Study On The Molecular Genetic Diversity Of Jiaozhou Bay Phytoplankton

Study on the molecular genetic diversity of Jiaozhou Bay phytoplanktonRribulose - 1, 5 - bisphosphate carboxylase/ oxygenase (hereafter RubisCO) is the most important enzyme for photobiosynthesis. It catalyzes both the reduction of CO2 and the oxygenolysis of ribulose -1,5- bisphosphate. As the most abundant protein on earth, RubisCO exists in diverse organisms including photosynthetic bacteria, algae and high plants. RubisCO has three forms different in advanced structures. Form I, found in all plants and some bacteria, is composed of 8 large (L) and 8 small (S) subunits in a hexadecamer L8S8. Two genes named rbcL and rbcS adjacent in chloroplast genome encode L and S subunits respectively. Form II is usually a dimmer of large subunit L2. It exists in dinoflagellate and some photosynthetic bacteria. Recently, novel form III RubisCo has been identified in archaeobacteria, which is composed of only large subunit in an unique decamer (L2)5. Based on amino acid sequence similarity, form I RubisCO rbcL can be clustered into four main types. Type A is found mainly in alpha-, beta- and gamma-proteobacteria. Type B is found in chlorophyta, high plant chloroplasts and cyanobacteria with two exceptions, Prochlorococcus marinus and Synechococcus sp. strain WH7803 whose rbcLs are closer to type A. Type C exists in another alpha- and beta-proteobacteria. Type D is mainly from chromophyta. RubisCo large subunit gene, rbcL, has served as appropriate markers for the systematic studies of plants and phytoplankton, the diversity description of deep-sea microorganisms and the association analysis between gene expression and marine environment.Ribulose -1,5- bisphosphate carboxynase/ oxygenase large subunit gene (rbcL) of Jiaozhou Bay phytoplankton was amplified from spring, summer and autumn surface seawater DNAs and cloned respectively. One hundred and forty five clones,about 50 each library, were randomly selected and sequenced. If identical amino acid sequences are considered as the same operational taxonomy unit (OTU), 59 OTUs are identified according to inferred amino acid sequences, among them, 21 are specific for spring seawater, 13 for summer seawater and 23 for autumn seawater. Summer and autumn seawaters share 2 OTUs. Shannon's index calculated from OTU abundances reflects the genetic diversity level of a community. The indexes of spring, summer and autumn surface seawater phytoplankton are 2.69, 2.44 and 2.76 respectively, indicating that phytoplankton genetic diversity of autumn seawater is the richest. Seasonal variation of phytoplankton community is significant; the community compositions of three seasons are almost completely different except for two OTUs shared by summer and autumn. Surface seawater phytoplankton communities are possibly metacommunities different spatially and temporally.In this study, we have also designed three primers to amplify Jiaozhou Bay dinoflagellate ribosomal RNA small subunit gene fragment. It has been found that the primers are dinoflagellate specific. Preliminary analysis has shown that the diversity of Jiaozhou Bay dinoflagellate is rich.