AUTHOR=Xu Shuaishuai , Wang Xiaodong , Liu Jie , Zhou Fengli , Guo Kangli , Chen Songze , Wang Zhao-hui , Wang Yan 

TITLE=Bacteria Associated With Phaeocystis globosa and Their Influence on Colony Formation

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.826602

DOI=10.3389/fmicb.2022.826602

ISSN=1664-302X

ABSTRACT=<p><italic>Phaeocystis globosa</italic> (<italic>P. globosa</italic>) is one of the dominant algae during harmful algal blooms (HABs) in coastal regions of Southern China. <italic>P. globosa</italic> exhibits complex heteromorphic life cycles that could switch between solitary cells and colonies. The ecological success of <italic>P. globosa</italic> has been attributed to its colony formation, although underlying mechanisms remain unknown. Here, we investigated different bacterial communities associated with <italic>P. globosa</italic> colonies and their influence on colony formation of two <italic>P. globosa</italic> strains isolated from coastal waters of Guangxi (GX) and Shantou (ST). Eight operational taxonomic units (OTUs) were observed in ST co-cultures and were identified as biomarkers based on Linear discriminant analysis Effect Size (LEfSe) analysis, while seven biomarkers were identified in <italic>P</italic>. <italic>globosa</italic> GX co-cultures. Bacterial communities associated with the <italic>P. globosa</italic> GX were more diverse than those of the ST strain. The most dominant phylum in the two co-cultures was Proteobacteria, within which <italic>Marinobacter</italic> was the most abundant genus in both GX and ST co-cultures. Bacteroidota were only observed in the GX co-cultures and Planctomycetota were only observed in the ST co-cultures. Co-culture experiments revealed that <italic>P</italic>. <italic>globosa</italic> colony formation was not influenced by low and medium cell densities of <italic>Marinobacter</italic> sp. GS7, but was inhibited by high cell densities of <italic>Marinobacter</italic> sp. GS7. Overall, these results indicated that the associated bacteria are selected by different <italic>P</italic>. <italic>globosa</italic> strains, which may affect the colony formation and development of <italic>P. globosa</italic>.</p>