Sison-Mangus Marilou P, Jiang Sunny, Kudela Raphael M, Mehic Sanjin
Department of Ocean Sciences and Institute of Marine Sciences, University of California, Santa Cruz, Santa Cruz, CA USA.
Department of Civil and Environmental Engineering, University of California, Irvine, Irvine, CA USA.
Front Microbiol. 2016 Sep 12;7:1433. doi: 10.3389/fmicb.2016.01433. eCollection 2016.
Pseudo-nitzschia blooms often occur in coastal and open ocean environments, sometimes leading to the production of the neurotoxin domoic acid that can cause severe negative impacts to higher trophic levels. Increasing evidence suggests a close relationship between phytoplankton bloom and bacterial assemblages, however, the microbial composition and succession during a bloom process is unknown. Here, we investigate the bacterial assemblages before, during and after toxic and non-toxic Pseudo-nitzschia blooms to determine the patterns of bacterial succession in a natural bloom setting. Opportunistic sampling of bacterial community profiles were determined weekly at Santa Cruz Municipal Wharf by 454 pyrosequencing and analyzed together with domoic acid levels, phytoplankton community and biomass, nutrients and temperature. We asked if the bacterial communities are similar between bloom and non-bloom events and if domoic acid or the presence of toxic algal species acts as a driving force that can significantly structure phytoplankton-associated bacterial communities. We found that bacterial diversity generally increases when Pseudo-nitzschia numbers decline. Furthermore, bacterial diversity is higher when the low-DA producing P. fraudulenta dominates the algal bloom while bacterial diversity is lower when high-DA producing P. australis dominates the algal bloom, suggesting that the presence of algal toxin can structure bacterial community. We also found bloom-related succession patterns among associated bacterial groups; Gamma-proteobacteria, were dominant during low toxic P. fraudulenta blooms comprising mostly of Vibrio spp., which increased in relative abundance (6-65%) as the bloom progresses. On the other hand, Firmicutes bacteria comprising mostly of Planococcus spp. (12-86%) dominate during high toxic P. australis blooms, with the bacterial assemblage showing the same bloom-related successional patterns in three independent bloom events. Other environmental variables such as nitrate and phosphate and temperature appear to influence some low abundant bacterial groups as well. Our results suggest that phytoplankton-associated bacterial communities are strongly affected not just by phytoplankton bloom in general, but also by the type of algal species that dominates in the natural bloom.
拟菱形藻水华经常出现在沿海和开阔海洋环境中，有时会导致产生神经毒素软骨藻酸，这会对较高营养级产生严重负面影响。越来越多的证据表明浮游植物水华与细菌群落之间存在密切关系，然而，水华过程中的微生物组成和演替情况尚不清楚。在此，我们调查了有毒和无毒拟菱形藻水华之前、期间和之后的细菌群落，以确定自然水华环境中细菌演替的模式。通过454焦磷酸测序每周在圣克鲁斯市码头对细菌群落概况进行机会性采样，并与软骨藻酸水平、浮游植物群落和生物量、营养物质及温度一起进行分析。我们研究了水华事件和非水华事件之间的细菌群落是否相似，以及软骨藻酸或有毒藻类物种的存在是否作为一种驱动力，能够显著构建与浮游植物相关的细菌群落。我们发现，当拟菱形藻数量下降时，细菌多样性通常会增加。此外，当低产软骨藻酸的欺诈拟菱形藻在藻华中占主导时，细菌多样性较高；而当高产软骨藻酸的南方拟菱形藻在藻华中占主导时，细菌多样性较低，这表明藻毒素的存在能够构建细菌群落。我们还在相关细菌类群中发现了与水华相关的演替模式；γ-变形菌在低毒性欺诈拟菱形藻水华期间占主导，主要由弧菌属组成，随着水华的进展，其相对丰度增加（6%-65%）。另一方面，主要由动性球菌属组成的厚壁菌门细菌（12%-86%）在高毒性南方拟菱形藻水华期间占主导，在三个独立的水华事件中，细菌群落呈现出相同的与水华相关的演替模式。其他环境变量，如硝酸盐、磷酸盐和温度，似乎也会影响一些低丰度细菌类群。我们的结果表明，与浮游植物相关的细菌群落不仅受到一般浮游植物水华的强烈影响，还受到自然水华中占主导的藻类物种类型的影响。
