Kinetics of Halophilic Enzymes

Hypersaline environments are those with salt concentrations 9–10 times higher (30–35% of NaCl) than sea water (3.5% of NaCl). At high concentrations of soluble salts, cytoplasm—mainly of bacteria and archaea—is exposed to high ionic strength and achieves osmotic equilibrium by maintaining a cytoplasmic salt concentration similar to that of the surrounding media. Halophilic enzymes are extremozymes produced by halophilic microorganisms; they have similar characteristics to regular enzymes but different properties, mainly structural. Among these properties is a high requirement of salt for biological functions. Furthermore, the discovery of enzymes capable of degrading biopolymers offer a new perspective in the treatment of residues from oil deposits, under typically high conditions of salt and temperature, while giving valuable information on heterotrophic processes in saline environments

Microbacterium plantarum sp. nov. and Microbacterium thalli sp. nov., two endophytic metal-resistant bacteria isolated from Sphaeralcea angustifolia (Cav.) G. Don and Prosopis laevigata (Humb. et Bonpl. ex Willd) M.C. Johnston

12 páginas, 4 figuras, 2 tablasFour Gram-positive, aerobic, catalase- and oxidase-negative, rod-shaped, motile endophytic bacterial strains, designated NM3R9T, NE1TT3, NE2TL11 and NE2HP2T, were isolated from the inner tissues (leaf and stem) of Sphaeralcea angustifolia and roots of Prosopis laevigata. They were characterized using a polyphasic approach, which revealed that they represent two novel Microbacterium species. Phylogenetic analysis based on 16S rRNA gene sequencing showed that the species closest to NE2HP2T was Microbacterium arborescens DSM 20754T (99.6 %) and that closest to NM3R9T, NE2TL11 and NE2TT3 was Microbacterium oleivorans NBRC 103075T (97.4 %). The whole-genome average nucleotide identity value between strain NM3R9T and Microbacterium imperiale DSM 20530T was 90.91 %, and that between strain NE2HP2T and M. arborecens DSM 20754T was 91.03 %. Digital DNA-DNA hybridization showed values of less than 70 % with the type strains of related species. The polar lipids present in both strains included diphosphatidylglycerol, phosphatidylglycerol, glycolipids and unidentified lipids, whereas the major fatty acids included anteiso-C15 : 0, anteiso-C17 : 0, iso-C16 : 0 and C16 : 0. Whole-cell sugars included mannose, rhamnose and galactose. Strains NM3R9T and NE2HP2T showed physiological characteristics different from those present in closely related Microbacterium species. According to the taxonomic analysis, both strains belong to two novel species. The name Microbacterium plantarum sp. nov. is proposed for strain NE2HP2T (=LMG 30875T=CCBAU 101117T) and Microbacterium thalli sp. nov. for strains NM3R9T (=LMG 30873T=CCBAU 101116T), NE1TT3 (=CCBAU 101114) and NE2TL11 (=CCBAU 101115).This study was financially supported by Secretaría de Investigación y Posgrado del Instituto Politécnico Nacional (IPN) grant numbers SIP20170544, SIP20180115, SIP20196674, SIP20196729, SIP20200229 and SIP20200310.Peer reviewe

Development of a Quality Index to Evaluate the Impact of Abiotic Stress in Saline Soils in the Geothermal Zone of Los Negritos, Michoacán, Mexico

In recent years, salinity-induced soil quality impairment and the misuse of management practices have led to the reduced productivity of agroecosystems. This has prompted a search for simple and effective agricultural management strategies that improve the sustainability of agricultural production through soil quality assessments. In this context, the objective of this study was to establish an integrated soil quality index (SQI) by assessing the influence of different types of abiotic stress in two different seasons, using physical, chemical and biological indicators at three sites in the geothermal zone of “Los Negritos”, Michoacán, Mexico. Thirty-nine indicators related to soil fertility attributes and C, N, P, and S cycling—identified as the total dataset (TDS)—were evaluated. Principal component analysis (PCA) and the Spearman correlation matrix (r2 ≥ 0.6) were used to calculate the SQI using an integrated quality index (IQI) equation, with the indicators total nitrogen (TN), cation exchange capacity (CEC), lithium (Li), and zinc (Zn) identified as the minimum dataset (MDS). Significantly higher SQI values related to the better performance of soil functions were detected during the rainy season

Suelos salinos: fuente de microorganismos halófilos asociados a plantas y resistentes a metales

