Isolation and Characterization of Halotolerant 2,4- Dichlorophenoxyacetic Acid Degrading Bacteria From Sulfidic, Low Salinity Salt Springs

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.