Linking microbial genes to plasma and stool metabolites uncovers host-microbial interactions underlying ulcerative colitis disease course.

Understanding the role of the microbiome in inflammatory diseases requires the identification of microbial effector molecules. We established an approach to link disease-associated microbes to microbial metabolites by integrating paired metagenomics, stool and plasma metabolomics, and culturomics. We identified host-microbial interactions correlated with disease activity, inflammation, and the clinical course of ulcerative colitis (UC) in the Predicting Response to Standardized Colitis Therapy (PROTECT) pediatric inception cohort. In severe disease, metabolite changes included increased dipeptides and tauro-conjugated bile acids (BAs) and decreased amino-acid-conjugated BAs in stool, whereas in plasma polyamines (N-acetylputrescine and N1-acetylspermidine) increased. Using patient samples and Veillonella parvula as a model, we uncovered nitrate- and lactate-dependent metabolic pathways, experimentally linking V. parvula expansion to immunomodulatory tryptophan metabolite production. Additionally, V. parvula metabolizes immunosuppressive thiopurine drugs through xdhA xanthine dehydrogenase, potentially impairing the therapeutic response. Our findings demonstrate that the microbiome contributes to disease-associated metabolite changes, underscoring the importance of these interactions in disease pathology and treatment.

Inflammation-associated nitrate facilitates ectopic colonization of oral bacterium Veillonella parvula in the intestine.

Colonization of the intestine by oral microbes has been linked to multiple diseases such as inflammatory bowel disease and colon cancer, yet mechanisms allowing expansion in this niche remain largely unknown. Veillonella parvula, an asaccharolytic, anaerobic, oral microbe that derives energy from organic acids, increases in abundance in the intestine of patients with inflammatory bowel disease. Here we show that nitrate, a signature metabolite of inflammation, allows V. parvula to transition from fermentation to anaerobic respiration. Nitrate respiration, through the narGHJI operon, boosted Veillonella growth on organic acids and also modulated its metabolic repertoire, allowing it to use amino acids and peptides as carbon sources. This metabolic shift was accompanied by changes in carbon metabolism and ATP production pathways. Nitrate respiration was fundamental for ectopic colonization in a mouse model of colitis, because a V. parvula narG deletion mutant colonized significantly less than a wild-type strain during inflammation. These results suggest that V. parvula harness conditions present during inflammation to colonize in the intestine.

Roles and regulation of Spx family transcription factors in Bacillus subtilis and related species.

Bacillus subtilis Spx is the prototype for a large family of redox-responsive transcription factors found in many bacteria, most notably those from the phylum Firmicutes. Unusually for a transcription factor, B. subtilis Spx protein modulates gene expression by binding as a monomer to the αCTD domain of RNA polymerase (RNAP), and only interacts with DNA during subsequent promoter engagement. B. subtilis Spx drives the expression of a large regulon in response to proteotoxic conditions, such as heat and disulfide stress, as well as cell wall stress. Here, we review the detailed mechanisms that control the expression, stability, and activity of Spx in response to a variety of stress conditions. We also summarize current knowledge regarding Spx homologs in other Firmicutes, the environmental conditions in which those homologs are activated, and their biological role.

Identification of Novel Spx Regulatory Pathways in Bacillus subtilis Uncovers a Close Relationship between the CtsR and Spx Regulons.

