Rhizobial strains isolated from soil have copious expolysaccharide.

Emiliano D Primo, Sacha Cossovich, Fiorela Nievas, Pablo Bogino, Ethan A Humm, Ann M Hirsch, Walter Giordano

Overview

Ensifer meliloti strains isolated from the field are more mucoid than lab strains and do not differ from the lab strains in terms of nodule development. However, lab strains are not real life bacteria and to grow more food in the future in the field, we need to look beyond the lab.

Summary

Although our experiments show little effect on nodule development under lab conditions, native E. meliloti strains are often mucoid in the field suggesting that they are better adapted to soil environments. Upon legume inoculation, the presence of excess polysaccharide may increase legume productivity in the field by desiccation protection, by enhancing plant tolerance to stress, and by promoting bacteria consortium development.

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Author Comments

Dr. Ann M Hirsch, PhD
Dr. Ann M Hirsch, PhD
University of California-Los Angeles
Distinguished Professor
plant-microbe interactions
Los Angeles, CA | United States
Our goal is to improve plant growth and yield by employing plant growth-promoting bacteria instead of synthetic chemicals. The use of the latter has significantly damaged soils, which negatively affects plant growth.Dr. Ann M Hirsch, PhD

Exopolysaccharide production in Ensifer meliloti laboratory and native strains and their effects on alfalfa inoculation.

Authors:
Dr. Ann M Hirsch, PhD
Dr. Ann M Hirsch, PhD
University of California-Los Angeles
Distinguished Professor
plant-microbe interactions
Los Angeles, CA | United States

Arch Microbiol 2020 Mar 3;202(2):391-398. Epub 2019 Nov 3.

Departamento de Biología Molecular, Universidad Nacional de Río Cuarto, Río Cuarto, Córdoba, Argentina.

Bacterial surface molecules have an important role in the rhizobia-legume symbiosis. Ensifer meliloti (previously, Sinorhizobium meliloti), a symbiotic Gram-negative rhizobacterium, produces two different exopolysaccharides (EPSs), termed EPS I (succinoglycan) and EPS II (galactoglucan), with different functions in the symbiotic process. Accordingly, we undertook a study comparing the potential differences in alfalfa nodulation by E. meliloti strains with differences in their EPSs production. Strains recommended for inoculation as well as laboratory strains and native strains isolated from alfalfa fields were investigated. This study concentrated on EPS-II production, which results in mucoid colonies that are dependent on the presence of an intact expR gene. The results revealed that although the studied strains exhibited different phenotypes, the differences did not affect alfalfa nodulation itself. However, subtle changes in timing and efficacy to the effects of inoculation with the different strains may result because of other as-yet unknown factors. Thus, additional research is needed to determine the most effective inoculant strains and the best conditions for improving alfalfa production under agricultural conditions.

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Source
http://dx.doi.org/10.1007/s00203-019-01756-3DOI Listing
March 2020
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