Project description:We show that the RNA leves of many genes in the S. meliloti overexpressing strain (OE) 2011 (pRK-RcsR1) are more similar to the levels of in wild type (WT) strain 2011 than in the empty vector control (EVC) strain 2011(pRK4352). Since the plasmid-containing strains were grown in the presence of 10 µg/ml tetracycline (Tc), while the WT was grown without Tc, the results suggest that the intrecellular Tc concentration in the OE strain are lower than in the EVC. This is explained by an increased efflux pump activity in the OE strain.
Project description:Nitrogen (N) and phosphorus (P) are the most limiting factors for plant growth. Some microorganisms improve the uptake and availability of N and P minimizing chemical fertilizers dependence. It has been published that the RD64 strain, a Sinorhizobium meliloti 1021 strain engineered to overproduce indole-3-acetic acid (IAA), showed improved nitrogen fixation ability as compared to the wild type 1021 strain. We present here data showing that RD64 is also highly effective in mobilizing P from insoluble sources such as phosphate rock (PR). Under P-limiting conditions, the higher P-mobilizing activity of RD64, as compared to 1021 wild type strain, is connected with the up-regulation of genes coding for the high-affinity P transport system, the induction of acid phosphatase activity and the increased secretion into the growth media of malic, succinic and fumaric acids. Medicago truncatula plants nodulated by RD64 (Mt-RD64), when grown under P deficient conditions, released higher amounts of another P-solubilizing organic acid, the 2-hydroxyglutaric acid, as compared to the plants nodulated by the wild-type strain (Mt-1021). It has already been shown that Mt-RD64 plants exhibited a higher dry weight production as compared to Mt-1021 plants. Here we report that also P-starved Mt-RD64 plants show a significant increase both in shoot and root fresh weight when compared to P-starved Mt-1021 plants. We discuss how, in a rhizobium-legume model system, a balanced interplay of different factors linked to the bacterial IAA over-production rather than IAA production per se stimulates plant growth under stressful environmental conditions, and in particular, under P-starvation.
Project description:Many bacteria, often associated with eukaryotic hosts and of relevance for biotechnological applications, harbor a multipartite genome composed of more than one replicon. Biotechnologically relevant phenotypes are often encoded by genes residing on the secondary replicons. A synthetic biology approach to developing enhanced strains for biotechnological purposes could therefore involve merging pieces or entire replicons from multiple strains into a single genome. Here we report the creation of a genomic hybrid strain in a model multipartite genome species, the plant-symbiotic bacterium Sinorhizobium meliloti. We term this strain as cis-hybrid, since it is produced by genomic material coming from the same species' pangenome. In particular, we moved the secondary replicon pSymA (accounting for nearly 20% of total genome content) from a donor S. meliloti strain to an acceptor strain. The cis-hybrid strain was screened for a panel of complex phenotypes (carbon/nitrogen utilization phenotypes, intra- and extracellular metabolomes, symbiosis, and various microbiological tests). Additionally, metabolic network reconstruction and constraint-based modeling were employed for in silico prediction of metabolic flux reorganization. Phenotypes of the cis-hybrid strain were in good agreement with those of both parental strains. Interestingly, the symbiotic phenotype showed a marked cultivar-specific improvement with the cis-hybrid strains compared to both parental strains. These results provide a proof-of-principle for the feasibility of genome-wide replicon-based remodelling of bacterial strains for improved biotechnological applications in precision agriculture.
Project description:Root nodule bacteria of Sinorhizobium meliloti species live in a symbiotic relationship with alfalfa plants. We report here the draft genome sequence of S. meliloti strain AK170, recovered from nodules of Medicago orthoceras (Kar. & Kir.) growing in an area impacted by salinization.
Project description:Nitrogen (N) and phosphorus (P) are the most limiting factors for plant growth. Some microorganisms improve the uptake and availability of N and P, minimizing chemical fertilizer dependence. It has been published that the RD64 strain, a Sinorhizobium meliloti 1021 strain engineered to overproduce indole-3-acetic acid (IAA), showed improved nitrogen fixation ability as compared to the wild type 1021 strain. We present here data showing that RD64 is also highly effective in mobilizing P from insoluble sources such as phosphate rock (PR). Under P-limiting conditions, the higher P-mobilizing activity of RD64, as compared to the 1021 wild type strain, is connected with the up-regulation of genes coding for the high-affinity P transport system, the induction of acid phosphatase activity and the increased secretion into the growth media of malic, succinic and fumaric acids. Medicago truncatula plants nodulated by RD64 (Mt-RD64), when grown under P-deficient conditions, released higher amounts of another P-solubilizing organic acid, the 2-hydroxyglutaric acid, as compared to the plants nodulated by the wild-type strain (Mt-1021). It has already been shown that Mt-RD64 plants exhibited a higher dry weight production as compared to Mt-1021 plants. Here we report that also P-starved Mt-RD64 plants show a significant increase both in shoot and root fresh weight when compared to P-starved Mt-1021 plants. We discuss how, in a rhizobium-legume model system, a balanced interplay of different factors linked to the bacterial IAA over-production rather than IAA production per se stimulates plant growth under stressful environmental conditions, and in particular, under P-starvation.
Project description:Nitrogen (N) and phosphorus (P) are the most limiting factors for plant growth. Some microorganisms improve the uptake and availability of N and P, minimizing chemical fertilizer dependence. It has been published that the RD64 strain, a Sinorhizobium meliloti 1021 strain engineered to overproduce indole-3-acetic acid (IAA), showed improved nitrogen fixation ability as compared to the wild type 1021 strain. We present here data showing that RD64 is also highly effective in mobilizing P from insoluble sources such as phosphate rock (PR). Under P-limiting conditions, the higher P-mobilizing activity of RD64, as compared to the 1021 wild type strain, is connected with the up-regulation of genes coding for the high-affinity P transport system, the induction of acid phosphatase activity and the increased secretion into the growth media of malic, succinic and fumaric acids. Medicago truncatula plants nodulated by RD64 (Mt-RD64), when grown under P-deficient conditions, released higher amounts of another P-solubilizing organic acid, the 2-hydroxyglutaric acid, as compared to the plants nodulated by the wild-type strain (Mt-1021). It has already been shown that Mt-RD64 plants exhibited a higher dry weight production as compared to Mt-1021 plants. Here we report that also P-starved Mt-RD64 plants show a significant increase both in shoot and root fresh weight when compared to P-starved Mt-1021 plants. We discuss how, in a rhizobium-legume model system, a balanced interplay of different factors linked to the bacterial IAA over-production rather than IAA production per se stimulates plant growth under stressful environmental conditions, and in particular, under P-starvation.