Ochrobactrum sp. Pv2Z2 exhibits multiple traits of plant growth promotion, biodegradation and N-acyl-homoserine-lactone quorum sensing

Abstract

Rhizosphere bacteria play a vital role in plant growth, pathogen control, biodegradation and rhizosphere signaling. A motile, rod-shaped bacterium, Pv2Z2, isolated from the nodules of the common bean grown in Tanzanian soil was characterized using a polyphasic approach. The traits assessed included the production of indole-3-acetic acid and N-acyl homoserine lactone (AHL) molecules, solubilization of insoluble phosphate and zinc compounds and biodegradation of a number of toxic compounds. The 16S rRNA sequence of Pv2Z2 (EU399793) showed 99 % homology to Ochrobactrum anthropi isolates (Accession no. AJ867292, AJ867291, AJ867290) from soil samples of wheat root. Phylogenetic analysis showed relatedness to nodulating strain Ochrobactrum cytisi rather than to the clinical/pathogenic type strain of O. anthropi. Moreover, it showed unique fingerprints in the randomly amplified polymorphic DNA (RAPD) and two primers-RAPD assays which were different from those of the pathogenic type strain of O. anthropi. The bacterium produced 6.68 μg/mL -1 indoleacetic acid in the presence of tryptophan, released 25.7 μg/mL -1 phosphorus from inorganic tri-calcium phosphate in the Pikoviskaya's medium and solubilized zinc sulphate and zinc oxide in the LG1 medium. The production of AHLs (e.g. 3O-C7-HSL, 3OH-C7-HSL) was detected with biosensor strains CV026 using reverse phase thin layer chromatography. The bacterium was able to grow in minimal salt medium supplemented with 100 mg/L each of phenol, 2-bromophenol, 2,4-diamino phenol hydrochloride, 3,4-dimethoxy benzyl alcohol and 4-methoxy benzyl alcohol. Phenol degradation was recorded up to a level of 94 % within 12 days. Inoculation of common bean plants resulted in a significant increase in plant height, fresh/dry weight and nitrogen uptake as compared to non-inoculated plants. The data suggest that the plant growth-promoting and biodegradation potential of this bacterium may be exploited on a large scale. The capacity to produce AHL molecules by members of the Ochrobactrum genus has not been previously reported and needs to be explored in detail.

Isolation and characterization of plant growth-promoting rhizobacteria from wheat rhizosphere and their effect on plant growth promotion

“…In addition to some other parameters positively influenced the growth of plant, auxin production by the isolates is proposed as a major means of attaining growth promotion (Deepa et al, 2010). Furthermore, the inoculation of PGPR having multi-functional traits is better than having single traits (Imran et al, 2014). IAA is involved in root initiation, cell division, cell enlargement, increases root surface area, and consequent access to soil nutrients by enhanced formation of roots (Dey et al, 2004; Gray and Smith, 2005).…”

Isolation and Characterization of Phosphorus Solubilizing Bacteria With Multiple Phosphorus Sources Utilizing Capability and Their Potential for Lead Immobilization in Soil

“…After four rounds of acclimation, we gained 18 PSB belonging to eight genera including Acinetobacter, Arthrobacter, Bacillus, Cupriavidus, Massilia, Ochrobactrum, Pseudomonas, and Stenotrophomonas. Previous literatures have reported that some PSB belong to these genera (Yu et al, 2011;Imran et al, 2014;Liu et al, 2014;Silva et al, 2017), but most studies have not reported PSB possessing multiple P sources utilizing abilities. For instance, strain gp-1 identified as Acinetobacter genus in our study presented good performance for solubilizing Ca 3 (PO 4 ) 2 , FePO 4 , and AlPO 4 , and for digesting phytate, with corresponding P solubilizing levels were 250.77, 46.10, 81.99, and 7.91 mg/L PO 4 3− -P, respectively.…”

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“…In addition, there is a research on Ochrobactrum sp. Pv2Z2 belonging to Ochrobactrum sp., however phylogenetic analysis showed the relatedness to nodulating strain Ochrobactrum cytisi rather than to the clinical/pathogenic type strain of O. anthropi (Imran et al, 2014). Therefore, our research on Ochrobactrum sp.…”

“…Previously, Ochrobactrum sp. Pv2Z2 was reported to show multiple plant growth-promoting characteristics and biodegradation (Imran et al, 2014), but Figure 1：These seven nitrogen fixing bacteria used in the pot experiment increase the cucumber plant height (A), dry weight (B), and fresh weight (C). Figure 1A shows that the cucumber height treated by NW-3 inoculants is significantly higher than others, increased 16% after inoculation 20 days when compared with CK, followed by N-YM-3, and NW-4 treatment.…”

“…Moreover, the use of Ochrobactrum sp. for phytoremediation of heavy metal or other organic pollutants have also been studied (Imran et al, 2014;Pandey et al, 2013). Previous studies show that Ochrobactrum sp.…”