Divergent microbial traits influence the transformation of living versus dead root inputs to soil carbon

Abstract

Soil microorganisms influence the global carbon cycle by transforming plant inputs into soil organic carbon (SOC), but the microbial traits that facilitate this process are unresolved. While current theory and biogeochemical models suggest microbial carbon-use efficiency and growth rate are positive predictors of SOC, recent observations demonstrate these relationships can be positive, negative, or neutral. To parse these contradictory effects, we used a 13C-labeling experiment to test whether different microbial traits influenced the transformation of plant C into SOC within the microbial habitats surrounding living root inputs (rhizosphere) versus decaying root litter (detritusphere), under both normal soil moisture and droughted conditions. In the rhizosphere, bacterial-dominated communities with fast growth, high carbon-use efficiency, and high production of extracellular polymeric substances formed microbial-derived SOC under normal moisture conditions. However, in the detritusphere — and the rhizosphere under drought — more fungal-dominated communities with slower growth but higher exoenzyme activity formed plant-derived SOC. These findings emphasize that microbial traits linked with SOC accrual are not universal, but contingent on how microorganisms allocate carbon under different resource conditions and environmental stressors.

Improved characterization of soil organic matter by integrating FTICR-MS, liquid chromatography tandem mass spectrometry and molecular networking: a case study of root litter decay under drought conditions

“…The limited number of library matches provide an incomplete picture of SOM composition, however together with findings of overall changes in molecular class composition and reduced average NOSC with drought, we can discuss some possible biological processes underlying our observations. Microbial analyses from this same study indicated that microbial exoenzyme activity was reduced under drought, as was cumulative 13 C carbon assimilation, and fungi were the dominant community members present under both conditions [57]. It is possible that secondary fungal metabolites with condensed-ring structures such as melanins, aromatic polyketides and hydroxy anthraquinones could represent some of the condensed hydrocarbonlike (H/C < 0.8) compounds found in greater relative proportion under normal conditions [58][59][60].…”

“…Top carbon assimilators in both fungal and bacterial communities were found to shift with soil moisture treatment [57]. While the amount of 13 C labeled mineral associated organic matter (MAOM) from active microbes was similar under drought and control conditions after 12 weeks, the composition differed [57], suggesting that production and fate of different SOM components may impact the type of carbon that persists in these soils under drought.…”

“…Rhapontin, esculetin and herticin A also confer antimicrobial and antioxidant properties and are commonly found in medicinal plants [54,64,65]. On the other hand, significantly higher abundance of nucleic acids adenine and guanine in the control could be related to higher microbial activity under normal moisture conditions [51,52,57].…”

Fosthiazate inhibits root-knot disease and alters rhizosphere microbiome of Cucumis melo var. saccharinus

“…Species annotation analysis of OTU sequences was conducted at various taxonomic levels (kingdom, phylum, class, order, family, genus, and species) through the SSUrRNA database of SILVA138.1 4 (July 16, 2022) set as threshold of 0.8-1. The MAFFT (v7.490 5 , July 06, 2022) software was used for prompt multiple sequence alignment (MSA) to obtain all OTUs signifying the phylogentic relationship of all sequences (Sokol et al, 2022). Moreover, the data from each sample was normalized in comparison with the samples containing minimum data quantity in order to get standardized results.…”