Peanut rhizobia under salt stress: role of trehalose accumulation in strain ATCC 51466

Abstract

Strain ATCC 51466, a motile peanut Rhizobium sp., showed patterns of utilization of diverse carbon sources characteristic of fast growers. Bacteria had periplasmic neutral glucans with molecular weight close to 3000. When the extracellular concentration of NaCl was raised to 400 mM, the lag phase of the culture was prolonged about threefold and the generation time was increased almost twice. The changes in growth behavior of salt-stressed bacteria were accompanied by the full suppression of periplasmic oligoglucans and the accumulation of cellular trehalose. Almost identical changes in cell-associated oligoglucans were observed after exposing peanut Rhizobium sp. strain ATCC 10317 to hypersalinity. When the osmotic pressure of the medium was augmented by the addition of either 200 mM mannitol or 16% (w/v) polyethylene glycol, cells of strain ATCC 51466 contained decreased levels of oligoglucans and accumulated trehalose. On the other hand, the content of cellular trehalose increased throughout logarithmic and stationary phases of growth of strain ATCC 51466 in a medium supplemented with 400 mM NaCl. When bacterial cultures were shifted from hypersaline to basal media, oligoglucans were the only oligosaccharides detected. The addition of 10 mM proline to bacteria grown under hypersalinity led to a 50% decrease in the level of trehalose and to the accumulation of oligoglucans. The addition of 10 mM glycine betaine to bacteria grown under hypersalinity also produced accumulation of oligoglucans, but the level of trehalose did not decrease. The results presented here are consistent with a role for trehalose as a compatible solute in peanut Rhizobium ATCC 51466, and they suggest that exogenously added proline may act as a compatible solute in preference to trehalose.Key words: periplasmic glucans, trehalose, peanut Rhizobium, osmotic stress.

Synthesis, accumulation and hydrolysis of trehalose during growth of peanut rhizobia in hyperosmotic media

“…USDA 3187 was a gift from the IPAGRO Rhizobium Culture Collection, Porto Alegre, RS, Brazil. Bacteria were maintained as previously described (GHITTONI and BUENO 1995) and their abilities to nodulate Blanco Manfredi 68 INTA peanut cultivar, currently used in Córdoba State (Argentina) were examined. Nodulation tests were done as described by WILSON et al (1987).…”

“…We had identified trehalose as the compatible solute which was accumulated to significant levels in stationary phase-cells from some peanut rhizobia exposed to hyperosmolarity (GHITTONI and BUENO 1995, DARDANELLI et al 1997. In order to obtain some helpful information about the metabolism of the disaccharide, in this study we compared data indicating trehalose synthesis and degradation in peanut rhizobia grown under either normal or hyperosmotic media.…”

An Insight into the Legume–Rhizobium Interaction

“…The bacteria adapt to saline conditions by the intracellular accumulation of low molecular weight organic solute osmolytes (Csonka and Hanson 1991 ); increase in intracellular free glutamate and/or K + (Zahran 1999 ); release of osmoprotectants such as sucrose, ectoine, mannitol, lactose, etc. (Talibort et al 1994 ;Ghittoni and Bueno 1995 ;Gouffi et al 1999 ); accumulation of glycine betaine (Fougère et al 1991 ); and increase in the content of polyamines (Fujihara and Yoneyama 1993 ). In a study by Sharma et al ( 2013 ), the isolated rhizobial strains from the root nodules of three leguminous plants, namely, sesbania ( Sesbania sesban ), lablab ( Lablab purpureus ) and pigeon pea ( Cajanus cajan ), growing at a research farm in Dubai were able to nodulate in saline water 12 dS m −1 on 21-day-old seedlings.…”

Legumes in the reclamation of marginal soils, from cultivar and inoculant selection to transgenic approaches

“…Decreasing exopolysaccharide synthesis (Breedveld et al 1991;Lloret et al 1998;Vanderlinde et al 2010), structural alterations, and changes in side chain length of lipopolysaccharides (Lloret et al 1995;Soussi et al 2001;Bhattacharya and Das 2003;Campbell et al 2003;Vanderlinde et al 2009), as well as the suppression or Fig. 1 Some benefits of nitrogen fixation by legumes alteration of periplasmic oligosaccharides that are involved in bacterial osmotic adaptation (Miller et al 1986;Ghittoni and Bueno 1995) have been reported. Under osmotic stress, the general metabolism of the Rhizobium slows down, and there is a repression of genes involved in the tricarboxylic acid cycle, in the uptake of carbon supply, in glycogen metabolism, in the respiratory chains, and in ribosomal genes (Dominguez-Ferreras et al 2006).…”