Diversity, Cyanotoxin Production, and Bioactivities of Cyanobacteria Isolated from Freshwaters of Greece.

Spyros Gkelis,Giorgia Di Lorenzo,Triantafyllos Kaloudis,Antonia Kasampali,Despoina Konstantinou,Theodoros Triantis,Dominiki Kati,Manthos Panou,Christophoros Christophoridis,Sevasti-Kiriaki Zervou,Stamatia Ioakeim,Panagiotis Apostolidis,Anastasia Hiskia,Sofia Papadimitriou,Minas Arsenakis

doi:10.3390/toxins11080436

Abstract

Cyanobacteria are a diverse group of photosynthetic Gram-negative bacteria that produce an array of secondary compounds with selective bioactivity against a broad spectrum of organisms and cell lines. In this study, 29 strains isolated from freshwaters in Greece were classified using a polyphasic approach and assigned to Chroococcales, Synechococcales, and Nostocales, representing 11 genera and 17 taxa. There were good agreements between 16S ribosomal RNA (rRNA)–cpcBA–internal genetic spacer (IGS) characterization and morphological features, except for the Jaaginema–Limnothrix group which appears intermixed and needs further elucidation. Methanol extracts of the strains were analyzed for cyanotoxin production and tested against pathogenic bacteria species and several cancer cell lines. We report for the first time a Nostoc oryzae strain isolated from rice fields capable of producing microcystins (MCs) and a Chlorogloeopsis fritschii strain isolated from the plankton of a lake, suggesting that this species may also occur in freshwater temperate habitats. Strains with very high or identical 16S rRNA gene sequences displayed different antibacterial and cytotoxic activities. Extracts from Synechococcus cf. nidulans showed the most potent antibacterial activity against Staphylococcus aureus, whereas Jaaginema sp. strains exhibited potent cytotoxic activities against human colorectal adenocarcinoma and hepatocellular carcinoma cells. Jaaginema Thessaloniki Aristotle University Microalgae and Cyanobacteria (TAU-MAC) 0110 and 0210 strains caused pronounced changes in the actin network and triggered the formation of numerous lipid droplets in hepatocellular carcinoma and green monkey kidney cells, suggesting oxidative stress and/or mitochondrial damage leading to apoptosis.

Highlights

Cyanobacteria are an ancient lineage of photosynthetic prokaryotes and important components of microbial communities of a wide range of habitats, including extreme environments
Materials) and the phylogeny based on 16S–23S ribosomal RNA and cpcBA–internal genetic spacer (IGS) regions (Figure 1), our strains were classified into 11 genera and 17 taxa belonging to Chroococcales, Synechococcales, and Nostocales (Table 1)
Synechococcus strains (Figure 2h) formed two subclades with other strains identified as Cyanobium and Aphanothece (Figure 1)

Summary

Introduction

Cyanobacteria are an ancient lineage of photosynthetic prokaryotes and important components of microbial communities of a wide range of habitats, including extreme environments A recent review revealed that the known chemical diversity of cyanobacterial natural products exceeds 1100 secondary metabolites with highly complex chemical structures; more than two-thirds of these are reported from the marine Lyngbya, the freshwater Microcystis and Nostoc, and the terrestrial Hapalosiphon [7]. These structural diverse substances have promising therapeutic potential, with anticancer, multidrug-reversing, antifungal, antibacterial, anti-inflammatory, antiviral, and potent enzyme-inhibiting bioactivities [8,9]. To date, more than 40 anticancer biomolecules were characterized from cyanobacteria [10], such as cryptophycins and curacins

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Discussion

Conclusion