Instituto Oceanográfico, Universidade de São Paulo, São Paulo, 05508-120, Brazil.
Research School of Earth Sciences, Australian National University, Canberra, ACT 2601, Australia.
Environ Microbiol Rep. 2018 Jun;10(3):337-343. doi: 10.1111/1758-2229.12644. Epub 2018 Apr 23.
Magnetotactic bacteria are a multi-phyletic group of bacteria that synthesize membrane-bound magnetic minerals. Understanding the preservation of these minerals in various environments (e.g., with varying oxygen concentrations and iron supply) is important for understanding their role as carriers of primary magnetizations in sediments and sedimentary rocks. Here we present X-ray near edge structure (XANES) spectra for Fe in magnetotactic bacteria samples from recent sediments to assess surface oxidation and crystal structure changes in bacterial magnetite during early burial. Our results are compared with a XANES spectrum of cultivated Magnetofaba australis samples, and with magnetic properties, and indicate that oxidation of magnetite to maghemite increases with depth in the sediment due to longer exposure to molecular oxygen. These results are relevant to understanding magnetic signatures carried by magnetofossils in oxic sediments and sedimentary rocks of different ages.
趋磁细菌是一类能合成膜结合型磁性矿物的多生源细菌。了解这些矿物在不同环境（如不同的氧浓度和铁供应）中的保存情况，对于理解它们作为沉积物和沉积岩中原生磁化载体的作用非常重要。在这里，我们展示了来自近代沉积物的趋磁细菌样品的 X 射线近边结构（XANES）谱，以评估细菌磁铁矿在早期埋藏过程中表面氧化和晶体结构的变化。我们的结果与培养的南方磁小体（Magnetofaba australis）样品的 XANES 谱进行了比较，并与磁性特性进行了比较，结果表明，由于更长时间暴露于分子氧，磁铁矿向磁赤铁矿的氧化随着沉积物深度的增加而增加。这些结果对于理解在不同年龄的含氧沉积物和沉积岩中磁化石所携带的磁性特征具有重要意义。
