RESUMO
A link between the T3SS and inhibition of swimming motility by the transcriptional regulator TtsI in Mesorhizobium japonicum MAFF303099 has been previously reported. Here, we show that mutants in T3SS components display impaired biofilm formation capacity, indicating that a functional T3SS, or at least pili formation, is required for this process. As a first approach to the cdiG regulation network in this bacterium, we started a study of the second messenger cdiG by overexpressing or by deleting some genes encoding cdiG metabolizing enzymes. Overexpression of two putative PDEs as well as deletion of various DGCs led to reduced biofilm formation on glass tubes. Mutation of dgc9509 also affected negatively the nodulation and symbiosis efficiency on Lotus plants, which can be related to the observed reduction in adhesion to plant roots. Results from transcriptional nopX- and ttsI-promoter-lacZ fusions suggested that cdiG negatively regulates T3SS expression in M. japonicum MAFF303099.
Assuntos
Mesorhizobium , Simbiose , Mesorhizobium/genética , Membrana Celular , BiofilmesRESUMO
OBJECTIVE: The effects of monosaccharide constituents of lignocellulosic materials on exopolysaccharide (EPS) production by Mesorhizobium sp. Semia 816 were studied. RESULTS: According to the results, by using sugars commonly found in lignocellulosic biomass as carbon sources (glucose, arabinose and xylose), no significant differences were observed in the production of EPS, reaching 3.39 g/L, 3.33 g/L and 3.27 g/L, respectively. Differences were observed in monosaccharide composition, mainly in relation to rhamnose and glucuronic acid contents (1.8 times higher when arabinose was compared with xylose). However, the biopolymers showed no differences in relation to rheological properties, with EPS aqueous-based suspensions (1.0% w/v) presenting pseudoplastic behavior, and a slight difference in degradation temperatures. Using soybean hulls hydrolysate as carbon source, slightly higher values were obtained (3.93 g/L). CONCLUSION: The results indicate the potential of the use of lignocellulosic hydrolysates containing these sugars as a source of carbon in the cultivation of Mesorhizobium sp. Semia 816 for the production of EPS with potential industrial applications.
Assuntos
Glycine max/química , Lignina/química , Mesorhizobium/crescimento & desenvolvimento , Monossacarídeos/química , Arabinose/química , Biomassa , Fermentação , Glucose/química , Hidrólise , Mesorhizobium/química , Xilose/químicaRESUMO
Three symbiotic nitrogen-fixing bacteria (BD68T, BD66 and BD73) isolated from root nodules of Lotus tenuis in lowland soils of the Flooding Pampa (Argentina), previously classified as members of the Mesorhizobium genus, were characterized in this study. Phylogenetic analysis of their 16S rRNA gene sequences showed a close relationship to M. japonicum MAFF 303099T, M. erdmanii USDA 3471T, M. carmichaelinearum ICMP 18942T, M. opportunistum WSM 2975T and M. jarvisii ATCC 33699T, with sequence identities of 99.72%-100%. Multilocus sequence analysis of other housekeeping genes revealed that the three isolates belonged to a phylogenetically distinct clade within the genus Mesorhizobium. Strain BD68T was designated as the group representative and its genome was fully sequenced. The average nucleotide identity and in silico DNA-DNA hybridization comparisons between BD68T and the most related type strains showed values below the accepted threshold for species discrimination. Phenotypic and chemotaxonomic features were also studied. Based on these results, BD68T, BD66 and BD73 could be considered to represent a novel species of the genus Mesorhizobium, for which the name Mesorhizobium intechi sp. nov. is hereby proposed. The type strain of this species is BD68T (=CECT 9304T=LMG 30179T).
