Isolation and characterization of Bacillus firmus strain SWPA-1 from Marcellus Shale flowback water

Flowback water generated during unconventional natural gas extraction in the Marcellus Shale contains elevated levels of total dissolved solids (TDS). Microbial growth is stimulated in these fluids during storage in open impoundments. The current study was conducted to isolate a strain from flowback water enrichment cultures and characterize it. An isolate was obtained by plate streaking and serial dilution methods and maintained on a nutrient broth with high TDS. Phylogenetic analysis using the 16S rRNA sequence revealed that bacterium was most closely related to Bacillus firmus. Strain SWPA-1 is an aerobic, spore forming, gram-positive, rod capable of growing over a wide range of salinities (0-12% NaCl). Biofilms enriched in strontium and potassium were formed at the air-medium interface in liquid cultures that had been incubated for a few weeks. This study suggests that flowback water harbors microbes well adapted to high salt conditions uncommon in local fresh water ecosystems.