蓝细菌毒素研究进展

蓝细菌毒素是水华中有毒蓝细菌产生的体内次生代谢产物 ,根据其毒性可分为肝毒素和神经毒素 ,是强烈的癌促进剂。蓝细菌裂解后释放蓝细菌毒素 ,污染饮用水源 ,危害人类的健康。阐述蓝细菌毒素的种类、性质、制备、检测 ,以及从饮用水中去除蓝细菌毒素的方法。     

蓝细菌制氢研究进展

蓝细菌具有很低的营养需求,能够利用太阳能直接光解水产生氢能,利用蓝细菌产氢是理想的生物制氢方式之一。目前,蓝细菌氢的产率尚未达到实际应用的要求。蓝细菌产氢依赖于菌株的遗传背景和产氢的环境条件。对蓝细菌产氢生理、产氢速率、产氢的环境条件、菌株筛选和突变株构建以及在光生物反应器中产氢的特征作了综述,以期有利于蓝细菌产氢水平的提高。     

蓝细菌光敏色素的分子结构、生物合成和可逆光致变色效应

蓝细菌光敏色素(CBCRs)是蓝细菌中感受光的重要光受体,能够响应从紫外光到红外光范围内的光信号,进而影响蓝细菌的光化学行为。蓝细菌光敏色素通过N-末端GAF(cGMP phosphodiesterase,adenylyl cyclase and FhlA domain)结构域中保守性半胱氨酸共价结合藻胆色素,形成具有感光生理功能的色素蛋白质。本文重点在分子水平上综述了蓝细菌光敏色素的分子结构、生物合成和可逆光致变色效应机理,并基于最新的研究进展,就蓝细菌光敏色素今后的研究方向进行了展望。     

应用合成生物学策略改良光合蓝细菌

蓝细菌是一类能够直接利用光能和CO_2作为唯一能源和碳源进行生长的光合微生物。近年来,光合蓝细菌以其独特的优势作为"自养型细胞工厂"合成了多种燃料及化学品。以光合蓝细菌中的几种模式生物为例,总结近年来以蓝细菌为工程菌株合成生物燃料及化学品的研究进展,对目前蓝细菌菌株存在的固有问题进行分析,并提出应用合成生物学进行菌种改良的方案。     

蓝细菌的固氮

蓝细菌又称蓝藻,有许多种,其中有些营自由生活,有些和其它生物营共生生活,其中有许多种类能够固氮,大都属于念球蓝细菌科(Nostoceae),胶须蓝细菌科(Rivulariaceae)和伪歧蓝细菌科(Scytonemataceae)及真枝蓝细菌科(Stigonemataceac)。本文介绍自由生活蓝细菌和营共生生活的蓝细菌固氮的一些问题。一、自生蓝细菌的固氮蓝细菌能生长于有光的无机培养基中,利用CO_2作为碳源,N_2作为氮源,并且能产氧。但这里显然有矛盾,因固氮作用的关健酶——固氮酶在有氧的情况下将失去活性,固氮将停止。那么这个矛盾是如何解决的,通过研究发现,已知的固氮的蓝细菌除少数种外,都是丝状体,丝状体中有一种特殊细胞——异形胞。实验证明固氮作用可以在异形胞中完成。这类专化性细胞与营养细胞有如下几点区别:1.有厚外衣,2.色素弱而不强,3.与营养细胞接合处有明显的折光性颗粒。另     

蓝细菌对汞耐受机制的研究进展

蓝细菌对不同形态的汞具有很强的耐受和富集能力，能够改变环境中的汞浓度，影响汞的生物地球化学循环。同时，蓝细菌是生态系统中重要的初级生产者，经过蓝细菌富集的汞更容易进入食物链，影响人类健康。本文系统总结了蓝细菌对汞的耐受机制，主要包括：(1)在细胞壁外合成胶质鞘隔离汞；(2)通过与自身化合物结合钝化汞的毒性；(3)利用自身抗氧化机制修复汞对细胞的损伤；(4)利用自身酶转化汞的形态降低毒性；(5)与抗汞细菌共生抵御汞。基于此，本文展望了蓝细菌汞耐受机制的进一步研究方向，以及利用蓝细菌进行汞解毒和污染修复的前景。     

