Anatoxin-a producing Tychonema (Cyanobacteria) in European waterbodies

Abstract

Keywords:Anatoxin a Tychonema Cell quotaPolyphasic approach Phylogenetic analysis European waterbodies a b s t r a c tIn order to identify the cyanobacterial species responsible of anatoxin a (ATX) production in Lake Garda (Northern Italy), an intensive isolation and culturing of filamentous cyano bacteria were established since 2014 from environmental samples. In this work, we report a detailed account of the strategy adopted, which led to the discovery of a new unexpected producer of ATX, Tychonema bourrellyi. So far, this species is the first documented example of cultured Oscillatoriales able to produce ATX isolated from pelagic freshwater ecosys tems. The isolated filaments were identified adopting a polyphasic approach, which included microscopic species identification, genetic characterisation and phylogenetic analyses based on 16S rRNA genes. The taxonomic identification was further confirmed by the high (>99%) rbcLX sequence similarities of the T. bourrellyi strains of Lake Garda with those deposited in DNA sequence databases. More than half of the isolates were shown to produce a significant amount of ATX, with cell quota ranging between 0.1 and 2.6 mg mm 3 , and 0.01 and 0.35 pg cell 1 . The toxic isolates were tested positive for anaC of the anatoxin a synthetase (ana) gene cluster. These findings were confirmed with the discovery of one ATX producing T. bourrellyi strain isolated in Norway. This strain and a further non ATXproducing Norwegian Tychonema bornetii strain tested positive for the presence of the anaF gene of the ana gene cluster. Conversely, none of the Italian and Norwegian Tychonema strains were positive for microcystins (MCs), which was also confirmed by the absence of mcyE PCR products in all the samples analysed. This work suggests that the only reliable strategy to identify cyanotoxins producers should be based on the isolation of strains and their identification with a polyphasic approach associated to a concurrent metabolomic profiling.

A comparative study of the metabolic profiles of common nuisance cyanobacteria in southern perialpine lakes

“…This was not unexpected, considered that recent investigations had already shown that the populations isolated in the Italian district do not have the capability to produce ATX. T. bourrellyi was found to produce ATX, as reported also in recent papers Shams et al, 2015). Moreover, based on evidences collected in this work, this species was possibly able to synthesize PSP toxins, possibly sulfated variants (like C3/4 toxins).…”

“…In particular, based on the analysis of isolated strains (Bernard et al, 2016), Aph. flos-aquae and T. bourrellyi were reported as ATX producers (Sivonen et al, 1989;Osswald et al, 2009;Salmaso et al, 2015;2016;Shams et al, 2015), whereas M. aeruginosa and P. rubescens were mainly reported as MC producers (Metcalf and Codd, 2012), and D. lemmermannii as MCs and anatoxin-a(S) producer (Sivonen et al, 1992;Onodera et al, 1997). Our targeted analysis confirmed this behavior for M. aeruginosa and P. rubescens, but not for Aph.…”

Interspecific Relationship and Ecological Requirements of Two Potentially Harmful Cyanobacteria in a Deep South-Alpine Lake (L. Iseo, I)

“…The species did not show differences in cell dimension at the different depths along the water column, but seasonal variations were observed. In April, P. rubescens considerably increased in biovolume compared to T. bourrellyi, as its cells displayed the highest diameter (6.33 µm), with a cell volume of 150 µm 3 . The average annual cell volume of P. rubescens and T. bourrellyi had the same value (63 ± 4 and 63 ± 2 µm 3 respectively), with a mean annual diameter of 4.38 ± 0.11 and 4.2 ± 0.08 µm, and a mean annual length of 3.95 ± 0.04 and 4.50 ± 0.08 µm, respectively.…”

“…As a result of their long evolutionary history (~2 by) [1,2], and due to their high ecological plasticity, Cyanobacteria are able to adapt to geochemical and climatic changes [3,4]. Consequently, these organisms are also capable of adapting to anthropogenic modifications of aquatic environments [5], such as enhanced nutrient loading or increasing temperatures.…”

Distribution and population dynamics of potential anatoxin-a-producing cyanobacteria in Lake Dianchi, China

“…Cyanobacteria produce a wide range of toxic compounds, including neurotoxins and hepatotoxins, which can have adverse effects on environmental and public health (Sivonen, 1996). Anatoxin-a (ATX-a), one of the main neurocyanotoxins produced by several genera of cyanobacteria, including Anabaena, Aphanizomenon, Oscillatoria, Cylindrospermum, Planktothrix, Phormidium and Tychonema, was first identified from an Anabaena flos-aquae strain in the 1970s (Osswald et al, 2007;Shams et al, 2015;Devlin et al, 1977). It exhibits extreme toxicity, killing mice within 2-5 min, and was initially known as ''very fast death factor'' (Devlin et al, 1977).…”