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The bacterial communities at two sulfidic, low salinity springs with no history of herbicide contamination were screened for their ability to grow on 2,4-dichlorophenoxyacetic acid (2,4-D). Nineteen isolates, closely matching the genera Bacillus, Halobacillus, Halomonas, Georgenia and Kocuria, showed diverse growth strategies on NaCl-supplemented and NaCl-free 2,4-D medium. The majority of isolates were halotolerant, growing best on nutrient rich broth with 0% or 5% NaCl; none of the isolates thrived in medium with 20% NaCl. The tfdA gene, which codes for an a – ketoglutarate dioxygenase and catalyzes the first step in 2,4-D degradation, was detected in nine of the salt spring isolates. The tfdAa gene, which shows ~60% identity to tfdA, was present in all nineteen isolates. Many of the bacteria described here were not previously associated with 2,4-D degradation suggesting these salt springs may contain microbial communities of interest for bioremediation.

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The performance of microscale fuel cells with high-aspect-ratio electrodes, defined as the ratio of electrode length to width, is often limited by the depletion of fuel along the length of the anode. Here we present a mathematical model to study electrode aspect ratio in a direct methanol microscale fuel cell. The model is supported with experimental data to show that low-aspect-ratio electrodes achieve higher power densities via improved mass transport to electrodes. The influence of electrode width on overall cell performance was investigated by varying the catalyst deposition region in low-aspect-ratio electrodes. The performance of our experimental fuel cell is consistent with our modeling studies, achieving a maximum power density of 25.3 mW/cm2 at room temperature with 1 M methanol. The model presented here can be used to further improve the geometric design of electrodes in a microscale fuel cell.