In Bacillus subtilis, the Spx transcription factor controls a large regulon in response to disulfide, heat, and cell wall stresses. The regulatory mechanisms that activate the Spx regulon are remarkably complex and involve changes in transcription, proteolysis, and posttranslational modifications. To identify genes involved in Spx regulation, we performed a transposon screen for mutations affecting expression of trxB, an Spx-dependent gene. Inactivation of ctsR, encoding the regulator of the Clp proteases, reduced trxB expression and lowered Spx levels. This effect required ClpP, but involved ClpC rather than the ClpX unfoldase. Moreover, cells lacking McsB, a dual function arginine kinase and ClpCP adaptor, largely reverted the ctsR phenotype and increased trxB expression. The role of McsB appears to involve its kinase activity, since loss of the YwlE phosphoarginine phosphatase also led to reduced trxB expression. Finally, we show that Spx is itself a regulator of the ctsR operon. Altogether, this work provides evidence for a role of CtsR regulon members ClpC, ClpP, and McsB in Spx regulation and identifies a new feedback pathway associated with Spx activity in B. subtilisIMPORTANCE In Bacillus subtilis, the Spx transcription factor is proteolytically unstable, and protein stabilization figures prominently in the induction of the Spx regulon in response to oxidative and cell envelope stresses. ClpXP is largely, but not entirely, responsible for Spx instability. Here, we identify ClpCP as the protease that degrades Spx under conditions that antagonize the ClpXP pathway. Spx itself contributes to activation of the ctsR operon, which encodes ClpC as well as the McsB arginine kinase and protease adaptor, thereby providing a negative feedback mechanism. Genetic studies reveal that dysregulation of the CtsR regulon or inactivation of the YwlE phosphoarginine phosphatase decreases Spx activity through mechanisms involving both protein degradation and posttranslational modification.

Stabilization of Bacillus subtilis Spx under cell wall stress requires the anti-adaptor protein YirB.

Spx is a global transcriptional regulator present in low-GC Gram-positive bacteria, including the model bacterium Bacillus subtilis and various human pathogens. In B. subtilis, activation of Spx occurs in response to disulfide stress. We recently reported, however, that induction of Spx also occurs in response to cell wall stress, and that the molecular events that result in its activation under both stress conditions are mechanistically different. Here, we demonstrate that, in addition to up-regulation of spx transcription through the alternative sigma factor σM, full and timely activation of Spx-regulated genes by cell wall stress requires Spx stabilization by the anti-adaptor protein YirB. YirB is itself transcriptionally induced under cell wall stress, but not disulfide stress, and this induction requires the CssRS two-component system, which responds to both secretion stress and cell wall antibiotics. The yirB gene is repressed by YuxN, a divergently transcribed TetR family repressor, and CssR~P acts as an anti-repressor. Collectively, our results identify a physiological role for the YirB anti-adaptor protein and show that induction of the Spx regulon under disulfide and cell wall stress occurs through largely independent pathways.

Induction of the Spx regulon by cell wall stress reveals novel regulatory mechanisms in Bacillus subtilis.

The transcription factor Spx is the master regulator of the disulfide stress response in Bacillus subtilis. Intriguingly, the activation of Spx by diamide relies entirely on posttranslational regulatory events in spite of the complex transcriptional control of the spx gene. Here, we show that cell wall stress, but not membrane stress, also results in induction of the Spx regulon. Remarkably, two major differences were found regarding the mechanism of induction of Spx under cell wall stress in comparison to disulfide stress. First, transcriptional induction of the spx gene from a σM -dependent promoter is required for accumulation of Spx in response to cell wall stress. Second, activation of the Spx regulon during cell wall stress is not accompanied by oxidation of the Spx disulfide switch. Finally, we demonstrate that cells lacking Spx have increased sensitivity toward antibiotics inhibiting both early and late steps in peptidoglycan synthesis, suggesting that the Spx regulon plays an important adaptive role in the cell wall stress response. This study expands the functional role of the Spx regulon and reveals novel regulatory mechanisms that result in induction of Spx in B. subtilis.

