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

• Published in: PloS one 2020-10, Vol.15 (10), p.e0240545
• Main Authors: Cesa-Luna, Catherine, Baez, Antonino, Aguayo-Acosta, Alberto, Llano-Villarreal, Roberto Carlos, Juárez-González, Víctor Rivelino, Gaytán, Paul, Bustillos-Cristales, María Del Rocío, Rivera-Urbalejo, América, Muñoz-Rojas, Jesús, Quintero-Hernández, Verónica
• Format: Article
• Language: English
• Subjects: Agar; Anti-Infective Agents - isolation & purification; Anti-Infective Agents - metabolism; Anti-Infective Agents - therapeutic use; Anti-Infective Agents - toxicity; Antibacterial agents; Antibiosis; Antibiotics; Antiinfectives and antibacterials; Antimicrobial agents; Antimicrobial peptides; Bacteria; Bacterial infections; Bacterial Infections - drug therapy; Bacterial Infections - microbiology; Bacteriocins; Bacteriocins - isolation & purification; Bacteriocins - metabolism; Bacteriocins - therapeutic use; Bacteriocins - toxicity; Biology and Life Sciences; Clinical isolates; Computer and Information Sciences; Corn; Deoxyribonucleic acid; DNA; DNA topoisomerase; Drug resistance; Drug Resistance, Multiple, Bacterial - drug effects; Ecology; Ecology and Environmental Sciences; Flowers & plants; Fluorescence; Funding; Fungi; Gene sequencing; Genes; Infectious diseases; Klebsiella; Leaching; Medicine and Health Sciences; Microbial Sensitivity Tests; Microbiological research; Microbiological synthesis; Microorganisms; Molecular weight; Multidrug resistance; Mycoses - drug therapy; Mycoses - microbiology; Pathogenic microorganisms; Pathogens; Phylogenetics; Phylogeny; Physiological aspects; Plant Diseases - prevention & control; Production processes; Pseudomonas; Pseudomonas - metabolism; Pseudomonas protegens; Research and Analysis Methods; Rhizosphere; RpoB protein; rRNA 16S; Streptococcus; Testing; Thermal stability; Tuberculosis; Ultrafiltration; Zea mays - microbiology
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0240545

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.