Ecological and Biogeochemical Characterization of a Dominant Lineage of Coastal Ocean Bacterioplankton

在美国东南部的沿海海水和河口中发现了数量丰富的海洋浮游细菌的系统发育群。这些细菌被称为“海洋α”群，在沿海海水和主要东南河口的高盐度水域中，它们始终占细菌核糖体DNA （rDNA）的30%，并且可能构成这些系统中最主要的单一细菌谱系。利用低营养培养技术可以很容易地从海水样品中分离出海洋α细菌，因此它们潜在的生物地球化学作用的一些迹象已经出现。许多海洋α分离物能够在木质素相关化合物和腐殖质物质上生长，这两种天然存在的芳香化合物高浓度存在于美国东南部的盐沼和出口到沿海海洋的河流物质中。其他菌株能够代谢有机硫分子，如DMSP和甲烷磺酸，它们是海洋硫循环和大气过程中的重要化合物。本提案描述了对这些数字优势的沿海海洋细菌的生态学，生物地球化学作用和生理能力的调查。我们将确定海洋α浮游细菌在美国东南部水域和其他选定的美国沿海地区的分布和丰度，构建海洋α序列克隆文库，分离和表征该群体的可培养成员，并使用分子技术（基于原位PCR和16S rDNA方法）研究该群体在天然海水中的生物地球化学作用。

A phylogenetic cluster of marine bacterioplankton has been identified that is numerically abundant in coastal seawater and estuaries of the southeastern U.S. These bacteria, termed the `marine alpha` group, consistently account for up to 30% of the bacterial ribosomal DNA (rDNA) in coastal seawater and in high salinity reaches of major southeastern estuaries, and may constitute the single most dominant bacterial lineage in these systems. Marine alpha bacteria can be readily isolated from seawater samples using low nutrient culturing techniques, and thus some indications of their potential biogeochemical roles have emerged. Many marine alpha isolates are capable of growth on lignin related compounds and humic substances, two types of naturally occurring aromatic compounds found in high concentrations in southeastern U.S. salt marshes and in riverine material exported to the coastal ocean. Other isolates are capable of metabolizing organic sulfur molecules, such as DMSP and methanesulfonic acid, which are important compounds in oceanic sulfur cycling and atmospheric processes. This proposal describes an investigation into the ecology, biogeochemical roles, and physiological capabilities of these numerically dominant coastal marine bacteria. We will determine the distribution and abundance of marine alpha bacterioplankton in southeastern U.S. waters and other selected coastal sites around the U.S., to construct a clone library of marine alpha sequences, to isolate and characterize culturable members of the group, and to use molecular techniques (based on in situ PCR and 16S rDNA approaches) to study the biogeochemical roles of the group in natural seawater.