During the anaerobic biodegradation of naphthalene and methylnaphthalene, unique metabolites are formed by specific microbial carboxylation and ring-reduction reactions. Groundwater samples from an anoxic, shallow aquifer contaminated with gasoline were examined for the presence of these metabolites by extraction, derivatization and gas chromatography coupled to mass spectroscopy. Several metabolites [2-naphthoic acid (2-NA), tetrahydro-2-naphthoic acid (TH-2-NA), hexahydro-2-naphthoic acid (HH-2-NA) and methylnaphthoic acid (MNA)] were found to be present in the groundwater samples. The concentration of 2-NA at each monitoring well was quantified and correlated to the zones of contamination. The presence of the other metabolites in the same wells as 2-NA was used as confirmation that the anaerobic pathway was indeed active. The distribution of metabolites at this site shows that they can be used as biomarkers for demonstrating in situ biodegradation.

Wastewater contamination and urbanization contribute to the spread of antibiotic resistance in aquatic environments. This is a particular concern in areas receiving chronic pollution of untreated waste via combined sewer overflow (CSO) events. The goal of this study was to expand knowledge of CSO impacts, with a specific focus on multidrug resistance. We sampled a CSO-impacted segment of the James River (Virginia, USA) during both clear weather and an active overflow event and compared it to an unimpacted upstream site. Bacteria resistant to ampicillin, streptomycin, and tetracycline were isolated from all samples. Ampicillin resistance was particularly abundant, especially during the CSO event, so these isolates were studied further using disk susceptibility tests to assess multidrug resistance. During a CSO overflow event, 82% of these isolates were resistant to five or more antibiotics, and 44% were resistant to seven or more. The latter statistic contrasts starkly with the upstream reference site, where only 4% of isolates displayed resistance to more than seven antibiotics. DNA sequencing (16S rRNA gene) revealed that ~35% of our isolates were opportunistic pathogens, comprised primarily of the genera Stenotrophomonas, Pseudomonas, and Chryseobacterium. Together, these results demonstrate that CSOs can be a significant source of viable clinically-relevant bacteria to the natural environment and that multidrug resistance is an important understudied component of the environmental spread of antibiotic resistance.

Engineered systems that mimic tidal wetlands are ideal for point-of-source treatment of wastewater due to their low energy requirements and small physical footprint. In this study, vertical columns were constructed to mimic the flood-and-drain cycles of tidal wetland treatment systems (TWTS) in order to study how variations in the

Biology is an increasingly quantitative science. Thus, it is important that undergraduate biology curricula include frequent opportunities for students to practice their quantitative skills.

Most domestic wastewater can be effectively treated for secondary uses by engineered biological systems. These systems rely on microbial activity to reduce nitrogen (N) content of the reclaimed water. Such systems often employ a tidal-flow process to minimize space requirements for the coupling of aerobic and anaerobic metabolic processes. In this study, laboratory-scale tidal-flow treatment systems were studied to determine how the frequency and duration of tidal cycling may impact reactor performance. Fluorescent in situ hybridization and epifluorescence microscopy were used to enumerate the key functional groups of bacteria responsible for nitrification and anaerobic ammonium oxidation (anammox), and N-removal efficiency was calculated via a mass-balance approach. When water was cycled (i.e., reactors were filled and drained) at high frequencies (16-24 cycles day −1), nitrate accumulated in the columns-presumably due to inadequate periods of anoxia that limited denitrification. At lower frequencies, such as 4 cycles day −1 , nearly complete N removal was achieved (80-90%). These fill-and-drain systems enriched heavily for nitrifiers, with relatively few anammox-capable organisms. The microbial community produced was robust, surviving well through short (up to 3 h) anaerobic periods and frequent system-wide perturbation.