Assuntos
Lotus/microbiologia , Mesorhizobium/classificação , Filogenia , Nódulos Radiculares de Plantas/microbiologia , Argentina , DNA Bacteriano/genética , Ácidos Graxos/análise , Genes Bacterianos/genética , Genes Essenciais/genética , Genoma Bacteriano/genética , Mesorhizobium/química , Mesorhizobium/citologia , Mesorhizobium/fisiologia , Hibridização de Ácido Nucleico , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Microbiologia do SoloRESUMO
Cover crop suppression with glyphosate-based herbicides (GBHs) represents a common agricultural practice. The objective of this study was to compare rhizospheric microbial communities of A. sativa plants treated with a GBH relative to the mechanical suppression (mowing) in order to assess their differences and the potential implications for soil processes. Samples were obtained at 4, 10, 17 and 26 days post-suppression. Soil catabolic profiling and DNA-based methods were applied. At 26 days, higher respiration responses and functional diversity indices (Shannon index and catabolic evenness) were observed under glyphosate suppression and a neat separation of catabolic profiles was detected in multivariate analysis. Sarcosine and Tween 20 showed the highest contribution to this separation. Metabarcoding revealed a non-significant effect of suppression method on either alpha-diversity metrics or beta-diversity. Conversely, differences were detected in the relative abundance of specific bacterial taxa. Mesorhizobium sequences were detected in higher relative abundance in glyphosate-treated plants at the end of the experiment while the opposite trend was observed for Gaiella. Quantitative PCR of amoA gene from ammonia-oxidizing archaea showed a lower abundance under GBH suppression again at 26 days, while ammonia-oxidizing bacteria remained lower at all sampling times. Broad host range plasmids IncP-1ß and IncP-1ε were exclusively detected in the rhizosphere of glyphosate-treated plants at 10 days and at 26 days, respectively. Overall, our study demonstrates differential effects of suppression methods on the abundance of specific bacterial taxa, on the physiology and mobile genetic elements of microbial communities while no differences were detected in taxonomic diversity.
Assuntos
Avena/microbiologia , Glicerol/análogos & derivados , Glicina/análogos & derivados , Herbicidas/farmacologia , Metagenoma , Microbiota/efeitos dos fármacos , Rizosfera , Archaea/genética , Avena/efeitos dos fármacos , Código de Barras de DNA Taxonômico , Glicerol/farmacologia , Glicina/farmacologia , Mesorhizobium/genética , Metagenômica , Microbiota/genéticaRESUMO
Biological nitrogen fixation performed by diazotrophic bacteria is a vital process for agricultural and environmental sustainability. In recent years, bacterial classification has been based on genomic data, accelerating our understanding about the diversity, and resulting in the description of several new species. In this study, four strains (CNPSo 3140T, CNPSo 3235, CNPSo 3236 and CNPSo 3237) trapped by Phaseolus vulgaris and Mimosa pudica from soil samples of the Brazilian Atlantic Forest biome (Mata Atlântica) were submitted to polyphasic analysis to investigate their proper classification within the genus Mesorhizobium. The 16S rRNA gene phylogram showed that the strains present sequences identical to those of Mesorhizobium acaciaeand Mesorhizobium plurifarium, not allowing a clear taxonomic classification; however, when using multilocus sequence analysis methodology, the strains were grouped into a well-supported distinct clade, with <94.5â% nucleotide identity with the other species of the genus. The average nucleotide identity of CNPSo 3140T genome showed values below the threshold in relation to the closest species, of 89.75â% with Mesorhizobium plurifariumand of 88.83â% with Mesorhizobium hawassense; the digital DNA-DNA hybridization values were 39 and 37.70â% with the same species, respectively. Nodulation gene (nodC) phylogeny positioned the strains in an isolated cluster, showing greater similarity to Mesorhizobiumshonense. All data obtained in this study support the description of the novel species Mesorhizobiumatlanticum sp. nov. The type strain is CNPSo 3140T (=ABIP 206T=LMG 30305T=U1602T), isolated from a nodule of Phaseolus vulgaris.