La salinidad en los suelos representa una extensión de 1128 millones de hectáreas a nivel mundial, teniendo en cuenta la superficie afectada de manera natural (primaria) o inducida por el hombre (secundaria). Por lo que se estima una tendencia a aumentar en los próximos años, representando un problema en la actividad agrícola debido a los cambios fisiológicos y bioquímicos en el metabolismo de las plantas; afectando la producción de alimentos. Es por ello, que las investigaciones en la actualidad buscan nuevas maneras de restaurar o aprovechar estos suelos, como es el caso de estudiar a los microorganismos presentes y las posibles interacciones con algunas plantas. El objetivo de este trabajo es abordar la importancia de los suelos salinos y la capacidad de los microorganismos presentes mediante la activación de mecanismos de tolerancia, resistencia y promoción de crecimiento vegetal en presencia de sales y metales potencialmente tóxicos que contribuyen a minimizar los daños ocasionados. En la actualidad el uso de técnicas moleculares es una de las principales herramientas para identificar microorganismos presentes y la relación de moléculas implicadas en la resistencia hacia la presencia de sales (transportadores y síntesis de solutos compatibles). Los microorganismos halófilos pueden producir enzimas, sintetizar exopoli-sacáridos, fitohormonas y compuestos quelantes, que ayudan a algunas plantas a crecer en estos ambientes y llevar a cabo la desalinización de estos suelos. Teniendo una gran capacidad de adaptación y potencial para ser propuestos en diversos bioprocesos.J. Guevara-Luna, I. Arroyo- Herrera y Y. Bahena- Osorio agradecen el apoyo de la beca del Consejo Nacional de Ciencia y Tecnología (CONACyT) y de BEIFI-IPN. B. Román-Ponce agradece el apoyo de CONACyT para su estancia posdoctoral. M. S. Vásquez-Murrieta agradece el apoyo de la Comisión de Operación y Fomento de Actividades Académicas (COFAA), del Estímulo al Desempeño de los Investigadores (EDI-IPN) y del Sistema Nacional de Investigadores (SNI-CONACyT)

ACCIÓN SINÉRGICA DEL ÁCIDO INDOL BUTÍRICO Y UNA RIZOBACTERIA, EN LA FITOEXTRACCIÓN ASISTIDA DE ARSÉNICO Y CADMIO POR Sedum praealtum A. DC.

La fitoextracción asistida implica la participación de especies vegetales y agentes suplementarios (aditivos químicos o biológicos) que incrementan la biodisponibilidad de los contaminantes y su acumulación. El empleo de reguladores del crecimiento vegetal (fitohormonas) crea un efecto neutral por estrés ocasionado por los metales en las plantas y favorecen su desarrollo. El presente trabajo evaluó el efecto de la relación sinérgica entre Sedum praealtum A. DC.- rizobacterias-fitohormonas, como alternativa de fitoextracción asistida combinada de arsénico y cadmio. La presencia de arsénico y cadmio en el crecimiento de S. praealtum A. DC. evidenció un daño en su desarrollo; pero la adición de ambos agentes quelantes resultó eficiente no solamente al facilitar la biodisponibilidad de estos metales para ser absorbidos por las plantas; sino también para demostrar la acción sinérgica que se estableció entre la rizobacteria, la fitohormona y las plantas de esta especie al potenciar su crecimiento radical que favoreció la absorción de los nutrientes evaluados.

Identification of Halophilic and Halotolerant Bacteria from the Root Soil of the Halophyte <i>Sesuvium verrucosum</i> Raf

Soil salinity is a condition that limits crop growth and productivity, and soil-dwelling bacteria from halophytic plant roots may be a viable strategy to cope with low productivity due to salt stress. Halophilic and halotolerant bacteria of the root soil of Sesuvium verrucosum were analyzed in this study as there is little evidence regarding its associated microbiology. Soil was sampled from the roots of Sesuvium verrucosum to obtain the cultivable bacteria. Their morphological characteristics were identified and they were molecularly identified by the 16S sequence. The growth capacity of the bacteria was determined at different levels of pH and salinity, and several growth promotion characteristics were identified, such as phosphorus solubilization, indole acetic acid production by the tryptophan-dependent (AIAt) and tryptophan-independent (IAA) pathways, ammonium production from organic sources, solubilization of carbonates, and zinc and sodium capture capacity. In addition, the bacteria that presented the best characteristics for germination variables of Solanum lycopersicum were evaluated. A total of 20 bacteria from root soil of Sesuvium verrucosum Raf. belonging to the phyla Proteobacteria (50%), Firmicutes (45%) and Actinobacteria (5%) were identified, with each one having different morphological characteristics. Among the bacterial isolates, 45% had the ability to resist different levels of salinity and pH, ranging from 0 to 20% of NaCl, and pH between 5 and 11. Moreover, these bacteria had the capacity to solubilize carbonates, phosphorus and zinc, capture sodium, produce ammonium from organic substrates and IAA (indole acetic acid), and promote enzymatic activity of amylases, proteases, lipases and cellulases. The bacteria evaluated on the germination of Solanum lycopersicum had an influence on germination at different salinity levels, with greater influence at 100 mM NaCl. This demonstrated that halophilic bacteria belonging to the rhizosphere of Sesuvium verrucosum have the ability to promote growth in extreme salinity conditions, making them candidates for the recovery of productivity in saline soils

