AUTHOR=Zhang Yingjiao , Zhou Xiaowen , Tang Weiqi , Zhou Konglin , Wang Zonghua , Shi Xinguo 

TITLE=Decoding the influence of bacterial community structure and algicidal bacteria in a Karenia longicanalis bloom event

JOURNAL=Frontiers in Marine Science

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2023.1242319

DOI=10.3389/fmars.2023.1242319

ISSN=2296-7745

ABSTRACT=<sec><title>Introduction</title><p>Harmful algal blooms (HABs) have been increasing in frequency and expanding their ranges on coastlines worldwide in recent decades. Algicidal bacteria play a pivotal role in eliminating HABs, yet the characteristics of bacterial communities and their algicidal activity during a <italic>Karenia longicanalis</italic> bloom remain poorly understood.</p></sec><sec><title>Methods</title><p>In this study, we investigated bacterial communities using 16S rRNA sequencing during a <italic>K. longicanalis</italic> bloom to identify bacteria with high algicidal activity that could be isolated. Five sampling sites in Tongxin Bay, located in Lianjiang County, China, including TX1 to TX5, were selected based on the concentration of <italic>K. longicanalis</italic> cells.</p></sec><sec><title>Results</title><p>Our 16S rRNA sequencing results revealed that the TX4 site was enriched with genera known to contain algicidal bacteria, such as <italic>Pseudoalteromonas</italic> and <italic>Alteromonas</italic>, which are members of the Gammaproteobacteria class, while <italic>Sulfitobacter</italic>, a member of the Alphaproteobacteria class, was enriched in the TX5 site. Among the 100 cultivable bacteria isolated from the 5 sampling sites, 6 exhibited an algicidal rate of over 80%, with FDHY-MQ5, isolated from the TX4 site, exhibiting an algicidal rate of approximately 100% against <italic>Karenia mikimotoi</italic> after 48 hours of challenge with 2% (v/v) bacterial volume (OD600=4.5) concentration. Our 16S rRNA sequencing result showed FDHY-MQ5 was a member of the <italic>Pseudoalteromonas</italic> genus, and this bacterium also demonstrated high algicidal activity against <italic>Heterosigma akashiwo</italic> and <italic>Alexandrium tamarense</italic>.</p></sec><sec><title>Discussion</title><p>Our findings shed light on the changes in bacterial community structure and the algicidal behavior of bacteria towards algae during a <italic>K. longicanalis</italic> bloom, providing a research basis for a better understanding of HAB management.</p></sec>