Plantibacter flavus, Curtobacterium herbarum, Paenibacillus taichungensis, and Rhizobium selenitireducens Endophytes Provide Host-Specific Growth Promotion of Arabidopsis thaliana, Basil, Lettuce, and Bok Choy Plants

Abstract

A collection of bacterial endophytes isolated from stem tissues of plants growing in soils highly contaminated with petroleum hydrocarbons were screened for plant growth-promoting capabilities. Twenty-seven endophytic isolates significantly improved the growth of Arabidopsis thaliana plants in comparison to that of uninoculated control plants. The five most beneficial isolates, one strain each of Curtobacterium herbarum, Paenibacillus taichungensis, and Rhizobium selenitireducens and two strains of Plantibacter flavus were further examined for growth promotion in Arabidopsis, lettuce, basil, and bok choy plants. Host-specific plant growth promotion was observed when plants were inoculated with the five bacterial strains. P. flavus strain M251 increased the total biomass and total root length of Arabidopsis plants by 4.7 and 5.8 times, respectively, over that of control plants and improved lettuce and basil root growth, while P. flavus strain M259 promoted Arabidopsis shoot and root growth, lettuce and basil root growth, and bok choy shoot growth. A genome comparison between P. flavus strains M251 and M259 showed that both genomes contain up to 70 actinobacterial putative plant-associated genes and genes involved in known plant-beneficial pathways, such as those for auxin and cytokinin biosynthesis and 1-aminocyclopropane-1-carboxylate deaminase production. This study provides evidence of direct plant growth promotion by Plantibacter flavus. IMPORTANCE The discovery of new plant growth-promoting bacteria is necessary for the continued development of biofertilizers, which are environmentally friendly and cost-efficient alternatives to conventional chemical fertilizers. Biofertilizer effects on plant growth can be inconsistent due to the complexity of plant-microbe interactions, as the same bacteria can be beneficial to the growth of some plant species and neutral or detrimental to others. We examined a set of bacterial endophytes isolated from plants growing in a unique petroleum-contaminated environment to discover plant growth-promoting bacteria. We show that strains of Plantibacter flavus exhibit strain-specific plant growth-promoting effects on four different plant species.

Potential of Bradyrhizobia inoculation to promote peanut growth and beneficial Rhizobacteria abundance

“…Thus, the interactions between Bradyrhizobium and Rhizobium or Burkholderia is direct or indirect, which might be regulated by the complex relationship between rhizobacteria and host plants. Overall, these results point to complex microbe-microbe interactions in peanut rhizosphere communities and suggest that exogenous bradyrhizobia inoculants increase the relative abundances of potentially PGPR populations, since both Rhizobium and Burkholderia are PGPR (Vurukonda et al 2018;Mayer et al 2019).…”

“…4 and S8; Table S8). Since CCBAU 051107 T treatment had the most specific hub taxa in the harvest stage, including Bradyrhizobium, which is well known symbiotic nitrogen fixers associated with leguminous plants to promote plants growth, and also used as PGPR for non-legumes including peppers, radishes and tomatoes by producing auxins and siderophores (Antoun et al 1998;Mayer et al 2019). Therefore, these results indicated that the inoculation of bradyrhizobia might have profound impacts on the host plant growth via the regulation of complex interaction networks of rhizobacteria.…”

Profiling, isolation and characterisation of beneficial microbes from the seed microbiomes of drought tolerant wheat

“…sp D4-14 inhibited the growth of barley and oats. Curtobacterium has been found to associate with roots and promote plant growth in Arabidopsis , lettuce, basil, red clover and cucumber 55 – 57 .…”

Drought Tolerant Wheat Varieties Enrich Seed Microbiomes For Beneficial Microbes Under Drought Conditions

“…sp D4-14 inhibited the growth of barley and oats. Curtobacterium has been found to associate with roots and promote plant growth in Arabidopsis, lettuce, basil, red clover and cucumber [56][57][58].…”