Petroleum contamination poses a serious threat to human health and ecosystems worldwide, and microbially driven natural attenuation is an effective approach for accelerating hydrocarbon removal. Species of the genus Rhodococcus are recognized for their ability to degrade long chain petroleum hydrocarbons. However, their physiological traits and degradation mechanisms under alkaline conditions remain insufficiently understood. In this study, soil samples were collected from the Dagang oilfield in Tianjin, China, and Rhodococcus sp. A17 was isolated as an active indigenous strain for genomic and physiological characterization under high pH petroleum degradation conditions. The results showed that strain A17 grew optimally at 30 °C, pH 9.0, and 2% salinity. Petroleum hydrocarbon degradation reached 67.8% within 72 h, with a degradation half life of 34.2 h. Genome sequencing identified 18 oxygenase related genes involved in alkane degradation, including alkB, cytochrome P450 monooxygenases, and the long chain alkane monooxygenase ladA, together with four antibiotic resistance genes. Metabolite analysis suggested that alkane degradation might proceed via terminal and subterminal oxidation pathways. Overall, these findings indicate that Rhodococcus sp. A17 exhibits multiple adaptive traits that support its potential application in the bioremediation of petroleum contaminated alkaline environments.

Chlorite plays an essential role in transporting water into the deep Earth. This study investigates the high-pressure behaviour of clinochlore up to ∼20 GPa at room temperature, using synchrotron X-ray diffraction and infrared spectroscopy. We identified a polytypic phase transition (from II b -2 to II a -1) at ∼9 GPa and a structural distortion at ∼12 GPa. The polytypic phase transition at ∼9 GPa is characterised by a significant reorganization of interlayer hydrogen bonding, transitioning to states of weakly bonded or non-hydrogen-bonded hydroxyl groups. The phase transition showed reversibility during the experiment. The structural distortion near 12 GPa indicates adjustments in the compression mechanism related to the hydroxyl groups across both the brucite-like and 2:1 sheets. The unit-cell volume of the low-pressure II b -2 phase was fitted to the second-order Birch-Murnaghan equation of state, and the resulting parameters are V ₀ = 710.9(3) Å ³ and K ₀ = 83.4(8) GPa. Our results exhibit a marked deviation from prior experimental findings, potentially attributable to the presence of Fe ²⁺ cation incorporation in the natural chlorite investigated in this work. This study emphasises the complexity of the hydroxyl group in response to pressure in layered-structure silicates.