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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

Bashan Y.,Environmental Microbiology Group | Trejo A.,Environmental Microbiology Group | de-Bashan L.E.,Environmental Microbiology Group
Biology and Fertility of Soils

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. Source

de-Bashan L.E.,Environmental Microbiology Group | Hernandez J.-P.,Environmental Microbiology Group | Bashan Y.,Environmental Microbiology Group
Applied Soil Ecology

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. Source

Lopez B.R.,Environmental Microbiology Group | Bashan Y.,Environmental Microbiology Group | Bacilio M.,Environmental Microbiology Group
Archives of Microbiology

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. Source

de-Bashan L.E.,Environmental Microbiology Group | Bashan Y.,Environmental Microbiology Group
Bioresource Technology

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. Source

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