Azotobacter chroococcum as a potentially useful bacterial biofertilizer for cotton (Gossypium hirsutum): Effect in reducing N fertilization / Azotobacter chroococcum como biofertilizante bacteriano potencialmente útil para el algodón (Gossypium hirsutum L.): efecto en la reducción de la fertilización nitrogenada

The aim of this research was to evaluate whether the application of two plant growth-promoting (rhizo)bacteria might reduce nitrogen fertilization doses in cotton. We used strains Azotobacter chroococcum AC1 and AC10 for their proven ability to promote seed germination and cotton growth. These microorganisms were characterized by their plant growth-promoting activities. Then, we conducted a glasshouse study to evaluate the plant growth promoting ability of these strains with reduced doses of urea fertilization in cotton. Results revealed that both strains are capable of fixing nitrogen, solubilizing phosphorus, synthesizing indole compounds and producing hydrolytic enzymes. After 12 weeks, the glasshouse experiment showed that cotton growth was positively influenced due to bacterial inoculation with respect to chemical fertilization. Notably, we observed that microbial inoculation further influenced plant biomass (p<0.05) than nitrogen content. Co-inoculation, interestingly, exhibited a greater beneficial effect on plant growth parameters compared to single inoculation. Moreover, similar results without significant statistical differences were observed among bacterial co-inoculation plus 50% urea and 100% fertilization. These findings suggest that coinoculation of A. chroococcum strains allow to reduce nitrogen fertilization doses up to 50% on cotton growth. Our results showed that inoculation with AC1 and AC10 represents a viable alternative to improve cotton growth while decreasing the N fertilizer dose and allows to alleviate the environmental deterioration related to N pollution.

El objetivo de esta investigación fue evaluar si la aplicación de 2 (rizo)bacterias promotoras del crecimiento vegetal podría reducir la dosis de fertilizante nitrogenado en el cultivo de algodón. Se usaron las cepas Azotobacter chroococcum AC1 y AC10 por su habilidad para promover la germinación de semillas y el crecimiento del algodonero. Estos microorganismos fueron caracterizados sobre la base de sus actividades de promoción del crecimiento vegetal. Luego se realizó un estudio de invernadero con plantas de algodón para evaluar la capacidad de promoción del crecimiento vegetal de dichas cepas con dosis reducidas de urea. Los resultados revelaron que ambas cepas son capaces de fijar nitrógeno, solubilizar fósforo, sintetizar compuestos indólicos y producir enzimas hidrolíticas. Después de 12 semanas, el experimento de invernadero permitió observar que el crecimiento del algodón fue influido positivamente por la inoculación bacteriana con respecto a la fertilización química. En particular, se evidenció que la inoculación microbiana impactó más en la biomasa vegetal (p<0,05) que en el contenido de nitrógeno. Curiosamente, la coinoculación exhibió un mayor efecto positivo sobre los parámetros de crecimiento en comparación con la inoculación simple. Además, se observaron resultados similares, sin diferencias estadísticamente significativas, entre la coinoculación bacteriana más del 50% de urea y el 100% de fertilización. Estos hallazgos indican que la coinoculación de las cepas de A. chroococcum AC1 y AC10 permitiría reducir las dosis de fertilización nitrogenada del cultivo de arroz en hasta el 50% y aliviar, de esta manera, el deterioro ambiental relacionado con la contaminación por N.

Azotobacter chroococcum as a potentially useful bacterial biofertilizer for cotton (Gossypium hirsutum): Effect in reducing N fertilization.

The aim of this research was to evaluate whether the application of two plant growth-promoting (rhizo)bacteria might reduce nitrogen fertilization doses in cotton. We used strains Azotobacter chroococcum AC1 and AC10 for their proven ability to promote seed germination and cotton growth. These microorganisms were characterized by their plant growth-promoting activities. Then, we conducted a glasshouse study to evaluate the plant growth promoting ability of these strains with reduced doses of urea fertilization in cotton. Results revealed that both strains are capable of fixing nitrogen, solubilizing phosphorus, synthesizing indole compounds and producing hydrolytic enzymes. After 12 weeks, the glasshouse experiment showed that cotton growth was positively influenced due to bacterial inoculation with respect to chemical fertilization. Notably, we observed that microbial inoculation further influenced plant biomass (p<0.05) than nitrogen content. Co-inoculation, interestingly, exhibited a greater beneficial effect on plant growth parameters compared to single inoculation. Moreover, similar results without significant statistical differences were observed among bacterial co-inoculation plus 50% urea and 100% fertilization. These findings suggest that co-inoculation of A. chroococcum strains allow to reduce nitrogen fertilization doses up to 50% on cotton growth. Our results showed that inoculation with AC1 and AC10 represents a viable alternative to improve cotton growth while decreasing the N fertilizer dose and allows to alleviate the environmental deterioration related to N pollution.

