The plant growth promoting rhizobacterium Achromobacter sp. 5B1, rescues Arabidopsis seedlings from alkaline stress by enhancing root organogenesis and hormonal responses.

Soil alkalinity is a critical environmental factor for plant growth and distribution in ecosystems. An alkaline condition (pH > 7) is imposed by the rising concentration of hydroxides and cations, and prevails in semiarid and arid environments, which represent more than 25% of the total arable land of the world. Despite the great pressure exerted by alkalinity for root viability and plant survival, scarce information is available to understand how root microbes contribute to alkaline pH adaptation. Here, we assessed the effects of alkalinity on shoot and root biomass production, chlorophyll content, root growth and branching, lateral root primordia formation, and the expression of CYCB1, TOR kinase, and auxin and cytokinin-inducible trangenes in shoots and roots of Arabidopsis seedlings grown in Petri plates with agar-nutrient medium at pH values of 7.0, 7.5, 8.0, 8.5, and 9.0. The results showed an inverse correlation between the rise of pH and most growth, hormonal and genetic traits analyzed. Noteworthy, root inoculation with Achromobacter sp. 5B1, a beneficial rhizospheric bacterium, with plant growth promoting and salt tolerance features, increased biomass production, restored root growth and branching and enhanced auxin responses in WT seedlings and auxin-related mutants aux1-7 and eir1, indicating that stress adaptation operates independently of canonical auxin transporter proteins. Sequencing of the Achromobacter sp. 5B1 genome unveiled 5244 protein-coding genes, including genes possibly involved in auxin biosynthesis, quorum-sensing regulation and stress adaptation, which may account for its plant growth promotion attributes. These data highlight the critical role of rhizobacteria to increase plant resilience under high soil pH conditions potentially through genes for adaptation to an extreme environment and bacteria-plant communication.

Pseudomonas aeruginosa LasI-dependent plant growth promotion requires the host nitrate transceptor AtNRT1.1/CHL1 and the nitrate reductases NIA1 and NIA2.

MAIN CONCLUSION: In P. aeruginosa, mutation of the gene encoding N-acyl-L-homoserine lactone synthase LasI drives defense and plant growth promotion, and this latter trait requires adequate nitrate nutrition. Cross-kingdom communication with bacteria is crucial for plant growth and productivity. Here, we show a strong induction of genes for nitrate uptake and assimilation in Arabidopsis seedlings co-cultivated with P. aeruginosa WT (PAO1) or ΔlasI mutants defective on the synthesis of the quorum-sensing signaling molecule N-(3-oxododecanoyl)-L-homoserine lactone. Along with differential induction of defense-related genes, the change from plant growth repression to growth promotion upon bacterial QS disruption, correlated with upregulation of the dual-affinity nitrate transceptor CHL1/AtNRT1/NPF6.3 and the nitrate reductases NIA1 and NIA2. CHL1-GUS was induced in Arabidopsis primary root tips after transfer onto P. aeruginosa ΔlasI streaks at low and high N availability, whereas this bacterium required high concentrations of nitrogen to potentiate root and shoot biomass production and to improve root branching. Arabidopsis chl1-5 and chl1-12 mutants and double mutants in NIA1 and NIA2 nitrate reductases showed compromised growth under low nitrogen availability and failed to mount an effective growth promotion and root branching response even at high NH4NO3. WT P. aeruginosa PAO1 and P. aeruginosa ΔlasI mutant promoted the accumulation of nitric oxide (NO) in roots of both the WT and nia1nia2 double mutants, whereas NO donors SNP or SNAP did not improve growth or root branching in nia1nia2 double mutants with or without bacterial cocultivation. Thus, inoculation of Arabidopsis roots with P. aeruginosa drives gene expression for improved nitrogen acquisition and this macronutrient is critical for the plant growth-promoting effects upon disruption of the LasI quorum-sensing system.

Screening of Phosphate Solubilization Identifies Six Pseudomonas Species with Contrasting Phytostimulation Properties in Arabidopsis Seedlings.

