Truncated betB2-144 plays a critical role in Sinorhizobium meliloti Rm2011 osmoprotection and glycine-betaine catabolism

High Salt Tolerance of a Bradyrhizobium Strain and Its Promotion of the Growth of Stylosanthes guianensis

“…It has been showed that under salt stress, the growth of B. japonicum strain RCR 3827 is enhanced when trehalose was added into the medium, suggesting that trehalose may act as an osmoregulator in Bradyrhizobium strains in response to salt stress [ 37 ]. These results are also consistent with those from other rhizobia, such as M. ciceri and S. meliloti [ 6 , 16 ] suggesting that the ability to accumulate osmoprotectants in the salt-tolerant rhizobial strain RJS9-2 may be beneficial to bacterial growth through reducing osmotic stress caused by salts. However, the effects of proline, ectoine, and glycine betaine on the growth of rhizobia under salt stress do not seem to be general or to directly contribute to growth enhancement, which might depend on the rhizobial species [ 14 , 38 , 39 ].…”

“…For example, proline is a highly soluble neutral compound that is regarded as an osmoprotectant involved in the bacterial response to osmotic stress [ 10 ]. Compounds structurally related to betaines, such as glycine betaine, proline betaine, and carnitine, play a major role in osmoregulation in rhizobial bacteria under salt stress, such as in R. meliloti , Rhizobium sp., Mesorhizobium sp., and S. meliloti [ 12 , 14 , 15 , 16 ]. Furthermore, trehalose is an important osmoprotectant for increasing osmotolerance in S .…”

Molecular Phylogenetic Analysis of Salt-Tolerance-Related Genes in Root-Nodule Bacteria Species Sinorhizobium meliloti

“…It has been shown that the betC product is involved in the replenishment of the sulfur pool in P. aeruginosa, while in S. meliloti, the betC gene encodes choline sulfatase, which hydrolyzes choline-O-sulfate, with the subsequent conversion of choline into glycine betaine [43]. It is important to note that the activity of the bet genes in S. meliloti is significant in symbiosomes; therefore, it is necessary for benefiting the function of the legume-rhizobium symbiotic system [44][45][46]. Both types of the above operons have the betI gene, which encodes an HTH-type transcription regulator of the betAB genes in S. meliloti and E. coli.…”

“…The betI gene is induced by outside transported choline, for example, from plant root exudates [44]. In alfalfa rhizobia, a homolog of the betB gene (betB2) on the megaplasmid pSymA was identified, whose function is predicted to be a "switch" of the possibility of using GB as a source of carbon or nitrogen in the last stage of glycine betaine biosynthesis [46].…”

“…Schematic representation of the osmostress response systems of E. coli K-12 (a) and S. meliloti Rm1021 (b). Graphical sketch of osmostress response systems was designed using literature data[33,36,37,[43][44][45][46][47]. The presence of BCCT (betaine/carnitine/choline transporter) transport systems are indicated in (a,b) according[5,35,[43][44][45][46][47].…”