Bacteria-Phytoplankton Interactions: The Influence of Marine Bacteria on Alexandrium spp. Blooms in the Gulf of Maine

亚历山大藻属有毒甲藻的水华已成为一个慢性问题，几乎每年影响缅因湾(GOM)的大片地区。这些藻类是麻痹性贝类中毒的病原体，这是一种潜在的致命神经疾病。对公共卫生的担忧导致频繁的贝类隔离，一些贝类养殖场被永久关闭，并在GOM实施了昂贵的PSP毒素监测项目。尽管已经做出了相当大的努力来确定影响亚历山大藻的环境因素。在GOM中，控制亚历山大藻种群就地消长的因素仍然知之甚少。海洋细菌和有毒浮游植物之间的相互作用被认为在控制有毒藻类水华方面发挥了重要作用，但它们在GOM中潜在的重要作用几乎没有受到关注。众所周知，细菌和浮游植物的动态在沿海海洋环境中紧密联系在一起，细菌和浮游植物生物量之间经常观察到强烈的关联。此外，细菌对特定有害藻华(HAB)生物的积极和消极影响都已被记录在案。初步研究结果表明，GOM细菌能够在实验室条件下显著刺激亚历山大藻，这些相互作用可能会随季节而变化。该项目将阐明细菌在亚历山大藻中的作用。GOM中的种群动态。将研究细菌-亚历山大藻相互作用的几个方面，包括：抑制或促进亚历山大藻生长的细菌的季节和空间分布；细菌-亚历山大藻相互作用的特殊性；以及影响细菌群落动态的生物和非生物因素。实地研究将与加拿大合作者一起在西南部的芬迪湾进行。此外，1998年和2000年与ECOHAB-GOM抽样计划合作从东部和西南部GOM收集的存档细菌群落样本将被分析，以确定发现与亚历山大菌相互作用的特定细菌的地理分布。与ECOHAB-GOM团队和DFO HAB计划的密切合作将提供广泛的数据阵列和对研究船的访问。分析细菌与亚历山大藻相互作用的实验方法将包括：(1)分子系统发育(PCR-DGGE和MPN-PCR)和基于培养的分析抑制或促进亚历山大藻的细菌组合的季节和地理分布；(2)丰富和分离与亚历山大藻密切相互作用的新细菌菌株；(3)分析亚历山大藻促进或抑制亚历山大藻细菌对GOM中其他藻类物种的影响；以及(4)分析分离株对亚历山大藻混合培养中生长的影响。这项研究将深入了解亚历山大藻与GOM中细菌之间的相互作用，并最终可能提高我们模拟和预测给定水体中亚历山大藻动态的能力。这项研究将确定某些细菌组合是否与亚历山大藻有关。并将探索亚历山大藻与细菌之间的相互作用，这些相互作用可能促进或抑制亚历山大藻的生长。

Blooms of the toxic dinoflagellates of the genus Alexandrium have become a chronic problem affecting large areas of the Gulf of Maine (GOM) on a near-annual basis. These algae are the causative agents of paralytic shellfish poisoning, a potentially fatal neurological disorder. Concerns for public health have resulted in frequent shellfish quarantines, permanent closure of some shellfish beds, and the implementation of costly PSP toxin monitoring programs in the GOM. Although considerable effort has been made to determine the environmental factors that influence Alexandrium spp. population dynamics in the GOM, the factors that control in situ growth and decline of Alexandrium populations remain poorly understood. Interactions between the marine bacteria and toxic phytoplankton are thought to play a major role in controlling toxic algal blooms, but their potentially important rolein the GOM has received little attention. It is well known that bacteria and phytoplankton dynamics are tightly linked in coastal marine environments, with strong associations frequently observed between bacterial and phytoplankton biomass. In addition, both positive and negative influences of bacteria on specific harmful algal bloom (HAB) organisms have been documented. Initial research results have indicated GOM bacteria capable of dramatically stimulating Alexandrium under laboratory conditions andthat these interactions may vary seasonally. This project will elucidate the role of bacteria in Alexandrium spp. population dynamics in the GOM. Several aspects of bacteria-Alexandrium interactions will be investigated, including: the seasonal and spatial distribution of bacteria that inhibit or promote Alexandrium growth; the specificity of bacteria-Alexandrium interactions; and the biotic and abiotic factors that influence bacterial community dynamics. Field research will be conducted in the southwestern Bay of Fundy with Canadian collaborators. In addition, archived bacterial community samples that were collected from the eastern and southwestern GOM in collaboration with the ECOHAB-GOM sampling program in 1998 and 2000 will be analyzed to determine the geographic distribution of specific bacteria found to interact with Alexandrium. Close collaboration with the ECOHAB-GOM team and the DFO HAB program will provide an extensive array of data and access to research vessels. Experimental methods to analyze bacteria-Alexandrium interactions will include: (1) molecular phylogenetic (PCR-DGGE and MPN-PCR) and cultivation-based analysis of the seasonal and geographic distribution of bacterial assemblages that inhibit or promote Alexandrium; (2) enrichment and isolation of novel bacterial strains that interact closely with Alexandrium; (3) analysis of the influence of Alexandrium- promoting or Alexandrium-inhibiting bacteria on other algal species present in the GOM; and (4) analysis of the isolates' influence on Alexandrium growth in mixed cultures. The study will provide insight into interactions between Alexandrium and bacteria in the GOM and may ultimately improve our ability to simulate and predict Alexandrium dynamics within a given body of water. This research will determine whether certain bacterial assemblages are associated with Alexandrium spp. in the GOM and will also explore Alexandrium -bacteria interactions that may promote or inhibit Alexandrium growth.