Pengaruh pH dan Suhu terhadap Aktivitas Pereduksi Merkuri Bakteri Resisten Merkuri Tinggi Bacillus cereus yang Diisolasi dari Urin Pasien dengan Amalgam Gigi

Mercury is a very toxic compound to humans, therefore, a method to overcome its presence in the environment is required. Detoxification of mercury can be done by using mercury resistant bacteria. Mercury-resistant bacteria Bacillus cereus isolate FUA have been obtained from the urine of patients with dental mercury amalgam. This study was aimed to determine the mercury detoxification activity of Bacillus cereus isolate FUA at varying pH medium and incubation temperature. The study was carried out by growing Bacillus cereus isolate FUA on oblique media, then were planted in the growth media of LB broth containing mercury compounds of 10 ppm HgCl2 with varying pHs of 5, 7, and 9 and incubation temperatures of 15, 25 and 35oC. The amount of bacterial growth was analyzed by using spectrophotometer and mercury levels were analyzed by using CV-AAS method. The results showed that the growth and mercury reducing activity of Bacillus cereus isolate FUA were optimum at pH 7 and incubation temperature of 35oC. In conclusion, the growth of Bacillus cereus isolate FUA and its mercury reducing activity were optimum at pH 7 and temperature of 35oC. It is expected that the results of this study can be the basis for further research on the process of mercury detoxificationKeywords: Bacillus cereus, urine, mercury resistance, pH, temperature Abstrak: Merkuri adalah senyawa yang sangat beracun bagi manusia sehingga diperlukan metode untuk mengatasi keberadaannya di lingkungan. Detoksifikasi merkuri dapat dilakukan dengan menggunakan bakteri resisten merkuri. Bakteri yang resisten merkuri Bacillus cereus isolat FUA telah diperoleh dari urin pasien dengan amalgam gigi. Penelitian ini bertujuan untuk mengetahui aktivitas detoksifikasi merkuri Bacillus cereus isolat FUA pada berbagai variasi pH medium dan suhu inkubasi. Bakteri Bacillus cereus isolat FUA ditumbuhkan pada media miring, kemudian ditanam pada media pertumbuhan bakteri LB broth yang mengandung senyawa merkuri 10 ppm HgCl2 dengan berbagai pH 5, 7 dan 9 dan suhu inkubasi 15, 25 dan 35oC. Jumlah pertumbuhan bakteri dianalisis menggunakan spektrofotometer dan kadar merkuri dianalisis menggunakan metode CV-AAS. Hasil penelitian menunjukkan bahwa aktivitas pertumbuhan dan aktivitas pereduksi merkuri Bacillus cereus isolat FUA optimum pada lingkungan pertumbuhan dengan pH 7 dan suhu inkubasi 35oC. Simpulan penelitian ini ialah aktivitas pertumbuhan dan pereduksi merkuri Bacillus cereus isolat FUA yang optimum pada pH 7 dan suhu 35oC. Diharapkan hasil penelitian ini dapat menjadi dasar untuk penelitian lebih lanjut tentang proses detoksifikasi merkuri.Kata kunci: Bacillus cereus, urin, resistensi merkuri, pH, suhu

Isolation and characterization of mercury-resistant bacteria from wastewater sources in Egypt

An important mechanism for microbial resistance to mercury is its reduction into elemental mercury (facilitated by the merA gene). Thirty-eight microbial isolates from a variety of wastewater sources in Egypt were collected. Approximately 14 of the 38 isolates exhibited not only a high degree of tolerance to mercury (up to 160 ppm) but also a high degree of resistance to other tested heavy metals (Cu, Co, Ni, and Zn). From these 14, the 10 most resistant isolates were selected for further study and were found to include 9 Gram-negative and 1 Gram-positive bacterial strains. Multi-antibiotic-resistance profiles were detected for 6 out of the 10 selected isolates. All the tested Gram-negative isolates (n = 9) harbored a plasmid-encoded merA gene. The mercury removal effectiveness for the 10 selected isolates ranged between 50% and 99.9%, among which Stenotrophomonas maltophilia ADW10 recorded the highest rate (99.9%; at an initial mercury concentration of 20 ppm). To the best of our knowledge, this is the first study to (i) demonstrate the presence of a multimetal-resistant S. maltophilia bacterium with a high mercury tolerance capacity that would make it a suitable candidate for future bioremediation efforts in heavy-metal-polluted areas in Egypt and (ii) report Pseudomonas otitidis as one of the mercury-resistant bacteria.