Population densities of indigenous Acidobacteria change in the presence of plant growth promoting rhizobacteria (PGPR) in rhizosphere

Abstract

Rhizosphere microbial community has diverse metabolic capabilities and plays a crucial role in maintaining plant health. Oligotrophic plant growth promoting rhizobacteria (PGPR), along with difficult-to-culture microbial fractions, might be involved synergistically in microbe-microbe and plant-microbe interactions in the rhizosphere. Among the difficult-to-culture microbial fractions, Acidobacteria constitutes the most dominant phylum thriving in rhizospheric soils. We selected effective PGPR for tomato and black gram and studied their effect on population densities of acidobacterial members. Three facultatively oligotrophic PGPR were identified through 16S rRNA gene sequencing as Sphingobacterium sp. (P3), Variovorax sp. (P4), and Roseomonas sp. (A2); the latter being a new report of PGPR. In presence of selected PGPR strains, the changes in population densities of Acidobacteria were monitored in metagenomic DNA extracted from bulk and rhizospheric soils of tomato and black gram using real time qPCR. A gradual increase in equivalent cell numbers of Acidobacteria members was observed over time along with a simultaneous increase in plant growth promotion by test PGPR. We report characterization of three effective PGPR strains and their effects on indigenous, underexplored difficult-to-culture phylum-Acidobacteria. We suggest that putative interactions between these two bacterial groups thriving in rhizospheric soils could be beneficial for plant growth.

Application of Bacillus velezensis NJAU-Z9 Enhanced Plant Growth Associated with Efficient Rhizospheric Colonization Monitored by qPCR with Primers Designed from the Whole Genome Sequence

“…During the pot experiments, B. velezensis strain NJAU-Z9 stably colonized the rhizosphere, and the number present at the mature stage was positively correlated with plant growth. The results were consistent with common growth-promoting effects among numerous PGPR in that a gradual increase in equivalent cell numbers of PGPR detected by qPCR was observed over time, along with a simultaneous increase in plant growth promotion [ 46 ].…”

Heritable associations with microbial communities are essential for necrotrophic pathogen resistance

“…The ubiquity of these species in healthy plants' microbiomes suggests that these taxa may be of general importance and not specific to the confines of our study, though further validation will be necessary to support this. Nevertheless, it supports the hypothesis of a healthy bacterial community increasing resistance to biotic stress in the common sunflower [38][39][40][41][42][43][44] .…”

Recent Understanding of Soil Acidobacteria and Their Ecological Significance: A Critical Review

“…Studies focusing on 16S rRNA genes provide taxonomic status in any bacterial community, while metagenomics can provide both taxonomic and functional profiles of the microbiota. Metagenomic DNA extracted from the environment is often amplified using group or species-specific primers targeting 16S rRNA genes (Kalam et al, 2017a). Metagenomics has facilitated in an apt understanding of the diversity, abundance, genomic make-up, and ecological roles of acidobacterial members in various ecosystems (Tyson et al, 2004;Venter et al, 2004;Parsley et al, 2011).…”