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In a 338-d microcosm incubation experiment, greenhouse gas emissions (GHG) and bacterial diversity were studied in a clayey soil amended with 5% (w/w) biochar in the presence or absence of 4% (w/w) peat- and shrimp-based compost used as an additional C source. Two maple biochars produced at 400 °C (M400) or 700 °C (M700) and pine chips produced at 700 °C (P700) were tested. In comparison with soil supplemented or not with compost, the addition of any biochar resulted in lower total cumulative N2O emission (90% to 97%). The low porosity of M400 and M700 increased soil anaerobic conditions and resulted in higher total cumulative CH4 emission compared to the other soil treatments. In addition, the lowest total cumulative CO2 emission was observed with M700, probably due to its low-priming effect on native soil C decomposition. In all treatments, compost addition had the highest impact on both soil bacterial richness and community composition, particularly on bacteria of the class Anaerolineae. At day 338, results showed that modification of soil properties by maple biochars reduced bacterial diversity and induced shifts in the taxonomic composition of their community. In fact, heterotrophic bacteria involved in denitrification, such as genera Haliangium, Hyphomicrobium, Opititus, and Pedomicrobium, increased in abundance in response to the amendment with maple biochars. We conclude that the nature of biochar feedstock can impact soil bacterial diversity by changing soil physicochemical properties, thus influencing C dynamics, porosity, and pH, and by mitigating total cumulative GHG emissions. [ABSTRACT FROM AUTHOR]

Four phosphate rock-solubilizing bacteria (PRSB) (Asaia lannensis Vb1, Pseudomonas sp. Vr14, Rahnella sp. Sr24, and Pantoea sp. Vr25) isolated from the mycorrhizosphere of maize were evaluated as inoculants, individually or in different combinations, together with Rhizophagus irregularis DAOM 197198, under greenhouse conditions. To create an effective bacterial mix for P solubilization and growth promotion, parameters such as the ability of the strains (individually or in mixture) to mobilize phosphate rock (PR), their biocompatibility, and their capacity for biofilm formation over PR particles and root colonization were tested. Accompanying PR solubilization, the bacteria produced organic acids and reduced the pH of the medium, produced exopolysaccharides, and had variable capacity to colonize the roots of maize plantlets. In low-phosphorus soil amendment with PR, all strains, regardless of their capacity to solubilize PR, increased dry weight, nutrient (N, P, and K) uptake, and the percentage of indigenous arbuscular mycorrhizae (iAM) root colonization in maize plants, compared to the non-inoculated control. However, mixed inoculation of the strains showed significantly better results. Addition of Rhizophagus irregularis resulted in further growth stimulation. Overall results showed that two combinations—Rahnella sp. Sr24 + Pantoea sp. Vr25 + R. irregularis, and Pantoea sp. Vr25 + Pseudomonas sp. Vr14 + R. irregularis—were better inoculants. We concluded that an effective PRSB combination of biocompatible strains with capacity for PR solubilization, successful biofilm formation, effective root colonization, different growth promotion traits, and the addition of AM has potential as inoculants for more sustainable agriculture in low-phosphorus soils amended with low-reactivity PR. [ABSTRACT FROM AUTHOR]

However, in 1998, Professor Bashan proposed two new terms for general scientific use that would seem to encompass all the plant beneficial bacteria: "biocontrol plant growth-promoting bacteria" (Biocontrol-PGPB) and "plant growth-promoting bacteria" (PGPB) (Bashan and Holguin [4]). In 1986, Professor Bashan developed an alginate-based encapsulated inoculants of I Azospirillum brasilense i (Bashan [2]); that was the start point of the use of synthetic inoculants as an alternative to the delivery of PGPB in the field. Work on plant-microorganisms interaction of arid ecosystems Prof. Bashan contributed significatively to the knowledge of the interactions between microorganisms and plants in the desert. 10.1007/s00203-011-0695-8 21 Lopez BR, Tinoco-Ojanguren C, Bacilio M, Mendoza A, Bashan Y. Endophytic bacteria of the rock-dwelling cactus Mammillaria fraileana affect plant growth and mobilization of elements from rocks. [Extracted from the article]