Genetic Relationship Of 5 Samples Of Arthrospira From 16S RRNA And CpcHID Sequence

As a group of autotrophic prokaryote,Arthrospira is a type of nonheterocystous and filamentous cyanobacteria found in most lakes,ponds and coastal water.It not only can be used as food,feed and bait,but also can be applied in many other fields,such as medical treatment,health care,fine chemical industry and cosmetic industry,etc.At present,in large commercial exploitation,what is so-called Spirulina is almost that of Arthrospira.A. platensis in Chad Lake in Africa and A.maxima in Texcoco Lake in Mexico.In 1996,three species of Arthrospira and a species of Spirulina were found in the alkaline lake of Erdos Plateau by Professor Qiao et al.,filled the blank of Arthrospira and Spirulina resources of our country.In recent years, many studies on Arthrospira of Erdos Plateau,which is mainly about morphology anatomic structure and physic biochemical character,has been reported.But there is little literature on gene sequencing,especially on 16S rRNA gene and cpcHID operon sequences analysis about genetic relationship of 5 samples of Arthrospira.In this paper,the materials are Arthrospira platensis(A₁) of Erdos,A. erdosensis(A₂),A.jenneri(A₃),A.platensis(A₄) in the Lake of Chad and A. maxima(A₅) in the Lake of Texcoco.Genome DNA of 5 samples were obtained by Lysozyme.Partial sequences of 16S rRNA gene and cpcHID operon sequences of 5 Arthrospira samples were cloned by specific primers and then sequenced.In order to create phylogenetic trees,to explore their evolutionary status and genetic relationship at gene level,and to enrich the basic research of Arthrospira,the obtained sequences data were compared, aligned and analyzed by BioEdit,MEGA4.1 and DNAStar software package, which is significant for the resources development and utilization of Arthrospira in the alkaline lake of Erdos Plateau. The results showed,the alignment of the 5 sequences totaled of 16S rRNA are between 1334bp and 1335bp;and cpcHID operon are between 1420 and 1424bp.The sequences of 16S rRNA from the five strains were highly homologous,reaching 84.4%～99.8%;and cpcHID operon are between 42.1% and 98.7%.The GC content of cpcHID operon in the five samples was generally less than that based on 16S rRNA,but the ratio of different sites was larger than 16S rRNA.A₁ and A₃ species of Arthrospira of Erdos Plateau have the smallest euclidean distance;A₁ and A₄ species of Arthrospira ptatensis of different origin don't have the smallest euclidean distance.For the same species,the difference was due to a large variation in gene level caused by the evolutionary pressure.At the long course of evolution,the environment of Erdos Plateau is bad and variously.In order to survive,the genomic DNA of Arthrospira platensis A₁ changed larger than Arthrospira platensis A₄ in lake of Chad.The cluster analysis of 16S rRNA gene sequences showed that A₂ and A₅ have a largest Euclidean distance,but cpcHID operon sequence analysis showed that the relationships of A₂ and A₅ is the nearest.Combine with the result of Isoenzymes and soluble protein in Arthrospira from alkaline lakes in Erdos Plateau by Yang Q,this paper considers that the genetic relationship of A₂ and A₅ by 16S rRNA gene sequence analysis may be more actually,while the evolutionary status and genetic relationship of A₂ should be confirmed by further in-depth study.