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Strains of the freshwater filamentous, benthic cyanobacterium Scytonema crispum Agardh isolated from six sites in subtropical south-east Queensland were characterised using a combination of phenotypic and genetic traits. Morphologically, the strains were consistent with the description of Scytonemataceae sensu stricto, and the description of Scytonema crispum. However, phylogenetic analysis of the 16S rRNA gene, the 16S-23S rRNA operon, and the nifH gene revealed that these strains and three others from outside Australia formed a monophyletic clade distinct from Scytonema and other species in the Scytonemataceae. Collectively, this data suggests this group is sufficiently evolutionarily distinct to be placed in a new family, Heteroscytonemataceae fam. nov. Accordingly, the taxon previously known as S. crispum has been transferred to a new genus Heteroscytonema gen nov., as H. crispum. Some strains of H. crispum exhibited facultative production of paralytic shellfish toxins (PSTs). The concentration of PSTs produced by individual strains varied widely, from 2.7 μg g -1 to 171.3 μg g -1 , and included C toxins, decarbamoyl saxitoxin (dcSTX), gonyautoxins (GTX2, GTX3 and GTX5), saxitoxin (STX) and uncharacterised PSTs. The majority of the Australian strains produced dcSTX as the dominant saxitoxin analogue, a significant finding given that dcSTX has approximately half the relative toxicity of STX. The PST profile varied within and between Australian strains of H. crispum and in strains collected from New Zealand and the United States. The sxtA gene, one of the determinants for the production of PSTs, was present in all strains in which PSTs were detected. The discovery of PST-producing H. crispum in the headwaters of a major drinking water reservoir presents a serious risk for potential human and animal exposure to these neurotoxic compounds and further highlights the importance of monitoring benthic cyanobacteria populations for potentially toxigenic species., (Crown Copyright © 2018. Published by Elsevier B.V. All rights reserved.)

A new nodularin producing benthic cyanobacterium Iningainema pulvinus gen nov., sp nov. was isolated from a freshwater ambient spring wetland in tropical, north-eastern Australia and characterised using combined morphological and phylogenetic attributes. It formed conspicuous irregularly spherical to discoid, blue-green to olive-green cyanobacterial colonies across the substratum of shallow pools. Morphologically Iningainema is most similar to Scytonematopsis Kiseleva and Scytonema Agardh ex Bornet & Flahault. All three genera have isopolar filaments enveloped by a firm, often layered and coloured sheath; false branching is typically geminate, less commonly singly. Phylogenetic analyses using partial 16S rRNA sequences of three clones of Iningainema pulvinus strain ES0614 showed that it formed a well-supported monophyletic clade. All three clones were 99.7-99.9% similar, however they shared less than 93.9% nucleotide similarity with other cyanobacterial sequences including putatively related taxa within the Scytonemataceae. Amplification of a fragment of the ndaF gene involved in nodularin biosynthesis from Iningainema pulvinus confirmed that it has this genetic determinant. Consistent with these results, analysis of two extracts from strain ES0614 by HPLC-MS/MS confirmed the presence of nodularin at concentrations of 796 and 1096μgg -1 dry weight. This is the third genus of cyanobacteria shown to produce the cyanotoxin nodularin and the first report of nodularin synthesis from the cyanobacterial family Scytonemataceae. These new findings may have implications for the aquatic biota at Edgbaston Reserve, a spring complex which has been identified as a priority conservation area in the central Australian arid and semiarid zones, based on patterns of endemicity., (Crown Copyright © 2016. Published by Elsevier B.V. All rights reserved.)