Biological chlorine cycling in the Arctic Coastal Plain

Organohalide respiration in pristine environments: implications for the natural halogen cycle

“…Inspiring findings have been obtained from interdisciplinary research on natural halogen cycling (Krzmarzick et al, 2012;Futagami et al, 2013;Weigold et al, 2016;Zlamal et al, 2017), and a further understanding will benefit from collaborative efforts across disciplines, as happens in natural complex microbial communities.…”

“…Significant growth of these putative OHRB without a lag phase was noted in soil microcosms amended with a mixture of enzymatically produced organohalogens (Krzmarzick et al, 2012) indicating their active state in their natural habitat. A survey of coastal Arctic wet tundra soils revealed substantial concentrations of organochlorine compounds (245 ppm on average) and different halogenase-encoding and rdhA genes were recovered by metagenomic analysis (Zlamal et al, 2017). Genome sequences with close similarity to the genome of D. mccartyi were found, and laboratory incubations with a mixture of PCE and DCE led to significant chloride release that was not observed in corresponding abiotic controls.…”

“…Genome sequences with close similarity to the genome of D. mccartyi were found, and laboratory incubations with a mixture of PCE and DCE led to significant chloride release that was not observed in corresponding abiotic controls. However, neither presence of daughter products of PCE/DCE respiration nor growth of putative OHRB was surveyed (Zlamal et al, 2017). Similarly, studies on halogenation and dehalogenation potential in a German forest soil detected the biotic formation of chloroform and bromoform and co-occurrence of genes coding for specific and unspecific halogenases as well as metabolic and cometabolic dehalogenases in corresponding metagenomic data sets (Weigold et al, 2016).…”

“…Rather, the large number, phylogenetic depth and molecular dating of the key reductive dehalogenase homologous ( rdh ) genes (McMurdie et al ., ; Hug et al ., ) indicate the ancient origin of OHR, probably dating back at least to the ‘Great Oxidation Event’ over two billion years ago (Zinder, ). Moreover, recent studies not only showed co‐occurrence of OHRB and natural organohalogens (Krzmarzick et al ., ; Zlamal et al ., ), but also of the genes encoding halogenating and dehalogenating enzymes (Weigold et al ., ; Zlamal et al ., ). This implies that OHRB thrive on naturally produced organohalogens and thereby contribute to natural cycling of halogens.…”

Microbial Synthesis and Transformation of Inorganic and Organic Chlorine Compounds

“…Using PCR-based methods, rdhA genes are commonly found in contaminated sites (Hug and Edwards, 2013; Atashgahi et al, 2017b), implying a cause-and-effect relationship between the occurrences of these genes and organochlorine contaminants. With the recent advances in metagenomic sequencing, environmental distribution of rdhA genes has been extended to environments not known to be contaminated with anthropogenic organohalogens such as a remote meromictic lake, Arctic tundra and forest soils, and marine sediments (Biderre-Petit et al, 2016; Weigold et al, 2016; Starnawski et al, 2017; Zlamal et al, 2017). It is likely that natural organohalogens accounting at these environments are substrates of the microbes harboring rdhA genes (Krzmarzick et al, 2012; Atashgahi et al, 2018a).…”