蛇神经毒素的研究进展

蛇毒是由许多种蛋白质、多肽、酶类以及其他小分子物质组成的混合物.在蛇毒中已经分离了许多种毒素分子,其中有一大类分子对哺乳动物的神经系统具有毒性效应,习惯上把这类分子成为蛇神经毒素.蛇神经毒素根据其作用位点的不同可以分为四大类:突触前蛇神经毒素、突触后蛇神经毒素、抗胆碱酯酶的蛇神经毒素和离子通道蛇神经毒素.许多蛇神经毒素已经分离纯化并进行了结构与功能的研究,几十近百种蛇神经毒素一级结构和空间结构已经得到测定.近几年来一些蛇神经毒素的基因文库以及cDNA文库已经构建出来,从中分离出的基因已经用于重组蛇神经毒素的生产研究.蛇神经毒素的分子结构与其功能具有较好的对应关系,即作用机制相同的毒素具有类似的空间结构.天然的蛇神经毒素以及重组的蛇神经毒素都已广泛应用于理论研究和一些临床应用.分离新的蛇神经毒素及其基因以及根据需要设计新的蛇神经毒素分子已成为该领域的热点,采用生物工程的方法规模生产蛇神经毒素也是当前及今后的研究方向.     

四川广安谢家槽下三叠统夜郎组底部凝块岩中疑似的蓝细菌化石及蓝细菌生物膜

我国华南二叠纪-三叠纪之交的地层中,微生物岩发育,其中所发现的蓝细菌以结构、构造比较简单的微球状蓝细菌为主。四川广安谢家槽剖面下三叠统夜郎组底部产有一套厚约20m的凝块岩,通过对凝块岩薄片的显微镜照片观察,发现其中产有丰富的、保存精美的疑似的蓝细菌化石,它们清楚地展现了比此前所报道的蓝细菌更为复杂的内部结构、构造。根据其特点,可以分辨出四种主要类型:疑似的花冠状蓝细菌,疑似的蛛网状蓝细菌,疑似的嫩芽状蓝细菌和疑似的似管状蓝细菌,文中对它们进行了详细描述。另外,在研究的凝块岩薄片中,还发现了有些黑色的条带,这些条带并没有覆盖整个凝块岩,只是覆盖一部分,其中蓝细菌的结构、构造与条带外的微生物岩中的蓝细菌有着很大区别,条带中的黑色物质远比条带外的多,围绕这些黑色物质的丝状体呈网孔状,而条带外的丝状体则呈长条形或椭球状。这些黑色的条带很可能是原始的蓝细菌生物膜,文中称之为疑似的蓝细菌生物膜,这也是早三叠世蓝细菌生物膜的首次报道。对蓝细菌生物膜的进一步研究,可以帮助我们了解蓝细菌的生长过程以及生物膜在微生物岩形成中的作用。     

蓝细菌基因组拷贝数的研究进展与展望

蓝细菌是一类古老的光合原核微生物。就基因组拷贝数(倍性)而言,蓝细菌是原核生物中基因组低、中、高拷贝共存的典型类群之一,而基因组多拷贝特性是制约蓝细菌高效遗传改造的瓶颈。已有研究表明,蓝细菌的基因组拷贝数表现出生长周期的依赖性并受多种遗传、环境因子的影响。文中综述了蓝细菌基因组拷贝数的国内外最新研究进展、分析方法及影响因素,并讨论了蓝细菌基因组多拷贝研究的环境生态和生物技术意义。最后,对未来蓝细菌基因组拷贝数相关的研究方向作出展望。     

微宇宙模拟溢油条件下沉积物中蓝细菌多样性

【目的】在不同浓度原油胁迫下,研究沉积物中原油降解规律及蓝细菌的响应机制,探讨蓝细菌对原油的耐受程度,并揭示蓝细菌种属结构组成的演替规律,为预测和判断溢油污染是否会造成富营养化等次生环境问题提供依据。【方法】建立微宇宙模拟实验体系,设置未添加原油对照组(CK组)及一系列高浓度原油处理组(25、125和250 g/kg干重,分别为LO组、MO组和HO组),通过气相色谱-氢火焰离子化检测器分析微宇宙培养期间原油降解规律。采用蓝细菌16SrRNA基因分析蓝细菌多样性和丰度变化规律,以及蓝细菌各种属的演替情况。【结果】微宇宙培养第31天时,在最低浓度处理组(LO组)沉积物表层出现片状绿色菌苔,而其他处理组和对照组未出现此现象。蓝细菌16SrRNA基因克隆文库结果表明,在溢油条件下所有处理组的蓝细菌多样性均降低,但有一些种属出现富集,如Oscillatoria和Prochlorococcus等。此外,也监测到大量的不可培养种属,预示着沉积物中可能存在新种属的蓝细菌。【结论】蓝细菌对原油具有较高耐受性,25 g/kg浓度原油会对蓝细菌生长产生刺激作用,且可能进一步引起蓝细菌富集。原油会引起蓝细菌多样性降低,但个别种属会发生富集,说明这些种属对原油具有较高耐受性,甚至发挥重要功能,如Oscillatoria具有固氮功能。本研究在分子水平上研究了蓝细菌对原油的响应,对蓝细菌分子生态研究具有重要意义。     

