Antagonistic activity of endophytic actinobacteria from native potatoes (Solanum tuberosum subsp. tuberosum L.) against Pectobacterium carotovorum subsp. carotovorum and Pectobacterium atrosepticum.

BACKGROUND: The native potatoes (Solanum tuberosum subsp. tuberosum L.) grown in Chile (Chiloé) represent a new, unexplored source of endophytes to find potential biological control agents for the prevention of bacterial diseases, like blackleg and soft rot, in potato crops. RESULT: The objective of this study was the selection of endophytic actinobacteria from native potatoes for antagonistic activity against Pectobacterium carotovorum subsp. carotovorum and Pectobacterium atrosepticum, and their potential to suppress tissue maceration symptoms in potato tubers. This potential was determined through the quorum quenching activity using a Chromobacterium violaceaum ATCC 12472 Wild type (WT) bioassay and its colonization behavior of the potato plant root system (S. tuberosum) by means of the Double labeling of oligonucleotide probes for fluorescence in situ hybridization (DOPE-FISH) targeting technique. The results showed that although Streptomyces sp. TP199 and Streptomyces sp. A2R31 were able to inhibit the growth of the pathogens, only the Streptomyces sp. TP199 isolate inhibited Pectobacterium sp. growth and diminished tissue maceration in tubers (p ≤ 0.05). Streptomyces sp. TP199 had metal-dependent acyl homoserine lactones (AHL) quorum quenching activity in vitro and was able to colonize the root endosphere 10 days after inoculation. CONCLUSIONS: We concluded that native potatoes from southern Chile possess endophyte actinobacteria that are potential agents for the disease management of soft rot and blackleg.

Drimendiol, a drimane sesquiterpene with quorum sensing inhibition activity.

Quorum sensing (QS) is a regulatory mechanism that enables bacteria to make collective decisions such as an increase in virulence factors and biofilm production. Inhibitors of QS are important research tools in the discovery of new potential anti-bacterial agents. Polygodial, drimenol and drimendiol are drimane sesquiterpenoids isolated from Drimys winteri, a Chilean native tree. Their QS activity, when tested on Chromobacterium violaceum ATCC 12472, showed that drimendiol is an inhibitor of QS, decreasing violaceine production in C violaceum and decreasing biofilm formation of Pseudomonas syringae strains. Consequently it increased the biocide effects of CuSO4 on biofilms of P. syringae.

Anaerobic treatment of low-strength synthetic TCF effluents and biomass adhesion in fixed-bed systems.

Toxicity effects produced by kraft mill effluents are due to the productive process. New bleaching processes have been proposed (e.g. total chlorine free, TCF) to reduce the production of toxic chlorine compounds. In the TCF processes large amounts of chelating compounds like the ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DPTA) are used. The aim of this work is to research the feasibility of the degradation of low-strength synthetic TCF effluents in a anaerobic filter reactor (AF) and the biomass adhesion. The effects on the operation of the AF at different EDTA loading rates were tested in the range from 0.07 to 0.51 g EDTA l(-1) days(-1). The maximum EDTA removal percentage achieved was of 27%. Acute toxicity (measured as 24 h-LC(50)) with Daphnia magna was reduced from 14.23 to 54.53% before and after anaerobic treatment, respectively. Observations of biomass samples from the AF under the scanning microscope verified the attached biomass.