Biodegradación de fenol en aguas tratadas de la industria petrolera para re-uso en cultivos agrícolas / Biodegradation of phenol in treated water from the oil industry to re-use in agricultural crops

ResumenLa explotación del petróleo y el uso de sus derivados han contribuido para el desarrollo tecnológico a nivel mundial. Esta actividad, no obstante, genera muchos subproductos los cuales atentan contra la salud del ambiente. Las aguas de producción, por ejemplo, pueden contener trazas de metales pesados e hidrocarburos, razón por la cual deben ser reincorporadas de forma adecuada al ambiente. En este trabajo, se aislaron, caracterizaron e identificaron molecularmente ocho bacterias en base a su capacidad para degradar fenol. Primero, se evaluó el crecimiento y la degradación de fenol bajo diferentes concentraciones (500, 800 y 1 200 mg / L), y posteriormente se emplearon diseños estadísticos para la selección de condiciones óptimas de degradación. Los resultados mostraron que las ocho cepas evaluadas fueron capaces de usar el fenol como fuente única de carbono; no obstante, las cinéticas de degradación y la máxima tolerancia de las cepas al fenol variaron ampliamente. Debido a su tolerancia y capacidad para metabolizar fenol, la cepa Pseudomonas sp. Sps1 fue seleccionada para posteriores estudios. Mediante el uso de un diseño de Plackett Burman y un diseño factorial fraccionado en el cual diferentes fuentes de carbono, nitrógeno, y fósforo fueron evaluadas y degradación de fenol fue usado como variable de respuesta, fue posible seleccionar las condiciones óptimas para la degradación de fenol por Sps1. Finalmente, se emplearon estas condiciones para evaluar la degradación de fenol en aguas de re-uso provenientes directamente de la industria petrolera. Los resultados, mostraron que la bioestimulación favoreció el proceso de degradación del fenol comparado con el control. En conclusión, en este estudio se demostró que la bioaumentación con bacterias nativas acompañada de bioestimulación generan una tecnología económica y ambientalmente amigable para la remoción de contaminantes en aguas residuales tratadas de la industria petrolera.

AbstractOil exploitation and the usage of its derivatives have undeniably contributed to the technological advance worldwide. This industrial activity, however, generates several by-products that can threaten environmental sustainability. Seawage, for example, can contain organic pollutants and heavy metals; therefore, its deposition must be preceded by adequate water treatment. In this study, we isolated, characterized, and molecularly identified eight bacteria on the basis of their capability to degrade phenol. First, we determined the rates of bacterial growth and phenol degradation using different concentrations of the aromatic hydrocarbon (500, 800 and 1 200 mg / L), and then used sequential statistical designs to select optimal conditions for its degradation. Results showed that all isolated strains were capable of degrading phenol as the sole carbon source; the degradation kinetics and phenol tolerance, however, widely varied among strains. We chose the strain Pseudomonas sp. Sps1 for further studies due to its remarkable tolerance and capability to degrade phenol. By using a Plackett Burman design, followed by a fractionated factorial design in which several carbon, nitrogen, and phosphorus sources were evaluated, and phenol degradation was used as the response variable, we found optimal conditions for phenol degradation by Sps1. Finally, we compared phenol degradation in seawage by the use or not of the optimal conditions established by the statistical methods. Results showed that biostimulation dramatically increased phenol degradation compared with the control. In conclusion, we found that bioaugmentation with the native bacteria Sps1 and a statistically-based biostimulation approach provided an economically and environmentally friendly alternative for the removal of pollutants from oil industry sewage.

