Illuminating microbial species-specific effects on organic matter remineralization in marine sediments

Abstract

26Marine microorganisms play a fundamental role in the global carbon cycle by mediating 27 the sequestration of organic matter in ocean waters and sediments. A better understanding of 28 how biological factors, such as microbial community composition, influence the lability and fate 29 of organic matter is needed. Here, we explored the extent to which organic matter 30 remineralization is influenced by species-specific metabolic capabilities. We carried out aerobic 31 time-series incubations of Guaymas basin sediments to quantify the dynamics of carbon 32 utilization by two different heterotrophic marine isolates. Continuous measurement of respiratory 33 CO 2 production and its carbon isotopic compositions ( 13 C and 14 C) shows species-specific 34 differences in the rate, quantity, and type of organic matter remineralized. Each species was 35 incubated with hydrothermally-influenced vs. unimpacted sediments, resulting in a ~3-fold 36 difference in respiratory CO 2 yield across the experiments. Genomic analysis indicated that the 37 observed carbon utilization patterns may be attributed in part to the number of gene copies 38 encoding for extracellular hydrolytic enzymes. Our results demonstrate that the lability and 39 remineralization of organic matter in marine environments is not only a function of chemical 40 composition and/or environmental conditions, but also a function of the microorganisms that are 41 present and active. 423 Introduction 43