INFLUENCIA DE HONGOS MICORRÍZICOS ARBUSCULARES Y UNA BACTERIA DIAZOTRÓFICA NATIVA EN LA SOBREVIVENCIA Y TUBERIZACIÓNDE PLANTAS DE PAPA EX VITRO

The inoculation of several species of micropropagated plantlets with native diazotrophic bacteria and arbuscular mycorrhizal fungi has been reported to increase growth and survival percentage compared to plantlets without inoculation. The survival of in vitro developed potato (Solarium tuberosum L. cv. Alfa) plantlets co-inoculated with Glomus fasciculatum (Thaxter sensu Gerd.) Gerd & Trappe, G. claroideum (Schenck & Smith emend. Walker & Vestberg) and a native diazotrophic bacteria was evaluated at room temperature (16-35°C) or in a growth chamber (20-22°C). Obtained plantlets for micropropagation were placed in a peat moss/agrolite (2:1 v/v) mixture, inoculated with arbuscular mycorrhizal (AM) fungi (2250 spores plant"') and native diazotrophic bacteria (3 x 108 cell plant"') and grown in the greenhouse at 18±2°C for 4 weeks and at 20-26°C for another 4 weeks. Plantlets were then transferred to near-commercial greenhouse and plant growth and minitubers yield were determined 15 weeks after ex vitro growth. Survival of the plantlets at room temperature doubled when inoculated with the two AM fungi and also biomass and minituber yield of plants compared to untreated plants. It was found that the added microorganisms increased survival of potato plantlets and AM fungi improved potato plant growth and minituber production.La inoculación de varias especies de plantas micropropagadas con bacterias diazotróficas nativas y hongos micorrízicos arbusculares se ha reportado que incrementa el crecimiento y el porcentaje de sobrevivencia comparado con plantas sin inocular. Se evaluó la sobrevivencia de plántulas de papa (Solanum tuberosum L. cv. Alfa) desarrolladas in vitro, coinoculadas con Glomus fasciculatum (Thaxter sensu Gerd.) Gerd & Trappe, G. claroideum (Schenck & Smith emend. Walker & Vestberg) y una bacteria diazotrófica nativa, a temperatura ambiente (16-35°C) o en una cámara de cultivo (20-22°C). Las plántulas obtenidas por micropropagación se colocaron en una mezcla de turba/agrolita (2:1 v/v), se inocularon con los hongos micorrízicos arbusculares (HMA) (2250 esporas planta"') y la bacteria diazotrófica nativa (3 x 108 células mi"') y se cultivaron en el invernadero a 18±2°C por 4 semanas y a 20-26°C por otras 4 semanas. Posteriormente las plántulas se transfirieron a un invernadero semicomercial en donde se les determinó el crecimiento y el rendimiento de los minitubérculos a las 15 semanas después de crecimiento ex vitro. A temperatura ambiente, la sobrevivencia de las plántulas, la biomasa y el rendimiento de los minitubérculos se duplicaron cuando las plántulas se inocularon con los dos HMA en comparación con las plantas sin inoculación. Se encontró que los microorganismos adicionados incrementaron la sobrevivencia de las plántulas de papa y los HMA mejoraron el crecimiento de las plantas de papa y el rendimiento de los minitubérculos

Archaeal Communities in a Heterogeneous Hypersaline-Alkaline Soil

In this study the archaeal communities in extreme saline-alkaline soils of the former lake Texcoco, Mexico, with electrolytic conductivities (EC) ranging from 0.7 to 157.2 dS/m and pH from 8.5 to 10.5 were explored. Archaeal communities in the 0.7 dS/m pH 8.5 soil had the lowest alpha diversity values and were dominated by a limited number of phylotypes belonging to the mesophilic Candidatus Nitrososphaera. Diversity and species richness were higher in the soils with EC between 9.0 and 157.2 dS/m. The majority of OTUs detected in the hypersaline soil were members of the Halobacteriaceae family. Novel phylogenetic branches in the Halobacteriales class were detected in the soil, and more abundantly in soil with the higher pH (10.5), indicating that unknown and uncharacterized Archaea can be found in this soil. Thirteen different genera of the Halobacteriaceae family were identified and were distributed differently between the soils. Halobiforma, Halostagnicola, Haloterrigena, and Natronomonas were found in all soil samples. Methanogenic archaea were found only in soil with pH between 10.0 and 10.3. Retrieved methanogenic archaea belonged to the Methanosarcinales and Methanomicrobiales orders. The comparison of the archaeal community structures considering phylogenetic information (UniFrac distances) clearly clustered the communities by pH

Nitrogen fertilizer application alters the root endophyte bacterial microbiome in maize plants, but not in the stem or rhizosphere Soil

