Ndlela L L, Oberholster P J, Van Wyk J H, Cheng P H
Council for Scientific and Industrial Research, 11 Jan Celliers Road, Stellenbosch, 7600, South Africa; Department of Botany and Zoology, Faculty of Science, Stellenbosch University, Matieland 7600, South Africa.
Council for Scientific and Industrial Research, 11 Jan Celliers Road, Stellenbosch, 7600, South Africa; Department of Botany and Zoology, Faculty of Science, Stellenbosch University, Matieland 7600, South Africa.
Toxicon. 2019 Jul;165:1-12. doi: 10.1016/j.toxicon.2019.04.002. Epub 2019 Apr 17.
Biological control of cyanobacteria is a viable means of controlling nuisance bloom occurrences; however the majority of studies done are against Microcystis sp., with a commonly lytic effect caused. Filamentous cyanobacteria such as Oscillatoria are not as extensively studied in this area of biological control and are often part of Microcystis dominated blooms. This study employed heterotrophic bacterial isolates selected from bloom waters that indicated potential predatory behaviour against both filamentous and colonial cyanobacterial isolates. In comparison to a known Bacillus isolate, which is often reported among bacterial control agents, three other bacteria isolates were tested as control agents against non-axenic Oscillatoria and Microcystis cyanobacterial cultures. Assessments of cyanobacterial cell responses to the bacteria were conducted through water chemistry, chlorophyll a, alkaline phosphatase activity, microscopy and cyanotoxin measurements. The changes in these parameters were compared to untreated cyanobacterial cultures where no bacteria were added. The study found that at ratios of bacteria half that of Microcystis, minimal changes in chlorophyll a were observed, whilst Oscillatoria showed a decreased chlorophyll a more in the presence of isolates 1 and 3w. The assessment of alkaline phosphatase activity showed decreased activity in both cyanobacterial isolates exposed to the bacteria, relative to the untreated control sample. Microscopy analysis through fluorescence indicated that the attachment of the bacteria to the surface of the cyanobacteria hampered with the fluorescence and scanning electron microscopy indicated that the cells were damaged by the addition of the bacterial isolates. Cyanotoxin detection through the ELISA kit testing indicated that there was toxin reduction in samples treated with the bacterial isolates, with the highest reduction being close to 60% in the case of Microcystis sp. treated with isolate 3w. Similar reductions were noted in the filamentous cyanobacterium Oscillatoria, in the presence of isolate 1.
蓝藻的生物控制是控制有害藻华发生的一种可行方法；然而，大多数已开展的研究针对的是微囊藻属，通常会产生溶菌作用。丝状蓝藻，如颤藻，在生物控制领域的研究并不广泛，并且常常是微囊藻占主导的藻华中的一部分。本研究采用了从藻华水体中分离出的异养细菌，这些细菌对丝状和群体蓝藻分离株均表现出潜在的捕食行为。与一种已知的芽孢杆菌分离株（该分离株常在细菌控制剂中被报道）相比，另外三种细菌分离株被作为控制剂，用于处理非无菌的颤藻和微囊藻蓝藻培养物。通过水化学、叶绿素a、碱性磷酸酶活性、显微镜检查和蓝藻毒素测量，对蓝藻细胞对这些细菌的反应进行了评估。将这些参数的变化与未添加细菌的未处理蓝藻培养物进行了比较。研究发现，当细菌与微囊藻的比例为1:2时，叶绿素a的变化极小，而在分离株1和3w存在的情况下，颤藻的叶绿素a下降更为明显。碱性磷酸酶活性评估表明，相对于未处理的对照样品，暴露于细菌的两种蓝藻分离株的活性均有所下降。通过荧光显微镜分析表明，细菌附着在蓝藻表面会干扰荧光，扫描电子显微镜表明，添加细菌分离株会使细胞受损。通过酶联免疫吸附测定试剂盒检测蓝藻毒素表明，用细菌分离株处理的样品中存在毒素减少的情况，在用分离株3w处理的微囊藻属样品中，毒素减少最多接近60%。在分离株1存在的情况下，丝状蓝藻颤藻也有类似的减少情况。