Entrapment of Rhizobium sp. by fluidized bed technique using polymers as coating materials / Encapsulación de Rhizobium sp. por medio de la técnica de lecho fluidizado utilizando polímeros como material de recubrimiento / Aprisionamento de Rhizobium sp. pela técnica de leito fluidizado utilizando polímeros como material de revestimento

Abstract The spray-drying technique was applied for the development of three solid formulations of Rhizobium. Sodium alginate and hydroxypropyl methylcellulose (HPMC) with concentrations of 0.5 % were used as polymers. Results showed that none of the solid formulations had negative effects in vitro on the growth-promoting capacities of Rhizobium sp. G58 (p < 0.05). PCA's first three components explained 84.5 % of the total variance. This analysis concluded that the solid formulation had not negative effects on the biological nitrogen fixation activity in vitro or on the process of nodulation in greenhouse experiments. Symbiosis between Rhizobium and the plant was effective, which suggested that, under controlled conditions, the coating process with the polymers had allowed a controlled release of the bacteria and a proper transfer of Rhizobium sp. from the microparticles to the root of the plant.

Resumen Se aplicó la técnica de secado por aspersión para desarrollar tres formulaciones sólidas de Rhizobium. Se utilizaron polímeros como el alginato de sodio e hidroxipropilmetilcelulosa (HPMC) a una concentración de 0.5 %. La viabilidad de las células encapsuladas de Rhizobium sp. en las formulaciones sólidas fueron de 10 UFC/g. Los resultados mostraron que ninguna de las formulaciones sólidas tuvo efectos negativos in vitro sobre las capacidades de Rhizobium sp. G58 como bacteria promotora de crecimiento (p < 0.05). En el ACP, los tres primeros componentes explicaron el 84.5 % de la varianza observada. Este análisis concluyó que la formulación sólida no tuvo efectos negativos sobre la actividad de fijación biológica de nitrógeno in vitro ni sobre el proceso de nodulación en los experimentos de invernadero. La simbiosis entre Rhizobium y la planta fue efectiva, lo cual sugiere que el proceso de recubrimiento con los polímeros permitió una liberación controlada de la bacteria y, bajo condiciones controladas, una transferencia apropiada de Rhizobium sp. desde las micropartículas a la raíz de las plantas.

Resumo A técnica de secagem por pulverização (Spray-Drying) foi aplicada para o desenvolvimento de três formulações sólidas de Rhizobium, utilizando como polímeros alginato de sódio e hidroxipropilmetilcelulose (HPMC), com concentração de 0,5 %. Viabilidade de células encapsuladas de Rhizobium sp. nas formulações sólidas foram de 107 UFC/g. Os resultados mostraram que nenhuma das formulações sólidas teve efeitos negativos sobre a capacidade de promoção do crescimento de Rhizobium sp. G58 in vitro (p < 0.05). 84,5 % do experimento foram explicados por análise multivariada com três componentes principais. Esta análise revelou que as formulações sólidas não tiveram efeitos negativos in vitro sobre a atividade de fixação de nitrogênio biológico e nem no processo de nodulação em experimentos em estufas de invernadeiro. O processo de simbiose foi realizado de forma eficaz, o que sugere que o processo de revestimento com polímeros permitiu uma libertação controlada e adicionalmente uma transferência adequada de Rhizobium sp. das micropartículas para as raízes da planta baixo condições controladas.

