鱼腥藻藻华水体一株溶藻菌BWFA55的鉴定及溶藻特性

Identification and Algicidal Characteristics of an Algicidal Bacterium BWFA55 in Anabaena Bloom Water

【目的】鉴定一株鱼腥藻藻华水体的溶藻菌,分析菌株的溶藻特性。【方法】从佛山近郊湖泊鱼腥藻水华水体中分离到一株溶藻菌BWFA55,通过菌株生理生化鉴定和16S rDNA基因序列分析鉴定菌种。将该菌株培养4 d,分析菌株的生长特征和溶藻活性。将BWFA55发酵上清液与水华鱼腥藻(Anabaena flos-aquae)共培养168 h,通过扫描电镜观察藻细胞形态。将BWFA55菌悬液接种至不同浓度的水华鱼腥藻(A.flos-aquae)藻液,另按不同接种量将BWFA55接种至同浓度藻液,分析藻液浓度及接种量对溶藻效果的影响。测定BWFA55无细胞上清液、菌体悬液、菌株原发酵液的溶菌活性,分析BWFA55的主要溶藻方式。采用透析和有机溶剂萃取分离溶藻物质,在不同温度、pH条件下研究溶藻活性物质的特性。【结果与结论】经鉴定,溶藻菌株BWFA55为地衣芽孢杆菌(Bacillus licheniformis)。该菌株24 h发酵液的溶藻活性最高,在接种量(体积分数)为10%的条件下,水体中水华鱼腥藻的叶绿素a(Chl-a)含量在7 d内下降80%以上。该菌通过分泌溶藻化合物间接攻击水华鱼腥藻,使丝状群体的藻细胞数量明显降低,群体连接结构被破坏。BWFA55主要的溶藻活性物质存在于发酵上清液中,分子质量大于3 ku,且可被乙酸乙酯萃取,在高温下保持60%以上的溶藻率,且不受pH影响,有良好的酸碱、温度耐受性。

【Objective】To identify an alginolytic bacterium from algal bloom water,and analyze its alginolytic activities.【Method】A strain named BWFA55 with high algolytic activity against Anabaena flos-aquae isolated from Anabaena bloom lakes in the suburbs of Foshan was identified by API 50 CHB/E physiological-biochemical properties and 16S rDNA sequence analysis.The strain was cultured for 4 days to analyze its growth characteristics and alginolytic activity against A.flos-aquae.The fermentation supernatant of BWFA55 was co-cultured with A.flos-aquae for 168 h,and then,the cell morphology of the algae was observed by scanning electron microscopy.The algicidal effects of the algal concentrations and the inoculation quantity of BWFA55 were analyzed.The methods for BWFA55 to dissolve the algae were analyzed by measuring the lytic activities of sterile supernatant from BWFA55 cell suspension and fermentation broth.The alginolytic substances were separated by dialysis and organic solvent extraction.The characteristics of alginolytic substances were studied at different temperatures and pH conditions.【Result and Conclusion】The BWFA55 was identified as Bacillus licheniformis.When 10%24-hour fermentation broth was co cultured with Anabaena bloom,the algicidal activity was the highest.The chlorophyll a(chl-a)content was reduced by>80%in 7 days.This strain attacked A.flos-aquatica indirectly by secreting alginolytic compounds.This process significantly reduced the number of cells in filamentous population and the population connection structure was destroyed.The major alginolytic compounds of BWFA55 in the fermentation supernatant had a molecular mass>3 ku,and it could be extracted by ethyl acetate.A alginolytic rate of more than 60%could be maintained at high temperature and were not affected by pH.Therefore it was confirmed that the active substances had a good thermal stability and acid-base stability.