The Occurrence of MerR and MerC Gene Sequences Among Mercury Resistant Determinants in River Sediments Containing Elevated Levels of Mercury

Sediments in the River Yare, Norfolk, UK have been contaminated with mercury by the discharge of heavy metal-laden effluents from a local chemical company. In this study probes specific for different genes within commonly occurring gram-negative mercury resistance determinants were used to investigate the occurrence of the mercury resistance transposons Tn21 and Tn501 in bacteria isolated from river-sediments. This work shows that the major class of mercury resistance determinants isolated from these sediments is Tn21-1ike. In addition a low frequency of Tn501-like elements were present at all sites. At one site there was a significant increase in the relative abundance of Tn501- like elements. The occurrence of novel mercury resistance determinants which differ in structure from Tn21 and Tn501 was suggested at all sites.