Preservation of Azotobacter chroococcum vegetative cells in dry polymers / Preservación de células vegetativas de Azotobacter chroococcum en polímeros secos / Preservação de células vegetativas de Azotobacter chroococcum em polímeros secos

We studied the preservation of Azotobacter chroococcum C26 using three dry polymers: carrageenin, sodium alginate, and HPMC, using a method of accelerated degradation. Bacterial viability, as response variable, was measured at three temperatures in four different times, which was followed by calculation of bacterial degradation rates. Results showed that temperature, time of storage, and protective agent influenced both viability and degradation rates (P<0.05). We observed, using the Arrhenius thermodynamic model, that the use of polymers increased the activation energy of bacterial degradation compared to control. We obtained thermodynamic models for each polymer, based on the Arrhenius equation, which predicted the required time for thermal degradation of the cells at different temperatures. Analysis of the models showed that carrageenin was the best polymer to preserve A. chroococcum C26 since ~ 900 days are required at 4 °C to reduce its viability in two log units. We conclude, therefore, that long-term preservation of A. chroococcum C26 using dry polymers is suitable under adequate preservation and storage conditions.

Se estudió la preservación de Azotobacter chroococcum C26 usando tres polímeros secos: carragenina, alginato de sodio y HPMC, usando un método de degradación acelerada. Viabilidad bacteriana, como variable de respuesta, fue medida a tres temperaturas en cuatro tiempos diferentes, lo cual fue seguido por el cálculo de tasas de degradación bacteriana. Los resultados mostraron que la temperatura, el tiempo de almacenamiento, y el agente protectivo influenciaron tanto la viabilidad como las tasas de degradación (P<0.05). Se observó, usando el modelo termodinàmico de Arrhenius, que el uso de polímeros incremento la energía de activación de degradación bacteriana comparado con el control. Adicionalmente, se obtuvieron modelos para cada polímero, basados en la ecuación de Arrhenius, para predecir el tiempo requerido para la degradación térmica de las células a diferentes temperaturas. El análisis de los modelos mostró que la carragenina fue el mejor polímero para preservar A. chroococcum C26 dado que un tiempo de aproximadamente 900 días a 4 °C son necesarios para reducir en dos unidades logarítmicas la viabilidad. Se concluye, por lo tanto, que la preservación a largo término usando polímeros es eficaz para la preservación de A. chroococcum C26 bajo condiciones adecuadas de preservación y mantenimiento.

Estudamos a preservado do Azotobacter chroococcum C26 utilizando tres polímeros secos: carragenina, alginato de sòdio, e HPMC, utilizando um método de degradado acelerada. Viabilidade bacteriana, como variável de resposta, foi medida a tres temperaturas em quatro momentos diferentes, que foi seguido pelo cálculo das taxas de degradado bacteriana. Os resultados mostraram que a temperatura, tempo de armazenamento, e agente protetor influenciado as taxas de viabilidade e de degradado (P <0,05). Observou-se, utilizando o modelo de Arrhenius termodinàmico, que a utilizac.ao do polímeros de aumento da energia de activado do degradado bacteriana em comparado com o controlo. Adicionalmente, obtivemos modelos termodinámicos para cada polímero, com base na equação de Arrhenius, para prever o tempo necessàrio para a degradação térmica das células a diferentes temperaturas. Análise dos modelos mostrou que a carragenina é o melhor polímero para preservar A. chroococcum C26, porque ~ 900 dias são necessários a 4 °C para reduzir a viabilidade de duas unidades logarítmicas. Nós concluímos, portanto, a preservação a longo prazo de A. chroococcum C26 utilizando polímeros secos é adequado sob condic.öes de preservalo e armazenamento adequadas.

Evaluation of polymers for the liquid rhizobial formulation and their influence in the Rhizobium-Cowpea interaction / Evaluación de polímeros para la formulación líquida de rizobios e influencia en la interacción Rhizobium-caupí / Avaliação de polímeros para a formulação líquida de rizobios e influência na interação Rhizobium-caupí