Plant-associated microorganisms that affect plant development, their composition, and their functionality are determined by the host, soil conditions, and agricultural practices. How agricultural practices affect the rhizosphere microbiome has been well studied, but less is known about how they might affect plant endophytes. In this study, the metagenomic DNA from the rhizosphere and endophyte communities of root and stem of maize plants was extracted and sequenced with the “diversity arrays technology sequencing,” while the bacterial community and functionality (organized by subsystems from general to specific functions) were investigated in crops cultivated with or without tillage and with or without N fertilizer application. Tillage had a small significant effect on the bacterial community in the rhizosphere, but N fertilizer had a highly significant effect on the roots, but not on the rhizosphere or stem. The relative abundance of many bacterial species was significantly different in the roots and stem of fertilized maize plants, but not in the unfertilized ones. The abundance of N cycle genes was affected by N fertilization application, most accentuated in the roots. How these changes in bacterial composition and N genes composition might affect plant development or crop yields has still to be unraveled

Effect of vermicompost, worm-bed leachate and arbuscular mycorrizal fungi on lemongrass ( Cymbopogon citratus (DC) Stapf.) growth and composition of its essential oil

The objective of this study was to investigate the effect of vermicompost, worm-bed leachate (WBL) and Glomus mosseae , an arbuscular mycorrhizal fungi (AMF), on growth of lemongrass ( Cymbopogon citratus (DC.) Stapf). A response surface methodology, i.e. a three-level Box Benhen design with three repetitions and three blocks, was applied to optimize biomass production, essential oil yield and its composition. Application rates of Glomus mosseae were 0, 1 or 2 g plant-1, vermicompost 0, 5 or 10 g plant-1 and WBL 0, 10 and 20%. The AMF had no significant effect on the variables tested, but vermicompost had a significant effect on essential oil yield and WBL on essential oil yield, myercene concentration and shoot dry weigh (p < 0.05). It was found that lemongrass fertilized with 2.0 g G. mosseae, 5.0 g vermicompost and 20% worm-bed leachate would yield 0.797% essential oil of which 62.6% was citral

Application of ammonium to a N limited arable soil enriches a succession of bacteria typically found in the rhizosphere

Crop residue management and tillage are known to affect the soil bacterial community, but when and which bacterial groups are enriched by application of ammonium in soil under different agricultural practices from a semi-arid ecosystem is still poorly understood. Soil was sampled from a long-term agronomic experiment with conventional tilled beds and crop residue retention (CT treatment), permanent beds with crop residue burned (PBB treatment) or retained (PBC) left unfertilized or fertilized with 300 kg urea-N ha-1 and cultivated with wheat (Triticum durum L.)/maize (Zea mays L.) rotation. Soil samples, fertilized or unfertilized, were amended or not (control) with a solution of (NH4)2SO4 (300 kg N ha-1) and were incubated aerobically at 25 ± 2 °C for 56 days, while CO2 emission, mineral N and the bacterial community were monitored. Application of NH4+ significantly increased the C mineralization independent of tillage-residue management or N fertilizer. Oxidation of NH4+ and NO2- was faster in the fertilized soil than in the unfertilized soil. The relative abundance of Nitrosovibrio, the sole ammonium oxidizer detected, was higher in the fertilized than in the unfertilized soil; and similarly, that of Nitrospira, the sole nitrite oxidizer. Application of NH4+ enriched Pseudomonas, Flavisolibacter, Enterobacter and Pseudoxanthomonas in the first week and Rheinheimera, Acinetobacter and Achromobacter between day 7 and 28. The application of ammonium to a soil cultivated with wheat and maize enriched a sequence of bacterial genera characterized as rhizospheric and/or endophytic independent of the application of urea, retention or burning of the crop residue, or tillage

Identificación morfológica y filogenética de un consorcio microbiano fotosintético de posible interés biotecnológico

