Kuttim, M. | bioRxiv Science

bioRxiv2024

Development of a ddPCR approach for the absolute quantification of soil microorganisms involved in atmospheric CO2 fixation

Carbon fixing microorganisms (CFMs) play a crucial role in soil carbon (C) cycling contributing to carbon uptake and sequestration through various metabolic pathways. Despite their significance, quantification of the absolute abundance of CFMs in soils remains elusive. This study employed a digital droplet PCR (ddPCR) approach to quantify the abundance of key and emerging CFM pathways in fen and bog across different depths (0-15 cm). Targeting total prokaryotes (16S rRNA gene), oxygenic phototrophs (23S rRNA gene), aerobic anoxygenic phototrophic bacteria (AAnPB, pufM gene), and chemoautotrophs (cbbL gene), we optimized ddPCR conditions to achieve absolute quantification of these genes. Overall, our results revealed that oxygenic phototrophs were the most abundant CFMs, constituting 12% of total prokaryotic abundance, followed by chemoautotrophs (10%) and AAnPBs (9%). Fen exhibited higher gene concentrations than bog. Depth variations were also observed, differing between fen and bog for all genes. Our findings highlight the abundance of oxygenic phototrophs and chemoautotrophs in peatlands, challenging previous estimations that relied solely on oxygenic phototrophs for microbial CO2 fixation assessments. Incorporating absolute gene quantification is crucial for a comprehensive understanding of microbial contributions to soil processes, shedding light on the intricate mechanisms of soil functioning in peatlands.

microbiology↗

bioRxiv2020

Morphological and biochemical responses of Sphagnum mosses to environmental changes

* Background and AimsSphagnum mosses are vital for peatland carbon (C) sequestration, although vulnerable to environmental changes. For averting environmental stresses such as hydrological changes, Sphagnum mosses developed an array of morphological and anatomical peculiarities maximizing their water holding capacity. They also produce plethora of biochemicals that could prevent stresses-induced cell-damages but these chemicals remain poorly studied. We aimed to study how various anatomical, metabolites, and antioxidant enzymes vary according to Sphagnum taxonomy, phylogeny and environmental conditions. * MethodsWe conducted our study in five Sphagnum-dominated peatlands distributed along a latitudinal gradient in Europe, representing a range of local environmental and climate conditions. We examined the direct and indirect effects of latitudinal changes in climate and vegetation species turnover on Sphagnum anatomical (cellular and morphological characteristics) and biochemical (spectroscopical identification of primary and specialized metabolites, pigments and enzymatic activities) traits. * Key resultsWe show that Sphagnum traits were not driven by phylogeny, suggesting that taxonomy and/or environmental conditions prevail on phylogeny in driving Sphagnum traits variability. We found that moisture conditions were important determinants of Sphagnum anatomical traits, especially those related to water holding capacity. However, the species with the highest water holding capacity also exhibited the highest antioxidant capacity, as showed by the high flavonoid and enzymatic activities in their tissues. Our study further highlighted the importance of vascular plants in driving Sphagnum biochemical traits. More particularly, we found that Sphagnum mosses raises the production of specific compounds such as tannins and polyphenols known to reduce vascular plant capacity when herbaceous cover increases. * ConclusionsOur findings show that Sphagnum anatomical and biochemical traits underpin Sphagnum niche differentiation through their role in specialization towards biotic stressors, such as plant competitors, and abiotic stressors, such as hydrological changes, which are important factors governing Sphagnum growth.

ecology↗