The fossilization of microorganisms in sedimentary environments

要被认为是生命的证据，微生物化石必须包含化学和结构属性，这些属性是微生物细胞或细胞过程的独特指标。 尽管潜在的生物特征的多样性，它仍然是巨大的挑战，以证明微化石和微生物沉积结构的生物成因。 然而，越来越多的人一致认为微生物对沉积矿床的形成有很大的贡献。我建议特别关注富含铁的沉积岩，以寻找微生物在其形成中发挥关键作用的证据。 铁是所有生命的基本元素，它已经进化出对铁的独特化学性质的亲密依赖。然而，对于铁氧化和铁还原细菌，铁在呼吸中起着额外的关键作用。 呼吸作用引起的铁的化学状态的变化导致新矿物相的形成。活性铁也可以通过硫酸盐还原菌的活性间接产生。 无论来源如何，在某些情况下，铁似乎起到了保护细菌细胞壁的作用，导致埋葬和最终的细菌化。 我提议调查铁和硫酸盐呼吸在细菌保存和微生物化石的起源中的作用，以及我的NSERC发现资助将支持的研究生和本科生。

To be recognized as evidence of life, microbial fossils must contain chemical and structural attributes that are unique indicators of microbial cells or cellular processes. In spite of the diversity of potential biosignatures, it remains enormously challenging to demonstrate the biogenicity of microfossils and microbial sedimentary structures. There is, however, a growing consensus that microorganisms contribute greatly to the development of sedimentary deposits. I propose to focus in particular on iron-rich sedimentary rocks to look for evidence that microorganisms had a key role in their formation. Iron is an essential element for all life, which has evolved an intimate dependency on iron's unique chemistry. For the iron-oxidizing and iron-reducing bacteria, however, iron plays an additional key role in respiration. The change in iron's chemical state consequent to respiration leads to the formation of new mineral phases. Reactive iron may also be generated indirectly through the activity of sulfate-reducing bacteria. Regardless of the source, it appears that under some circumstances iron acts to preserve the bacterial cell wall, leading to entombment and eventual fossilization. I propose to investigate the role of iron and sulfate respiration in the preservation of bacteria and the genesis of microbial fossils, together with the graduate and undergraduate students that my NSERC Discovery grant will support.