ABUNDANCE AND DISTRIBUTION OF ACIDOPHILIC GALLIONELLA-LIKE BACTERIA IN PENNSYLVANIA COAL MINE DRAINAGE

Coal extraction in Pennsylvania has caused widespread and locally intense acid mine drainage (AMD), creating environmental threats in multiple watersheds. One promising remediation strategy is to remove iron before neutralization by enhancing site specific iron-oxidizing microbial communities. Understanding and characterizing native acidophilic Fe-oxidizing bacteria is crucial to this strategy. 16S rRNA gene sequencing of the AMD spring at Lower Red Eyes in Somerset County, PA, revealed a novel acidophilic betaproteobacterium in a distant sister group to Gallionella spp. A fluorescent in situ hybridization (FISH) probe specific to the Gallionella-like population was designed to determine the abundance and distribution of these novel bacteria at several other Pennsylvania AMD discharges. At Lower Red Eyes, the Gallionella-like population is most abundant (>70% of bacteria) 10 m downstream from the emergence (pH 3.75, [Fe²⁺] = 8.1 mM), and decreases to 10% of bacteria at 25 m (pH 3.25, [Fe²⁺] ~ 6 mM). Near the emergence at the neighboring Upper Red Eyes site, the Gallionella-like population is >90% of bacteria (pH 4, [Fe²⁺] > 6.8mM), and decreases in abundance downstream. At 115 m, no Gallionella-like cells were detected (pH < 3.1, [Fe²⁺] < 2 mM). We noted two distinct morphologies of the acidophilic Gallionella-like cells: A) thick (2µm), short (3mm) bacilli and B) thin (0.5mm), long (4-6 mm) rods. Further studies will determine the distribution of the Gallionella-like populations in other Pennsylvania AMD sites. Moreover, gradient enrichments are underway in order to better characterize the iron-oxidation potential and ecological role of the acidophilic Gallionella-like populations.