Role of Bacteria in Detrital Marine Foodwebs: Mechanisms inBacteria-Organic Matter Interactions

建议继续研究异养浮游细菌利用海洋中颗粒有机物(POM)和溶解有机物(DOM)的机制。海洋生态研究所还在研究上层和中层带进入细菌的有机质通量的大小和模式，以确定异养细菌如何影响海洋生物生产的垂直运输。本研究将重点研究细小碎屑(1-50微米)的细菌利用机制和利用率。PI将使用实验室生产的和特征良好的“模型碎屑”，由被杀死的浮游植物、微鞭毛虫和嗜铬蓝细菌组成。他将研究细菌在POM上的定植生长速度，并将检查细菌将POM水解成可利用的DOM的酶机制；确定由于附着或释放POM而导致细菌细胞大小、生长速度和有机物水解方式的变化。PI询问被定植的颗粒是否成为DOM和细菌的点源(“婴儿机器”)。将检验一种假设，即牢固地附着在POM上是细菌的一种生存/传播策略；它们通过后生动物肠道存活下来，并在粪便颗粒中茁壮成长。在野外工作中使用统一的ı14C！被标记为碎屑的PI将测量广泛大小范围的碎屑的周转时间、生化成分和来源。拟议的研究将有助于在生态系统背景下开发细菌-有机物相互作用的机制框架。这一知识对于阐明浮游细菌在海洋有机质通量中的作用应该是有价值的。

Research is proposed to continue the study of the mechanisms whereby heterotrophic bacterioplankton utilize particulate organic matter (POM) and dissolved organic matter (DOM) in the sea. The PI is also studying the magnitude and patterns of organic matter flux into bacteria in both the epipelagic and the mesopelagic zones to determine how heterotrophic bacteria may influence the vertical transport of biogenic production in the sea. The research will focus on studying the mechanisms and rates of bacterial utilization of small detritus (1-50 um). The PI will use laboratory produced and well-characterized "model detritus" consisting of killed phytoplankton, microflagellates, and chroococoid cyanobacteria. He will study colonization growth rates of bacteria on POM and will examine enzymic mechanisms whereby bacteria hydrolyze POM into utilizable DOM; determine shifts in bacterial cell-size, growth rate, and modes of organic matter hydrolysis as a consequence of attachment to, or release from, POM. The PI asks whether a colonized particle becomes a point-source of DOM as well as of bacteria ("baby-machine"). A hypothesis will be tested that firm attachment to POM is a survival/dispersal strategy of bacteria; they survive the passage through metazoan gut and thrive in the fecal pellets. In field work using uniformly ı14C! labeled detritus, the PI will measure the turnover times of detritus of a broad size range, biochemical composition, and origins. The research proposed will contribute towards developing a mechanistic framework for bacteria-organic matter interactions in an ecosytem context. This knowledge should be of value in elucidating the role of bacterioplankton in organic matter fluxes in the oceans.