Yoav Bashan | Centro de Investigaciones Biológicas del Noroeste S.C. (original) (raw)

Papers by Yoav Bashan

Journal of Phycology, 2008

Enzymatic activities of glutamate dehydrogenase (GDH) and glutamine synthetase (GS) participating... more Enzymatic activities of glutamate dehydrogenase (GDH) and glutamine synthetase (GS) participating in the nitrogen metabolism and related ammonium absorption were assayed after the microalga Chlorella vulgaris Beij. was jointly immobilized with the microalgae-growth-promoting bacterium Azospirillum brasilense. At initial concentrations of 3, 6, and 10 mg AE L )1 NH 4 + , joint immobilization enhances growth of C. vulgaris but does not affect ammonium absorption capacity of the microalga. However, at 8 mg AE L )1 NH 4 + , joint immobilization enhanced ammonium absorption by the microalga without affecting the growth of the microalgal population. Correlations between absorption of ammonium per cell and per culture showed direct (negative and positive) linear correlations between these parameters and microalga populations at 3, 6, and 10 mg AE L )1 NH 4 + , but not at 8 mg AE L )1 NH 4 + , where the highest absorption of ammonium occurred. In all cultures, immobilized and jointly immobilized, having the four initial ammonium concentrations, enzymatic activities of Chlorella are affected by A. brasilense. Regardless of the initial concentration of ammonium, GS activity in C. vulgaris was always higher when jointly immobilized and determined on a per-cell basis. When jointly immobilized, only at an initial concentration of 8 mg AE L )1 NH 4 + was GDH activity per cell higher.

FEMS Microbiology Ecology, 2000

Growth of and the capacity to take up nitrogen in the freshwater microalgae Chlorella vulgaris we... more Growth of and the capacity to take up nitrogen in the freshwater microalgae Chlorella vulgaris were studied while varying the concentrations of ammonium and nitrate, the pH and the source of carbon in a synthetic wastewater growth medium when co-immobilized in alginate beads with the microalgae growth-promoting bacterium Azospirillum brasilense. Analyses of 29 independent experiments showed that co-immobilization of the microalgae with A. brasilense could result in two independent phenomena directly affected by cultivation factors, such as nitrogen species, pH and presence of a carbon source. First, growth of the microalgal population increased without an increase in the capacity of the single cells to take up nitrogen, or second, the capacity of cells to take up nitrogen increased without an increase of the total microalgal population. These phenomena were dependent on the population density of the microalgae, which was in turn affected by cultivation factors. This supports the conclusion that the size of the microalgal population controls the uptake of nitrogen in C. vulgaris cells -the higher the population (regardless the experimental parameters), the less nitrogen each cell takes up.

The capacity of Azospirillum brasilense to enhance the accumulation of K, P, Ca, Mg, S, Na, Mn, F... more The capacity of Azospirillum brasilense to enhance the accumulation of K, P, Ca, Mg, S, Na, Mn, Fe, B, Cu, and Zn in inoculated wheat and soybean plants was evaluated by using two different analytical methods with five A. brasilense strains originating from four distinct geographical regions. A Pseudomonas isolate from the rhizosphere of Zea mays seedlings was included as a control. All A. brasilense strains significantly improved wheat and soybean growth by increasing root and shoot dry weight and root surface area. The degree of plant response to inoculation varied among the different strains of A. brasilense. All strains were capable of colonizing roots, but the best root colonizer, Pseudomonas sp., had no effect on plant growth. The numbers of organisms of Brazilian strains Sp-245 and Sp-246 colonizing roots were similar regardless of the host plant. Numbers of organisms for the other strains were directly dependent on the host plant. The main feature characterizing mineral accumulation in inoculated plants was that all inoculation treatments changed the mineral balance of the plants, but in an inconsistent manner. Enhancement of mineral uptake by plants also varied among strains to a great extent and was directly dependent on the strain-plant combination; i.e., a strain capable of increasing accumulation of a particular ion in one plant species or cultivar often lacked the ability to do so in another. Minerals in inoculated plants were not evenly distributed in different plant tissues, and the changes varied among groups of plants within each bacterial strain inoculation treatment. We suggest that, although A. brasilense strains are capable of changing the mineral balance and content of plants, it is unlikely that this ability is a general mechanism responsible for plant improvement by A. brasilense.

