Microbial Diversity Of Pyropia Haitanensis Phycosphere During Cultivation In Wenzhou

Pyropia haitanensis is wildly cultivated in Zhejiang and Fujian province with greatcommercial importance. To observe the characteristics and changes of phycosphere microbialcommunities during seaweeds cultivation can help us monitor the potential pathogens andmicrobial factors affecting the health of cultivated seaweeds.The morphological characteristics and the diversity of phycosphere and surrounding seawatermicrobes were studied by pure culture method and PCR-DGGE. Similarity analysis was carriedout online with the16S rDNA (bacteria) and18S rDNA (fungi) sequences in GeneBank. Thephycosphere microbial diversity during different growth stages, cultivated areas and periods wasstudied. Totally467bacteria strains and55fungi strains were isolated. The diversity of fungi wassignificantly smaller than that of bacteria. The bacteria were classified into41genera, belongingto Alphaproteobacteria, Gammaproteobacteria, Firmicutes, Actinobacteria and Bacteroidetes. Thedominant bacterial communities were Alphaproteobacteria and Gammaproteobacteria. Most of thefungi were classified into Ascomycota, only one strain belonged to the Basidiomycota,Agaricomycetes. Bacteria of19specific genera were isolated from P. haitanensis while13specific genera were isolated from the surrounding seawater. Most actinomyces and fungi wereisolated from the conchocelis cultured indoors, which was quiet different from the microbialcommunities of the thalli in intertidal zone. Within the isolated microbes, we found that somestrains had very high similarity with those pathogens, such as Cobetia marina (causing red-rottingdisease in P. haitanensis), Phoma porphyrae (causing white rotting disease in Pyropia yezoensischoncocelis)，and saprotrophic fungi Fusarium spp. and Aspergillus spp.Real-time qPCR was used to detect the ratio of Pseudoalteromonas sp. in the co-culturesystem of two baceteriastrains (Pseudoalteromonas sp. NPyS3and Bacillus sp. WPySW2). Thespectrophotometry and hemacytometry methods were applied also to depict the growth curves ofthe bateria. The stardand curve of Pseudoalteromonas sp. and total bacteria were formulated asCt=-3.288×lg(copies)+38.37(R2=0.999) and Ct=-3.725×lg(copies)+39.35(R2=0.999),respectively. The inconformity between the growth curve results tested by spectrophotometry andhemacytometry might due to the difference between the cell sizes of two bacteria types.Comparing the growth curves of Pseudoalteromonas sp. NPyS3and Bacillus sp. WPySW2tested by Real-time qPCR with spectrophotometry and hemacytometry, we found that WPySW2grewfaster than NPyS3at the first16h since coculture, while decreased after that time, and NPyS3increased sharply. Refer to the results of interaction test cultured in solid2216E Zobell nutrientplates, it was indicated that NPyS3was superior than WPySW2in the later coculture period.