Methodological Study Of Marine Bioavailable Dissolved Organic Carbon And Characterization Of A New Species Of Seohaeicola Bacterium

Dissolved organic matter (DOM) in the ocean is well known as a major carbon reservoir on the Earth, which is compared favourably with the atmosphere CO2. Marine heterotrophic bacteria play an important role in marine carbon cycle and carbon sequestration though taking part in food chain, microbial loop and microbial carbon pump (MCP). Basic studied for marine bioavailable dissolved organic carbon (BDOC) quantification and the heterotrophic bacterial diversity study should be meaningful. However, existed methods for BDOC quantification are inconformity. It impedes the development of the global BDOC research by lacking of very well incomparable studies results. Hence, common understandings and more accurate assessments on the impact of these different parameters are imperative. We reviewed different parameters of those existing BDOC quantify methods, and summarised the controversial parameters, in order to set a method with good operability for BDOC quantification. Based on that, we studied a new method for BDOC quantification. Furthermore, we isolated a new species of Seohaeicola from western Pacific, the strain was characterized based on morphological, physiological and biochemical study, and phylogenetic analysis. This work contributes basic knowledge to bacteria phylogeny and metabolism. Results are given as follows:Marine BDOC was studied based on the evaluation of different filtrate ways and membranes. We made efforts to evaluate the impact of "bottle effect" and dilution gradient of cultivation system on the result of BDOC quantification. Results show that different area-to-volume ratios of bottles have little effect on the growth and the DOC utilization of bacteria in the system while different dilution gradients have obviously effects on the growth and the DOC utilization of bacteria in the system. In consideration of the analysis for other parameters, the purpose of BDOC quantitative assay and site condition, we recommend a full protocol for BDOC quantification: natural seawater was filtrated though a 0.80?m pore-sized filter, then the filter was transferred into glass culture bottles with TPFE septa on the cap, and the water volume must be enough for sampling, then it was incubated in a dark room at room temperature (it is closed to the condition of in situ) for at least 14 days. Within this period, medium was withdrawn at least 5 times for sampling. The TOC sampling intervals though out the incubation time were from less than 1 day at the beginning to several days to the end. TOC consumption during incubation can be fitted using linear regression analysis or exponential decay analysis, the TOC consumed during incubation is the BDOC in this period.In the isolation and characterization of the marine new species, we take 16S rRNA gene sequence comparison to JL2247T which was isolated from the western Pacific at the depth of 2000m and the result reveals that strain JL2247T fell into the genus Seohaeicola, family Rhodobacteraceae, order Rhodobacterales, class Alphaproteobacteria, sharing the highest similarity with Seohaeicola saemankumensis(96.4% similarity). On the basis of phylogenetic distance and the physiological and biochemical data, strain JL2247T represents a novel species within the genus Seohaeicola and the name Seohaeicola. westpacificsissp. nov. is proposed.