Abstract
Cyanobacteria are photosynthetic prokaryotes found in a range of environments. They are infamous for the production of toxins, as well as bioactive compounds, which exhibit anticancer, antimicrobial and protease inhibition activities. Cyanobacteria produce a broad range of antifungals belonging to structural classes, such as peptides, polyketides and alkaloids. Here, we tested cyanobacteria from a wide variety of environments for antifungal activity. The potent antifungal macrolide scytophycin was detected in Anabaena sp. HAN21/1, Anabaena cf. cylindrica PH133, Nostoc sp. HAN11/1 and Scytonema sp. HAN3/2. To our knowledge, this is the first description of Anabaena strains that produce scytophycins. We detected antifungal glycolipopeptide hassallidin production in Anabaena spp. BIR JV1 and HAN7/1 and in Nostoc spp. 6sf Calc and CENA 219. These strains were isolated from brackish and freshwater samples collected in Brazil, the Czech Republic and Finland. In addition, three cyanobacterial strains, Fischerella sp. CENA 298, Scytonema hofmanni PCC 7110 and Nostoc sp. N107.3, produced unidentified antifungal compounds that warrant further characterization. Interestingly, all of the strains shown to produce antifungal compounds in this study belong to Nostocales or Stigonematales cyanobacterial orders.
Highlights
Cyanobacteria are photosynthetic cosmopolitan prokaryotic organisms that have been isolated from aquatic, terrestrial, and different aquatic and terrestrial extreme environments [1,2]
The screening for antifungal compounds produced by cyanobacteria led us to discover new strains producing scytophycins and hassallidins
The comparison of the 16S rRNA gene sequence of this strain with other sequences in the NCBI led us to investigate if the first hit, Anabaena cf. cylindrica PH133, could produce scytophycin
Summary
Cyanobacteria are photosynthetic cosmopolitan prokaryotic organisms that have been isolated from aquatic (freshwater, brackish and marine), terrestrial (soil, lichen-associated and the surface of leaves), and different aquatic and terrestrial extreme environments (hot springs, high salinity, deserts) [1,2] In these environments, cyanobacteria face competitors and predators, including parasitic fungi, such as chytrids. Antifungal compounds have been previously detected in cyanobacterial extracts, such as fischerellin A, hapalindole, hassallidin/balticidins, carazostatin, phytoalexin, tolytoxin, scytophycin, toyocamycin, tjipanazole, nostocyclamide, nostodione and nostofungicidine [5,6,7]. Most of these compounds are synthetized by ribosomal pathways or by nonribosomal pathways. We screened cyanobacteria for antifungal compounds, and we were able to detect known, and potential new antifungal natural products
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