Environmental Microbiology Group

Santa María de la Paz, Mexico

Environmental Microbiology Group

Santa María de la Paz, Mexico
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Bashan Y.,Environmental Microbiology Group | Bashan Y.,The Bashan Foundation | Trejo A.,Environmental Microbiology Group | de-Bashan L.E.,Environmental Microbiology Group | de-Bashan L.E.,The Bashan Foundation
Biology and Fertility of Soils | Year: 2011

High yield culture medium is fundamental for production of inoculants for plant growth-promoting bacteria. Based on substitution of glucose in tryptone-yeast extract-glucose medium by Na-gluconate or glycerol, two new culture media were developed for mass cultivation of the commonly used plant growth-promoting bacterium Azospirillum sp. After 18 h of incubation, these modifications increased populations of different strains of Azospirillum (to ~1011 cells ml-1 [single cell count] and ~5 × 109 CFU ml-1 [plate count method]), significantly reduced generation time, and were also suitable for production of common synthetic inoculants. © 2011 Springer-Verlag.

Perez-Garcia O.,Environmental Microbiology Group | de-Bashan L.E.,Environmental Microbiology Group | Hernandez J.,Environmental Microbiology Group | Bashan Y.,Environmental Microbiology Group | Bashan Y.,The Bashan Foundation
Journal of Phycology | Year: 2010

Heterotrophic growth of microalgae presents significant economic advantages over the more common autotrophic cultivation. The efficiency of growth and nitrogen, phosphorus, and glucose uptake from synthetic wastewater was compared under heterotrophic, autotrophic, and mixotrophic regimes of Chlorella vulgaris Beij. immobilized in alginate beads, either alone or with the bacterium Azospirillum brasilense. Heterotrophic cultivation of C. vulgaris growing alone was superior to autotrophic cultivation. The added bacteria enhanced growth only under autotrophic and mixotrophic cultivations. Uptake of ammonium by the culture, yield of cells per ammonium unit, and total volumetric productivity of the culture were the highest under heterotrophic conditions when the microalga grew without the bacterium. Uptake of phosphate was higher under autotrophic conditions and similar under the other two regimes. Positive influence of the addition of A. brasilense was found only when light was supplied (autotrophic and mixotrophic), where affinity to phosphate and yield per phosphate unit were the highest under heterotrophic conditions. The pH of the culture was significantly reduced in all regimes where glucose was consumed, similarly in heterotrophic and mixotrophic cultures. It was concluded that the heterotrophic regime, using glucose, is superior to autotrophic and mixotrophic regimes for the uptake of ammonium and phosphate. Addition of A. brasilense positively affects the nutrient uptake only in the two regimes supplied with light. © 2010 Phycological Society of America.

Perez-Garcia O.,Environmental Microbiology Group | Escalante F.M.E.,Environmental Microbiology Group | de-Bashan L.E.,Environmental Microbiology Group | de-Bashan L.E.,The Bashan Foundation | And 2 more authors.
Water Research | Year: 2011

This review analyzes the current state of a specific niche of microalgae cultivation; heterotrophic growth in the dark supported by a carbon source replacing the traditional support of light energy. This unique ability of essentially photosynthetic microorganisms is shared by several species of microalgae. Where possible, heterotrophic growth overcomes major limitations of producing useful products from microalgae: dependency on light which significantly complicates the process, increase costs, and reduced production of potentially useful products. As a general role, and in most cases, heterotrophic cultivation is far cheaper, simpler to construct facilities, and easier than autotrophic cultivation to maintain on a large scale. This capacity allows expansion of useful applications from diverse species that is now very limited as a result of elevated costs of autotrophy; consequently, exploitation of microalgae is restricted to small volume of high-value products. Heterotrophic cultivation may allow large volume applications such as wastewater treatment combined, or separated, with production of biofuels. In this review, we present a general perspective of the field, describing the specific cellular metabolisms involved and the best-known examples from the literature and analyze the prospect of potential products from heterotrophic cultures. © 2010 Elsevier Ltd.

de-Bashan L.E.,Environmental Microbiology Group | de-Bashan L.E.,The Bashan Foundation | Hernandez J.-P.,Environmental Microbiology Group | Hernandez J.-P.,The Bashan Foundation | And 2 more authors.
Applied Soil Ecology | Year: 2012

