. The LC-MS/MS analyzes of N. edaphicum CCNP1411 cell extracts prepared in aqueous methanol revealed several products of the genes. Besides the known peptides, Ncp-A1 and Ncp-A2, six other compounds putatively characterized as new noctocyclopeptide analogues were detected. This includes Ncp-E1 and E2 and their linear forms (Ncp-E1-L and E2-L), a cyclic Ncp-E3 and a linear Ncp-E4-L. Regardless of the extraction conditions, the cell contents of the linear nostocyclopeptides were found to be higher than the cyclic ones, suggesting a slow rate of the macrocyclization process.

Highlights

Secondary metabolites produced by cyanobacteria of the genus Nostoc (Nostocales) are characterized by a high variety of structures and biological activities [1,2,3,4,5,6]
Total DNA has been isolated from N. edaphicum CCNP1411, and the whole genome sequence has been determined
Genes coding for subunits of the non-ribosomal peptide synthetase, in nostocyclopeptideproducing N. edaphicum CCNP1411, revealed differences in nucleotide compositions, compared to the previously described ncp cluster of Nostoc sp

Summary

Introduction

Secondary metabolites produced by cyanobacteria of the genus Nostoc (Nostocales) are characterized by a high variety of structures and biological activities [1,2,3,4,5,6]. On the basis of chemical structure, these compounds are mainly classified to peptides, polyketides, lipids, polysaccharides and alkaloids [7]. Produced cyanopeptides with anticancer, antimicrobial, antiviral and enzyme-inhibiting activity, have attracted attention of many research groups [6,8,9,10,11,12]. Some of the metabolites, such as nostocyclopeptides (Ncps) or cryptophycins are exclusively produced by the cyanobacteria of the genus Nostoc (Figure 1A). Ncps constitute a small class of nonribosomal peptides. Only three analogues of the compounds and their linear forms have been discovered

Methods

Results

Conclusion