MICROBIAL ECOLOGY AND GENOMICS IN BIOGEOCHEMICAL CYCLING

Abstract

Microbial communities are key drivers of biogeochemical cycling since they affect the transformation and movements of such essential elements like carbon, nitrogen, and sulfur.  The role of microbes in a range of ecosystem of study ranged with wetlands, forest soils, marine sediments, and permafrost terrains were explored in research studies with view of a mixed- methods experimental strategy that incorporated metagenomics, isotopic labeling, as well as environmental chemistry in the study.  A total of nine datasets were generated and these contained distinct functional and geographical signatures of microbial activity.  Though the highest production of methane was observed in marine and wetland samples, revealing the existence of active methanogenic niches, the rates of nitrate reduction differed distinctly according to the environments studied, with the highest rates observed in forest soils and estuary-based sampling sites.  The number of active genes such as dsrA and mcrA was positively related to the sulfate respiration that had a moderate consistency among samples.  Isotopic analyses that involved the use of ^13C and ^15N tracers allowed accurate quantification of rates as they helped in validation of active elemental conversions.  Log10-transformed abundance data on functional genes were normalized with respect to process rates that were measured, and they revealed that the abundance was significantly correlated with those measured processes and that it was a strong predictor of metabolic potentials.  Visual analysis including hybrid plots or multidimensional scatter projections depicts that coupled or decoupled elemental pathways mediated by microbial guilds depend on the type of the ecosystem and environmental aspects.  The reproducibility of such patterns was found in terms of temporal replication, which further confirmed the reliability of this methodology.  Importantly, the microbial responses to anthropogenic stress varied, which indicates that nutrient loading and land use altered the structure and the functionality of communities.  The paper reaches a conclusion that along with biogeochemical observations, microbial genomics provides a solid premise to understand as well as model the active participation of microorganisms in the saga of global nutrient cycles.  This integrative approach can be very helpful in monitoring the microbial resources, in controlling the ecosystems, and in climate modeling.