Plant growth-promoting bacteria (PGPB) are commonly used to improve crop yields. In addition to their proven usefulness in agriculture, they possess potential in solving environmental problems. Some examples are highlighted. PGPB may prevent soil erosion in arid zones by improving growth of desert plants in reforestation programs; in turn, this reduces dust pollution. PGPB supports restoration of mangrove ecosystems that lead to improve fisheries. PGPB participate in phytoremediation techniques to decontaminate soils and waters. These include: phytodegradation, phytotransformation, bioaugmentation, rhizodegradation, phytoextraction, phycoremediation, and phytostabilization, all leading to healthier environments. This review describes the state-of-the-art in these fields, examples from peer-reviewed literature, pitfalls and potentials, and proposes open questions for future research. © 2011 Elsevier B.V.

de-Bashan L.E.,Environmental Microbiology Group | de-Bashan L.E.,The Bashan Foundation | Bashan Y.,Environmental Microbiology Group | Bashan Y.,The Bashan Foundation
Bioresource Technology | Year: 2010

This review analyzes the state-of-the-art of a specific niche in biological wastewater treatment that uses immobilized eukaryotic microalgae (and several prokaryotic photosynthetic cyanobacteria), with emphasis on removing nutrients with the support of microalgae growth-promoting bacteria. Removal of other pollutants by this technology, such as heavy metals and industrial pollutants, and technical aspects related to this specific subfield of wastewater treatment are also presented. We present a general perspective of the field with most known examples from common literature, emphasizing a practical point of view in this technologically oriented topic. The potential venues of future research in this field are outlined and a critical assessment of the failures, limitations, and future of immobilized microalgae for removal of pollutants is presented. © 2009 Elsevier Ltd.

Covarrubias S.A.,Environmental Microbiology Group | De-Bashan L.E.,Environmental Microbiology Group | De-Bashan L.E.,Bashan Foundation | Moreno M.,Environmental Microbiology Group | And 2 more authors.
Applied Microbiology and Biotechnology | Year: 2012

When the freshwater microalga Chlorella sorokiniana and the plant growth-promoting bacterium Azospirillum brasilense were deployed as free suspensions in unsterile, municipal wastewater for tertiary wastewater treatment, their population was significantly lower compared with their populations in sterile wastewater. At the same time, the numbers of natural microfauna and wastewater bacteria increased. Immobilization of C. sorokiniana and A. brasilense in small (2-4 mm in diameter), polymer Ca-alginate beads significantly enhanced their populations when these beads were suspended in normal wastewater. All microbial populations within and on the surface of the beads were evaluated by quantitative fluorescence in situ hybridization combined with scanning electron microscopy and direct measurements. Submerging immobilizing beads in wastewater created the following sequence of events: (a) a biofilm composed of wastewater bacteria and A. brasilense was created on the surface of the beads, (b) the bead inhibited penetration of outside organisms into the beads, (c) the bead inhibited liberation of the immobilized microorganisms into the wastewater, and (d) permitted an uninterrupted reduction of ammonium and phosphorus from the wastewater. This study demonstrated that wastewater microbial populations are responsible for decreasing populations of biological agents used for wastewater treatment and immobilization in alginate beads provided a protective environment for these agents to carry out uninterrupted tertiary wastewater treatment. © Springer-Verlag 2011.

Perez-Garcia O.,Environmental Microbiology Group | Bashan Y.,Environmental Microbiology Group | Bashan Y.,Bashan Foundation | Esther Puente M.,Environmental Microbiology Group
Journal of Phycology | Year: 2011

Heterotrophic growth of the microalga Chlorella vulgaris Beij. in synthetic as well as sterilized municipal wastewater of a nonindustrialized city was measured. The city wastewater contained high levels of ammonium and nitrate, medium levels of phosphate, and low levels of nitrite and organic molecules and could not support heterotrophic growth of C. vulgaris. Evaluation of 11 known carbon sources for this microalga that were added to standard synthetic wastewater containing the same levels of nitrogen and phosphorus as the municipal wastewater revealed that the best carbon sources for heterotrophic growth were Na-acetate and d-glucose. These provided the highest growth rates and the largest removal of ammonium. Growth increased with concentration of the supplement to an optimum at 0.12M Na-acetate. This carbon source was consumed completely within 10d of incubation. Higher concentrations inhibited the growth of C. vulgaris. The microalgal populations under heterotrophic growth conditions were one level of magnitude higher than that under autotrophic growth conditions that served as a comparison. No growth occurred in the dark in the absence of a carbon source. Na-acetate was superior to d-glucose. In municipal wastewater, when Na-acetate or d-glucose was added, C. vulgaris significantly enhanced ammonium removal under heterotrophic conditions, and its capacity was equal to ammonium removal under autotrophic growth conditions. This study showed that sterilized wastewater can be treated by C. vulgaris under heterotrophic conditions if supplemented with the appropriate organic carbon source for the microalgae. © 2010 Phycological Society of America.