Toxin-Producing Anabaena flos-aquae Induces Settling of Chlamydomonas reinhardtii,a Competing Motile Alga

Toxin production is an adaptation that allows cyanobacteria in resource-limiting environments to ameliorate the effects of herbivory and competition with other phototrophs. We demonstrate that the cyanobacterial toxins anatoxin-a and microcystin-LR paralyze the motile green alga Chlamydomonas reinhardtii. In addition, both purified toxins and cyanobacterial extracellular products containing these toxins cause the alga to settle faster than in nontoxic media. In microcosm experiments, the presence of either the cyanobacterium or its extracellular products induce settling in the alga, similar to the response observed with the addition of both anatoxin-a and microcystin-LR. The cyanobacterial production of paralyzing toxins represents a novel mechanism for phytoplankton settling. This prokaryotic/eukaryotic chemical interaction may create a competitor-free zone for cyanobacteria in lake environments, predicating optimal conditions for a toxic cyanobacterial bloom.     

微囊藻毒素在滇池鱼体内的积累水平及分布特征

为了解富营养化水体中鱼体内微囊藻毒素(MC)的积累水平及其分布特征,2003年4月和9月份两次在滇池试验区采集了鲢、鳙和草鱼等鱼种,用ELISA方法对鱼体中肝、肾、空肠、胆、肌肉等不同组织中MC的含量进行了检测。结果表明,MC在所有样品中均能检测到,且主要分布在鱼体的肝肾脏和消化道等器官,而肌肉和非消化道器官中毒素含量相对较低。不同鱼种不同组织对MC的富集程度也明显不同,鲢鳙中肝脏和肾脏这两个主要的靶器官对MC的蓄积能力就远高于草鱼。同时,不同季节MC在鱼体内的积累水平也明显不同,4月份鱼样中MC的含量普遍低于9月份鱼样中MC的含量。最后按照WHO生活饮用水安全标准的建议进行推算,所有鱼肉中的MC均没有超过其推荐的人体每日可允许摄入量(≤0.04μg/kg人体重),初步推断鱼肉中MC暂时还未危及到人体健康,但仍具有潜在的风险性。     

Genotoxicity and potential carcinogenicity of cyanobacterial toxins - a review

The occurrence of cyanobacterial blooms has increased significantly in many regions of the world in the last century due to water eutrophication. These blooms are hazardous to humans, animals, and plants due to the production of cyanotoxins, which can be classified in five different groups: hepatotoxins, neurotoxins, cytotoxins, dermatotoxins, and irritant toxins (lipopolysaccharides). There is evidence that certain cyanobacterial toxins are genotoxic and carcinogenic; however, the mechanisms of their potential carcinogenicity are not well understood. The most frequently occurring and widespread cyanotoxins in brackish and freshwater blooms are the cyclic heptapeptides, i.e., microcystins (MCs), and the pentapeptides, i.e., nodularins (NODs). The main mechanism associated with potential carcinogenic activity of MCs and NOD is the inhibition of protein phosphatases, which leads to the hyperphosphorylation of cellular proteins, which is considered to be associated with their tumor-promoting activity. Apart from this, MCs and NOD induce increased formation of reactive oxygen species and, consequently, oxidative DNA damage. There is also evidence that MCs and NOD induce micronuclei, and NOD was shown to have aneugenic activity. Both cyanotoxins interfere with DNA damage repair pathways, which, along with DNA damage, is an important factor involved in the carcinogenicity of these agents. Furthermore, these toxins increase the expression of TNF-α and early-response genes, including proto-oncogenes, genes involved in the response to DNA damage, cell cycle arrest, and apoptosis. Rodent studies indicate that MCs and NOD are tumor promotors, whereas NOD is thought to have also tumor-initiating activity. Another cyanobacterial toxin, cylindrospermopsin (CYN), which has been neglected for a long time, is lately being increasingly found in the freshwater environment. The principal mechanism of its toxicity is the irreversible inhibition of protein synthesis. It is pro-genotoxic, and metabolic activation by cytochrome P-450 enzymes is needed for its genotoxic activity. In metabolically competent cells, it induces DNA strand breaks and exerts clastogenic and aneugenic activity. In addition, CYN increased the expression of p53 regulated genes involved in cell cycle arrest, DNA damage repair, and apoptosis. It also has cell transforming potential, and limited preliminary rodent studies indicate that CYN could have tumor-initiating activity. In 2010, the International Agency for Research on Cancer (IARC) classified MCLR as possible human carcinogen (Group 2B). Although there is not enough available information for the classification of other cyanobacterial toxins, the existing data from in vitro and in vivo studies indicate that NOD and especially CYN may be even more hazardous than MCLR to human and animal health. In addition in the environment, cyanobacterial toxins occur in complex mixtures as well as together with other anthropogenic contaminants, and numerous studies showed that the toxic/genotoxic potential of the extracts from cyanobacterial scums is higher than that of purified toxins. This means that the mixtures of toxins to which humans are exposed may pose higher health risks than estimated from the toxicological data of a single toxin. Future research efforts should focus on the elucidation of the carcinogenic potential of NOD, CYN, and the mixture of cyanobacterial extracts, as well as on the identification of possible novel toxins.     

