Exploring the links between groundwater quality and bacterial communities near oil and gas extraction activities.

Bacterial communities in groundwater are very important as they maintain a balanced biogeochemical environment. When subjected to stressful environments, for example, due to anthropogenic contamination, bacterial communities and their dynamics change. Studying the responses of the groundwater microbiome in the face of environmental changes can add to our growing knowledge of microbial ecology, which can be utilized for the development of novel bioremediation strategies. High-throughput and simpler techniques that allow the real-time study of different microbiomes and their dynamics are necessary, especially when examining larger data sets. Matrix-assisted laser desorption-ionization (MALDI) time-of-flight mass spectrometry (TOF-MS) is a workhorse for the high-throughput identification of bacteria. In this work, groundwater samples were collected from a rural area in southern Texas, where agricultural activities and unconventional oil and gas development are the most prevalent anthropogenic activities. Bacterial communities were assessed using MALDI-TOF MS, with bacterial diversity and abundance being analyzed with the contexts of numerous organic and inorganic groundwater constituents. Mainly denitrifying and heterotrophic bacteria from the Phylum Proteobacteria were isolated. These microorganisms are able to either transform nitrate into gaseous forms of nitrogen or degrade organic compounds such as hydrocarbons. Overall, the bacterial communities varied significantly with respect to the compositional differences that were observed from the collected groundwater samples. Collectively, these data provide a baseline measurement of bacterial diversity in groundwater located near anthropogenic surface and subsurface activities.