Kaiwen Ta

Microbial communities inhabiting oil-contaminated soils from two major oilfields in Northern China: Implications for active petroleum-degrading capacity

Although oilfields harbor a wide diversity of microorganisms with various metabolic potentials, our current knowledge about oil-degrading bacteria is limited because the vast majority of oil-degrading bacteria remain uncultured. In the present study, microbial communities in nine oil-contaminated soils collected from Daqing and Changqing, two of the largest oil fields in China, were characterized through highthroughput sequencing of 16S rRNA genes. Bacteria related to the phyla Proteobacteria and Actinobacteria were dominant in four and three samples, respectively. At the genus level, Alkanindiges, Arthrobacter, Pseudomonas, Mycobacterium, and Rhodococcus were frequently detected in nine soil samples. Many of the dominant genera were phylogenetically related to the known oil-degrading species. The correlation between physiochemical parameters within the microbial communities was also investigated. Canonical correspondence analysis revealed that soil moisture, nitrate, TOC, and pH had an important impact in shaping the microbial communities of the hydrocarbon-contaminated soil. This study provided an in-depth analysis of microbial communities in oilcontaminated soil and useful information for future bioremediation of oil contamination.

Hydrothermal nontronite formation associated with microbes from low-temperature diffuse hydrothermal vents at the South Mid-Atlantic Ridge

Oceanic nontronite deposits have been identified to be closely related to low- temperature hydrothermal activities. However, their formation mechanisms associated with microbes in diffuse hydrothermal vents still remain largely unknown. The friable deposits, collected from the low-temperature diffuse flow at the Southern Atlantic Ridge, display a layered structure. Scanning electron microscope (SEM) and transmission electron microscope (TEM) analyses reveal that abundant filamentous, spherical and rod-shaped mineralized forms are preserved in the yellowish-green layer of the deposits. These mineralized forms primarily consist of Si and Fe. Selected area electron diffraction (SAED) patterns of the mineralized forms indicate that they are composed of nontronite. High intensities of 12C and 12C14N signals derived from cellular structures determined by nano secondary ion mass spectrometry (nanoSIMS) suggest the intimate relationship between nontronite and microbes. The results of 454 pyrosequencing analyses provide insights into the microbial communities involved in the biologically-induced mineralization in the yellowish-green layer. We propose an evolutionary model for establishing paragenetic sequences among nontronite, Mn-oxide and Fe-oxyhydroxide in the deposits. This paragenetic sequence could be widespread in modern and ancient low-temperature hydrothermal fields.