Methods: In this study, the recombinant ND6 in which pND6 - 1 and pND6 - 2 were labeled with gentamicin and kanamycin-encoding genes, respectively, was constructed to investigate the conjugative transfer behavior of the two plasmids in distinct aqueous matrices. Results: The results indicated that both pND6 - 1 and pND6 - 2 plasmids could transfer from donor strain ND6 to - 2 P. putida a recipient strain KT2440, while the transfer frequency of pND6 -2 (1.90 × 10 ) was significantly - 9 higher than that of pND6 -1 (3.12 × 10 ). Furthermore, the concomitant transfer of pND6 - 1 and pND6 - 2 was - 9 confirmed at a lower frequency of 10 colonies per recipient similar with that of pND6 - 1. The conjugative transfer efficiency was obviously affected by the initial inoculum and the stability of microbes. Moreover, more than 90% of the transconjugants lost the plasmids after 20 generations cultivation without resistance pressure, suggesting the importance of selective pressure to maintain the plasmid stability. Finally, the naphthalene degradation analysis by mixed ND6 and KT2440 revealed that conjugative transfer of catabolic plasmids contributed to the rapid dispersion of the degradation genes on plasmids and enhanced the naphthalene removal.

Wang, S., Luan, H., Liang, X., Wang, L., Guo, Y., 2020. Recognition and characterization of active fractions from petroleum sulfonate. Journal of Petroleum Science and Engineering 187, 106797.

http://www.sciencedirect.com/science/article/pii/S092041051931215X Petroleum sulfonates are widely used in chemical flooding in China. The samples are complicated and not all the fractions are effective. To recognize effective fraction with excellent interfacial activity and emulsifying property, a preparative liquid chromatography technology was adopted to perform the fraction separation for ， petroleum sulfonate. Structural composition, interfacial activity emulsifying property and flooding efficiency of obtained fractions were also analyzed and discussed. It was shown that petroleum sulfonate can be effectively separated into different fractions with obvious structural differences, among which one fraction with the most excellent interfacial activity and the emulsifying property was recognized. The average molecular weight and molecular weight distribution range of this active fraction were 455.5 and 428 - 468, respectively, which are both crucial for activities. Alkylbenzene dicyclohexane sulfonates, alkyl indan sulfonates, and alkyl naphthalene sulfonates are major structure types, and alkyl chain length is mainly distributed between 12 - 15, 15 - 17 and 15 - 17 respectively. Besides, this active fraction is universal, and it can produce ultralow interfacial - 3 tension (~10 mN/m) and good emulsifying property against different crude oils including Xinjiang, Changqing, Liaohe Oilfields, etc. in China. The developed technology herein can be used to track and confirm the characteristics and/or active fraction in petroleum sulfonate accurately.

Wang, T., Cheng, X., Xu, H., Meng, Y., Yin, Z., Li, X., Hang, W., 2020. Perspective on advances in laser-based high-resolution mass spectrometry imaging. Analytical Chemistry 92, 543-553.

https://doi.org/10.1021/acs.analchem.9b04067 Mass spectrometry imaging (MSI) has become a powerful tool in diverse fields, such as chemistry, physics, materials, and life science. Although such research is getting more prevalent, it is limited by high-resolution (HR) instrumental development. Recently, unceasing efforts have been made toward taking spatial resolution from the microscale to nanoscale, especially for near-field based techniques. These emerging and unique features behind high-resolution mass spectrometry imaging (HR-MSI) provide new possibilities in various aspects of biological researches. Since many technological advances provided a forefront for HR-MSI, compelling challenges including sensitivity, specificity, multimodal imaging, data acquisition, and processing follow undoubtedly. Gratifyingly, with attempts and experiences in the infancy, the emerging techniques move toward much more mature to deal with underlying conundrums in the future. Not only confined to commercial instruments, this perspective highlights recent innovations covering all emerging HR-MSI (with spatial resolution below 5 μm) techniques. Besides, vital limitations and handicaps at this stage are presented while corresponding schemes are proposed. This perspective also gives the authors' personal outlooks of developments and applications for HR-MSI in coming years.