Assuntos
Florestas , Mesorhizobium/classificação , Fixação de Nitrogênio , Phaseolus/microbiologia , Filogenia , Microbiologia do Solo , Técnicas de Tipagem Bacteriana , Composição de Bases , Brasil , DNA Bacteriano/genética , Mesorhizobium/isolamento & purificação , Mimosa , Tipagem de Sequências Multilocus , Hibridização de Ácido Nucleico , RNA Ribossômico 16S/genética , Análise de Sequência de DNARESUMO
Two rhizobial strains, BSA136T and BSA150, related to the genus Mesorhizobium were isolated from root nodules of Lotus tenuis grown in saline-alkaline lowlands soil from Argentina. These strains showed different repetitive element palindromic PCR fingerprinting patterns but shared more than 99â% sequence similarity for both 16S rRNA and recA genes. Despite the symbiotic nodC gene sequences of our strains being related to the canonical Lotus biovar species comprising Mesorhizobium loti and Mesorhizobium japonicum, the 16S rRNA phylogenetic marker suggests that their taxonomical identities are closely related to Mesorhizobium helmanticense, Mesorhizobium metallidurans, Mesorhizobium thianshanense, Mesorhizobium gobiense and Mesorhizobium tarimense. Multilocus sequence analysis performed with seven housekeeping genes confirmed that BSA136T belongs to a separate clade within the genus Mesorhizobium. The results of comparisons for in silico DNA-DNA hybridization and average nucleotide identity indexes between the genomes of BSA136T and closest-related Mesorhizobium species were below the threshold for species delineation. Phenotypic features differentiated BSA136T from its closest-related species. On the basis of our results, BSA136T and BSA150 can be considered to represent a novel species of the genus Mesorhizobium, for which the name Mesorhizobium sanjuanii sp. nov. is hereby proposed. The type strain of this species is BSA136T (=CECT 9305T=LMG 30060T), for which the draft genome sequence is available.
Assuntos
Lotus/microbiologia , Mesorhizobium/classificação , Filogenia , Nódulos Radiculares de Plantas/microbiologia , Argentina , Técnicas de Tipagem Bacteriana , Composição de Bases , DNA Bacteriano/genética , Ácidos Graxos/química , Mesorhizobium/genética , Mesorhizobium/isolamento & purificação , Tipagem de Sequências Multilocus , Hibridização de Ácido Nucleico , RNA Ribossômico 16S/genética , Análise de Sequência de DNARESUMO
In the present study, a new extracellular polysaccharide (EPS-M816) was obtained during the growth of Mesorhizobium loti Semia 816 on a crude glycerol-based medium. EPS-M816 precipitate mainly consisted of carbohydrates (82.54%) and proteins (11.31%), and the weight average molecular weight was estimated at 1.646â¯×â¯106â¯Da. The biopolymer was characterized by FT-IR and NMR spectroscopy, and was found to have typical functional groups of other rhizobial polysaccharides. Furthermore, the rheological and emulsifying properties were investigated. The EPS-M816 solution (1.0% w/v) showed typical pseudoplastic non-Newtonian fluid behavior, and the addition of sodium and potassium chloride (1â¯molâ¯L-1) increased the apparent viscosity. Regarding its emulsification activity, EPS-M816 formed emulsions with different food-grade vegetable oils (soybean, rice, canola, sunflower and corn oils), showing emulsification index values over 65% in 24â¯h, indicative of strong emulsion-stabilizing capacity. The biopolymer was able to form gels with texture parameters similar to those reported for xanthan gum and low syneresis. Overall, these results suggest that EPS-M816 is a good candidate for application in the food, cosmetics and pharmaceutical industries as a thickening, gelling, stabilizing and emulsifying agent.
Assuntos
Meios de Cultura/química , Emulsificantes/metabolismo , Glicerol/farmacologia , Mesorhizobium/crescimento & desenvolvimento , Mesorhizobium/metabolismo , Polissacarídeos Bacterianos/biossíntese , Reologia , Emulsificantes/química , Mesorhizobium/efeitos dos fármacos , Peso Molecular , Polissacarídeos Bacterianos/químicaRESUMO
The aminopeptidase gene from Mesorhizobium SEMIA3007 was cloned and overexpressed in Escherichia coli. The enzyme called MesoAmp exhibited optimum activity at pH 8.5 and 45 °C and was strongly activated by Co2+ and Mn2+. Under these reaction conditions, the enzyme displayed Km and kcat values of 0.2364 ± 0.018 mM and 712.1 ± 88.12 s-1, respectively. Additionally, the enzyme showed remarkable stability in organic solvents and was active at high concentrations of NaCl, suggesting that the enzyme might be suitable for use in biotechnology. MesoAmp is responsible for 40% of the organism's aminopeptidase activity. However, the enzyme's absence does not affect bacterial growth in synthetic broth, although it interfered with biofilm synthesis and osmoregulation. To the best of our knowledge, this report describes the first detailed characterization of aminopeptidase from Mesorhizobium and suggests its importance in biofilm formation and osmotic stress tolerance. In summary, this work lays the foundation for potential biotechnological applications and/or the development of environmentally friendly technologies and describes the first solvent- and halo-tolerant aminopeptidases identified from the Mesorhizobium genus and its importance in bacterial metabolism.