Background. Microbial consortia have ecological and biotechnological importance since they contribute to thebiogeochemical cycles in nature and produce compounds of high economical value. Goals. Research for this paperinvolved the polyphasic study of a photosynthetic microbial consortium (MC) in order to identify the microorganisms thatcomprise it, in addition to exploring the theory of the biotechnological potential of each partner within the consortium.Methods. Study of morphological and phylogenetic diversity. Results. Twenty-one different microorganisms wereidentified that make up the MC belonging to the phyla Proteobacteria (Rhodobacter sp., Devosia insulae, Pedomicrobiumamericanum, Alpha proteobacteria, Aquaspirillum delicatum, Methylibium petroleiphilum and Nannocystis sp.), Bacteriodetes (Flavobacterium sp. and Flavobacterium aquatile), Cyanobacteria (Aphanizomenon aphanizomenoides, Leptolyngbya sp. and Anabaena oscillarioides), Chlorophyta (Monoraphidium sp. and Chlorella sp.), Heterokontophyta (Cyclotella meneghiniana, Melosira varians, Cocconeis placentula, Achnanthidium chlidanos, Navicula radiosa, Fragilaria ulna and Nitzschia sp.). This microbial consortium was shown to have a high capacity for nitrogen fixation (10,294 nmol ethylene g-1 dry weight h-1). Conclusions. The identification of microorganisms that form the MC and their capacity for growth and nitrogen fixation in a photobioreactor, give us a glimpse of their possible biotechnological application as a biofertilizer.Antecedentes. Los consorcios microbianos son de importancia ecológica y biotecnológica por que contribuyen a los ciclosbiogeoquímicos y producen compuestos de alto valor añadido. Objetivos. Realizar el estudio polifásico de un consorciomicrobiano (CM) fotosintético, con el fin de identificar los microorganismos que lo integran, además del aporte teóricodel potencial biotecnológico de cada uno de ellos como parte del consorcio. Métodos. Se empleó un estudio de la diversidad morfológica y filogenética. Resultados. En el CM se identificaron 21 microorganismos diferentes pertenecientes a los phyla Proteobacteria (Rhodobacter sp., Devosia insulae, Pedomicrobium americanum, Alpha proteobacteria, Aquaspirillum delicatum, Methylibium petroleiphilum y Nannocystis sp.), Bacteroidetes (Flavobacterium sp. y Flavobacterium aquatile), Cyanobacteria (Aphanizomenon aphanizomenoides, Leptolyngbya sp. y Anabaena oscillarioides), Chlorophyta (Monoraphidium sp., Chlorella sp.), Heterokontophyta (Cyclotella meneghiniana, Melosira varians, Cocconeis placentula, Achnanthidium chlidanos, Navicula radiosa, Fragilaria ulna y Nitzschia sp.). Este consorcio microbiano ha mostrado tener una elevada capacidad de fijación de nitrógeno (10,294 nmoles etileno g-1 peso seco h-1). Conclusiones. La identificación de los microorganismos que conforman el CM, su capacidad de crecimiento y la fijación de nitrógeno en un fotobiorreactor, permiten vislumbrar su posible aplicación biotecnológica como biofertilizante

Changes in the bacterial and microeukaryotic communities in the bioreactor upon increasing heavy metal concentrations

Heavy metals are necessary at low concentration for biological activity, but they are often toxic for microorganisms at high concentrations. Amplicon sequencing of 16S rRNA and 18S rRNA was used to investigate changes in the bacterial and microeukaryotic communities in an activated sludge bioreactor incrementally contaminated with nickel (Ni), copper (Cu), and zinc (Zn) with an IC50 value ranging from 0% to 100%, as previously determined, while an uncontaminated bioreactor served as a control. The chemical oxygen demand (COD) was on average 90% in the uncontaminated bioreactor but dropped to 49% when the heavy metal concentration was 100% IC50. The bacterial community in the uncontaminated bioreactor was dominated by Alphaproteobacteria (mostly Agrobacterium and Brevundimonas) when the heavy metal concentrations were low and Bacteroidetes (mostly Sphingobacterium) when the highest amounts of heavy metal concentrations were applied. The members of Ciliophora, Ascomycota, and Basidiomycota alternatively dominated in the uncontaminated bioreactor, while Ascomycota (mostly Fusarium) dominated in the contaminated bioreactor. The results revealed that increased concentrations of Ni, Cu, and Zn altered the bacterial and microeukaryotic communities and some putative metabolic functions

Conversion of a High-Altitude Temperate Forest for Agriculture Reduced Alpha and Beta Diversity of the Soil Fungal Communities as Revealed by a Metabarcoding Analysis

Land-use change is one of the most important drivers of change in biodiversity. Deforestation for grazing or agriculture has transformed large areas of temperate forest in the central highlands of Mexico, but its impact on soil fungal communities is still largely unknown. In this study, we determined how deforestation of a high-altitude temperate forest for cultivation of maize (Zea mays L.) or husbandry altered the taxonomic, phylogenetic, functional, and beta diversity of soil fungal communities using a 18S rRNA metabarcoding analysis. The true taxonomic and phylogenetic diversity at order q = 1, i.e., considering frequent operational taxonomic units, decreased significantly in the arable, but not in the pasture soil. The beta diversity decreased in the order forest > pasture > arable soil. The ordination analysis showed a clear effect of intensity of land-use as the forest soil clustered closer to pasture than to the arable soil. The most abundant fungal phyla in the studied soils were Ascomycota, Basidiomycota, and Mucoromycota. Deforestation more than halved the relative abundance of Basidiomycota; mostly Agaricomycetes, such as Lactarius and Inocybe. The relative abundance of Glomeromycota decreased in the order pasture > forest > arable soil. Symbiotrophs, especially ectomycorrhizal fungi, were negatively affected by deforestation while pathotrophs, especially animal pathogens, were enriched in the pasture and arable soil. Ectomycorrhizal fungi were more abundant in the forest soil as they are usually associated with conifers. Arbuscular mycorrhizal fungi were more abundant in the pasture than in the arable soil as the higher plant diversity provided more suitable hosts. Changes in fungal communities resulting from land-use change can provide important information for soil management and the assessment of the environmental impact of deforestation and conversion of vulnerable ecosystems such as high-altitude temperate forests