Lysogenic cyanophages; molecular mechanisms of lysogeny and their role in marine ecosystems

最近的研究表明，噬藻体不仅存在于沿海地区附近的污染沃茨中，而且也存在于清洁沃茨，如公海。这些噬藻体被认为在蓝藻门（蓝藻）种群的调节中具有重要作用。大多数分离的噬藻体是毒性类型的，并且细胞在感染后不久迅速裂解。溶原性细菌对蓝藻种群的调节作用尚不清楚。了解溶原性噬藻体在海洋蓝藻中的分布和溶原性的分子机制是评估溶原性噬藻体在海洋生态系统中可能作用的基础。在前期的工作中，我们发现一种噬藻体在海洋蓝藻--太平洋席藻（Phormidium persicinum Provasoli）中建立了稳定的溶源性。通过添加丝裂霉素C或短暂的UV照射诱导溶原化噬菌体的裂解周期。(1)利用桃疫霉的培养物 ...更多信息 在没有任何人工诱导的情况下，我发现相当大一部分溶原性噬藻体在Phormidium acrylicinum培养物中被检测到处于裂解周期。(2)大量分离自不同地区的海洋席藻菌株都含有溶原性噬藻体。形态学特征、DNA-DNA杂交和噬菌体蛋白的Western分析表明，不同的噬藻体家族在海洋蓝藻中建立了稳定的溶源性。这些结果表明，溶原性噬藻体是生态学上重要的，因为它们不仅调节宿主藻类种群，而且它们成为游离噬菌体颗粒的连续供应到周围的海水沃茨的来源。(3)利用分离的菌株（NIBB 1067）和从加勒比海的Carrie Bow Cay，伯利兹采集的现场样品研究了溶原性噬藻体在调节海洋好氧重氮营养蓝细菌Trichodesmium中的可能作用。束毛藻属是贫营养、热带和亚热带海洋中最重要的初级生产者。丝裂霉素C对束毛藻细胞的快速溶解作用在培养和自然样品中都有观察到。噬藻体颗粒分离自束毛藻NIBB 1067。这些结果表明溶源性噬藻体在贫营养海洋的食物网中起着重要的作用。少

Recent studies have revealed that cyanophages are found not only in polluted waters near the coastal areas but also in clean waters such as the open ocean. These cyanophages are thought to have an important role in the regulation of cyanophyta (cyanobacterial) populations. Most of the isolated cyanophages are of the virulent type, and cells are rapidly lysed shortly after infection. The contribution of lysogenic phages to the regulation of cyanobacterial populations is unknown. The basic knowledge such as distribution of lysogenic cyanophages among marine cyanobacteria and molecular mechanisms for lysogeny are required to estimate the possible role of lysogenic cynophages in marine ecosystems. In our previous work, we found that a cyanophage had established the stable lysogeny in marine cyanobacteria, Phormidium persicinum Provasoli strain. The lytic cycle of lysogenized phage was induced by the addition of mitomicyn C or a brief UV-illumination. (1) Using the culture of P. persicinum … More cultures, I found that considerably large part of the lysogenized cyanophage were detected to be in lytic cycle in the Phormidium percicinum cultures without any artificial induction. (2) Considarably large numbers of marine Phormidium strains isolated from different areas harbored lysogenic cyanophages. Morphological characters, DNA-DNA hybridization and Western analysis of phage proteins suggested that different family of cyanophages were established the stable lysogeny in marine cyanobacteria. These results indicated that lysogenic cyanophages are ecologically important, because not only they regulated the host algal populations but also they become the source for continuous supply of free phage particles to the ambient sea waters. (3) A possible role of lysogenic cyanophage(s) in regulation of marine, aerobic diazotrophic cyanobacteria, Trichodesmium was studied using both isolated strains (NIBB 1067) and field samples collected from Caribbean Sea off Carrie Bow Cay, Belize. Trichodesmium spp. Are the most important primary producer in oligotrophic, tropical and sub-tropical oceans. The rapid cell lysis of Trichodesmium caused by the addition of mitomycin C was observed in both cultured and natural samples. Cyanophage particles were isolated from Trichodesmium NIBB1067. These results suggested that the lysogenic cyanophage(s) must play an important role in the food web of oligotrophic oceans. Less