The interaction of plants with bacteria and the long-term success of their adaptation to challenging environments depend upon critical traits that include nutrient solubilization, remodeling of root architecture, and modulation of host hormonal status. To examine whether bacterial promotion of phosphate solubilization, root branching and the host auxin response may account for plant growth, we isolated and characterized ten bacterial strains based on their high capability to solubilize calcium phosphate. All strains could be grouped into six Pseudomonas species, namely P. brassicae, P. baetica, P. laurylsulfatiphila, P. chlororaphis, P. lurida, and P. extremorientalis via 16S rRNA molecular analyses. A Solibacillus isronensis strain was also identified, which remained neutral when interacting with Arabidopsis roots, and thus could be used as inoculation control. The interaction of Arabidopsis seedlings with bacterial streaks from pure cultures in vitro indicated that their phytostimulation properties largely differ, since P. brassicae and P. laurylsulfatiphila strongly increased shoot and root biomass, whereas the other species did not. Most bacterial isolates, except P. chlororaphis promoted lateral root formation, and P. lurida and P. chlororaphis strongly enhanced expression of the auxin-inducible gene construct DR5:GUS in roots, but the most bioactive probiotic bacterium P. brassicae could not enhance the auxin response. Inoculation with P. brassicae and P. lurida improved shoot and root growth in medium supplemented with calcium phosphate as the sole Pi source. Collectively, our data indicate the differential responses of Arabidopsis seedlings to inoculation with several Pseudomonas species and highlight the potential of P. brassicae to manage phosphate nutrition and plant growth in a more eco-friendly manner.

Micrococcus luteus LS570 promotes root branching in Arabidopsis via decreasing apical dominance of the primary root and an enhanced auxin response.

The interaction of plant roots with bacteria is influenced by chemical signaling, where auxins play a critical role. Auxins exert positive or negative influences on the plant traits responsible of root architecture configuration such as root elongation and branching and root hair formation, but how bacteria that modify the plant auxin response promote or repress growth, as well as root structure, remains unknown. Here, we isolated and identified via molecular and electronic microscopy analysis a Micrococcus luteus LS570 strain as a plant growth promoter that halts primary root elongation in Arabidopsis seedlings and strongly triggers root branching and absorptive potential. The root biomass was exacerbated following root contact with bacterial streaks, and this correlated with inducible expression of auxin-related gene markers DR5:GUS and DR5:GFP. Cellular and structural analyses of root growth zones indicated that the bacterium inhibits both cell division and elongation within primary root tips, disrupting apical dominance, and as a consequence differentiation programs at the pericycle and epidermis, respectively, triggers the formation of longer and denser lateral roots and root hairs. Using Arabidopsis mutants defective on auxin signaling elements, our study uncovers a critical role of the auxin response factors ARF7 and ARF19, and canonical auxin receptors in mediating both the primary root and lateral root response to M. luteus LS570. Our report provides very basic information into how actinobacteria interact with plants and direct evidence that the bacterial genus Micrococcus influences the cellular and physiological plant programs ultimately responsible of biomass partitioning.

The plant beneficial rhizobacterium Achromobacter sp. 5B1 influences root development through auxin signaling and redistribution.

