Drought is a major limiting factor of crop productivity worldwide and its incidence is predicted to increase under climate change. Drought adaptation of cool-season grasses is thus a major challenge to secure the agricultural productivity under current and future climate conditions. Endophytes are non-pathogenic plant-associated bacteria that can play an important role in conferring resistance and improving plant tolerance to drought. In this study, the effect of inoculation of the bacterial endophyte Bacillus subtilis strain B26 on growth, water status, photosynthetic activity and metabolism of timothy (Phleum pratense L.) subjected to drought stress was investigated under controlled conditions. Under both drought-stress and non-stressed conditions, strain B26 successfully colonized the internal tissues of timothy and had a positive impact on plant growth. Exposure of inoculated plant to a 8-week drought-stress led to significant increase in shoot and root biomass by 26.6 and 63.8%, and in photosynthesis and stomatal conductance by 55.2 and 214.9% respectively, compared to non-inoculated plants grown under similar conditions. There was a significant effect of the endophyte on plant metabolism; higher levels of several sugars, notably sucrose and fructans and an increase of key amino acids such as, asparagine, glutamic acid and glutamine were recorded in shoots and roots of colonized plants compared to non-colonized ones. The accumulation of the non-protein amino acid GABA in shoots of stressed plants and in roots of stressed and unstressed plants was increased in the presence of the endophyte. Taken together, our results indicate that B. subtilis B26 improves timothy growth under drought stress through the modification of osmolyte accumulation in roots and shoots. These results will contribute to the development of a microbial agent to improve the yield of grass species including forage crops and cereals exposed to environmental stresses.

Plant growth-promoting bacteria (PGB) induce positive effects in plants, for instance, increased growth and reduced abiotic stresses susceptibility. The mechanisms by which these bacteria impact the host plant are numerous, diverse and often specific. Here, we studied the agronomical, molecular and biochemical effects of the endophytic PGB Bacillus subtilis B26 on the full life cycle of Brachypodium distachyon Bd21, an established model species for functional genomics in cereal crops and temperate grasses. Inoculation of Brachypodium with B. subtilis strain B26 increased root and shoot weights, accelerated growth rate and seed yield as compared to control plants. B. subtilis strain B26 efficiently colonized the plant and was recovered from roots, stems and blades as well as seeds of Brachypodium, indicating that the bacterium is able to migrate, spread systemically inside the plant, establish itself in the aerial plant tissues and organs, and is vertically transmitted to seeds. The presence of B. subtilis strain B26 in the seed led to systemic colonization of the next generation of Brachypodium plants. Inoculated Brachypodium seedlings and mature plants exposed to acute and chronic drought stress minimized the phenotypic effect of drought compared to plants not harbouring the bacterium. Protection from the inhibitory effects of drought by the bacterium was linked to upregulation of the drought-response genes, DREB2B-like, DHN3-like and LEA-14-A-like and modulation of the DNA methylation genes, MET1B-like, CMT3-like and DRM2-like, that regulate the process. Additionally, total soluble sugars and starch contents increased in stressed inoculated plants, a biochemical indication of drought tolerance. In conclusion, we show a single inoculation of Brachypodium with a PGB affected the whole growth cycle of the plant, accelerating its growth rates, shortening its vegetative period, and alleviating drought stress effects. These effects are relevant to grasses and cereal crops.

