Growth inhibition of pathogenic microorganisms by Pseudomonas protegens EMM-1 and partial characterization of inhibitory substances

Abstract

The bacterial strain, EMM-1, was isolated from the rhizosphere of red maize ("Rojo Criollo") and identified as Pseudomonas protegens EMM-1 based on phylogenetic analysis of 16S rDNA, rpoB, rpoD, and gyrB gene sequences. We uncovered genes involved in the production of antimicrobial compounds like 2,4-diacetylphloroglucinol (2,4-DAPG), pyoluteorin, and lectin-like bacteriocins. These antimicrobial compounds are also produced by other fluorescent pseudomonads alike P. protegens. Double-layer agar assay showed that P. protegens EMM-1 inhibited the growth of several multidrug-resistant (MDR) bacteria, especially clinical isolates of the genera Klebsiella and β-hemolytic Streptococcus. This strain also displayed inhibitory effects against diverse fungi, such as Aspergillus, Botrytis, and Fusarium. Besides, a crude extract of inhibitory substances secreted into agar was obtained after the cold-leaching process, and physicochemical characterization was performed. The partially purified inhibitory substances produced by P. protegens EMM-1 inhibited the growth of Streptococcus sp. and Microbacterium sp., but no inhibitory effect was noted for other bacterial or fungal strains. The molecular weight determined after ultrafiltration was between 3 and 10 kDa. The inhibitory activity was thermally stable up to 60˚C (but completely lost at 100˚C), and the inhibitory activity remained active in a wide pH range (from 3 to 9). After treatment with a protease from Bacillus licheniformis, the inhibitory activity was decreased by 90%, suggesting the presence of proteic natural compounds. All these findings suggested that P. protegens EMM-1 is a potential source of antimicrobials to be used against pathogens for humans and plants.

Phyto-Beneficial Traits of Rhizosphere Bacteria: In Vitro Exploration of Plant Growth Promoting and Phytopathogen Biocontrol Ability of Selected Strains Isolated from Harsh Environments

“…Many works described P. protegens as an effective antimicrobial agent. Cesa-Luna and collaborators [34] evaluated the ability of P. protegens strain EMM-1 against different fungal species, reporting significant activity against Aspergillus spp. and Fusarium spp.…”

Exploring the Status of an Urban Coral and the Presence of Potential Probiotic Traits in Culturable Bacteria

“…The test isolate was streaked across the agar plates, and V. coralliilyticus was perpendicularly streaked to the test isolate. After 24 h of incubation, the presence of halos indicated the inhibition of growth [67]. The antiQS activity was tested by the ability of the isolate to inhibit the bioluminescence of the biosensor Photobacterium sp.…”

Draft Genome Sequence of Pseudomonas protegens Strain MWU12-2233, Isolated from Wild Cranberry Fruit in Provincetown, Massachusetts

“…Protected wetlands represent an understudied ecosystem that harbors diverse communities of phyllosphere bacteria, including those associated with wild cranberry flowers and fruits ( 1 , 2 ). Some of these bacteria are pseudomonads that produce secondary metabolites with biological activity against fungi and insects ( 3 ), including the plant-growth-promoting and insectivorous bacterium Pseudomonas protegens ( 4 – 7 ), potentially making them a component of the indigenous disease-suppressive microflora. P. protegens MWU12-2233 was isolated in July 2012 from cranberry fruit as part of a culture-dependent survey of bacteria from wild cranberry bogs in the Cape Cod National Seashore, Provincetown, MA (42.070624 N, 70.210548 W).…”