Molecular and Physiological Characterization of Copper-Resistant Bacteria Isolated from Activated Sludge in an Industrial Wastewater Treatment Plant in Rungkut-Surabaya, Indonesia

Optimising Wastewater Treatment: Acinetobacter sp. IrC1 as a potential multi-resistant bacterium for copper accumulation and dyes decolourisation

Improper disposal of waste containing copper and dye is an environmental issue that must be resolved immediately due to its harmful, non-degradable and toxic properties. Bioremediation efficiency can improve by cultivating copper and dye multi-resistant bacteria to remove various pollutant types simultaneously. This study aims at establishing the multi-resistance of Acinetobacter sp. IrC1 to copper and dyes. The effects of copper concentration on growth were determined using a spectrophotometer, while accumulation was analysed using an atomic absorption spectrophotometer. Bacteria-mediated dye decolourisation dyes were observed based on clear zone formation around bacterial colonies, while decolourisation percentage was calculated using a spectrophotometer. Results demonstrate that Acinetobacter sp. IrC1 resisted up to 8 mM CuSO4 and accumulated up to 292.93 mg/g dry weight of copper cells. Acinetobacter sp. IrC1 isolates were also resistant to 500 ppm Methylene Blue, Malachite Green, Congo Red, Mordant Orange, Reactive Black, Direct Yellow, Reactive Orange, Remazol, Wantex Red and Wantex Yellow dye, successfully removing up to 68.35% and 79.50% Methylene Blue and Basic Fuchsine in a medium containing 3 mM CuSO4, respectively. Further investigations are required to analyse the genetic composition of multi-resistant bacteria to optimise the effectiveness of indigenous bacterial isolates as bioremediation agents.

Optimizing Bioremediation: Elucidating Copper Accumulation Mechanisms of Acinetobacter sp. IrC2 Isolated From an Industrial Waste Treatment Center

Acinetobacter sp. IrC2 is a copper-resistant bacterium isolated from an industrial waste treatment center in Rungkut, Surabaya. Copper-resistant bacteria are known to accumulate copper inside the cells as a mechanism to adapt to a copper-contaminated environment. Periplasmic and membrane proteins CopA and CopB have been known to incorporate copper as a mechanism of copper resistance. In the present study, protein profile changes in Acinetobacter sp. IrC2 following exposure to copper stress were analyzed to elucidate the copper resistance mechanism. Bacteria were grown in a Luria Bertani agar medium with and without CuSO4 supplementation. Intracellular copper ion accumulation was quantified using atomic absorption spectrophotometry. Changes in protein profile were assessed using sodium dodecyl sulfate polyacrylamide gel electrophoresis. The results showed that 6 mM CuSO4 was toxic for Acinetobacter sp. IrC2, and as a response to this copper-stress condition, the lag phase was prolonged to 18 h. It was also found that the bacteria accumulated copper to a level of 508.01 mg/g of cells' dry weight, marked by a change in colony color to green. The protein profile under copper stress was altered as evidenced by the appearance of five specific protein bands with molecular weights of 68.0, 60.5, 38.5, 24.0, and 20.5 kDa, suggesting the presence of CopA, multicopper oxidase (MCO), CopB, universal stress protein (Usp), and superoxide dismutase (SOD) and/or DNA-binding protein from starved cells, respectively. We proposed that the mechanism of bacterial resistance to copper involves CopA and CopB membrane proteins in binding Cu ions in the periplasm and excreting excess Cu ions as well as involving enzymes that play a role in the detoxification process, namely, SOD, MCO, and Usp to avoid cell damage under copper stress.