Bacterial community succession during the enrichment of chemolithoautotrophic arsenite oxidizing bacteria at high arsenic concentrations

To generate cost-effective technologies for the removal of arsenic from water, we developed an enrichment culture of chemolithoau- totrophic arsenite oxidizing bacteria （CAOs） that could effectively oxidize widely ranging concentrations of As（III） to As（V）. In addition, we attempted to elucidate the enrichment process and characterize the microbial composition of the enrichment culture. A CAOs enrichment culture capable of stably oxidizing As（III） to As（V） was successfully constructed through repeated batch cultivation for more than 700 days, during which time the initial As（iiI） concentrations were increased in a stepwise manner from 1 to 10-12 mmol/L. As（III） oxidation activity of the enrichment culture gradually improved, and 10-12 mmol/L As（III） was almost completely oxidized within four days. Terminal restriction fragment length polymorphism analysis showed that the dominant bacteria in the enrichment culture varied drastically during the enrichment process depending on the As（III） concentration. Isolation and characterization of bacteria in the enrichment culture revealed that the presence of multiple CAOs with various As（Ⅲ） oxidation abilities enabled the culture to adapt to a wide range of As（Ⅲ） concentrations. The CAOs enrichment culture constructed here may be useful for pretreatment of water from which arsenic is being removed.

Advances in the microbial mineralization of seafloor hydrothermal systems

Research on the biomineralization in modern seafloor hydrothermal systems is conducive to unveiling the mysteries of the early Earth’s history, life evolution, subsurface biosphere and microbes in outer space. The hydrothermal biomineralization has become a focus of geo-biological research in the last decade, since the introduction of the microelectronic technology and molecular biology technology. Microorganisms play a critical role in the formations of oxide/hydroxides (e.g. Fe, Mn, S and Si oxide/hydroxides) and silicates on the seafloor hydrothermal systems globally. Furthermore, the biomineralization of modern chemolithoautotrophic microorganisms is regarded as a nexus between the geosphere and the biosphere, and as an essential complement of bioscience and geology. In this paper, we summarize the research progress of hydrothermal biomineralization, including the biogenic minerals, the microbial biodiversity, and also the interactions between minerals and microorganisms. In the foreseeable future, the research on hydrothermal biomineralization will inspire the development of geosciences and biosciences and thus enrich our knowledge of the Earth’s history, life evolution and even astrobiology.