Roots provide physical and nutritional support to plant organs that are above ground and play critical roles for adaptation via intricate movements and growth patterns. Through screening the effects of bacterial isolates from roots of halophyte Mesquite (Prosopis sp.) on Arabidopsis thaliana, we identified Achromobacter sp. 5B1 as a probiotic bacterium that influences plant functional traits. Detailed genetic and architectural analyses in Arabidopsis grown in vitro and in soil, cell division measurements, auxin transport and response gene expression and brefeldin A treatments demonstrated that root colonization with Achromobacter sp. 5B1 changes the growth and branching patterns of roots, which were related to auxin perception and redistribution. Expression analysis of auxin transport and signaling revealed a redistribution of auxin within the primary root tip of wild-type seedlings by Achromobacter sp. 5B1 that is disrupted by brefeldin A and correlates with repression of auxin transporters PIN1 and PIN7 in root provasculature, and PIN2 in the epidermis and cortex of the root tip, whereas expression of PIN3 was enhanced in the columella. In seedlings harboring AUX1, EIR1, AXR1, ARF7ARF19, TIR1AFB2AFB3 single, double or triple loss-of-function mutations, or in a dominant (gain-of-function) mutant of SLR1, the bacterium caused primary roots to form supercoils that are devoid of lateral roots. The changes in growth and root architecture elicited by the bacterium helped Arabidopsis seedlings to resist salt stress better. Thus, Achromobacter sp. 5B1 fine tunes both root movements and the auxin response, which may be important for plant growth and environmental adaptation.

Síndrome de Burnout en el personal de enfermería de los Servicios Críticos del Hospital Central de la Fuerza Aérea del Perú - 2011 / Burnout syndrome in nurses of the Critical Services at the Central Hospital of the Force Air of Peru - 2011

El objetivo fue determinar el Síndrome de Burnout en el personal de enfermería de los servicios críticos del Hospital Central de la Fuerza Aérea del Perú 2011. Material y Método: El estudio es de tipo cuantitativo, nivel aplicativo, método descriptivo, de corte trasversal. La población estuvo conformada por 93, 53 enfermeras (os) y 39 técnicas (os) en enfermería. La técnica fue la encuesta y el instrumento el Maslach Burnout Inventory (MBI), aplicado previo consentimiento informado. Resultados: Del 100 por ciento (93), 13 por ciento (12) tiene alto, 68 por ciento (63) medio y 19 por ciento (18) bajo. En agotamiento emocional, del 100 por ciento (39) técnico en enfermería 58 por ciento (23) tienen medio, 21 por ciento (8) alto y 21 por ciento (8) bajo, las enfermeras (os) del 100 por ciento (54), 55 por ciento (30) medio, 19 por ciento (10) alto y 26 por ciento (14) bajo. En la despersonalización, el personal técnico 44 por ciento (17) tiene medio, 18 por ciento (7) alto y 38 por ciento (15) bajo, las enfermeras (os) 59 por ciento (32) tiene medio, 15 por ciento (8) alto y 26 por ciento (14) bajo. En realización personal, el técnico en enfermería 46 por ciento (18) es medio, 23 por ciento (9) bajo y 31 por ciento (12) alto y en las enfermeras (os) 61 por ciento (33) tienen medio, 17 por ciento (9) bajo y 22 por ciento (12) alto. Acerca de los servicios críticos en Sala de Operaciones del 100 por ciento (23) del personal, 74 por ciento (17) tienen medio, 9 por ciento (2) alto y 17 por ciento (4) bajo, en la Unidad de Terapia Intensiva del 100 por ciento (21), 62 por ciento (13) tienen medio, 19 por ciento (4) alto y 19 por ciento (4) bajo, y en Emergencia del 100 por ciento (24), 58 por ciento (14) tienen medio, 21 por ciento (5) alto y 21 por ciento (5) bajo. Conclusiones: El Síndrome de Burnout en la mayoría del personal de enfermería de los servicios críticos es medio a alto, de igual modo en la dimensión agotamiento emocional...

