Department of Marine Biotechnology, Stazione Zoologica Anton Dohrn, 80121 Naples, Italy.
Department of Biology, University of Naples Federico II, Complesso Universitario di Monte Sant'Angelo, Via Cinthia, 80126 Naples, Italy.
Toxins (Basel). 2019 Feb 8;11(2):99. doi: 10.3390/toxins11020099.
Organisms adaptable to extreme conditions share the ability to establish protective biofilms or secrete defence toxins. The extracellular substances that are secreted may contain monosaccharides and other toxic compounds, but environmental conditions influence biofilm characteristics. Microorganisms that are present in the same environment achieve similar compositions, regardless of their phylogenetic relationships. Alternatively, cyanobacteria phylogenetically related may live in different environments, but we ignore if their physiological answers may be similar. To test this hypothesis, two strains of cyanobacteria that were both ascribed to the genus Halomicronema were isolated. H. metazoicum was isolated in marine waters off the island of Ischia (Bay of Naples, Italy), free living on leaves of Posidonia oceanica. Halomicronema sp. was isolated in adjacent thermal waters. Thus, two congeneric species adapted to different environments but diffused in the same area were polyphasically characterized by microscopy, molecular, and toxicity analyses. A variable pattern of toxicity was exhibited, in accordance with the constraints imposed by the host environments. Cyanobacteria adapted to extreme environments of thermal waters face a few competitors and exhibit a low toxicity; in contrast, congeneric strains that have adapted to stable and complex environments as seagrass meadows compete with several organisms for space and resources, and they produce toxic compounds that are constitutively secreted in the surrounding waters.
适应极端条件的生物具有建立保护性生物膜或分泌防御毒素的能力。分泌的细胞外物质可能含有单糖和其他有毒化合物，但环境条件会影响生物膜的特征。在相同环境中存在的微生物无论其系统发育关系如何，都具有相似的组成。或者，具有系统发育关系的蓝细菌可能生活在不同的环境中，但我们不知道它们的生理反应是否相似。为了验证这一假设，分离了两株被归为 Halomicronema 属的蓝细菌。H. metazoicum 是在意大利那不勒斯湾伊斯基亚岛的海洋水域中分离出来的，在波西多尼亚海洋草的叶子上自由生活。Halomicronema sp. 是在相邻的温泉水中分离出来的。因此，两种同属的物种适应不同的环境，但在同一地区扩散，通过显微镜、分子和毒性分析进行了多相特征描述。表现出可变的毒性模式，符合宿主环境的限制。适应温泉极端环境的蓝细菌面临的竞争较少，毒性较低；相比之下，适应稳定而复杂的海草草甸环境的同属菌株为了空间和资源与多种生物竞争，并在周围水域中持续分泌有毒化合物。
