Microbial degradation of chloroform

Abstract

Chloroform (CF) is largely produced by both anthropogenic and natural sources. It is detected in ground and surface water sources and it represents the most abundant halocarbon in the atmosphere. Microbial CF degradation occurs under both aerobic and anaerobic conditions. Apart from a few reports describing the utilization of CF as a terminal electron acceptor during growth, CF degradation was mainly reported as a cometabolic process. CF aerobic cometabolism is supported by growth on short-chain alkanes (i.e., methane, propane, butane, and hexane), aromatic hydrocarbons (i.e., toluene and phenol), and ammonia via the activity of monooxygenases (MOs) operatively divided into different families. The main factors affecting CF cometabolism are (1) the inhibition of CF degradation exerted by the growth substrate, (2) the need for reductant supply to maintain MO activity, and (3) the toxicity of CF degradation products. Under anaerobic conditions, CF degradation was mainly associated to the activity of methanogens, although some examples of CF-degrading sulfate-reducing, fermenting, and acetogenic bacteria are reported in the literature. Higher CF toxicity levels and lower degradation rates were shown by anaerobic systems in comparison to the aerobic ones. Applied physiological and genetic aspects of microbial cometabolism of CF will be presented along with bioremediation perspectives.

Refined experimental annotation reveals conserved corrinoid autotrophy in chloroform-respiring Dehalobacter isolates

“…For example, chloroform (CF) and 1,1,1-trichloroethane (1,1,1-TCA) are frequent groundwater contaminants because of their widespread industrial use as solvents and historically poor disposal practices (Furukawa et al, 2005). CF is also one of the most abundant organohalides in the atmosphere (estimated annual global flux is from 0.7 to 4 million t) (Harper, 2000;Cappelletti et al, 2012). In fact, CF in the environment is primarily of natural origin (~90%; McCulloch, 2003), produced by algae in marine systems (Nightingale et al, 1995;Scarratt and Moore, 1999) and by termites in terrestrial systems (Khalil et al, 1990;Laturnus et al, 2002).…”

Unravelling long-term source removal effects and chlorinated methanes natural attenuation processes by C and Cl stable isotopic patterns at a complex field site

“…by persulfate) and CF alkaline hydrolysis have been proved as efficient CF remediation strategies (Torrentó et al, , 2017. Under anoxic conditions, direct or indirect "hydrolytic reduction" of CF and cometabolic hydrogenolysis are described, the latter being associated to methanogens, fermenting bacteria and sulfate reducers (Cappelletti et al, 2012). Finally, Dehalobacter and Desulfitobacterium genera are able to dechlorinate CF to DCM by organohalide respiration (Grostern et al, 2010;Chan et al, 2012;Lee et al, 2012;Deshpande et al, 2013;Tang and Edwards, 2013;Ding et al, 2014).…”

“…Under oxic conditions, cometabolic microbial reactions transform CF to CO 2 (Cappelletti et al, 2012). Abiotic reactions like oxidation (e.g.…”

“…Identifying sources and tracing their evolution over time is crucial to set up effective decontamination strategies (Penny et al, 2010;Cappelletti et al, 2012).…”

“…Aerobic CF cometabolism is supported by the presence of BTEXs in the studied field site. BTEXs can act as a primary substrate (carbon source) of monooxygenases (Cappelletti et al, 2012) and they were found ranging from 4 to 4000 μg/L in wells located in the source's areas in Mar-13. Alkaline hydrolysis might also be plausible given the hydraulic conductivity between the trench, where CF alkaline hydrolysis takes place, and the S1 well .…”