To develop proposals in bacterial formulations applicable to the agricultural sector, a study of physicochemical and biological parameters of the polymeric materials is essential. Here, we evaluated the effects of eight polymers on the cellular viability of Rhiyobium sp. G58 during a 2-month period. From these results, we selected the three polymers that yielded the best results in respect to the survival of the bacteria. An assay of the effect of the polymers on the symbiotic activity of Rhiyobium-Cowpea and the agronomic parameters was conducted under greenhouse conditions, based on the principal component analysis. A positive effect was found in Rhiyobium sp. G58 using the Tukey's Test (p<0.05) with sodium alginate (0.5-1%) and hydroxypropyl methylcellulose-HPMC (0.125-0.5%), while a significant decrease was established in cellular viability using polyethylene glycol-PEG, carbomer-Carbopol 940, and polyvinyl alcohol-PVA. The multivariate analysis indicated that the application of the polymers (sodium alginate and hydroxypropyl methylcellulose) in 0.5% concentration did not have negative effects on the symbiotic fixation of nitrogen or the process of nodulation. In conclusion, our results suggest the effectiveness of these polymers and the possibility of using them as carriers of bacterial formulation without affecting physiological processes.

Para el desarrollo de propuestas en formulaciones bacterianas aplicadas al sector agropecuario, se hace necesario el estudio de parámetros fisicoquímicos y biológicos de materiales poliméricos. En este estudio, evaluamos el efecto de ocho polímeros sobre la viabilidad celular de Rhiyobium sp. G58 durante 2 meses. Obtenidos estos resultados, se seleccionaron los 3 polímeros que tuvieron la mejor respuesta en la supervivencia de la bacteria. Se realizó un ensayo bajo invernadero del efecto de los polímeros sobre la actividad simbiótica de Rhiyobium-Cowpea y de los parámetros agronómicos, el cual fue realizado por un análisis multivariado de componentes principales. Se estableció un efecto positivo mediante el test de Tuckey's (p < 0.05) en Rhiyobium sp. G58 utilizando alginato de sodio (0.5-1%) e hidroxipropilmetilcelulosa-HPMC (0.125-0.5%). Mientras que, se obtuvo un descenso significativo en la viabilidad celular con polietilenglicol-PEG, carbomero-Carbopol 940, y alcohol polivinílico-PVA. El análisis multivariado indicó que la aplicación de los polímeros (alginato de sodio e hidroxipropilmetilcelulosa) a una concentración de 0.5%, no afectaron negativamente la actividad de fijación simbiótica de nitrógeno, ni el proceso de nodulación. En conclusión, nuestros resultados sugieren la efectividad de estos polímeros con Rhiyobium sp. y podrían ser empleados como soportes para formulaciones bacterianas sin afectar procesos fisiológicos.

Para o desenvolvimento de propostas em formulações bacterianas aplicadas ao setor agropecuário, faz-se necessário o estudo de parâmetros fisicoquímicos e biológicos de materiais poliméricos. Neste estudo, avaliamos o efeito de oito polímeros sobre a viabilidade celular de Rhiyobium sp. G58 durante 2 meses. Selecionaram-se os 3 polímeros que tiveram a melhor resposta na sobrevivência da bactéria. Estabeleceu-se um efeito positivo mediante o teste de Tuckey's (p < 0.05) em Rhiyobium sp. G58 usando alginato de sodio (0.5-1%) e hidroxipropilmetilcelulosa-HPMC (0.125-0.5%). Enquanto, obteve-se um descenso significativo na viabilidade celular com polietilenglicol-PEG, carbómero-Carbopol 940, e álcool polivinílico-PVA. A análise multivariado indicou que a aplicação dos polímeros (alginato de sodio e hidroxipropilmetilcelulose) a uma concentração de 0.5%, não afetaram negativamente a atividade de fixação simbiótica de nitrogénio, nem o processo de nodulación. Em conclusão, os resultados sugerem a efetividade destes polímeros com Rhiyobium sp. e poderiam ser empregues como suporte para formulações bacterianas sem afetar processos fisiológicos.

