BIODIVERSITAS ISSN: 1412-033X Volume 22, Number 7, July 2021 E-ISSN: 2085-4722 Pages: 2656-2666 DOI: 10.13057/biodiv/d220714 Isolation and characterization of mercury-resistant microbes from gold mine area in Mount Pongkor, Bogor District, Indonesia WILHELMUS TERANG ARGA SANJAYA 1 , NUR SYAFIRA KHOIRUNNISA 1 , SRI ISMIANI 1 , FAHRIZAL HAZRA 1 , DWI ANDREAS SANTOSA 1,2,♥ 1 Department of Soil Science and Land Resources, Faculty of Agriculture, Institut Pertanian Bogor. Jl. Meranti, Kampus IPB Darmaga, Bogor 16680, West Java, Indonesia, Tel.: +62-251-629360, 629354, Fax.: +62-251-629358, ♥ email: dsantosa@indo.net.id 2 Research Center for Bioresources and Biotechnology, Institut Pertanian Bogor. Jl. Kamper, Kampus IPB Darmaga, Bogor 16680, West Java, Indonesia Manuscript received: 11 March 2021. Revision accepted: 12 June 2021. Abstract. Sanjaya WTA, Khoirunnisa NS, Ismiani S, Hazra F, Santosa DA. 2021. Isolation and characterization of mercury-resistant microbes from gold mine area in Mount Pongkor, Bogor District, Indonesia. Biodiversitas 22: 2656-2666. Exploring novel wild-type microbes is very important to give more flexibility for bioremediation implementation. It is related to discovering strain with higher detoxification ability and more reliable degradation mechanisms. Moreover, novel strain can be used as genetic material for strain development by molecular genetic engineering and production design formulation. The aims of this experiment were to characterize and identify new mercury-resistant microbes, investigate their capacity to accumulate mercury, and analyze the reducing mercury toxicity in bioassay. Four strains of bacteria selected through the screening stage were characterized for their morphological, biochemical, physiological, and molecular genetic characteristics. Considering their characteristics and mercury resistance levels, there are two selected microbial strains: fungus strain Cladosporium halotolerans Hg32 and the bacterial strain Mycolicibacterium peregrinum Hg37 with a mercury resistance level up to 3000 mg L -1 . The C. halotolerans Hg32 could remove mercury with the highest potency up to 90.72% at a mercury concentration of 100 mg L -1 , while M. peregrinum Hg37 removes up to 77.10% at mercury concentrations of 10 mg L -1 . Toxicity bioassay tests using fish confirmed that C. halotolerans Hg32 and M. peregrinum Hg37 had the ability to detoxify mercury in contaminated water. Both have successfully proven to reduce the mortality rate to below 5%. Keywords: ASGM, bioremediation, contamination, fish bioassay, mercury removal Abbreviations: ASGM: Artisanal and Small-scale Gold Mining; MIC: Minimum Inhibitory Concentration; PCR: Polymerase Chain Reactions; AAS: Atomic Absorption Spectrophotometry INTRODUCTION Nowadays, mercury (Hg) contamination extends to environments such as soils, sediments, seawater, etc. In soil environment, Krisnayanti et al. (2012) reported that soil at Sekotong District of West Lombok was contaminated by mercury ranging from 25 to 40 mg kg -1 . It also caused plant poisoning symptoms (chlorosis, brown plant root, root hood damage) in the region, and the accumulation of mercury in plant seeds around 0.20 mg kg -1 . Meanwhile, in aquatic environment of southeastern coast of the Mediterranean Sea, total dissolved mercury ranged from 0.04 μg/L to 6.09 μg/L has been reported causing mercury accumulation in the fish up to 0.77 μg/g on the Siganus luridus (Abdallah 2020). In general, the concentration level of mercury in fishes was influenced by feeding habitat for each species. While for the human, organic mercury compounds (methyl mercury and phenyl mercury) which are highly reactive and can attack the human nervous system through the bloodstream (Rasmussen et al. 2008). The Mount Pongkor area is an area with the biggest Artisanal and Small-scale Gold Mining (ASGM) in Indonesia using mercury for gold leaching. There are 850 ASGM hotspots mined by more than 150.000 miners (Ismawati et al. 2013). The location of ASGM in Mount Pongkor is similar to the majority of ASGM in Indonesia generally which take place at the upland area around rice fields or residence. It makes mercury easily transported through water flow from the upland to the lowland area. Activity of ASGM at Mount Pongkor area is handled traditionally similar to other ASGM in Indonesia which excavate vertically and horizontally the soil. The gold is extracted by amalgamation technology using Hg. Residual mud from the extraction process is usually reprocessed through cyanidation. Then, the residue is discharged into land around the site, even agricultural land (Suhartini and Abubakar 2017). Yoga et al. (2014) have reported that mercury contamination caused by ASGM in Cikaniki River was higher than the maximum limit. In Cisarua Village, 60% of villagers have been reported poisoned by mercury (Hg) which was proven by mercury accumulation in their hair counted between 2.03 to 9.04 ppm (Sumantri et al. 2014). Until 2015, the Ministry of Environment reported that 90% of land, including residential housing in Mount Pongkor area, has been contaminated by heavy metal (Ismawati et al. 2015). Generally, there were three classes of the value range of the element mercury in active river sediments in the Mount Pongkor area, consisted of first-class around 18.5-220 ppm (ASGM Cikoret, Pasir Jawa and Ciguha), second class