Biology and Fertility of Soils

Growth promotion of the seawater-irrigated oilseed halophyte Salicornia bigelovii inoculated with... more Growth promotion of the seawater-irrigated oilseed halophyte Salicornia bigelovii inoculated with mangrove rhizosphere bacteria and halotolerant Azospirillum spp. Species of the shrub-like halophytic weed, Salicornia, are grown widely in climates ranging from temperate to tropical (Jefferies et al. 1981; Rey et al. 1990; Benito and Onaindia 1991). Monocultures and mixed cultures of Salicornia and other salt marsh weeds occur commonly in coastal salt marshes and inland salt pans where stands often exceed 10,000 plants m -2 (Ellison 1987). Although the plants can tolerate freshwater to some extent, NaCI is required for normal growth (Ayala and O'Leary 1995). Salicornia bigelovii Torr. is an annual, leafless, fastgrowing, succulent halophyte found along the coastline of Sonora and Baja California in Mexico (RodriguezMedina et al. 1998). Because S. bigelovii produces oilseeds and a high yield of foliage (Glenn et al. 1998), it is being evaluated as a new forage and oilseed crop for ...

1 1 G Gr ru up po o d de e M Mi ic cr ro ob bi io ol lo og gí ía a A Am mb bi ie en nt ta al l. .... more 1 1 G Gr ru up po o d de e M Mi ic cr ro ob bi io ol lo og gí ía a A Am mb bi ie en nt ta al l. . C Ce en nt tr ro o d de e I In nv ve es st ti ig ga ac ci io on ne es s B Bi io ol ló óg gi ic ca as s d de el l N No or ro oe es st te e ( (C CI IB BN NO OR R) ). . C Ca al ll le e M Ma ar r B Be er rm me ej jo o 1 19 95 5, , C Co ol l. . P Pl la ay ya a P Pa al lo o d de e S St ta a. . R Ri it ta a. . 2 23 30 09 90 0 L La a P Pa az z, , B Ba aj ja a C Ca al li if fo or rn ni ia a S Su ur r, , M Mé éx xi ic co o. . 2 2 Diversa Corporation. San Diego, CA, USA. 3 3 D De ep pa ar rt tm me en nt t o of f B Bi io ol lo og gy y. . U Un ni iv ve er rs si it ty y o of f W Wa at te er rl lo oo o, , W Wa at te er rl lo oo o, , O On nt ta ar ri io o, , C Ca an na ad dá á.

Developments in Plant Pathology, 1997

Handbook for Azospirillum, 2015

Journal of Applied Phycology, 2015

Molecular analyses employing sequencing of the complete ribosomal RNA cistron (18S rDNA, ITS1, 5.... more Molecular analyses employing sequencing of the complete ribosomal RNA cistron (18S rDNA, ITS1, 5.8S rDNA, ITS2, and 28S rDNA) and transcriptome analysis of the RuBisCO gene (rbcL) were done on Chlorella vulgaris UTEX 2714. The constructed phylogenetic trees showed that C. vulgaris UTEX 2714 is Chlorella sorokiniana. Growth analysis and production of chlorophyll a over a range of increasing cultivation temperatures (27-40°C) showed that this strain is far less thermotolerant in comparison to a common C. sorokiniana strain. A change in the taxonomic designation of strain UTEX 2714 is proposed.

Research in Microbiology, 2015

Accumulation of intra-cellular phosphate, as polyphosphate, was measured when the microalga Chlor... more Accumulation of intra-cellular phosphate, as polyphosphate, was measured when the microalga Chlorella vulgaris was immobilized in alginate with either of two wild-type strains of the microalgae growth-promoting bacterium Azospirillum brasilense or their corresponding IAA-attenuated mutants. Wild type strains of A. brasilense induced higher amounts of intra-cellular phosphate in Chlorella than their respective mutants. Calculations comparing intra-cellular phosphate accumulation by culture or net accumulation by the cell and the amount of IAA that was produced by each of these strains revealed that higher IAA was linked to higher accumulations of intra-cellular phosphate. Application of four levels of exogenous IAA reported for A. brasilense and their IAA-attenuated mutants to cultures of C. vulgaris enhanced accumulation of intra-cellular phosphate; the higher the content of IAA per culture or per single cell, the higher was the amount of accumulated phosphate. When an IAA-attenuated mutant was complemented with exogenous IAA, accumulation of intra-cellular phosphate at the culture level was even higher than phosphate accumulation with the respective wild type strains. When calculating the net accumulation of intra-cellular phosphate in the complementation experiment, net intra-cellular phosphate induced by the IAA-attenuated mutant was completely restored and was similar to the wild strains. We propose that IAA produced by A. brasilense is linked to polyphosphate accumulation in C. vulgaris.