The objective was to determine the burnout syndrome in nurses of the critical services the Central Hospital of the Air Force of Peru 2011. Material and Methods: The study is a quantitative, application level, descriptive method, cross-cutting. The population consisted of 93, 53 nurses and 39 techniques in nursing. The interview technique was the instrument and the Maslach Burnout Inventory (MBI). Results: 100 per cent (93), 13 per cent (12) is high, 68 per cent (63) medium and 19 per cent (18) low. In emotional exhaustion, the nursing staff have a higher percentage of high levels 21 per cent (08) means 58 per cent (23), a smaller percentage of staff nurses high levels in 19 per cent (10) and a half 55 per cent (30). In depersonalization, the nursing staff has higher percentage in the high 18 per cent (07) and a lower percentage in the middle 44 per cent (17), staff nurses have the lowest percentage, 15 per cent high (08) and the highest percentage in the middle 59 per cent (32). In fulfillment, staff nurses has a higher percentage in the middle 61 per cent (33) and a lower percentage in the high 22 per cent (12), the nursing staff have a higher percentage of the average 46 per cent (18) and a lower percentage in the high 31 per cent (12). About the critical services the highest percentage was found in the middle 74 per cent (17) in the operating room, under 19 per cent (04) in the Intensive Therapy Unit and high 21 per cent (05) Emergency 21 per cent (05). Conclusions: Burnout Syndrome in the majority of the nursing staff of critical services followed half high, just as in the emotional exhaustion and depersonalization dimension referred to feel tired at the end of the work day, do not care what will happen to patients believe they are working too hard, working all day with patients involves a lot of effort on your part and work directly with people it causes stress, while of most personal fulfillment is medium to low and as for the critical services...

In vitro antagonism of Thielaviopsis paradoxa by Trichoderma longibrachiatum.

Seventy-nine Trichoderma strains were isolated from soil taken from 28 commercial plantations of Agave tequilana cv. 'Azul' in the State of Jalisco, Mexico. Nine of these isolates produced nonvolatile metabolites that completely inhibited the growth of Thielaviopsis paradoxa on potato dextrose agar plates. These isolates were identified as Trichoderma longibrachiatum on the basis of their morphology and DNA sequence analysis of two genes (ITS rDNA and translation elongation factor EF-1alpha). Mycoparasitism of Th. paradoxa by T. longibrachiatum strains in dual cultures was examined by scanning electron microscopy. The Trichoderma hyphae grew alongside the Th. paradoxa hyphae, but penetration of Thielaviopsis hyphae by Trichoderma was no apparent. Aleurioconidia of Th. paradoxa were parasitized by Trichoderma. Both hyphae and aleurioconidia of Th. paradoxa lost turgor pressure, wrinkled, collapsed and finally disintegrated. In liquid cultures, all nine Trichoderma isolates produced proteases, beta-1,3-glucanases and chitinases that would be responsible for the degradation of Thielaviopsis hyphae. These results demonstrate that the modes of action of T. longibrachiatum involved against Th. paradoxa in vitro experiments are mycoparasitism and the production of nonvolatile toxic metabolites.

Efectos del potencial de agua en el crecimiento radical de plántulas de agave salmiana otto ex salm-dyck / Effects of the potential of water in the radical growth of plántulas of agave salmiana otto former salm-dyck

El objetivo de este estudio fue determinar el efecto del potencial de agua del substrato en las características fisiológicas y biofísicas de la raíz de plántulas de Agave salmiana Otto ex Salm-Dyck en condiciones de laboratorio. Las plántulas con raíz de 3 a 4 cm de longitud se mantuvieron por 24h en vermiculita con psi A de -0,03: -0,65; -,148 y -2,35MPa. Un lote de plántulas fue rehidratado y de otro las raices se recolectaron y se cuantificó el crecimiento, contenido de prolina, así como la conductividad eléctrica, pH, Cu, Fe, K, Mn, Na y Zn en el medio de resuspensión de las raices. Se calculó el índice de daño y se evaluó el efecto de la rehidratación en el crecimiento. Los psi A bajos del substrato no afectaron significativamente la longitud, pero afectaron significativamente el peso fresco (entre 23,5 y 49,2 por ciento) y el índice de daño incrementó 36,0 por ciento; los elementos liberados al medio no se modificaron significativamente y el contenido de prolina de la raíz se incrementó de 1,6 a 2,14 moles.mg1 de materia seca. Con la rehidratación la raíz continuó su crecimiento

