Rhizosheath–root system changes exopolysaccharide content but stabilizes bacterial community across contrasting seasons in a desert environment

Ramona Marasco*, Marco Fusi, Maria Mosqueira, Jenny Marie Booth, Federico Rossi, Massimiliano Cardinale, Grégoire Michoud, Eleonora Rolli, Gianmarco Mugnai, Lorenzo Vergani, Sara Borin, Roberto De Philippis, Ameur Cherif, Daniele Daffonchio*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Background: In hot deserts daily/seasonal fluctuations pose great challenges to the resident organisms. However, these extreme ecosystems host unique microenvironments, such as the rhizosheath–root system of desert speargrasses in which biological activities and interactions are facilitated by milder conditions and reduced fluctuations. Here, we examined the bacterial microbiota associated with this structure and its surrounding sand in the desert speargrass Stipagrostis pungens under the contrasting environmental conditions of summer and winter in the Sahara Desert. Results: The belowground rhizosheath–root system has higher nutrient and humidity contents, and cooler temperatures than the surrounding sand. The plant responds to the harsh environmental conditions of the summer by increasing the abundance and diversity of extracellular polymeric substances (EPS) compared to the winter. On the contrary, the bacterial community associated with the rhizosheath–root system and its interactome remain stable and, unlike the bulk sand, are unaffected by the seasonal environmental variations. The rhizosheath–root system bacterial communities are consistently dominated by Actinobacteria and Alphaproteobacteria and form distinct bacteria communities from those of bulk sand in the two seasons. The microbiome-stabilization mediated by the plant host acts to consistently retain beneficial bacteria with multiple plant growth promoting functions, including those capable to produce EPS, which increase the sand water holding capacity ameliorating the rhizosheath micro-environment. Conclusions: Our results reveal the capability of plants in desert ecosystems to stabilize their below ground microbial community under seasonal contrasting environmental conditions, minimizing the heterogeneity of the surrounding bulk sand and contributing to the overall holobiont resilience under poly-extreme conditions.

Original languageEnglish (US)
Article number14
JournalEnvironmental Microbiomes
Issue number1
StatePublished - Dec 2022

Bibliographical note

Funding Information:
This research was supported by the EU project BIODESERT (European Community’s Seventh Framework Programme CSA-SA REGPOT-2008–2 under grant agreement no. 245746), King Abdullah University of Science and Technology through the baseline research funds to DD, European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 841317 with the project “SENSE” for the funding support to ER and SB.

Publisher Copyright:
© 2022, The Author(s).


  • Desert
  • Desertification
  • Environmental fluctuation
  • Environmentally-independent microbiome
  • Extracellular polymeric substances (EPS)
  • PGP microorganisms
  • Plant legacy
  • Plant-microbiome
  • Rhizosheath

ASJC Scopus subject areas

  • Microbiology
  • Applied Microbiology and Biotechnology
  • Genetics


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