Journal of General Microbiology, 1993

... &amp; Stacey, 1990). To date, attachment of Azospiril-lum to roots has not been compa... more ... &amp; Stacey, 1990). To date, attachment of Azospiril-lum to roots has not been compared with attachment to other hydrophobic surfaces which are commonly used to evaluate the attachment of bacteria responsible for biofouling in other environments (Fletcher, 1977 ; Klotz, 1990). ...

Advances in Agronomy, 2010

La deforestación del desierto de Sonora en Baja California Sur se debe a una agricultura marginal... more La deforestación del desierto de Sonora en Baja California Sur se debe a una agricultura marginal dando como resultado una severa erosión del suelo y por consiguiente una contaminación por polvo cuando estos campos son abandonados después de varios años de cultivo. Esta contaminación por polvo origina un problema importante de salud pública (con altos índices de enfermedades respiratorias), especialmente entre los niños. Para dar marcha atrás a este efecto adverso en la salud pública, nuestro propósito es crear programas de revegetación para suelos abandonados por incidencia urbana y agrícola. Se proponen dos alternativas importantes para desarrollar exitosamente un programa de reforestación: (i) Simular el proceso natural de revegetación del desierto ("Islas de Recursos" por árboles leguminosos), (ii) Inoculación de árboles nativos con bacterias promotoras de crecimiento en plantas (PGPB) y hongos micorrizicos arbusculares (AM), o también aprovechando la combinación de ambos. Una fuente favorable de material microbiano para inoculación son las PGPB para uso agrícola (tales como Azospirillum sp., Pseudomonas sp., y Bacillus sp.) y AM hongos. Muchas plantas nativas responden positivamente a la inoculación mejorando su crecimiento. Sin embargo, aquellos microorganismos nativos que crezcan y sobrevivan en suelos con alta dureza son mejores candidatos para inocular las plantas nativas. Una fuente potencial de estos microorganismos son plantas del desierto creciendo en rocas en ausencia de suelo, siendo ésta una de las condiciones que inhibe el crecimiento en la mayoría de las plantas.

Naturwissenschaften, 2014

The relation between fatty acid accumulation, activity of acetyl-CoA carboxylase (ACC), and conse... more The relation between fatty acid accumulation, activity of acetyl-CoA carboxylase (ACC), and consequently lipid accumulation was studied in the microalgae Chlorella vulgaris co-immobilized with the plant growth-promoting bacterium Azospirillum brasilense under dark heterotrophic conditions with Na acetate as a carbon source. In C. vulgaris immobilized alone, cultivation experiments for 6 days showed that ACC activity is directly related to fatty acid accumulation, especially in the last 3 days. In co-immobilization experiments, A. brasilense exerted a significant positive effect over ACC activity, increased the quantity in all nine main fatty acids, increased total lipid accumulation in C. vulgaris, and mitigated negative effects of nonoptimal temperature for growth. No correlation between ACC activity and lipid accumulation in the cells was established for three different temperatures. This study demonstrated that the interaction between A. brasilense and C. vulgaris has a significant effect on fatty acid and lipid accumulation in the microalgae.

Trees, 2002

Although a few countries protect mangroves (USA, some states in Mexico), the systematic destructi... more Although a few countries protect mangroves (USA, some states in Mexico), the systematic destruction of these ecosystems is increasing. Deforestation of mangrove communities is thought to be one of the major reasons for the decline in coastal fisheries of many tropical and subtropical countries. Although mangroves in the tropics can regenerate themselves or be restored using low-technology propagule planting, arid mangroves (areas having limited or no access to fresh water) can seldom regenerate, and if they do, it happens very slowly. To conserve arid tropical mangrove ecosystems, maintenance and restoration of the microbial communities is required. There is sufficient published evidence to propose a close microbe-nutrient-plant relationship that functions as a major mechanism for recycling and conserving essential nutrients in the mangrove ecosystem. The highly productive and diverse microbial community living in tropical and subtropical mangrove ecosystems continuously transforms dead vegetation into sources of nitrogen, phosphorus, and other nutrients that can later be used by the plants. In turn, plant-root exudates serve as a food source for the microorganisms living in the ecosystem, with other plant material serving a similar role for larger organisms, such as crabs and detritusfeeding fish. This speculative synthesis of recent work on growth-promoting bacteria proposes that mangrove rhizosphere bacteria be used as a tool to enhance reforestation with mangrove seedlings. This can be done by inoculating seedlings with plant-growth-promoting bacteria participating in one or more of the microbial cycles of the ecosystem.