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.

Lopez B.R.,Environmental Microbiology Group | Bashan Y.,Environmental Microbiology Group | Bashan Y.,Bashan Foundation | Bacilio M.,Environmental Microbiology Group
Archives of Microbiology | Year: 2011

The small cactus Mammillaria fraileana is a pioneer rock-colonizing plant harboring endophytic bacteria with the potential for nitrogen fixation and rock weathering (phosphate solubilization and rock degradation). In seeds, only a combination of culture-independent methods, such as fluorescence in situ hybridization, scanning electron microscopy, and fluorescence vital staining, detected significant amounts of non-culturable, but living, endophytic bacteria distributed underneath the membrane covering the embryo, in the undifferentiated tissue of the embryo, and in the vascular tissue. Large populations of culturable endophytic bacteria were detected in stems and roots of wild plants colonizing rocks in the southern Sonoran Desert, but not in seeds. Among 14 endophytic bacterial isolates found in roots, four isolates were identified by full sequencing of their 16S rRNA gene. In vitro tests indicated that Azotobacter vinelandii M2Per is a potent nitrogen fixer. Solubilization of inorganic phosphate was exhibited by Pseudomonas putida M5TSA, Enterobacter sakazakii M2PFe, and Bacillus megaterium M1PCa, while A. vinelandii M2Per, P. putida M5TSA, and B. megaterium M1PCa weathered rock by reducing the size of rock particles, probably by changing the pH of the liquid media. Cultivated seedlings of M. fraileana, derived from disinfected seeds and inoculated with endophytic bacteria, showed re-colonization 105 days after inoculation. Their densities decreased from the root toward the stem and apical zones. Functional traits in planta of culturable and non-culturable endophytic bacteria in seeds remain unknown. © 2011 Springer-Verlag.

News Article | April 19, 2016
Site: phys.org

UAB researchers develop new paper-based biological tool. From left to right: Xavier Muñoz Berbel, Núria Vigués, Ferran Pujol and Jordi Mas. On the right, paper matrices with entrapped bacteria and colouring showing samples of different toxicity levels. Researchers of the Environmental Microbiology Group of the UAB Department of Genetics and Microbiology have developed a paper-based biosensor covered with bacteria to detect water toxicity. This is an innovative, simple and inexpensive biological tool that can detect several contaminants and can be easy to use in economically restricted areas, such as developing countries. The paper was recently published in Analytica Chimica Acta. The detection of toxic contaminants is an essential element of analysis and control of water quality, something very needed in an increasingly urbanised and industrialised world. Chemical analysis techniques are of great utility in determining specific substances, but are limited when used to analyse complex samples which can contain multiple contaminants. In this sense, the use of biosensors is appropriate, in which they measure the effect samples have on a biological element, such as enzymes or proteins, or on a vital parameter of an indicator organism. "The innovation provided by our sensor is based on the use of absorbent paper matrices with entrapped bacteria with the aim of conducting colorimetric measures of toxicity", explains UAB researcher Ferran Pujol, who conducted this study as part of his PhD thesis. The detection technique proposed and validated by researchers is quick and simple. In fact, its mechanisms is similar to that of paper strips used to measure the pH of water. The samples analysed are added to the matrices together with the colouring agent ferrocyanide, which ranges from yellow to transparent when breathed in by the microorganisms. The paper changes colours according to the intensity of the cell metabolism of the bacteria, inversely proportional to the toxicity of the sample: the more the colour changes, the less contamination detected. These changes can be measured with optical techniques, by analysing the image or with the naked eye. In this work, researchers used Escherichia coli (E. coli) cells were used as model bacteria. The bioassay, which researchers have applied a patent for, detects any contaminant which can be toxic for the microorganisms after some 15 to 30 minutes of coming into contact with the cells (time taken to conduct the test), such as heavy metals or hydrocarbons such as petroleum or benzene. The technique can be applied to both natural waters and urban and industrial wastewater. Using a material such as paper and without the need of complex tools makes this biosensor a simple and inexpensive technique which can be used to detect toxicity in contexts of economic restrictions or in developing countries, researchers indicate. Explore further: Chemist develops biosensor that changes color when bacteria are present in water samples More information: F. Pujol-Vila et al. Paper-based chromatic toxicity bioassay by analysis of bacterial ferricyanide reduction, Analytica Chimica Acta (2016). DOI: 10.1016/j.aca.2016.01.006

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