Assuntos
Aminopeptidases/química , Aminopeptidases/farmacologia , Biofilmes/efeitos dos fármacos , Mesorhizobium/metabolismo , Sequência de Aminoácidos , Aminopeptidases/genética , Aminopeptidases/metabolismo , Ativação Enzimática , Evolução Molecular , Genoma Bacteriano , Genômica/métodos , Multimerização Proteica , Relação Quantitativa Estrutura-Atividade , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Análise de Sequência de DNA , SoluçõesRESUMO
Plants on contaminated mining soils often show a reduced growth due to nutrient depletion as well as trace elements (TEs) toxicity. Since those conditions threat plant's survival, plant growth-promoting rhizobacteria (PGPRs), such as rhizobia, might be of crucial importance for plant colonization on TE-contaminated soils. Native rhizobia from mining soils are promising candidates for bioaugmented phytoremediation of those soils as they are adapted to the specific conditions. In this work, rhizobia from Zn- and Cd-contaminated mining soils were in vitro screened for their PGP features [organic acids, indole-3-acetic acid (IAA), and siderophore (SID) production; 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity; and Ca3(PO4)2 solubilization] and Zn and Cd tolerance. In addition, some type and reference rhizobia strains were included in the study as well. The in vitro screening indicated that rhizobia and other native genera have great potential for phytoremediation purposes, by exerting, besides biological N2 fixation, other plant growth-promoting traits. Leucaena leucocephala-Mesorhizobium sp. (UFLA 01-765) showed multielement tolerance and an efficient symbiosis on contaminated soil, decreasing the activities of antioxidative enzymes in shoots. This symbiosis is a promising combination for phytostabilization.
Assuntos
Fabaceae/metabolismo , Fabaceae/microbiologia , Bactérias Fixadoras de Nitrogênio/metabolismo , Microbiologia do Solo , Poluentes do Solo/metabolismo , Simbiose , Zinco/metabolismo , Biodegradação Ambiental , DNA Bacteriano/genética , Mesorhizobium/classificação , Mesorhizobium/genética , Mesorhizobium/metabolismo , Bactérias Fixadoras de Nitrogênio/classificação , Bactérias Fixadoras de Nitrogênio/genética , RNA Ribossômico 16S/genéticaRESUMO
The presence of chromium in soils not only affects the physiological processes of plants but also the microbial rhizosphere composition and metabolic activities of microorganisms. Hence, the inoculation of plants with Cr(VI)-tolerant rhizospheric microorganisms as an alternative to reduce Cr phytotoxicity was studied. In this work, chickpea germination was reduced by Cr(VI) concentrations of 150 and 250â mg/L (6 and 33%, respectively); however lower Cr(VI) concentrations negatively affected the biomass. On the other hand, its symbiont, Mesorhizobium ciceri, was able to grow and remove different Cr(VI) concentrations (5-20â mg/L). The inoculation of chickpea plants with this strain exposed to Cr(VI) showed a significantly enhanced plant growth. In addition, inoculated plants accumulated higher Cr concentration in roots than those noninoculated. It is important to note that Cr was not translocated to shoots independently of inoculation. These results suggest that Mesorhizobium's capability to remove Cr(VI) could be exploited for bioremediation. Moreover, chickpea plants would represent a natural system for phytoremediation or phytostabilization of Cr in situ that could be improved with M. ciceri inoculation. This strategy would be considered as a phytoremediation tool with great economic and ecological relevance.