Bacteria from extreme environments as candidate bioinoculants for drought tolerance in legumes: a critical appraisal of mechanisms and evidence
8 affiliations
- 1Programa de Doctorado en Ciencias Agropecuarias, Facultad de Recursos Naturales, Universidad Católica de Temuco
- 2Programa de Doctorado en Fisiología Vegetal, Departamento de Biologia Vegetal, Universidade Federal de Viçosa
- 3Laboratorio de Fisiología y Biotecnología Vegetal, Departamento de Ciencias Agropecuarias y Acuícolas, Facultad de Recursos Naturales, Universidad Católica de Temuco
- 4Núcleo de Investigación en Producción Alimentaria, Facultad de Recursos Naturales, Universidad Católica de Temuco
- 5Agencia Nacional de Investigación y Desarrollo - Millennium Science Initiative Program, Millennium Nucleus in Data Science for Plant Resilience (Phytolearning)
- 6Laboratorio de Ecofisiología Molecular y Funcional de Plantas, Departamento de Ciencias Químicas y Recursos Naturales, Facultad de Ingeniería y Ciencias, Universidad de La Frontera
- 7Center of Plant, Soil Interaction and Natural Resources Biotechnology, Scientific and Technological Bioresource Nucleus (BIOREN-UFRO), Universidad de La Frontera
- 8Instituto de Ciencias Aplicadas, Facultad de Ingeniería, Universidad Autónoma de Chile
Abstract
Drought is one of the major constraints limiting legume productivity, impairing plant growth, biological nitrogen fixation, and seed nutritional quality. The increasing frequency and intensity of water scarcity have intensified the search for sustainable strategies to improve crop resilience. Bacteria isolated from extreme environments have been proposed as candidate bioinoculants because adaptations to desiccation, salinity, or extreme temperatures may provide traits relevant to plant performance under water deficit. However, most of these isolates are extremotolerant rather than extremophilic sensu stricto, and much of the supporting evidence derives from stresses other than drought. The objective of this review is to synthesize current knowledge on the mechanisms through which extremophilic and extremotolerant bacteria may contribute to drought tolerance in legumes, using explicit operational definitions for these microbial categories and for drought, and a four-tier evidence classification applied at the level of individual studies. Candidate mechanisms include exopolysaccharide- and biofilm-mediated rhizosphere water retention, modulation of root architecture and auxin/ethylene balance through ACC deaminase activity, osmolyte accumulation, antioxidant responses, nutrient mobilization, maintenance of nodulation and biological nitrogen fixation, and regulation of host stress-responsive genes. Direct evidence, defined as extremophilic or extremotolerant strains evaluated in legumes under soil water deficit, is restricted to a small number of studies, whereas a large proportion of the literature relies on salinity, heat, or PEG-induced osmotic stress, non-legume hosts, genomic potential, or in vitro assays. We also discuss constraints that may limit the use of these bacteria, including rhizosphere colonization, persistence, and competitiveness against native microbiota under non-extreme conditions. Current findings provide plausible mechanisms and proof-of-concept results, but they do not yet demonstrate reliable field performance of extremophile-derived inoculants in legume production. Strain-level characterization, standardized drought protocols, and multi-environment field validation are required to establish their agronomic value.
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BibTeX
@article{lopez2026bacteria,
title = {{Bacteria from extreme environments as candidate bioinoculants for drought tolerance in legumes: a critical appraisal of mechanisms and evidence}},
author = {Deisy Johana Cuellar Lopez and Rodrigo Mora-Sanhueza and Ricardo Tighe-Neira and Braulio Soto-Cerda and Marjorie Reyes-Díaz and Kattia Núñez-Montero and Patricio Arce-Johnson and Dimas Mendes Ribeiro and Claudio Inostroza-Blancheteau},
journal = {Frontiers in Plant Science},
year = {2026},
month = oct,
doi = {10.3389/fpls.2026.1944380},
url = {https://www.frontiersin.org/articles/10.3389/fpls.2026.1944380/full},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Bacteria from extreme environments as candidate bioinoculants for drought tolerance in legumes: a critical appraisal of mechanisms and evidence
AU - Deisy Johana Cuellar Lopez
AU - Rodrigo Mora-Sanhueza
AU - Ricardo Tighe-Neira
AU - Braulio Soto-Cerda
AU - Marjorie Reyes-Díaz
AU - Kattia Núñez-Montero
AU - Patricio Arce-Johnson
AU - Dimas Mendes Ribeiro
AU - Claudio Inostroza-Blancheteau
PY - 2026
DA - 2026/10/20
JO - Frontiers in Plant Science
DO - 10.3389/fpls.2026.1944380
UR - https://www.frontiersin.org/articles/10.3389/fpls.2026.1944380/full
AB - Drought is one of the major constraints limiting legume productivity, impairing plant growth, biological nitrogen fixation, and seed nutritional quality. The increasing frequency and intensity of water scarcity have intensified the search for sustainable strategies to improve crop resilience. Bacteria isolated from extreme environments have been proposed as candidate bioinoculants because adaptations to desiccation, salinity, or extreme temperatures may provide traits relevant to plant performance under water deficit. However, most of these isolates are extremotolerant rather than extremophilic sensu stricto, and much of the supporting evidence derives from stresses other than drought. The objective of this review is to synthesize current knowledge on the mechanisms through which extremophilic and extremotolerant bacteria may contribute to drought tolerance in legumes, using explicit operational definitions for these microbial categories and for drought, and a four-tier evidence classification applied at the level of individual studies. Candidate mechanisms include exopolysaccharide- and biofilm-mediated rhizosphere water retention, modulation of root architecture and auxin/ethylene balance through ACC deaminase activity, osmolyte accumulation, antioxidant responses, nutrient mobilization, maintenance of nodulation and biological nitrogen fixation, and regulation of host stress-responsive genes. Direct evidence, defined as extremophilic or extremotolerant strains evaluated in legumes under soil water deficit, is restricted to a small number of studies, whereas a large proportion of the literature relies on salinity, heat, or PEG-induced osmotic stress, non-legume hosts, genomic potential, or in vitro assays. We also discuss constraints that may limit the use of these bacteria, including rhizosphere colonization, persistence, and competitiveness against native microbiota under non-extreme conditions. Current findings provide plausible mechanisms and proof-of-concept results, but they do not yet demonstrate reliable field performance of extremophile-derived inoculants in legume production. Strain-level characterization, standardized drought protocols, and multi-environment field validation are required to establish their agronomic value.
SN - 1664-462X
ER -