Stimulation of Organohalide Respiring Bacteria with Chloroperoxidase Produced Organochlorines

Abstract

Anaerobic microcosms were set up with CPO-produced organochlorines or control organic matter. Organohalide respirers from the phyla Chloroflexi, Proteobacteria and Firmicutes were measured with qPCR. Among all dechlorinators, Dehalogenimonas 16S rRNA had the most obvious and sustained growth from CPO-produced organochlorines. Other Dehalococcoides-like Chloroflexi were enriched as well and Dehalobacter had a temporary enrichment from CPO-produced organochlorines. The ratio of Dehalogenimonas/Bacteria in the microcosms amended with CPO increased from -1.40 � 0.27 on Day 7 to -0.60 � 0.40 (log10) on Day 82 while in the CTRL microcosms the ratio increased slightly from -1.58 � 0.19 (log10) to -1.42 � 0.10 (log10). In the TRFLP analysis, putative dechlorinating Chloroflexi was examined and a single OTU with a restriction fragment length (RFL) of 276 base pair (bp) was a major component in all three CPO microcosms on Days 61 and 84. The relative peak area of the OTU was 25.8, 15.1 and 72.6% on Day 61 compared to minimal abundance in controls. Another OTU with fragment length of 278 bp likely represents a non-chlorinating species, and had a significance presence in all microcosms after Day 0. The results in this research has shown that the CPO-produced organochlorines are able to stimulate the growth of Dehalococcoides-like Chloroflexi group and other organohalide respirers that are also known to dechlorinate PCBs and PCE in contaminated soils and sediment.