At present, there are numerous examples in which symbiotic nitrogen fixation by rhizobia can totally replace the use of nitrogen fertilizers in legume crops. Over the years, there has been a great effort by research institutions to develop and select rhizobial inoculants adapted for these crops. The symbiotic process is highly dependent on the dynamic exchange of signals and molecular nutrients between partners. Our focus in this review was to discuss the two key determinants in successful symbiotic interactions of rhizobia to nodulate pulses. One of them is the production of exopolysaccharides (EPS) and the other the presence of the type VI secretion system (T6SS). EPS are extracellular polymers weakly associated with the bacterial surface and are abundantly released into acid soils facilitating, among other functions, an adaptation of rhizobia to this environment. On the other hand, different protein secretion systems, involved in symbiosis, have been described in rhizobia. This is not the case with the T6SS. The current availability of various rhizobial genomes offers the possibility of discussing its role in symbiosis. The study of these determinants will be of great utility for the selection of effective inoculants for legumes, a promising way to improve nitrogen acquisition by legumes.

Many bacteria of the genus Bradyrhizobium are capable of inducing nodules in legumes. In this work, the importance of a type VI secretion system (T6SS) in a symbiotic strain of the genus Bradyrhizobium is described. T6SS of Bradyrhizobium sp. LmicA16 (A16) is necessary for efficient nodulation with Lupinus micranthus and L. angustifolius. A mutant in the gene vgrG, coding for a component of the T6SS nanostructure, induced less nodules and smaller plants than the wild type strain (wt) and was less competitive when coinoculated with the wt strain. A16 T6SS genes are organized in a 26 kb DNA region in two divergent gene clusters of nine genes each. One of these genes codes for a protein (Tsb1) of unknown function but containing a methyltransferase domain. A tsb1 mutant showed an intermediate symbiotic phenotype regarding vgrG mutant and higher mucoidy and motility than the wt strain in free living conditions. T6SS promoter fusions to the lacZ reporter indicate expression in nodules but not in free living cells grown in different media and conditions. The analysis of nodule structure revealed that the level of nodule colonization was significantly reduced in the mutants with respect to the wt strain.

The genes of the type VI secretion system (T6SS) from Rhizobium etli Mim1 (ReMim1) that contain possible effectors can be divided into three modules. The mutants in them indicated that they are not required for effective nodulation with beans. To analyze T6SS expression, a putative promoter region between the tssA and tssH genes was fused in both orientations to a reporter gene. Both fusions are expressed more in free living than in symbiosis. When the module-specific genes were studied using RT-qPCR, a low expression was observed in free living and in symbiosis, which was clearly lower than the structural genes. The secretion of Re78 protein from the T6SS gene cluster was dependent on the presence of an active T6SS. Furthermore, the expression of Re78 and Re79 proteins in E. coli without the ReMim1 nanosyringe revealed that these proteins behave as a toxic effector/immunity protein pair (E/I). The harmful action of Re78, whose mechanism is still unknown, would take place in the periplasmic space of the target cell. The deletion of this ReMim1 E/I pair resulted in reduced competitiveness for bean nodule occupancy and in lower survival in the presence of the wild-type strain.

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: Most legume species, such as soybeans, beans, and clover, have the ability to establish a symbiotic relationship with nitrogen-fixing bacteria in the soil, which promotes plant growth and productivity. Exopolysaccharide macromolecules are particularly necessary for binding the bacteria to root hairs and initiating the deformation of root hairs, thus trapping the bacteria to initiate root invasion through a tube-like infection thread. Very few studies have focused on the isolation and characterization of new rhizobial exopolysaccharides, despite their unique and specific biological and physicochemical properties. However, rhizobial exopolysaccharides may be studied in detail in the near future, for the development of suitable substitutes for xanthan gum. This review discusses some analytical strategies for characterization of rhizobial exopolysaccharide, the relation between their structure and properties, and a novel application of rhizobial exopolysaccharides. The potential application of exopolysaccharides and living cells as biosorbents has also been reviewed.

Biomedical and Biopharmaceutical Research J o r n a l d e I n v e s t i g a ç ã o B i o m é d i c a e B i o f a r m a c ê u t i c a Development and in vivo evaluation of the moisturising potential of cosmetic formulations containing Babassu (Orbignya phalerata Martius) oily extract AbstractThe objective of this study was to use oily extracts of the species Orbignya phalerata Martius (Babassu) from three ecological regions in Maranhão state, Brazil: Forest (BBF), Coast (BBC) and Lowlands (BBL) to develop cosmetic formulations. Formulations with 10 wt% of Babassu oily extracts were characterised regarding their stability for 30 days (separation of phases after centrifugation, pH, density, viscosity and droplets size distribution) and evaluation of efficacy in vivo by cutaneous biometry. Results indicated that the formulations were physically stable and presented pseudo-plastic fluid behavior as evaluated by rheology. Concerning the in vivo efficacy assays, the formulation containing BBL increased the hydration of the volunteers'skin when compared to a formulation containing only a commercial standard moisturising ingredient, without altering the skin pH. BBL showed to be a promising ingredient to cosmetics, behaving as an excellent moisturiser likely because it contains the highest amounts of lauric, myristic and oleic acids that present great emollient potential.Keywords: Cosmetic formulations, cutaneous biometry, in vivo evaluation of moisturising effect, Orbignya phalerata Martius, vegetal oily extract. ResumoO objetivo deste estudo foi utilizar extratos oleosos da espécie Orbignya phalerata Martius (Babaçu) de três regiões ecológicas do Estado do Maranhão (Brasil): Mata dos Cocais (BBF), Litoral (BBC) e Baixada Maranhense (BBL) para desenvolver formulações cosméticas. As formulações com 10% em peso de extratos oleosos de Babaçu foram caracterizadas quanto à sua estabilidade durante 30 dias (separação de fases após centrifugação, pH, densidade, viscosidade e distribuição de tamanho das gotículas) e avaliação da eficácia in vivo por biometria cutânea. Os resultados indicaram que as formulações foram fisicamente estáveis e apresentaram comportamento de fluido pseudoplástico, avaliado por reologia. Em relação aos ensaios de eficácia in vivo, a formulação contendo BBL aumentou a hidratação da pele dos voluntários quando comparada com uma formulação contendo apenas um ingrediente hidratante padrão comercial, sem alterar o pH da pele. BBL mostrou ser um ingrediente promissor para cosméticos, comportando-se como um excelente hidratante, provavelmente porque contém as maiores quantidades de ácidos láurico, mirístico e oleico que apresentam grande potencial emoliente.Palavras chave: Formulações cosméticas, biometria cutânea, avaliação in vivo do efeito hidratante, Orbignya phalerata Martius, extrato oleoso vegetal.

A Meliponicultura atua na conscientização ambiental e incrementa a renda de comunidades carentes no Maranhão Meliponicultura works to raise environmental awareness and increase the income of poor communities in Maranhão

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