Researches On The Filtration And Resistance Mechanisms Of The Host Plectonema Boryanum To Cyanophage PP

The Plectonema which is resistant to Cyanophage PP has been obtained through the separation and purification in this study.PP could't infect the resistant Plectonema normally in both the plaque assay and the liquid infection.Although there was no significant difference between the resistant and the sensitive Plectonema in cell size,their hormogonium length were significantly different.The coefficient of adsorption to the resistant Plectonema was markedly less than to the sensitive Plectonema,this result illuminated that the resistant Plectonema was counteractive to the adsorption of cyanophage.It was also informed that not all of the successful adsorption will cause the effective infection by comparing the successful infection rate and the adsorption rate. Besides,mitomycin C induced resistance Plectonema showed no lytic phenomenon; Above all,we deduce that the resistance isn't brought on by the lysogenesis,the possible resistant mechanisms include:1) resistant Plectonema prevents the adsorption of cyanophage by changing its cell surface receptors or secreting the capsule;2) resistanct Plectonema restrains the cyanophage from entering,replicating and releasing by mechanisms such as penetration blocking,abortive infection and restriction-modification systems.Therefore,the resistance of the host may be an associated effect of the several mechanisms.It is needed to account for specially that the inactivation rate of PP after the adsorption,which was induced by the resistant host,would be up to 27.97%·h^-1.In contrast,the inactivation rate of PP,was only 7.26-30.70%·h^-1,caused by the UV radiation in sunlight,which has always been widely considered to be the most important factor to lead to virioplankton,including cyanophage to inactivate.Thus,in addition to the daylight,the resistance mechanisms of the host to the cyanophage may be also one of the crucial factors,which induce the cyanophage to inactivate.The experiment of resistant and sensitive host and PP indicated that the three could not coexist for a long time,eyanophage would eventually disappear from this system.The reason may be that the sensitive host has already been dissolved absolutely or the resistant host accelerated the inactivation of virus.This phenomenon,which is incompatible with the research about the natural water body,may be due to the favourable conditions and the limited volume in the laboratory,just the opposite,the large space and the uncertain conditions and the complex interactions among viruses, heterotrophic bacteria,other microorganisms,as well as the existence of the large cyanophage repository in the natural environment,provide the greater possibility for the co-existence of resistant and sensitive host and cyanophage.To sum up,the resistance of host is the vital factor,which impact the dynamics of cyanophage and host population,so it is of great significance to continue to carry out the related research.