Cyanotoxins from Black Band Disease of Corals and from Other Coral Reef Environments

Many cyanobacteria produce cyanotoxins, which has been well documented from freshwater environments but not investigated to the same extent in marine environments. Cyanobacteria are an obligate component of the polymicrobial disease of corals known as black band disease (BBD). Cyanotoxins were previously shown to be present in field samples of BBD and in a limited number of BBD cyanobacterial cultures. These toxins were suggested as one of the mechanisms contributing to BBD-associated coral tissue lysis and death. In this work, we tested nine cyanobacterial isolates from BBD and additionally nine isolated from non-BBD marine sources for their ability to produce toxins. The presence of toxins was determined using cell extracts of laboratory grown cyanobacterial cultures using ELISA and the PP2A assay. Based on these tests, it was shown that cyanobacterial toxins belonging to the microcystin/nodularin group were produced by cyanobacteria originating from both BBD and non-BBD sources. Several environmental factors that can be encountered in the highly dynamic microenvironment of BBD were tested for their effect on both cyanobacterial growth yield and rate of toxin production using two of the BBD isolates of the genera Leptolyngbya and Geitlerinema. While toxin production was the highest under mixotrophic conditions (light and glucose) for the Leptolyngbya isolate, it was highest under photoautotrophic conditions for the Geitlerinema isolate. Our results show that toxin production among marine cyanobacteria is more widespread than previously documented, and we present data showing three marine cyanobacterial genera (Phormidium, Pseudanabaena, and Spirulina) are newly identified as cyanotoxin producers. We also show that cyanotoxin production by BBD cyanobacteria can be affected by environmental factors that are present in the microenvironment associated with this coral disease.     

纳米硒对微囊藻毒素致小鼠肝氧化损伤的保护作用

The occurrence of cyanobacterial blooms has been re-ported in fresh water all over the world~[1].Cyanobacterial bloom in ponds and reservoirs are associated with adverse ef-fects on organisms.including acute toxicity in animals and cases of illness in humans when the toxins released into the aquatic environment after cyanobacterial cell lysis~[2].     

