The core root microbiome of Spartina alterniflora is predominated by sulfur-oxidizing and sulfate-reducing bacteria in Georgia salt marshes, USA

Abstract

Background Salt marshes are dominated by the smooth cordgrass Spartina alterniflora on the US Atlantic and Gulf of Mexico coastlines. Although soil microorganisms are well known to mediate important biogeochemical cycles in salt marshes, little is known about the role of root microbiomes in supporting the health and productivity of marsh plant hosts. Leveraging in situ gradients in aboveground plant biomass as a natural laboratory, we investigated the relationships between S. alterniflora primary productivity, sediment redox potential, and the physiological ecology of bulk sediment, rhizosphere, and root microbial communities at two Georgia barrier islands over two growing seasons. Results A marked decrease in prokaryotic alpha diversity with high abundance and increased phylogenetic dispersion was found in the S. alterniflora root microbiome. Significantly higher rates of enzymatic organic matter decomposition, as well as the relative abundances of putative sulfur (S)-oxidizing, sulfate-reducing, and nitrifying prokaryotes correlated with plant productivity. Moreover, these functional guilds were overrepresented in the S. alterniflora rhizosphere and root core microbiomes. Core microbiome bacteria from the Candidatus Thiodiazotropha genus, with the metabolic potential to couple S oxidation with C and N fixation, were shown to be highly abundant in the root and rhizosphere of S. alterniflora. Conclusions The S. alterniflora root microbiome is dominated by highly active and competitive species taking advantage of available carbon substrates in the oxidized root zone. Two microbially mediated mechanisms are proposed to stimulate S. alterniflora primary productivity: (i) enhanced microbial activity replenishes nutrients and terminal electron acceptors in higher biomass stands, and (ii) coupling of chemolithotrophic S oxidation with carbon (C) and nitrogen (N) fixation by root- and rhizosphere-associated prokaryotes detoxifies sulfide in the root zone while potentially transferring fixed C and N to the host plant.

The Diversity and Functional Capacity of Microbes Associated with Coastal Macrophytes

“…may couple sox -oxidation with dissimilatory nitrate reduction, where nitrate is used as the terminal electron receptor ( 25 ). Sulfur oxidation may stimulate microbial and host productivity by replenishing the available stock of sulfate, which serves as both a nutrient and a terminal electron acceptor ( 65 ).…”

Soil Bacterial Community Structure in Different Micro-Habitats on the Tidal Creek Section in the Yellow River Estuary

“…Recent years, SRB and AAPB have got many attentions on sulfur cycling, carbon mineralization, and sequestration in the coastal wetland (Stegman et al, 2014;Jørgensen et al, 2019;Rolando et al, 2022). The present study found SRB and AAPB were characterized as the bacterial biomarkers in tidal creek salt marsh, and may partly result in the differences of structures and functions.…”

Plant invasion reconstructs soil microbial assembly and functionality in coastal salt marshes

“…Bacterial families involved in sulphate reduction, such as Desulfocapsaceae and Desulfosarcinaceae, were significantly enriched in invaded wetlands (Figure 2). A recent study by Rolando et al (2022) also found that the rhizosphere of S.…”

“…Bacterial families involved in sulphate reduction, such as Desulfocapsaceae and Desulfosarcinaceae, were significantly enriched in invaded wetlands (Figure 2). A recent study by Rolando et al (2022) also found that the rhizosphere of S. alterniflora was the hotspot of sulphate‐reducing bacteria in Georgia salt marshes, USA. In addition, a higher proportion of saprotrophic fungi was observed in invaded soils (Figure S10), which might be tightly associated with organic matter accumulation with plant invasion (Zhang et al, 2021).…”