Secondary Metabolites Production and Plant Growth Promotion by Pseudomonas chlororaphis and P. aurantiaca Strains Isolated from Cactus, Cotton, and Para Grass

Abstract

Fluorescent pseudomonads have been isolated from halophytes, mesophytes, and xerophytes of Pakistan. Among these, eight isolates, GS-1, GS-3, GS-4, GS-6, GS-7, FS-2 (cactus), ARS-38 (cotton), and RP-4 (para grass), showed antifungal activity and were selected for detailed study. Based on biochemical tests and 16S rRNA gene sequences, these were identified as strains of subsp. and . Secondary metabolites of these strains were analyzed by LC-MS. Phenazine-1-carboxylic acid (PCA), 2-hydroxy-phenazine, Cyclic Lipopeptide (white line-inducing principle (WLIP)), and lahorenoic acid A were detected in variable amounts in these strains. PB-St2 was used as a reference as it is known for the production of these compounds. The and genes were amplified to assure that production of these compounds is not an artifact. Indole acetic acid production was confirmed and quantified by HPLC. HCN and siderophore production by all strains was observed by plate assays. These strains did not solubilize phosphate, but five strains were positive for zinc solubilization. Wheat seedlings were inoculated with these strains to observe their effect on plant growth. strains PB-St2 and GS-6 and RP-4 significantly increased both root and shoot dry weights, as compared with uninoculated plants. However, strains FS-2 and ARS-38 significantly increased root and shoot dry weights, respectively. All strains except PB-St2 and ARS-38 significantly increased the root length. This is the first report of the isolation of from cotton and cactus, from para grass, WLIP and lahorenoic acid A production by, and zinc solubilization by and.

Impact of soil salinity on the cowpea nodule-microbiome and the isolation of halotolerant PGPR strains to promote plant growth under salinity stress

“…Our study also showed that isolates belonging to Pseudomonas , Paenibacillus, and Bacillus produced antifungal compounds against different fungal pathogens, including Fusarium oxysporum, Fusarium solani, Curvularia sp. Both Pseudomonas and Bacillus have been reported as growth inhibitors for different fungal pathogens and provide protection against a number of plant diseases (Ali et al 2015; Shahid et al 2017; Khan et al 2017). More than one-half of the isolated strains especially members of Paenibacillus, Bacillus, Pseudomonas and Enterobacter , exhibited cellulase, chitinase, amylase, and protease activity, and a large number of PGPR strains ( Pseudomonas , Enterobacter, Rhizobium and Bacillus ) promote plant growth and suppress plant diseases by producing siderophores, hydrolytic enzymes, and HCN (Mehnaz et al 2010; Chen et al 2013; Khan et al 2018).…”

A decade of understanding secondary metabolism in Pseudomonas spp. for sustainable agriculture and pharmaceutical applications

“…P. aurantiaca strain PB-St2 showed the production of three novel ortho-dialkyl substituted aromatic acids: Lahorenoic acid A, B and C, with limited antibacterial activities. Later on, P. chlororaphis strain RP-4 also exhibited the production of Lahorenoic acid A, indicating the higher biosynthetic capacity of this genus than anticipated previously (Shahid et al 2017). Diketopiperazines (DKPs) constitute the group of cyclodipeptides (CDPs) and are produced by many species of Pseudomonas.…”

“…aurantiaca gained a lot of attention being prolific producers of antagonistic secondary metabolites. Plant-commensal strains of P. chlororaphis group and their effective role as biocontrol agents distinguished them as microbes with significant effects on agricultural productivity (Al-Hinai et al 2010;Shanmugaiah et al 2010;Shahid et al 2017). To date, 28 genome sequences of strains of P. chlororaphis group are publically available from diverse hosts and have been reported for their effective suppression and inhibition of important plant pathogens.…”

“…In addition, many species of pseudomonads are also known for the production of iron-scavenging siderophores, extracellular hydrolytic enzymes, volatile organic compounds and plant growth promoting hormones. Many of these compounds are generated through complex metabolic pathways and are involved in competitive suppression and inhibition of plant pathogens (Al-Hinai et al 2010;Shanmugaiah et al 2010;Shahid et al 2017). Earlier, the research interest was to identify the secondary metabolites with antifungal and antibacterial activities.…”

“…aurantiaca, subsp. chlororaphis and P. pyrrocinia have been demonstrated in-vitro and in-vivo for their antagonism against bacterial and fungal plant pathogens (Al-Hinai et al 2010;Shanmugaiah et al 2010;Shahid et al 2017).…”