Prediction of bacteria transport to groundwater is very important to prevent water resources from coliform bacteria pollusion. The objective of this study was to investigate the effectiveness of microbially induced calcium carbonate precipitation (MICCP) in preventing the transport of Escherichia coli as an indicator coliform. For the MICCP process, the sand sample was poured into PVC tubes (with inside diameter of 4. 8 and height of 14. 92 cm) and incubated for 3 days in the presence of Sporosarcina pasteurii. After the stablishment of steady-state flow, 0. 1 pore volume of Escherichia coli suspension (10 8 CFU/mL) was added to the sand column and the leaching was followed with distilled water. The column effluent was sampled in 0. 1 to 5 pore volume. After leaching, the sand column was sliced into five sections (~3 cm), and the number of E. coli trapped in each slice was measured using the plate count method in EMB agar culture medium. Leaching was also carried out in control sand column. The effect of MICCP treatment and its interaction with pore volume was significant (p<0. 05) on Escherichia coli count in effluent. The effect of depth and its interaction with MICCP treatment were significant (p<0. 05) on E. coli residuals and bioprecipitated calcium carbonate in the column. Overall, the role of biopreciptated calcium carbonate was significant in bacteria filtration, as it decreased the sand column hydraulic conductivity and reduced the number of E. coli in column effluents.

In recent years, environmental friendly methods have been considered for managing hazardous chemicals in landfill leachates to prevent their entrance to surface and groundwater resources. This research was done in 2022 at University of Guilan. An ureolytic bacterium with the ability to precipitate calcium carbonate was isolated from the Saravan landfill leachate (SLL) firstly. Then, its potential was investigated along with the indicator bacteria Sporosarcina pasteurii in removing phosphate, calcium and fluoride ions from LLA through the calcium carbonate BIOPRECIPITATION process (MICP). The experiment was carried out as a 3 × 2 × 2 factorial in a completely randomized design with three replicates (36 samples). Factors include biocementing bacteria at three levels (no inoculation, inoculation with strain isolated from LLA and inoculation with S.  pasteurii), urea at two levels (0 and 2% (v/v)), and calcium chloride at two levels (0 and 50 mM). The highest phosphate removal rate (93%) was observed in the presence of calcium chloride without bacteria inoculation, and urea addition. However, ureolytic bacteria were needed for fluoride removal where the treatments of indicator bacteria and isolated strain in the presence of urea and calcium chloride removed 77% and 48% of fluoride, which was 14.4 and 9 times greater than the control treatment, respectively. The calcium removal rate in treatments with indicator and isolated bacteria was 93% and 90%, respectively. Although the removal rate of phosphate, calcium and fluoride was higher in the presence of the indicator bacteria compared to the isolated strain, there was no significant difference between them. Therefore, considering the application of native microorganisms, in addition to reducing costs, also creates less environmental concern than the indicator bacteria, it can be used to remove hazardous chemicals from landfill leachates through the MICP process.

Experimental studies were performed to evaluate the high capacity of cadmium removal by Desulfovibrio alaskensis strain 6SR, which is a sulfate-reducing bacterium. The study was conducted in batch cultures of D. alaskensis 6SR in a medium with a high cadmium concentration. The results indicated that bacterial growth was not dramatically affected by the presence of 170 mg/L of cadmium, following a similar behavior to that of the control culture. Besides, we observed a fast production of extracellular polymeric substances, which play an important role in cadmium removal. The bacterium was able to remove 99.9 % of cadmium at the tested concentration. The main mechanism of cadmium removal was its precipitation as cadmium sulfide (yellow precipitate), followed by its adsorption in the polymeric substances. Most cadmium up take occurred within the first 48 h, and the largest cadmium adsorption capacity was achieved at 144 h. Cadmium adsorption dynamics was evaluated by pseudo-first order and pseudo-second-order kinetic models; where the best adjustment was obtained with the pseudo-second-order model. The micrographs, obtained with transmission electron microscopy, showed a very low intracellular and periplasmic accumulation of cadmium in the cells. Thereby, this bacterium facilitates a process of removal and recovery of cadmium at high concentrations without the need of cellular lysis or special washes.

Background: Ice nucleation active (INA) bacteria have play a role in atmospheric processes and participate in assort of biological precipitation cycle. The most surveys on these bacteria were from subtropical area, so, studies of INA bacteria from other area are needed. The aim of current research was isolation and identification of INA bacteria from north of Tehran, Iran to investigate their ice nucleation property.Methods: Bacterial genus were isolated from plant surface (Japan allspice) and winter precipitation (snow and rain) after culturing on BHI medium and incubated in a various temperatures (4, 10, 15, 20 and 25oC) for 24-96 hours. Droplet freezing method was used to screen potential of ice nucleation producing bacteria. 16S rRNA analysis was applied to confirm genus and species of the isolates. Outer membrane protein of ice nucleation positive strain was purified and identified by SDS-PAGE method.Results: The results showed that among 50 isolates, 40 strains had the ability to produce ice nucleation and 10 strains showed extremely high ice nucleation activity. Gram positive cocobacilli (5%), gram negative bacilli and gram positive cocci (25%) were determined as the least and the most microbial populations, respectively.Conclusion: The best strain was a gram-negative rod shape with the ability of complete freezing of water in less than 5 minutes. It was identified as Pseudomonas syringea based on 16S rRNA gene sequencing. Selected isolate in this research could be a promising tool for biopercipitation.

The utility of alkaline phosphatase in the precipitation of heavy metals such as Ni2+, Cd2+, Cr3+/6+, and Co2+ (from single-ion solutions as well as tannery and electroplating industrial effluents) under alkaline pH was studied with respect to bacterial alkaline phosphatase (enzyme from Escherichia coli C90) and calf intestinal alkaline phosphatase using ascorbic acid 2-phosphate, a natural substrate. Kinetic characteristics of both the enzymes at different regimes of pH 8–11 were studied to find the potential of the enzymes to remain active at certain environmental conditions. Maximum enzymatic activity was recorded at pH 9.5 and 10 for bacterial alkaline phosphatase and calf intestinal alkaline phosphatase, respectively. The precipitation of metal ions from single-ion solutions by bacterial alkaline phosphatase and calf intestinal alkaline phosphatase occurred in the order: Cd2+ > Ni2+ > Co2+ > Cr3+ > Cr6+ and Co2+ > Cd2+ > Ni2+ > Cr6+ > Cr3+, respectively. The percentage of precipitation of Cr6+ from tannery effluent (initial concentration 560 ppm) by bacterial alkaline phosphatase was found to be 15.57 % at 300 min while it was 71.47 % by calf intestinal alkaline phosphatase within 120 min. Bacterial alkaline phosphatase was found to be more efficient than calf intestinal alkaline phosphatase in removing Cd2+ from electroplating effluents from an initial concentration of 734 ppm, and the percentage of precipitation by the enzymes was 94.6 and 66 %, respectively. This work demonstrates a promising eco-friendly approach for a sustainable environment, as ascorbic acid 2-phosphate is a naturally occurring and biodegradable substrate.