The discovery of novel biocontrol agents requires the continuous scrutiny of native microorganisms to ensure that they will be useful on a regional scale. The goal of the present work was to discover novel antagonistic bacteria against Fusarium oxysporum ff. spp. lycopersici race 3 ( Fol R3) and radicis-lycopersici ( Forl ) causing Fusarium wilt disease and Fusarium crown and root rot of tomatoes, respectively. High-throughput liquid antagonism screening of 1,875 rhizospheric bacterial strains followed by dual confrontation assays in 96-well plates was used to select bacteria exhibiting > 50% fungal growth inhibition. In a second dual confrontation assay in 10-cm Petri dishes, bacteria showing > 20% Fol R3 or Forl growth inhibition were further screened using a blood hemolysis test. After discarding β-hemolytic bacteria, a seedling antagonistic assay was performed to select five potential antagonists. A phylogenetic analysis of 16S rRNA identified one strain as Acinetobacter calcoaceticus ( Ac DB3) and four strains as members of the genus Bacillus ( B. amyloliquefaciens Ba MA26, Bacillus siamensis Bsi DA2, B. subtilis Bs TA16 and B. thuringiensis Bt MB9). Greenhouse assays demonstrated that Bs TA16 and Ac DB3 were the most promising antagonists against Fol R3 and Forl , respectively. Pathogen biocontrol and growth promotion mechanisms used by these bacteria include the production of siderophores, biofilm, proteases, endoglucanases and indole acetic acid, and phosphate solubilization. These five bacteria exerted differential responses on pathogen control depending on the tomato hybrid, and on the growth stage of tomatoes. We report for the first time the use of an Acinetobacter calcoaceticus isolate ( Ac DB3) to control Forl in tomato under greenhouse conditions.

No abstract

No abstract

BACKGROUND Recently, wastewater effluents from animal farms have been treated using microalgae for the removal of organic and inorganic compounds. Swine wastewater (SW) and wastewater treated by anaerobic digestion (TW) were used as culture media for a wild strain of microalga, Chlorella sp. (Chlorophyta), previously isolated for our research group. This was cultivated under laboratory conditions in a batch culture, and then inoculated in a cascade thin‐layer reactor under outdoor conditions. The kinetic behavior, nutrient removal (COD, NH4+‐N, NO3−‐N and PO34−‐P) efficiency and biochemical composition of the microalga biomass were evaluated. RESULTS SW supported the highest growth (339 × 106 cells mL−1 and μ = 0.42 d−1) and the maximal removal of COD (91%), nitrates (87%), ammonium (45%) and phosphate (70%) in a batch culture. Whereas, in continuous cultivation, an adequate operation was achieved at temperatures up to 42 °C, with removals greater than 80% of COD, 70% of nitrates, 90% of ammonium and 60% of phosphates. Also, the produced biomass achieved the highest content of proteins (386 mg g−1 dry weight), carbohydrates (291.49 mg g−1 dry weight) and saturated and monounsaturated fatty acids, reaching 74.76% of total fatty acids. CONCLUSIONS The SW medium showed greater growth of Chlorella than TW using the outdoor thin‐layer cascade reactor. This is an opportunity to use wastewater as nutrient to obtain biomass enriched in compounds with various possibilities for application. © 2019 Society of Chemical Industry

No abstract