No abstract

Spore-forming pathogenic bacteria, such as Clostridium difficile, are associated with nosocomial infection, leading to the increased use of sporicidal disinfectants, which impacts socioeconomic costs. However, C. difficile can be prevented using microorganisms such as Bacillus amyloliquefaciens, a prophylactic agent that has been proven to be effective against it in recent tests or it can be controlled by sporicidal disinfectants. These disinfectants against spores should be evaluated according to a known and recommended standard. Unfortunately, some newly manufactured disinfectants like Bioxy products have not yet been tested. ASTM E2197-11 is a standard test that uses stainless steel disks (1 cm in diameter) as carriers, and the performance of the test formulation is calculated by comparing the number of viable test organisms to that on the control carriers. Surface tests are preferable for evaluating disinfectants with sporicidal effects on hard surfaces. This study applies improved methods, based on the ASTM E2197-11 standard, for evaluating and comparing the sporicidal efficacies of several disinfectants against spores of C. difficile and B. amyloliquefaciens, which are used as the test organisms. With the improved method, all spores were recovered through vortexing and membrane filtration. The results show that chlorine-based products are effective in 5 min and Bioxy products at 5% w/v are effective in 10 min. Although Bioxy products may take longer to prove their effectiveness, their non-harmful effects to hospital surfaces and people have been well established in the literature.

Plant growth promoting bacteria (PGPB) represent a wide variety of soil and endophytic bacteria that have the ability to promote growth or to protect against stress of its host plant. Encapsulation of PGPB, using vegetable proteins instead of animal or petroleum-derived polymers, is a new technology to crop production and protection. Pea protein isolates (PPI) alginate capsules were synthesized and used for the protection and delivery of Bacillus subtilis B26 as plant inoculum for agricultural applications. The capsules provided a protective site to B26 strain allowing good survival, between 45 to 50%, after 112 days of incubation at different temperatures. The loaded microcapsules sustained a large population of bacteria, up to 8.3 LogCFUg -1 of soil after 3 weeks post application. The soil concentration stabilized to 7.3 Log CFUg -1 after 8 weeks post application. Capsules loaded with B26, once incorporated in the soil, successfully colonized test plants, and cell numbers inside plant tissues were sustained at 3.5 and 3.3 Log 7.3 CFUg -1 in the root and the shoot respectively. These results indicate that PPIalginate technology represents a good choice for commercial application of B. subtilis B26 in agriculture.Citation: Gagné-Bourque F, Meng Xu, Dumont MJ, Jabaji S (2015) Materials and Methods Maintenance and preparation of B. subtilis B26 inoculumThe B.subtilis strain B26, previously isolated from switchgrass and fully characterized [15], was maintained on Luria Broth (LB) (1.0% Tryptone, 0.5% Yeast Extract, 1.0% NaCl) with glycerol (25% final volume) and stored at-80°C. B. subtilis B26 was revived on LBA (1.5% Agar) plates. The inoculum was prepared by placing a single colony of B. subtilis B26 in 250 mL of LB and incubated for 18 h at 37°C until an OD600 of 0.7, representing colony forming units (CFU) of 3.38 × 10 8 / mL was reached on a shaker at 250 rpm to the mid-log phase, pelleted by centrifugation, washed and suspended in sterile distilled water. Preparation of alginate capsules and microencapsulationPea protein isolates (PPI) (Propulse N™) containing 81.73% protein, <10.3% sugars, <0.7% starch, <3.4% moisture, <0.5% fat, <4.0% ash was obtained from Nutri-Pea Ltd. (Portage la Prairie, MB, Canada). Alginic acid sodium salt with low viscosity (viscosity of 1% aq. solution: <300cps) was purchased from MP biomedicals (Solon, OH, USA). Calcium chloride (CaCl 2 ) dehydrate, hydrochloric acid (HCl) and dimethyl sulfoxide (DMSO) were purchased from Fisher Scientific (Fair Lawn, NJ). Sodium hydroxide was purchased from EMD (Damstadt, Germany). Tryptone, Yeast Extract, NaCl, and Agar were purchased from Difco (Franklin Lakes, NJ, USA). Ammonium sulphate, Potassium phosphate dibasic trihydrate, monopotassium phosphate, trisodium citrate and magnesium sulfate heptahydrate were purchased from Sigma-Aldrich (Co., St. Louis, MO). Glycerol was purchased from ThermoFisher Scientific (Waltham, MA). The qPCR SYBRII master mix and the ROX were purchased from Agilent Technologies (Morrisville, NC, USA) while B...