Drs. King and Tolli will analyze the significance, structure and function of bacterial facultative lithotroph and mixotroph (FL/M) communities along a near-shore to offshore transect in the water column of the marine Damariscotta River and the Gulf of Maine, and in intertidal sediments proximate to a near-shore sites. The investigators suggest that FL/M communities play important and poorly appreciated roles in heterotrophic carbon metabolism, as well as in the dynamics of carbon monoxide (CO), hydrogen and other reduced inorganic substrates. These researchers will investigate FL/M using molecular tools for the large sub-unit genes of form IA and IC bacterial ribulose-1,5-bisphosphate carboxylase/ oxygenase (rbcL), and CO dehydrogenase (coxL) that they have recently developed, and that they will apply for assays of marine systems for the first time. CoxL will provide insights regarding the distribution and diversity of some mixotrophs and facultative lithotrophs; rbcL will provide insights regarding both facultative and obligate lithotrophs. Recent analyses of various lithotrophic bacterial rbcL sequences and rbcL sequences from environmental DNA indicate that they can use phylogenetic tools to distinguish between facultative and obligate lithotrophs, thus allowing the PIs to answer questions about lithotrophic community structure that could not be addressed previously. In addition, these researchers will determine what relationships exist, if any, between the structure and diversity of FL/M communities and microbial abundance, cellular respiratory activity (ETS activity), and transformations of CO, hydrogen, ammonium and thiosulfate. The broader impacts of the proposed study will be derived from the investigator's efforts to train a postdoctoral research associate, Ph.D. student and undergraduate students in aspects of marine biogeochemistry, the physiology and ecology of specific groups of marine microbes and in molecular microbial ecology. In addition, they will contribute to a greater understanding of the Gulf of Maine and its near-shore ecosystems, both of which are ecologically and economically important a regional scales.
