Cyanobacteria possess a wide array of bioactive compounds including those with antimicrobial activities. The target was to investigate the UV effect on antimicrobial activity of cyanobacterial extracts. Several cyanobacterial strains were isolated from Eastern region of KSA as well as three plant pathogenic bacterial strains. Four cyanobacterial strains were used. Two strains were isolated from Al Uquair region, Arabian Gulf, and identified as Synechococcus sp. and Oscillatoria sp. The two other strains were collected from brackish stream of underground water and were characterized as Synechocystis sp. and Phormidium sp. The antimicrobial bioassay was then performed using cyanobacterial aqueous extracts. The antimicrobial effect was estimated by measuring the inhibition zone compared to that of control. The extract was divided into 2 parts: part was not exposed to UV and the other was exposed to UV-B irradiation for 10 min. The antimicrobial bioassay was performed for both parts of the extract, using plant pathogenic bacteria, namely, Erwinia sp., Pseudomonas sp., and Bacillus sp. The antimicrobial profile was examined and results showed that the extracts showed non-antimicrobial effect before UV irradiation, and antimicrobial effect after UV exposure. Also, those that were active against pathogenic bacteria were more active after UV exposure. This is mostly attributed to a high optical energy of UV irradiation that subsequently had a significant impact on the electron transitions in the molecules of the extract rendering some of them more effective in their antibacterial action. This short communication was the first report where the UV can alter the antimicrobial profile of cyanobacterial extracts. This is a novel approach in enhancing antibacterial activity. Future molecular investigations will be conducted to further characterize the isolate whose extract showed the highest response to UV treatment.

中文翻译：

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紫外线辐射促进蓝藻提取物对植物病原体抗菌活性的首次记录

蓝细菌拥有多种生物活性化合物，包括具有抗菌活性的生物活性化合物。目的是研究紫外线对蓝细菌提取物的抗菌活性的影响。从KSA东部地区分离了数种蓝细菌菌株，以及三株植物致病细菌菌株。使用了四个蓝细菌菌株。从阿拉伯海湾的Al Uquair地区分离出两个菌株，并将其鉴定为Synechococcus sp。和Oscillatoria sp。另外两个菌株是从微咸的地下水中收集的，其特征为集胞藻。和Phormidium sp。然后使用蓝细菌水提取物进行抗微生物生物测定。通过测量抑制区域与对照区域的比较来评估抗菌作用。提取物分为两部分：一部分未暴露于UV，另一部分暴露于UV-B辐射10分钟。使用植物病原细菌，即欧文氏菌属，假单胞菌属属和芽孢杆菌属，对提取物的两部分进行抗菌生物测定。检查抗菌谱，结果表明提取物在紫外线照射前显示出非抗菌作用，在紫外线照射后显示出抗菌作用。而且，那些对病原菌具有活性的化合物在紫外线照射后更具活性。这主要归因于紫外线辐射的高光能，其随后对提取物分子中的电子跃迁产生了重大影响，从而使其中一些在抗菌作用方面更有效。这种简短的交流是第一个报告，其中紫外线可以改变蓝藻提取物的抗菌特性。这是增强抗菌活性的新方法。未来将进行分子研究，以进一步鉴定其提取物对紫外线处理反应最高的分离株。