Evaluation of three methods for preservation of Azotobacter chroococcum and Azotobacter vinelandii

La preservación de bacterias es asunto de granimportancia debido a que muchas de ellas son usadas enprocesos biotecnológicos que requieren mantener su viabilidad ypropiedades genéticas. En este estudio, se evaluaron tres métodospara la preservación de A. chroococcum C26 y A. vinelandii C27;criopreservación, liofilización, e inmovilización en polímerossecos, durante 60, 30 y 60 días, respectivamente. A su vez, seestudió el efecto de tres agentes protectivos para la liofilizacióny para la criopreservación y cuatro polímeros. La eficiencia delos métodos fue evaluada contando células viables y midiendoactividad como fijación de nitrógeno. Los resultados mostraronque la mejor técnica, la cual mantuvo la viabilidad y la actividad,fue la liofilización, seguida por inmovilización y criopreservación.La liofilización mantuvo estable la habilidad bacteriana para fijarnitrógeno, la tasa de sobrevivencia bacteriana (TSB) fue superioral 80%; y el mejor resultado se evidenció cuando se usó S/BSAcomo agente protectivo. La inmovilización mantuvo la BSRsuperior al 80%, y la fijación de nitrógeno fue disminuida en 20%.La criopreservación tuvo pérdida sustancial de viabilidad para C26(TSB aprox. 70%); mientras que C27 se preservó bien. La fijaciónde nitrógeno fue significativamente disminuida para ambas cepasindependientemente del agente crioprotectivo usado (P < 0.05).Los resultados sugieren que el éxito de los métodos de preservaciónpara Azotobacter depende de la técnica, el agente protectivo y la cepausada; siendo la liofilización con S/BSA la técnica con mejoresresultados para preservar las bacterias de este género...

Because the use of bacteria for biotechnological processes requires maintaining their viability and geneticstability, preserving them becomes essential. Here, we evaluated three preservation methods for A.chroococcum C26 and A. vinelandii C27; preservation methods: cryopreservation and immobilization in drypolymers for 60 days, and freeze-drying for 30. We evaluated their efficiency by counting viable cells andmeasuring nitrogen fixation activity. Additionally, we assessed the effect of three protective agents forfreeze-drying, three for cryopreservation, and four polymers. Freeze-drying proved the best technique tomaintain viability and activity, followed by immobilization and cryopreservation. Bacterial nitrogen fixingability remained unchanged using the freeze-drying method, and bacterial survival exceeded 80%; S/BSAwas the best protective agent. Immobilization maintained bacterial survival over 80%, but nitrogen fixationwas decreased by 20%. Lastly, cryopreservation resulted in a dramatic loss of viability for C26 (BSRapprox. 70%), whereas C27 was well preserved. Nitrogen fixation for both strains decreased regardless ofthe cryoprotective agent used (P < 0.05). In conclusion, the success of Azotobacter preservation methodsdepend on the technique, the protective agent, and the strain used. Our results also indicated that freezedryingusing S/BSA is the best technique to preserve bacteria of this genus...

Porque o uso de bactérias para processos biotecnológicos,requer a manutenção da sua viabilidade e estabilidade genética,preserva-las é essencial Avaliaram-se três métodos de preservação deA. chroococcum C26 e A. vinelandii C27; criopreservação, liofilização, eimobilização de polímeros secos. Examinamos também o efeito deagentes protetores para liofilizar, para a criopreservação, e polímeros.A eficiência foi avaliada contando as células viáveis e medindoa atividade como a fixação do azoto. Os resultados mostraramque a melhor técnica foi a liofilização seguida de imobilização ecriopreservação. A liofilização manteve inalterada a capacidadeda bactéria para fixar o azoto, e o melhor resultado foi observadoquando se usou S/BSA como agente protetor. A criopreservaçãoresultou em uma perda dramática de viabilidade para C26 (TSBaprox. 70%.), enquanto que C27 foi bem preservada. A fixaçãode azoto foi significativamente diminuída para ambas as estirpes,independentemente do agente crioprotector utilizado (P < 0.05).Em conclusão, os resultados sugerem que o êxito dos métodosde conservação de Azotobacter dependem da técnica, do agente deproteção, e da estirpe utilizada, sendo a liofilizacao com S/BSA amelhor técnica para preservar as bactérias deste género...