Centro de Recursos Microbiológicos (CREM), Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, Caparica, Portugal.
Toxins (Basel). 2010 Oct;2(10):2359-410. doi: 10.3390/toxins2102359. Epub 2010 Oct 18.
Microorganisms are ubiquitous in all habitats and are recognized by their metabolic versatility and ability to produce many bioactive compounds, including toxins. Some of the most common toxins present in water are produced by several cyanobacterial species. As a result, their blooms create major threats to animal and human health, tourism, recreation and aquaculture. Quite a few cyanobacterial toxins have been described, including hepatotoxins, neurotoxins, cytotoxins and dermatotoxins. These toxins are secondary metabolites, presenting a vast diversity of structures and variants. Most of cyanobacterial secondary metabolites are peptides or have peptidic substructures and are assumed to be synthesized by non-ribosomal peptide synthesis (NRPS), involving peptide synthetases, or NRPS/PKS, involving peptide synthetases and polyketide synthases hybrid pathways. Besides cyanobacteria, other bacteria associated with aquatic environments are recognized as significant toxin producers, representing important issues in food safety, public health, and human and animal well being. Vibrio species are one of the most representative groups of aquatic toxin producers, commonly associated with seafood-born infections. Some enterotoxins and hemolysins have been identified as fundamental for V. cholerae and V. vulnificus pathogenesis, but there is evidence for the existence of other potential toxins. Campylobacter spp. and Escherichia coli are also water contaminants and are able to produce important toxins after infecting their hosts. Other bacteria associated with aquatic environments are emerging as toxin producers, namely Legionella pneumophila and Aeromonas hydrophila, described as responsible for the synthesis of several exotoxins, enterotoxins and cytotoxins. Furthermore, several Clostridium species can produce potent neurotoxins. Although not considered aquatic microorganisms, they are ubiquitous in the environment and can easily contaminate drinking and irrigation water. Clostridium members are also spore-forming bacteria and can persist in hostile environmental conditions for long periods of time, contributing to their hazard grade. Similarly, Pseudomonas species are widespread in the environment. Since P. aeruginosa is an emergent opportunistic pathogen, its toxins may represent new hazards for humans and animals. This review presents an overview of the diversity of toxins produced by prokaryotic microorganisms associated with aquatic habitats and their impact on environment, life and health of humans and other animals. Moreover, important issues like the availability of these toxins in the environment, contamination sources and pathways, genes involved in their biosynthesis and molecular mechanisms of some representative toxins are also discussed.
微生物广泛存在于所有栖息地，其代谢多样性和产生许多生物活性化合物的能力，包括毒素，使其特征明显。一些最常见的水中毒素是由几种蓝藻物种产生的。因此，它们的大量繁殖对动物和人类健康、旅游业、娱乐和水产养殖构成了重大威胁。已经描述了相当多的蓝藻毒素，包括肝毒素、神经毒素、细胞毒素和皮肤毒素。这些毒素是次生代谢物，具有广泛的结构和变体多样性。大多数蓝藻次生代谢物是肽或具有肽亚结构，被认为是由非核糖体肽合成（NRPS）合成的，涉及肽合成酶，或者 NRPS/PKS，涉及肽合成酶和聚酮合酶混合途径。除了蓝藻，与水生环境相关的其他细菌也被认为是重要的毒素生产者，这是食品安全、公共卫生以及人类和动物健康的重要问题。弧菌属是水生毒素生产者中最具代表性的群体之一，通常与海鲜源性感染有关。一些肠毒素和溶血素已被确定为霍乱弧菌和创伤弧菌发病机制的重要因素，但也有证据表明存在其他潜在毒素。弯曲杆菌属和大肠杆菌也是水污染物，在感染宿主后能够产生重要的毒素。与水生环境相关的其他细菌也正在成为毒素生产者，即嗜肺军团菌和嗜水气单胞菌，它们被描述为负责合成几种外毒素、肠毒素和细胞毒素。此外，几种梭菌属可以产生有效的神经毒素。虽然它们不被认为是水生微生物，但它们在环境中无处不在，很容易污染饮用水和灌溉水。梭菌成员也是形成孢子的细菌，可以在恶劣的环境条件下长时间存活，这增加了它们的危害等级。同样，假单胞菌属在环境中广泛存在。由于铜绿假单胞菌是一种新兴的机会性病原体，其毒素可能对人类和动物构成新的危害。本综述概述了与水生栖息地相关的原核微生物产生的毒素多样性及其对环境、人类和其他动物的生命和健康的影响。此外，还讨论了这些毒素在环境中的存在、污染来源和途径、参与其生物合成的基因以及一些代表性毒素的分子机制等重要问题。
