Profiling of antimicrobial metabolites of plant growth promoting spp. isolated from different plant hosts.

UNLABELLED

In this study, nine strains of and , and two isolates of sp: At1RP4 and RS-1, were characterized for the in-vitro production of secondary metabolites in LB, DMB, and King's B media, and of the genes responsible for the production of antagonistic metabolites. Based on 16S rRNA gene sequence, isolates At1RP4 and RS-1 were identified as strains of and . Five phenazine derivatives comprising phenazine, phenazine-1-carboxylic acid (PCA), 2-hydroxyphenazine-1-carboxylic acid (2-OH-Phz-1-COOH), phenazine-1,6-dicarboxylic acid (Phz-1,6-di-COOH), and 2-hydroxyphenazine (2-OH-Phz) were produced by all strains in all three culture media including DMB, King's B and LB. However, 2,8-dihydroxyphenazine, 6-methylphenazine-1-carboxylic acid, pyrrolnitrin, and the -dialkylaromatic acids, were produced by the and strains. In addition, all strains produced 2-acetamidophenol, pyochelin, and diketopiperazine derivatives in variable amounts in all three culture media used. Highest levels of quorum-sensing signal molecules including PQS, 2-Octyl-3-hydroxy-4(1H)-quinolone, and hexahydro-quinoxaline-1,4-dioxide were recorded for At1RP4. Moreover, all strains produced volatile hydrogen cyanide (0.95-6.68 µg/L) and the phytohormone indole-3-acetic acid (0.42-13.9 µM). Production of extracellular lipase and protease was recorded in all pseudomonads, whereas, cellulase production and phosphate solubilization were variable. Genes for hydrogen cyanide and phenazine-1-carboxylic acid were detected in all eleven strains while the gene for pyrrolnitrin biosynthesis was amplified in and strains. Comparative metabolomic analysis provided detailed insights about the strain-specific metabolites in pseudomonads, and their pseudo-relative quantification in different bacterial growth media to be used as single-strain biofertilizer and biocontrol inoculums.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-020-02585-8.