Thermophilic bacteria isolated from Mount Merapi, Java, Indonesia as a potential lead bioremediation agent

Rakhmawati A, Wahyuni ET, Yuwono T. 2021. Thermophilic bacteria isolated from Mount Merapi, Java, Indonesia as a potential lead bioremediation agent. Biodiversitas 22: 3101-3110. Contamination by lead (Pb) has become a serious health and environmental problem, that has to be urgently prevented. Bioremediation is one of the environmentally friendly methods for eliminating Pb from the contaminated environment. This study was aimed to investigate the potency of lead-tolerant thermophilic bacteria isolated from solfatara Mount Merapi, Indonesia. A total of 340 isolates of thermophilic bacteria were screened for lead tolerance at 55 °C. Five bacterial isolates were found to show tolerance to 100 mg/L Pb (II), and then were further evaluated and identified as Aeribacillus pallidus strains MRP112, MRP148, MRP272, MRP278, and MRP280 based on 16S rRNA gene sequences analysis. Among the five isolates, A. pallidus MRP 280 showed highest activity in removing Pb at pH 6, 55°C for 24 h. The analysis of scanning and transmission electron microscopy, biofilm formation, and siderophore production, demonstrated that lead tolerance of A. pallidus MRP 280 strain was also accompanied by morphological changes, bioaccumulation, biosorption, biofilm, and siderophore assembly. In conclusion A. pallidus MRP 280 was demonstrated as one of the most potential bacterial strains, can be recommended as an agent for high-temperature lead bioremediation.

Biosorption of lead by bacteria isolated from abattoir wastewater

Six bacteria were isolated from abattoir wastewater collected from Minna central abattoir. Lead tolerant bacteria were isolated from the wastewater. The isolates were then characterized on the basis of their colonial appearance and reaction to various biochemical tests. The lead tolerance profile of the isolates was carried out using agar diffusion method, with concentrations of Lead nitrate ranging from 50-250 mg/L. Two resistant isolates identified as species of Bacillus and Neisseria were selected for biosorption studies. Lead concentration was determined using Atomic Absorption Spectrophotometry. The lead biosorption capacity of the two isolates was studied by inoculating 2 mL of 24 hours old bacteria suspension in 50mL Nutrient broth, containing varying concentrations of lead (500 and 1000 mg/L) at varying pH (7 and 8), with representative samples being withdrawn at day 4, 8 and 12. The results showed that highest biosorption rate was recorded on day 10, at pH 7, in solution containing 500 mg/L of lead with 75.3% and 66% by Bacillus sp. and Neisseria sp. respectively. These results show that Bacillus sp. had better sorption capacity than Neisseria sp. Both organisms can be used for the removal of lead. Keywords: Wastewater, Biosorption, Abattoir, heavy metal, Bacteria

In Vitro Lead Tolerance Testing in White Poplar Genotypes on Acidic Medium

This study evaluates in vitro tolerance of white poplar genotypes to the presence of lead in an acidic rooting medium. Lead was supplemented in form of Pb(NO3)2, in the following concentrations: 0 M (Control), 10-6 M, 10-5 M, 10-4 M and 10-3 M. After four weeks of cultivation, the following characters were measured: number of roots, the length of the longest root, the shoot height, dry root mass and dry shoot mass, and parameters related to photosynthetic pigments: content of chlorophyll a, b, a+b, and of carotenoids in fresh mass, as well as chlorophyll a/b ratio. For further statistical analysis, tolerance indices by Turner and Marshal (TI) were calculated for each measured character. The strongest inhibitory effect was achieved on the medium with 10-4 M Pb(NO3)2, but the best differentiation between genotypes was achieved on the medium with 10-5 M Pb(NO3)2. The highest tolerance indices for the length of the longest root and shoot height had genotypes L-12 and LBM, and for root and shoot dry mass genotypes LCM and L-12. There were no significant differences between genotypes in tolerance indices by any of the examined photosynthetic parameters. The obtained results suggest that both low pH and the presence of citric acid as chelating agent improved evaluation of lead tolerance in comparison with the results obtained on media with standard pH and without citric acid in similar studies. In vitro tests on acidic medium with citric acid can efficiently differentiate examined genotypes for lead tolerance, which could be important for their use in phytoextraction projects, especially on acidic soils.