Use of modified ichip for the cultivation of thermo-tolerant microorganisms from the hot spring.

BACKGROUND: Thermostable microorganisms are extremophiles. They have a special genetic background and metabolic pathway and can produce a variety of enzymes and other active substances with special functions. Most thermo-tolerant microorganisms from environmental samples have resisted cultivation on artificial growth media. Therefore, it is of great significance to isolate more thermo-tolerant microorganisms and study their characteristics to explore the origin of life and exploit more thermo-tolerant enzymes. Tengchong hot spring in Yunnan contains a lot of thermo-tolerant microbial resources because of its perennial high temperature. The ichip method was developed by D. Nichols in 2010 and can be used to isolate so-called "uncultivable" microorganisms from different environments. Here, we describe the first application of modified ichip to isolate thermo-tolerant bacteria from hot springs. RESULTS: In this study, 133 strains of bacteria belonging to 19 genera were obtained. 107 strains of bacteria in 17 genera were isolated by modified ichip, and 26 strains of bacteria in 6 genera were isolated by direct plating methods. 25 strains are previously uncultured, 20 of which can only be cultivated after being domesticated by ichip. Two strains of previously unculturable Lysobacter sp., which can withstand 85 °C, were isolated for the first time. Alkalihalobacillus, Lysobacter and Agromyces genera were first found to have 85 °C tolerance. CONCLUSION: Our results indicate that the modified ichip approach can be successfully applied in a hot spring environment.

Effect of Fe3+ on the sludge properties and microbial community structure in a lab-scale A2O process.

During biological wastewater treatment, ferric salt (Fe3+) usually serves as an inorganic flocculant to improve the agglomeration and sedimentation of suspended solids, and thus the removal efficiency of pollutants to meet the increasing strictly regulated wastewater discharge standards. In this study, we investigated the effects of Fe3+ on the removal efficiencies of pollutants, sludge properties, dominant flora and metabolic pathways of bacterial community in a classical anaerobic-anoxic-oxic (A2O) process. The results showed that a Fe3+ concentration lower than 10 mg·L-1 could improve the removal efficiencies of chemical oxygen demand (COD) and total nitrogen (TN), while an inhibition effect was exerted at concentration higher than 10 mg·L-1. The maximum removal efficiencies of COD and TN were 97% and 89%, respectively, under the critical Fe3+ concentration of 10 mg·L-1. Total phosphorous (TP) removal was constantly positively correlated with Fe3+ concentration, due to the enhanced adsorption of phosphorus on activated sludge with the increase of surface roughness. Thauera displayed the highest relative abundance, and certain bacteria in Proteobacteria, Dehloromonas and Candidatus-Competibacter exhibited good adaptability to high concentration of Fe3+. In the context of metabolic collaterals, the most abundant functional gene families were identified to be Carbohydrate Metabolism, Amino Acid Metabolism, Cell Motility, Membrane Transport, and Replication and Repair. This study provides an extensive mechanistic insight into the impact of Fe3+ on the A2O process, which is of fundamental significance to exploit the contributions of inorganic salts to biological wastewater treatment.