Genotoxicity and potential carcinogenicity of cyanobacterial toxins – a review

The occurrence of cyanobacterial blooms has increased significantly in many regions of the world in the last century due to water eutrophication. These blooms are hazardous to humans, animals, and plants due to the production of cyanotoxins, which can be classified in five different groups: hepatotoxins, neurotoxins, cytotoxins, dermatotoxins, and irritant toxins (lipopolysaccharides). There is evidence that certain cyanobacterial toxins are genotoxic and carcinogenic; however, the mechanisms of their potential carcinogenicity are not well understood. The most frequently occurring and widespread cyanotoxins in brackish and freshwater blooms are the cyclic heptapeptides, i.e., microcystins (MCs), and the pentapeptides, i.e., nodularins (NODs). The main mechanism associated with potential carcinogenic activity of MCs and NOD is the inhibition of protein phosphatases, which leads to the hyperphosphorylation of cellular proteins, which is considered to be associated with their tumor-promoting activity. Apart from this, MCs and NOD induce increased formation of reactive oxygen species and, consequently, oxidative DNA damage. There is also evidence that MCs and NOD induce micronuclei, and NOD was shown to have aneugenic activity. Both cyanotoxins interfere with DNA damage repair pathways, which, along with DNA damage, is an important factor involved in the carcinogenicity of these agents. Furthermore, these toxins increase the expression of TNF-α and early-response genes, including proto-oncogenes, genes involved in the response to DNA damage, cell cycle arrest, and apoptosis. Rodent studies indicate that MCs and NOD are tumor promotors, whereas NOD is thought to have also tumor-initiating activity. Another cyanobacterial toxin, cylindrospermopsin (CYN), which has been neglected for a long time, is lately being increasingly found in the freshwater environment. The principal mechanism of its toxicity is the irreversible inhibition of protein synthesis. It is pro-genotoxic, and metabolic activation by cytochrome P-450 enzymes is needed for its genotoxic activity. In metabolically competent cells, it induces DNA strand breaks and exerts clastogenic and aneugenic activity. In addition, CYN increased the expression of p53 regulated genes involved in cell cycle arrest, DNA damage repair, and apoptosis. It also has cell transforming potential, and limited preliminary rodent studies indicate that CYN could have tumor-initiating activity. In 2010, the International Agency for Research on Cancer (IARC) classified MCLR as possible human carcinogen (Group 2B). Although there is not enough available information for the classification of other cyanobacterial toxins, the existing data from in vitro and in vivo studies indicate that NOD and especially CYN may be even more hazardous than MCLR to human and animal health. In addition in the environment, cyanobacterial toxins occur in complex mixtures as well as together with other anthropogenic contaminants, and numerous studies showed that the toxic/genotoxic potential of the extracts from cyanobacterial scums is higher than that of purified toxins. This means that the mixtures of toxins to which humans are exposed may pose higher health risks than estimated from the toxicological data of a single toxin. Future research efforts should focus on the elucidation of the carcinogenic potential of NOD, CYN, and the mixture of cyanobacterial extracts, as well as on the identification of possible novel toxins.     

Potent toxins in Arctic environments – Presence of saxitoxins and an unusual microcystin variant in Arctic freshwater ecosystems

Cyanobacteria are the predominant phototrophs in freshwater ecosystems of the polar regions where they commonly form extensive benthic mats. Despite their major biological role in these ecosystems, little attention has been paid to their physiology and biochemistry. An important feature of cyanobacteria from the temperate and tropical regions is the production of a large variety of toxic secondary metabolites. In Antarctica, and more recently in the Arctic, the cyanobacterial toxins microcystin and nodularin (Antarctic only) have been detected in freshwater microbial mats. To date other cyanobacterial toxins have not been reported from these locations. Five Arctic cyanobacterial communities were screened for saxitoxin, another common cyanobacterial toxin, and microcystins using immunological, spectroscopic and molecular methods. Saxitoxin was detected for the first time in cyanobacteria from the Arctic. In addition, an unusual microcystin variant was identified using liquid chromatography–mass spectrometry. Gene expression analyses confirmed the analytical findings, whereby parts of the sxt and mcy operon involved in saxitoxin and microcystin synthesis, were detected and sequenced in one and five of the Arctic cyanobacterial samples, respectively. The detection of these compounds in the cryosphere improves the understanding of the biogeography and distribution of toxic cyanobacteria globally. The sequences of sxt and mcy genes provided from this habitat for the first time may help to clarify the evolutionary origin of toxin production in cyanobacteria.     

Isolation and purification of peptide and alkaloid toxins from nabaena flos-aquae using high-performance thin-layer chromatography

A procedure has been developed for the sequential extraction and purification of the peptide and alkaloid toxins from a single batch of Anabaena flos-aquae cells. After solvent extraction and adsorption onto C₁₈ Sep-Pak cartridges, the cyanobacterial toxins were purified by high-performance thin-layer chromatography and identified by scanning with a densitometer. The purified components were tested separately by mouse bioassay. Liver damage and nervous disorder were induced by the two peptide and single alkaloid toxins, respectively.     

7-Deoxy-desulfo-cylindrospermopsin and 7-deoxy-desulfo-12-acetylcylindrospermopsin: Two new cylindrospermopsin analogs isolated from a Thai strain of Cylindrospermopsis raciborskii

As environmental changes such as eutrophication lead to increased size and frequency of cyanobacterial blooms, research into the toxins produced by these blooms becomes increasingly important. One of the common toxins produced by cyanobacterial blooms is cylindrospermopsin (1), a potent inhibitor of protein synthesis. To date, only two additional analogs of cylindrospermopsin have been isolated, namely 7-epicylindrospermopsin (2) and 7-deoxy-cylindrospermopsin (3). This report details the isolation and structure determination of an additional two new analogs, 7-deoxy-desulfo-cylindrospermopsin (4) and 7-deoxy-desulfo-12-acetylcylindrospermopsin (5). These are the first new analogs of cylindrospermopsin to be reported in over a decade. Based on their structural features, it is likely that these new analogs also possess the harmful biological activities displayed by the rest of the cylindrospermopsin family.