Xingyu Liu

Microbial community and metabolic pathway succession driven by changed nutrient inputs in tailings: effects of different nutrients on tailing remediation

To solve the competition problem of acidophilic bacteria and sulfate-reducing bacteria in the practical application of mine tailing bioremediation, research into the mechanisms of using different nutrients to adjust the microbial community was conducted. Competition experiments involving acidophilic bacteria and sulfate-reducing bacteria were performed by supplementing the media with yeast extract, tryptone, lactate, and glucose. The physiochemical properties were determined, and the microbial community structure and biomass were investigated using MiSeq sequencing and qRT-PCR, respectively. Four nutrients had different remediation mechanisms and yielded different remediation effects. Yeast extract and tryptone (more than 1.6 g/L) promoted sulfate-reducing bacteria and inhibited acidophilic bacteria. Lactate inhibited both sulfate-reducing and acidophilic bacteria. Glucose promoted acidophilic bacteria more than sulfate-reducing bacteria. Yeast extract was the best choice for adjusting the microbial community and bioremediation, followed by tryptone. Lactate kept the physiochemical properties stable or made slight improvements; however, glucose was not suitable for mine tailing remediation. Different nutrients had significant effects on the abundance of the second enzyme of the sulfate-reducing pathway (p < 0.05), which is the rate-limiting step of sulfate-reducing pathways. Nutrients changed the remediation effects effectively by adjusting the microbial community and the abundance of the sulfate-reducing rate-limiting enzyme.

Biogeographical distribution of acidophiles and their effects around the Zijinshan heap bioleaching plant

ABSTRACT The Zijin heap bioleaching plant started operation by the end of 2005; due to the proximity of the Ting River, concerns rose about the migration of acidophiles outside of the heap. In this study, 53 soil samples and 51 liquid samples were collected, and the biogeographical distribution of acidophiles was investigated using clone libraries and real-time polymerase chain reaction (PCR), the physicochemical characteristics were analysed by Inductively Coupled Plasma Optical Emission Spectrometry (ICP). The results indicated the bioleaching system had some influence on the surrounding environment. Both microbial community and physiochemical index emerged correlation with distance of sampling sites from bioleaching system, mainly limited in the zone 30 m outside bioleaching system. Correlation analysis indicated the migration of different acidophiles was influenced by different factors. Leptospirillum had higher migration capability than the other acidophiles, and such migration capability was one of the important influence factors for its distribution. Environment factors and survival ability were the key influence factors for Acidithiobacillus, Sulfobacillus and Ferroplasma to survive in the surrounding environment.

Geographic distribution of cadmium and its interaction with the microbial community in the Longjiang River: risk evaluation after a shocking pollution accident

A shocking Longjiang River cadmium pollution accident occurred in 2012, the effects of which on microbial communities remain unclear. Alkaline precipitation technology was applied for remediation, but concerns rose about the stability of this technology. To understand the geographic distribution of cadmium and its correlation with microbes, in this study, 39 water samples and 39 sludge samples from this river and 2 soil samples from the nearby farmland were collected for chemical and microbial analyses. The Cd concentrations of all water samples were lower than 0.005 mg/L and reached the quality standards for Chinese surface water. A ranking of sludge samples based on Cd contents showed sewage outfall > dosing sites > farmland, all of which were higher than the quality standard for soil. Alkaline precipitation technology was effective for Cd precipitation. Cd was unstable; it was constantly dissolving and being released from the sludge. The Cd content of each phase was mainly influenced by the total Cd content. Over 40,000 effective sequences were detected in each sample, and a total of 59,833 OTUs and 1,273 genera were found using Illumina MiSeq sequencing. Two phyla and 39 genera were notably positively correlated with the Cd distribution, while the cases of 10 phyla and 6 genera were the opposite.

Application of Phosphate-Solubilizing Bacteria Activating Phosphate Materials in Solidification of Soil Heavy Metal

Removal of heavy metals by phosphate-solubilizing bacteria (PSB) activating phosphate materials in simulated heavy metal liquid environment was studied. Calcium phosphate was a kind of functional carrier material under action of PSB, accelerating the reaction to form phosphate precipitation of heavy metal. The results indicated that the removal of heavy metals with activated phosphate materials by PSB occurred within 15 days, and achieved high removal rates of Pb2+, Cu2+, Zn2+ and Cd2+ comparing with the phosphate materials inactivated. Therefore the activated phosphate materials by PSB could be a functional material for efficiently removing heavy metal from contaminated soil.