Geochip-based analysis of microbial functional genes diversity in rutile bio-desilication reactor

Biological desilication process is an effective way to remove silicate from rutile so that high purity rutile could be obtained. However, little is known about the molecular mechanism of this process. In this work, a newly developed rutile bio-desilication reactor was applied to enrich rutile from rough rutile concentrate obtained from Nanzhao rutile mine and a comprehensive high through-put functional gene array(Geo Chip 4.0) was used to analyze the functional gene diversity, structure and metabolic potential of microbial communities in the biological desilication reactor. The results show that TiO2 grade of the rutile concentrate could increase from 78.21% to above 90% and the recovery rate could reach to 96% or more in 8-12 d. The results also show that almost all the key functional genes involved in the geochemical cycling process, totally 4324 and 4983 functional microorganism genes, are detected in the liquid and ore surface, respectively. There are totally 712 and 831 functional genes involved in nitrogen cycling for liquid and ore surface samples, respectively. The relative abundance of functional genes involved in the phosphorus and sulfur cycling is higher in the ore surface than liquid. These results indicate that nitrogen, phosphorus and sulfur cycling are also present in the desiliconization process of rutile. Acetogenesis genes are detected in the liquid and ore surface, which indicates that the desiliconizing process mainly depends on the function of acetic acid and other organic acids. Four silicon transporting genes are also detected in the sample, which proves that the bacteria have the potential to transfer silicon in the molecule level. It is shown that bio-desilication is an effective and environmental-friendly way for enrichment of rough rutile concentrate and presents an overview of functional diversity and structure of desilication microbial communities, which also provides insights into our understanding of metabolic potential in biological desilication reactor ecosystems.

Differences between hepatic and biliary lipid metabolism and secretion in genetically gallstone-susceptible and gallstone-resistant mice

OBJECTIVE: To investigate differences between hepatic and biliary lipid metabolism and secretion of genetically gallstone-susceptible (C57L) and resistant (AKR) mice and the mechanism of cholesterol gallstone formation. METHODS: The inbred C57L and AKR mice were fed a lithogenic diet containing 15% fat, 1.25% cholesterol and 0.5% cholic acid for four weeks. Hepatic cholesterol content and secretion rates of biliary lipids, as well as phenotypes of the liver and gallbladder were determined and examined before and after the feeding of the lithogenic diet. RESULTS: Both before and after ingestion of the lithogenic diet, hepatic secretion rates of all biliary lipids in C57L mice were markedly higher than that of AKR mice (P