Phylogeny and diversity of alkane-degrading enzyme gene variants in the laurentian great lakes and western atlantic.

Many aquatic environments are at risk for oil contamination and alkanes are one of the primary constituents of oil. The alkane hydroxylase (AlkB) is a common enzyme used by microorganisms to initiate the process of alkane-degradation. While many aspects of alkane bioremediation have been studied, the diversity and evolution of genes involved in hydrocarbon degradation from environmental settings is relatively understudied. The majority of work done to-date has focused on the marine environment. Here we sought to better understand the phylogenetic diversity of alkB genes across marine and freshwater settings using culture-independent methods. We hypothesized that there would be distinct phylogenetic diversity of alkB genes in freshwater relative to the marine environment. Our results confirm that alkB has distinct variants based on environment while our diversity analyses demonstrate that freshwater and marine alkB communities have unique responses to oil amendments. Our results also demonstrate that in the marine environment, depth is a key factor impacting diversity of alkB genes.

Microbial Community Dynamics During Lake Ice Freezing.

Many freshwater environments experience dramatic seasonal changes with some systems remaining ice-covered for most of the winter. Freshwater systems are also highly sensitive to environmental change. However, little is known about changes in microbial abundance and community composition during lake ice formation and times of persistent ice cover. The goal of this study is to characterize temporal dynamics of microbial communities during ice formation and persistent ice cover. Samples were collected in triplicate, five days per week from surface water in the Keweenaw Waterway between November and April. Environmental conditions along with microbial abundance and microbial community composition was determined. Distinct community composition was found between ice-free and ice-covered time periods with significantly different community composition between months. The microbial community underwent dramatic shifts in microbial abundance and diversity during the transitions into and out of ice cover. The richness of the microbial community increased during times of ice cover. Relatives of microbes involved in nitrogen cycling bloomed during times of ice cover as sequences related to known nitrifying taxa were significantly enriched during ice cover. These results help to elucidate how microbial abundance and diversity change over drastic seasonal transitions and how ice cover may affect microbial abundance and diversity.