Toner Brandy, Fakra Sirine, Villalobos Mario, Warwick Tony, Sposito Garrison
Department of Environmental Science, Policy and Management, Division of Ecosystem Sciences, University of California, CA, USA.
Appl Environ Microbiol. 2005 Mar;71(3):1300-10. doi: 10.1128/AEM.71.3.1300-1310.2005.
Pseudomonas putida strain MnB1, a biofilm-forming bacterial culture, was used as a model for the study of bacterial Mn oxidation in freshwater and soil environments. The oxidation of aqueous Mn+2 [Mn+2(aq)] by P. putida was characterized by spatially and temporally resolving the oxidation state of Mn in the presence of a bacterial biofilm, using scanning transmission X-ray microscopy (STXM) combined with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at the Mn L2,3 absorption edges. Subsamples were collected from growth flasks containing 0.1 and 1 mM total Mn at 16, 24, 36, and 48 h after inoculation. Immediately after collection, the unprocessed hydrated subsamples were imaged at a 40-nm resolution. Manganese NEXAFS spectra were extracted from X-ray energy sequences of STXM images (stacks) and fit with linear combinations of well-characterized reference spectra to obtain quantitative relative abundances of Mn(II), Mn(III), and Mn(IV). Careful consideration was given to uncertainty in the normalization of the reference spectra, choice of reference compounds, and chemical changes due to radiation damage. The STXM results confirm that Mn+2(aq) was removed from solution by P. putida and was concentrated as Mn(III) and Mn(IV) immediately adjacent to the bacterial cells. The Mn precipitates were completely enveloped by bacterial biofilm material. The distribution of Mn oxidation states was spatially heterogeneous within and between the clusters of bacterial cells. Scanning transmission X-ray microscopy is a promising tool for advancing the study of hydrated interfaces between minerals and bacteria, particularly in cases where the structure of bacterial biofilms needs to be maintained.
恶臭假单胞菌MnB1菌株是一种能形成生物膜的细菌培养物，被用作研究淡水和土壤环境中细菌锰氧化的模型。利用扫描透射X射线显微镜（STXM）结合锰L2,3吸收边的近边X射线吸收精细结构（NEXAFS）光谱，通过在细菌生物膜存在的情况下对锰的氧化态进行空间和时间分辨，对恶臭假单胞菌对水溶液中Mn+2 [Mn+2(aq)]的氧化进行了表征。在接种后16、24、36和48小时，从含有0.1和1 mM总锰的生长瓶中收集子样本。收集后立即对未处理的水合子样本进行40纳米分辨率的成像。从STXM图像（堆栈）的X射线能量序列中提取锰NEXAFS光谱，并与特征明确的参考光谱的线性组合进行拟合，以获得Mn(II)、Mn(III)和Mn(IV)的定量相对丰度。仔细考虑了参考光谱归一化的不确定性、参考化合物的选择以及辐射损伤引起的化学变化。STXM结果证实，恶臭假单胞菌从溶液中去除了Mn+2(aq)，并在紧邻细菌细胞的位置浓缩为Mn(III)和Mn(IV)。锰沉淀物被细菌生物膜材料完全包裹。锰氧化态的分布在细菌细胞簇内部和之间存在空间异质性。扫描透射X射线显微镜是推进矿物与细菌之间水合界面研究的一种有前途的工具，特别是在需要保持细菌生物膜结构的情况下。
