The potential of mercury-resistant bacteria isolated from small-scale gold mine tailings for accumulation of mercury

In certain small-gold mining activities in West Lombok, Indonesia, the tailings containing mercury are discharged to agricultural lands, reducing their productivity. One of the efforts to restore the land is by bioremediation of mercury, using mercury-resistant microbes. This study was aimed to isolate the mercury-resistant bacteria from small-scale gold mine tailings containing mercury, and to test their capability in accumulating mercury. Bacterial isolation and identification were conducted from nutrient broth supplemented with 5 ppm HgCl₂. The isolated bacteria were tested for mercury accumulation in the nutrient broth containing 10, 20 and 30 ppm Hg for 24 hours, and in small-scale gold mine tailing containing 41.37 ppm Hg for 2 weeks. The results showed that there were four pure isolates of mercury-resistant bacteria which were identified as Brevundimonas vesicularis, Nitrococcus mobilis, Fusobacterium aquatile and Fusobacterium necrogenes. The highest Hg accumulation from nutrient broth liquid media containing 10, 20 and 30 ppm Hg was observed for Brevundimonas vesicularis. The mercury accumulation efficiency of the four bacteria applied to small-scale gold mine tailing containing mercury was in the order of Fusobacterium aquatile (76.1%) > Brevundimonas vesicularis (75.6%) > Fusobacterium necrogenes (74.4%) > Nitrococcus mobilis (74.2%). On the basis of the Hg accumulation efficiency of more than 75%, Fusobacterium aquatile and Brevundimonas vesicularis are prospective for bioremediation of mercury-contaminated soils.