Permeabilidad de las membranas radicales de plántulas de frijol (phaseolus vulgaris L) silvestre y domesticado bajo déficit de humedad / Permeability of the radical membranes of bean plántulas (phaseolus vulgaris L) wild and domesticated low deficit of humidity

Se evaluó la permeabilidad de las membranas radicales de frijol silvestre y domesticado en respuesta al déficit de humedad. Se utilizó frijol silvestre originario de Chihuahua (SCH) y de Durango (SD) y el cultivar Bayomex. Plántulas de 72h, con raíz de 3-4cm de longitud se mantuvieron 24h en vermiculita con potenciales de agua (?A) de -0,03; -0,65; -1,48 y -2,35MPa. Las raíces recolectadas se mantuvieron en agua desionizada durante 3h. Se cuantificó el contenido relativo de agua (CRA) de la raíz y la concentración de K+ y Na+ en el medio de resuspensión. Cada 30min se evaluó conductividad eléctrica y pH del medio. En el cultivar y en SD el CRA disminuyó 46% con el déficit de humedad, mientras en SCH sólo disminuyó 15%. La salida de electrolitos mostró dos fases en todos los tratamientos. En los primeros 30min pasó de 0,8 a 3,2S·cm-1·g-1 de tejido seco para el cultivar; de 1,4 a 3,1 para SCH; y de 2,2 a 6,4 para SD. Al final de la segunda fase (2,5h después) los incrementos no fueron significativos. La interacción significativa mostró que SCH no tuvo daño con ninguno de los ?A probados (0,84%) y que tanto SD como el cultivar sufrieron daño (>50%) con -2,35MPa. En contraste con la conductividad eléctrica, el pH del medio continuó incrementándose en las primeras 3h. Los ?A bajos promovieron incrementos significativos del pH del medio de las raíces del cultivar (4,59 a 4,91) y SD (4,86 a 5,16). Las raíces de las tres variantes mantenidas en el?A más alto liberaron cantidades semejantes (P£0,75) de K+ (5,9mg·g-1 en promedio), pero el déficit de humedad promovió mayor liberación (hasta 2,5 veces); no se detectó Na+ en el medio. Con base en CRA, conductividad eléctrica, índice de daño y recuperación del crecimiento posterior al estrés, se concluyó que las membranas de la raíz de SCH son menos afectadas por el déficit de humedad que las de SD y el domesticado...

Wild and domesticated common bean root membrane permeability was evaluated in its response to water deficit. Wild common bean from Chihuahua (SCH) and Durango (SD) and the cv. Bayomex were used; 72h old seedlings of 3-4cm root length were maintained for 24h in vermiculite with water potentials (?W) of -0.03, -0.65, -1.48 and -2.35MPa. Roots collected were maintained in deionized water for 3h and then relative water content (CRA), and K+ and Na+ concentrations in the media were quantified; electrical conductivity and pH of the medium were measured every 30min. CRA sharply decreased (46%) in the cultivar and SD with water deficit, but diminished slightly in SCH (15%). Electrolyte leakage showed two phases in all treatments, in the initial 30min it went from 0.8 to 3.2S·cm-1·g-1 of dry tissue in the cultivar, from 1.4 to 3.1 in SCH and from 2.2 to 6.4 in SD; but, after the next 2.5h the increments were not significant. The significant interaction showed that although SCH was not damaged (0.84%) with any ?W tested, SD and the cultivar were drastically damaged (>50%) with -2.35MPa. In contrast with electrical conductivity, media pH continued increasing during the first 3h. The lower ?W promoted a significant pH increase for the domesticated common bean root (from 4.59 to 4.91) and SD (from 4.86 to 5.16). High YW produced significantly similar (P£0.75) K+ leakage (5.9mg·g-1 in average) in all three variants, but the water deficit caused increase of K+ leakage (up to 2.5 times), while Na+ leakage was not detected. Based on CRA, electrical conductivity, damage index and stress recovery data, it seems that low ?W affected root membranes of SCH less than those of SD and the domesticated common bean...