| Algae-bacteria relationship is a hot research topic in Marine biology.At present,there are mainly three types of algal bacteria relationship discovered:Mutualism relationship,competitive inhibition,and the dual relationship with dynamic,double relationship here refers to algae and bacteria can be a relationship to another kind of opposites,less than the other two relationships in the study of the algae bacteria relations,but also the dual relationship is part of the algae bacteria relationship can not be ignored in the study.The study of this relationship can further reveal the relationship between algal bacteria.In this paper,a symbiotic bacterium with algal lytic activity was isolated from Prorocentrum donghaiense.The dual relationship of algae and bacteria was investigated by fluorescence quantitative PCR,scanning electron microscopy and metabonomics.In this paper,a bacterial strain with alginolytic activity from Prorocentrum donghaiense was isolated and purified by dilution separation methods.This bacteria was identified as Alteromonas macleodii by molecular biological methods and named as H-2.The bacteria secreted extracellular substances for algal lysis.When 1%(v/v)of bacterial secretion was added into the cell culture medium of Prorocentrum donghaiense,the algal lysis rate of Prorocentrum donghaiense could reach 79.54%after 6 hours.The secretion of the bacteria had algolytic effect on Prorocentrum donghaiense and 12 different dinoflagellates and diatoms.Scanning electron microscopy(SEM)showed that in the process of lysis of Prorocentrum donghaiense,the algal cells were gradually damaged and the number of bacteria around the algal cells was gradually increased,and most of the bacteria attached to the algal cell wound.The results of non-targeted metabonomics identification and genomic analysis showed that the algae-lysing substances of this bacterium were more similar to plant cell wall enzymes and small molecule metabolites.In order to study the growth relationship between H-2 bacteria and their hosts,a fluorescence quantitative PCR method for detecting number of Alteromonas macleodii H-2 in alga cells was established in this paper.The method was accurate and sensitive,and the amplification efficiency was 96.63%.The concentration of bacteria was2.82 10~3-2.82 10~9copies/?L.By this method,it was found that the number of Alteromonas macleodii H-2 in Prorocentrum donghaiense increased from 361/m L to45,999/m L after 12 hours of algal dissolution.Through this experimental method,H-2 bacteria were detected in the other 12 different kinds of microalgal cells mentioned above.The experimental algal cells were dissolved in the secretion of alginolytic bacteria.After 12h,the growth of H-2 bacteria appeared in all samples to varying degrees.Non-targeted metabonomics was used to determine and screen out the differential metabolites in the algal cells before and after alginolysis of Prorocentrum donghaiense.A total of 182 differential metabolites were detected,among which 40 were amino acids and their derivatives.Among these metabolites,65 metabolites were significantly up-regulated and 36 metabolites were significantly down-regulated.The changes of metabolites indicated that during the process of algal cell lysis,cells could resist the attack of algal lytic substances by anti-toxicity,anti-oxidation and promoting cell growth.To sum up,it is believed that there is a dual algal relationship between Alteromonas macleodii H-2 and Prorocentrum donghaiense in this paper.Under the normal growth of Prorocentrum donghaiense,the bacteria co-exist with algal cells and do not show algal lytic activity.When algal cells enter the death stage,the number of the bacteria increases and shows algal lytic activity,accelerates the lytic death of algal cells.This relationship also exists in other algal environments,these include Scrippsiella trochoidea,Prodinoflagellates Prorocentrum minimum,Alexandrium tamarense,Alexandrium microflagellates Alexandrium minimum,etc. |
PDF Full Text Request