Queensland Department of Health, Forensic and Scientific Services, 39 Kessels Road, Coopers Plains, Qld 4108, Australia.
Queensland Department of Environment and Science, GPO Box 5078 Brisbane Qld 4001, Australia.
Harmful Algae. 2018 Dec;80:158-170. doi: 10.1016/j.hal.2018.11.002. Epub 2018 Nov 23.
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 to 171.3 μg g, 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.
从澳大利亚亚热带东南部的六个地点分离的淡水丝状、底栖蓝藻念珠藻属（Scytonema crispum）菌株，通过表型和遗传特征的组合进行了特征描述。形态上，这些菌株与 Scytonemataceae 严格意义上的描述和 Scytonema crispum 的描述一致。然而，16S rRNA 基因、16S-23S rRNA 操纵子和 nifH 基因的系统发育分析表明，这些菌株和来自澳大利亚以外的另外三个菌株形成了一个单系分支，与念珠藻属和 Scytonemataceae 中的其他物种不同。总的来说，这些数据表明，该群体在进化上足够独特，可以被置于一个新的科，异念珠藻科（Heteroscytonemataceae）科。因此，以前被称为 S. crispum 的分类群被转移到一个新的属 Heteroscytonema gen nov.，作为 H. crispum。一些 H. crispum 菌株表现出麻痹性贝类毒素（PSTs）的兼性产生。个别菌株产生的 PST 浓度差异很大，从 2.7μg g 到 171.3μg g，包括 C 毒素、脱羧基沙毒素（dcSTX）、GTX2、GTX3 和 GTX5、石房蛤毒素（STX）和未鉴定的 PST。大多数澳大利亚菌株以 dcSTX 作为优势石房蛤毒素类似物产生 PST，这是一个重要的发现，因为 dcSTX 的相对毒性约为 STX 的一半。H. crispum 的澳大利亚菌株之间以及从新西兰和美国收集的菌株之间 PST 谱存在差异。在检测到 PST 的所有菌株中都存在 PST 产生的 sxtA 基因。在主要饮用水水库的源头发现产 PST 的 H. crispum 对人类和动物潜在暴露于这些神经毒素化合物构成了严重风险，并进一步强调了监测底栖蓝藻种群中潜在产毒物种的重要性。
