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具有多样性，但证明微化石和微生物沉积结构的生物源性仍然是一个巨大的挑战。然而，越来越多的人认为微生物对沉积沉积物的形成起了很大的作用。我建议把重点放在富含铁的沉积岩上，寻找微生物在其形成过程中起关键作用的证据。铁是所有生命的基本元素，而生命的进化离不开铁的独特化学性质。然而，对于铁氧化和铁还原细菌来说，铁在呼吸中起着额外的关键作用。由于呼吸作用，铁的化学状态发生了变化，从而形成了新的矿物相。活性铁也可以通过硫酸盐还原菌的活性间接产生。不管来源如何，在某些情况下，铁似乎起到了保存细菌细胞壁的作用，导致细菌被埋葬并最终变成化石。我提议与我的NSERC发现基金将支持的研究生和本科生一起，研究铁和硫酸盐呼吸在细菌保存和微生物化石起源中的作用。

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.