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Auburn, AL, United States

Lopez-Lozano N.E.,Environmental Microbiology Group | Lopez-Lozano N.E.,San Luis Potosi Institute of Scientific Research and Technology | Carcano-Montiel M.G.,Autonomous University of Puebla | Bashan Y.,Environmental Microbiology Group | And 2 more authors.
Plant and Soil | Year: 2016

Background and aims: A major problem in all restoration and rehabilitation projects is to restore the function of the ecosystem. Nitrogen, next to water, is the most limiting factor for productivity of arid terrestrial ecosystems. Methods: We used a successful restored area, completed 10 years earlier, in comparison with an undisturbed scrubland area and a remaining, disturbed area in the southern Sonoran Desert in Baja California, Mexico. We compared the abundance of the nifH gene, estimated by qPCR, potential N2 fixation activity by acetylene reduction assay, and diversity of diazotrophs by denaturing gradient gel electrophoresis in the rhizosphere of the most representative plant species, the cardon cactus and the mesquite used for restoration. Results: The abundance of N2-fixing bacteria in the rhizosphere of cardon growing with mesquite had significantly higher abundance of nifH gene than the rhizosphere of cardon that grew separately. Across all samples, the potential N2 fixation was significantly higher in soil samples from the restored site than samples from the undisturbed and disturbed sites. Conclusions: Successful long-term restoration improved the potential N2 fixation to a level similar to undisturbed lands. Beneficial interactions between cardon and mesquite are a promising venue for desert reforestation by their contribution to improve N2 fixing potential in degraded arid lands and increasing the population of diazotrophs. © 2016 Springer International Publishing Switzerland Source

Pereg L.,University of New England of Australia | de-Bashan L.E.,Environmental Microbiology Group | de-Bashan L.E.,The Bashan Institute of Science | de-Bashan L.E.,Auburn University | And 3 more authors.
Plant and Soil | Year: 2016

Background: Azospirillum spp. are the most studied plant growth-promoting bacteria (PGPB). The genus represents a common model for plant-bacteria interactions. This genus was initially isolated and tested on cereals and was subsequently commercialized. Aims: Despite claims of plant specificity, particularly towards cereals, data over the past 40 years does not appear to substantiate claims of such specificity/affinity of Azospirillum species. Consequently an evaluation of the specificity/affinity of the genus Azospirillum across all plants, in general, and cereals, in particular, was undertaken. Results: Although the majority of studies focused on cereals, Azospirillum spp. increase growth of 113 plant species across 35 botanical families, including 14 species of cereals. Amongst Azospirillum spp. several well studied strains have been effective in several plant species, making these organisms potentially valuable for further study. Conclusions: This review demonstrates that azospirilla are not cereal-specific at the genus and species levels. Azospirillum serves as a general PGPB to every plant species tested so far. Given the paucity of widespread screening, affinity of strains to a plant genotype, cultivar, or plant species cannot be overruled. Definitive conclusions concerning such specificity require molecular and cross-inoculation studies, using various strains of bacteria, and re-isolation after growth of the plants in different plant species. (203 words). © 2015, Springer International Publishing Switzerland. Source

Palacios O.A.,Environmental Microbiology Group | Bashan Y.,Environmental Microbiology Group | Bashan Y.,The Bashan Institute of Science | Bashan Y.,Auburn University | And 5 more authors.
Journal of Applied Phycology | Year: 2015

Thiamine release during synthetic mutualism between Chlorella sorokiniana co-immobilized in alginate beads with the microalgae growth-promoting bacterium Azospirillum brasilense was measured under stress conditions of pH, light intensity, and nitrogen starvation in short-term experiments. Thiamine release in the co-immobilized treatment was significantly higher at acidic pH compared to thiamine released by either microorganism alone. Under slightly alkaline pH, C. sorokiniana released the highest amount of thiamine. At stressful pH 6, the co-immobilized treatment released a higher quantity of thiamine than the sum of thiamine released by either microorganisms when immobilized separately. Release of thiamine by C. sorokiniana alone or co-immobilized was light intensity dependent; with higher the light intensity, more thiamine was released. Extreme light intensity negatively affected growth of the microalgae and release of thiamine. Nitrogen starvation during the first 24 h of culturing negatively affected release of thiamine by both microorganisms, where C. sorokiniana was more severely affected. Partial or continuous nitrogen starvation had similar negative effects on C. sorokiniana, but co-immobilization improved thiamine release. These results indicate that thiamine is released during synthetic mutualism between C. sorokiniana and A. brasilense, and this happens specifically during the alleviation of pH stress in the microalgae. © 2015 Springer Science+Business Media Dordrecht Source

Bashan Y.,Environmental Microbiology Group | Bashan Y.,The Bashan Institute of Science | Bashan Y.,Auburn University | Lopez B.R.,Environmental Microbiology Group | And 5 more authors.
Journal of Applied Phycology | Year: 2015

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. © 2015 Springer Science+Business Media Dordrecht Source

de-Bashan L.E.,The Bashan Institute of Science | de-Bashan L.E.,Auburn University | de-Bashan L.E.,Environmental Microbiology Group | Mayali X.,Lawrence Livermore National Laboratory | And 10 more authors.
Algal Research | Year: 2016

The demonstration of a mutualistic interaction requires evidence of benefits for both partners as well as stability of the association over multiple generations. A synthetic mutualism between the freshwater microalga Chlorella sorokiniana and the soil-derived plant growth-promoting bacterium (PGPB) Azospirillum brasilense was created when both microorganisms were co-immobilized in alginate beads. Using stable isotope enrichment experiments followed by high-resolution secondary ion mass spectrometry (SIMS) imaging of single cells, we demonstrated transfer of carbon and nitrogen compounds between the two partners. Further, using fluorescent in situ hybridization (FISH), mechanical disruption and scanning electron microscopy, we demonstrated the stability of their physical association for a period of 10 days after the aggregated cells were released from the beads. The bacteria significantly enhanced the growth of the microalgae while the microalgae supported growth of the bacteria in a medium where it could not otherwise grow. We propose that this microalga-bacterium association is a true synthetic mutualism independent of co-evolution. © 2016 Elsevier B.V. Source

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