Potential of Burkholderia seminalis TC3.4.2R3 as Biocontrol Agent Against Fusarium oxysporum Evaluated by Mass Spectrometry Imaging.

Species of genus Burkholderia display different interaction profiles in the environment, causing either several diseases in plants and animals or being beneficial to some plants, promoting their growth, and suppressing phytopathogens. Burkholderia spp. also produce many types of biomolecules with antimicrobial activity, which may be commercially used to protect crops of economic interest, mainly against fungal diseases. Herein we have applied matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to investigate secondary metabolites produced by B. seminalis TC3.4.2R3 in monoculture and coculture with plant pathogen Fusarium oxysporum. The siderophore pyochelin and the rhamnolipid Rha-Rha-C15-C14 were detected in wild-type B. seminalis strain, and their productions were found to vary in mutant strains carrying disruptions in gene clusters associated with antimicrobial compounds. Two mycotoxins were detected in F. oxysporum. During coculture with B. seminalis, metabolites probably related to defense mechanisms of these microorganisms were observed in the interspecies interaction zone. Our findings demonstrate the effective application of MALDI-MSI in the detection of bioactive molecules involved in the defense mechanism of B. seminalis, and these findings suggest the potential use of this bacterium in the biocontrol of plant diseases caused by F. oxysporum. Graphical Abstract ᅟ.

High-cell-density poly (3-hydroxybutyrate) production from sucrose using Burkholderia sacchari culture in airlift bioreactor.

Burkholderia sacchari IPT 189 poly (3-hydroxybutyrate) (P3HB) production in airlift bioreactor were investigated in batch and fed-batch culture using sucrose as carbon source. In batch experiments it was observed that during the growth phase B. sacchari IPT 189 might display exponential growth even at very low carbohydrate concentration, as long as NH(4)(+) concentration was above 190 mg l(-1). The onset of accumulation phase took place when NH(4)(+) concentration dropped below this value and continued as long as carbohydrate was in excess, even with dissolved oxygen concentration at 0.0% of air saturation. In the fed-batch experiments, nitrogen limitation was used to induce P3HB biosynthesis in a two-phase process. In the first phase, an initial batch followed by a limited sucrose fed regime led to a growth with low-P3HB-content (less than 13%) and up to 60 g l(-1) of biomass concentration in c.a. 25 h. In the second phase, nitrogen concentration limitation induced P3HB accumulation up to 42%, raising the biomass concentration to c.a. 150 g l(-1). Calculated parameters for the experiments were P3HB productivity=1.7 gl(-1) h(-1) and P3HB yield factor from sucrose=0.22 g g(-1).

Burkholderia tropica sp. nov., a novel nitrogen-fixing, plant-associated bacterium.

In an ecological survey of nitrogen-fixing bacteria isolated from the rhizosphere and as endophytes of sugarcane, maize and teosinte plants in Brazil, Mexico and South Africa, a new phylogenetically homogeneous group of N(2)-fixing bacteria was identified within the genus Burkholderia. This polyphasic taxonomic study included microscopic and colony morphology, API 20NE tests and growth on different culture media at different pH and temperatures, as well as carbon source assimilation tests and whole-cell protein pattern analysis. Analysis of 16S rRNA gene sequences showed 99.2-99.9 % similarity within the novel species and 97.2 % similarity to the closest related species, Burkholderia sacchari. The novel species was composed of four distinct amplified 16S rDNA restriction analysis groups. The DNA-DNA reassociation values within the novel species were greater than 70 % and less than 42 % for the closest related species, B. sacchari. Based on these results and on many phenotypic characteristics, a novel N(2)-fixing species is proposed for the genus Burkholderia, Burkholderia tropica sp. nov., with the type strain Ppe8(T) (=ATCC BAA-831(T)=LMG 22274(T)=DSM 15359(T)). B. tropica was isolated from plants grown in geographical regions with climates ranging from temperate subhumid to hot humid.