Exopolysaccharide production in Ensifer meliloti laboratory and native strains and their effects on alfalfa inoculation
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.
KeywordsAlfalfa Sinorhizobium meliloti Ensifer meliloti Exopolysaccharides Symbiosis Biofertilization
Grants from the Secretaría de Ciencia y Técnica de la UNRC, Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT) and Consejo Nacional de Investigaciones Científicas y Técnicas of the República Argentina (CONICET) supported this work. EP and SC have a fellowship from the CONICET. FN, PB, and WG are Career Members of CONICET. Our thanks are due to Dr. Nicolás Ayub for helpful suggestions and useful discussions. Support from a Shanbrom Family Fund grant supported research on symbioses in arid environments in the Hirsch laboratory. This research was funded by FONCyT Grant number [PICT 1528/15].
Compliance with ethical standards
Conflict of interest
The authors have no conflicts of interest to declare.
- Abdelhadi LO, Lyons TP, Jacques KA (2004) Evaluating inoculants for forage crops in Argentine beef and milk grazing systems: effects on silage quality and system profitability. In: Lyons TP, Jacques KA (Eds.) Nutritional biotechnology in the feed and food industries. Alltech 20th Annual Symposium. Nicholasville, KY, USA pp. 171–177.Google Scholar
- Avci MA, Ozkose A, Tamkoc A (2013) Determination of yield and quality characteristics of alfalfa (Medicago sativa l.) varieties grown in different locations. J Amin Vet Adv 12:487–490Google Scholar
- Caviglia OP, Andrade FH (2010) Sustainable intensification of agriculture in the Argentinean Pampas: capture and use efficiency of environmental resources. Am J Plant Sci Biotechnol 3:1–8Google Scholar
- Evans LT (1993) Crop evolution. Adaptations and yield. Cambridge University Press, CambridgeGoogle Scholar
- Fujishige NA, Jankaew K, Hirsch AM (2008) Biofilm formation in Sinorhizobium meliloti. Biology of plant-microbe interactions, Volume 6. In: Proceedings of the 13th International Congress on Molecular Plant-Microbe Interactions. Eds. Lorito M, Woo SL, and Scala F. ISBN 0965462552Google Scholar
- Geisseler D, Horwath WR (2016) Alfalfa production in California. https://apps1.cdfa.ca.gov/FertilizerResearch/docs/Alfalfa_Production_CA.pdf. Accessed 16 Apr 2019
- Hirsch AM, Lum MR, Fujishige NA (2009) Microbial encounters of a symbiotic kind- attaching to roots and other surfaces. In: Emons AMC, Ketelaar T (eds) Root hairs. Plant cell monographs, 12th edn. Springer, Berlin, pp 295–314Google Scholar
- Jozefkowicz C, Brambilla S, Frare R, Stritzler M, Piccinetti C, Puente M, Berini C, Reyes Pérez P, Soto G, Ayub N (2017a) Stable symbiotic nitrogen fixation under water-deficit field conditions by a stress-tolerant alfalfa microsymbiont and its complete genome sequence. J Biotechnol 263:52–54PubMedCrossRefGoogle Scholar
- Kawaharada Y, Kelly S, Nielsen MW, Hjuler CT, Gysel K, Muszyński A, Carlson RW, Thygesen MB, Sandal N, Asmussen MH, Vinther M, Andersen SU, Krusell L, Thirup S, Jensen KJ, Ronson CW, Blaise M, Radutoiu S, Stougaard J (2015) Receptor-mediated exopolysaccharide perception controls bacterial infection. Nature 523:308–312PubMedCrossRefGoogle Scholar
- Keller M, Roxlau A, Weng WM, Schmidt M, Quandt J, Niehaus K, Jording D, Arnold W, Pühler A (1995) Molecular analysis of the Rhizobium meliloti mucR gene regulating the biosynthesis of the exopolysaccharides succinoglycan and galactoglucan. Mol Plant Microbe Interact 8:267–277PubMedCrossRefGoogle Scholar
- Ohyama T (2017) The role of legume-Rhizobium symbiosis in sustainable agriculture. In: Sulieman S, Tran LS (eds) Legume nitrogen fixation in soils with low phosphorus availability. Springer, Cham, pp 1–20Google Scholar