Reduction in Salt Stress Due to the Action of Halophilic Bacteria That Promote Plant Growth in <i>Solanum lycopersicum</i>

Soil salinity is one of the most important factors reducing agricultural productivity worldwide. Halophilic plant growth-promoting bacteria (H-PGPB) represent an alternative method of alleviating saline stress in crops of agricultural interest. In this study, the following halophilic bacteria were evaluated: Bacillus sp. SVHM1.1, Halomonas sp. SVCN6, Halomonas sp. SVHM8, and a consortium. They were grown under greenhouse conditions in Solanum lycopersicum at different salinity concentrations in irrigation water (0, 20, 60, and 100 mM NaCl) to determine the effects on germination, fruit quality, yield, and concentration of osmoprotectors in plant tissue. Our results demonstrate the influence of halophilic bacteria with the capacity to promote plant growth on the germination and development of Solanum lycopersicum at higher salinity levels. The germination percentage was improved at the highest concentration by the inoculated treatments (from 37 to 47%), as were the length of the radicle (30% at 20 mM) and plumule of the germinated seed, this bacterium also increased the weight of the plumule (97% at 100 mM). They also improved the yield. The dry weight of the plant, in addition to having an influence on the quality of the fruit and the concentration of osmoprotectors (Bacillus sp. SVHM 1.1) had the greatest effect on fruit yield (1.5 kg/plant at 20 mM), by the otherhand, Halomonas sp. SVHM8 provided the best fruit quality characteristics at 100 mM. According to the above results, the efficiency of halophilic PGPB in the attenuation of salt stress in Solanum lycopersicum has been proven

El cultivo del cacao, sus características y su asociación con microorganismos durante la fermentación

Theobroma cacao L. es un árbol del bosque tropical, se clasifica dentro de la familia Malvaceae originario del sur de América. El árbol se conoce comúnmente como cacao mientras que el término cocoa se refiere a los productos preparados con las semillas secas y fermentadas. El cacao es un “commodity” que representa la base de la economía de millones de pequeños productores en el mundo. En el año 2019, la producción a nivel mundial fue de 6,800 millones de dólares con más de 10 millones de toneladas obtenidas. En México, se produjeron 28,473 ton siendo Tabasco el mayor productor (18,331 ton), seguido de Chiapas con 9,857 ton y Guerrero con 285 ton. El cacao se clasifica en tres grupos genéticos: criollo, forastero y trinitario. El cacao criollo es el de mejor calidad, pero de mayor susceptibilidad a enfermedades. El cultivo de cacao requiere de condiciones de temperatura, humedad, suelo y sombra, determinadas para su crecimiento y producción. Para la fermentación de cacao, las semillas y la pulpa se colocan en tapetes cubiertos con hojas de plátano o en cajas de madera con drenaje. Los microorganismos involucrados principalmente en la fermentación incluyen levaduras, bacterias ácido lácticas y bacterias ácido acéticas. El proceso de fermentación es fundamental para la calidad de los productos. Esta revisión muestra las características del cacao, así como los microorganismos involucrados en su fermentación

Burkholderia caballeronis sp. nov., a nitrogen fixing species isolated from tomato (Lycopersicon esculentum) with the ability to effectively nodulate Phaseolus vulgaris.

During a survey of Burkholderia species with potential use in agrobiotechnology, a group of 12 strains was isolated from the rhizosphere and rhizoplane of tomato plants growing in Mexico (Nepantla, Mexico State). A phylogenetic analysis of 16S rRNA gene sequences showed that the strains are related to Burkholderia kururiensis and Burkholderia mimosarum (97.4 and 97.1 %, respectively). However, they induced effective nitrogen-fixing nodules on roots of Phaseolus vulgaris. Based on polyphasic taxonomy, the group of strains represents a novel species for which the name Burkholderia caballeronis sp. nov. is proposed. The type species is TNe-841(T) (= LMG 26416(T) = CIP 110324(T))

Burkholderia caballeronis sp. nov., a nitrogen fixing species isolated from tomato (Lycopersicon esculentum) with the ability to effectively nodulate Phaseolus vulgaris.

During a survey of Burkholderia species with potential use in agrobiotechnology, a group of 12 strains was isolated from the rhizosphere and rhizoplane of tomato plants growing in Mexico (Nepantla, Mexico State). A phylogenetic analysis of 16S rRNA gene sequences showed that the strains are related to Burkholderia kururiensis and Burkholderia mimosarum (97.4 and 97.1 %, respectively). However, they induced effective nitrogen-fixing nodules on roots of Phaseolus vulgaris. Based on polyphasic taxonomy, the group of strains represents a novel species for which the name Burkholderia caballeronis sp. nov. is proposed. The type species is TNe-841(T) (= LMG 26416(T) = CIP 110324(T))