Development and Validation of an Analytical Method for Assaying Bacterial Uptake of Methyl Iodide in Estuarine Systems

Noble kwame Asare


Methylotrophicbacterial activity has been reported to result in the oxidation of methylhalides (CH3Xs) in natural waters. However, little is known aboutmicrobial degradation of methyl iodide (CH3I), and it is uncertainwhether CH3I is utilized by methylotrophic bacteria as a sole carbonand energy source. To investigate the breakdown and utilization of CH3Iby methylotrophic bacteria in natural water samples, a rigorous carbon 14 (14C)analytical protocol was developed. This paper describes a reliable andreproducible method using 14C radiolabelled CH3I as asubstrate to examine the potential breakdown, remineralization and uptake of CH3Iin estuarine water samples. Application of the 14C method indicatedthat there is uptake of CH3I as a carbon source by methylotrophicbacteria present in water samples from the Tamar Estuary, Plymouth, UK.From the laboratory incubation experiment, up to 17.8% of the CH3Iwas oxidized to CO2 whilst up to 6.7% was incorporated intomethylotrophic bacterial protein. The recovery of this analytical approach was ≥97percent.  The detection limit andprecision of the method were 0.11 nmol L-1 and 5.2%, respectively.


14C Analytical Method; Methyl Iodide; Methylotrophs; Microbial Degradation; Estuaries


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