Evidence for signatures of ancient microbial life in paleosols

Abstract

Loess-paleosol sequences are terrestrial archives of past climate change. They may host traces of ancient microbial life, but little information is available on the recovery of microbial biomarkers from such deposits. We hypothesized that microbial communities in soil horizons up to an age of 127 kyr carry information related to past environments. We extracted DNA from a loess-paleosol sequence near Toshan, Northern Iran, with 26 m thick deposits showing different degrees of soil development, performed quantitative PCR and 16S rRNA gene amplicon sequencing. Periods of soil formation archived within the loess sediment led to higher diversity and bacterial abundance in the paleosol horizons. Community composition fluctuated over the loess-paleosol sequence and was mainly correlated with age and depth, (ADONIS R2 < 0.14, P ≤ 0.002), while responses to paleosol soil traits were weaker. Phyla like Bacteriodetes, Proteobacteria or Acidobacteria were more prevalent in paleosol horizons characterized by intense soil formation, while weakly developed paleosols or loess horizons hosted a higher percentage and diversity of Actinobacteria. Taken together, our findings indicate that the microbial community in loess-paleosol sequences carries signatures of earlier environmental conditions that are preserved until today.

Process sequence of soil aggregate formation disentangled through multi-isotope labelling

“…A specific qPCR assay was developed for each of the four strains. The qPCR assays were prepared and DNA amplified as described by Frindte et al (2020). Specific details about primers and cycling conditions are given in Table S1, Supplementary Materials.…”

The microbiome of buried soils demonstrates significant shifts in taxonomic structure and a general trend towards mineral horizons

“…Microbial communities of paleosols are considered to be partially preserved, this provides some information about environmental conditions at the time of burial [ 2 , 9 , 22 , 27 , 30 ]. For example, according to radiocarbon analysis, the age of microbial biomass for the humic horizon of buried chestnut soil corresponds to the time of its burial [ 31 ].…”

A Case Study for the Recovery of Authentic Microbial Ancient DNA from Soil Samples

“…Ancient DNA can be readily recovered from deposited sediments, thereby providing novel insights into past microbial communities of diverse environmental niches [5][6][7][8], and represents unexplored repositories of the past microbial life and the environmental conditions present at the time. Several studies successfully recovered aDNA from non-sediment sample types.…”