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.

从亚热带东南昆士兰州的六个地点分离出的淡水丝状底栖蓝细菌Scytonema crispum Agardh的菌株利用表型和遗传性状进行了表征。从形态上讲，该菌株与Scellnemataceae sensu stricto的描述和Scytonema crispum的描述一致。但是，对16S rRNA基因，16S-23S rRNA操纵子和nifH基因的系统发育分析显示，这些菌株和来自澳大利亚以外的其他三个菌株形成了不同于Scytone的单系进化枝。ma和其他物种。总体而言，该数据表明该组在进化上足够不同，可以放入一个新家族，杂种线虫病家族。十一月 因此，以前被称为该分类单元S. crispum已被转移到一个新属Heteroscytonema根十一月，如H. crispum。H.crispum的某些菌株表现出兼性产生麻痹性贝类毒素（PSTs）。各个菌株产生的PST浓度差异很大，从2.7μgg ^-1到171.3μgg ^-1，包括C毒素，脱氨甲酰基沙西毒素（dcSTX），淋菌毒素（GTX2，GTX3和GTX5），沙西毒素（STX）和未表征的PST。澳大利亚的大多数菌株生产dcSTX作为主要的毒素毒素类似物，鉴于dcSTX的毒性约为STX的一半，因此这是一个重要发现。在澳大利亚的H.crispum菌株内和之间以及从新西兰和美国收集的菌株中，PST谱均发生变化。所述的sxtA基因，决定用于生产的PST中的一个，是存在于在其中进行检测的PST的所有菌株。产生PST的H. crispum的发现 在主要饮用水水库的上游源头中，存在严重的潜在人类和动物接触这些神经毒性化合物的风险，并进一步突显了监测底栖蓝细菌种群中潜在的致毒物种的重要性。