Plant Growth-promoting Bacteria Bacillus Research Articles

Plant growth-promoting bacteria improve the Cd phytoremediation efficiency of soils contaminated with PE–Cd complex pollution by influencing the rhizosphere microbiome of sorghum

Composite pollution by microplastics and heavy metals poses a potential threat to the soilplant system and has received increasing attention. Plant growth-promoting bacteria (PGPB) have good application potential for the remediation of combined microplastic and heavy metal pollution, but few related studies exist. The present study employed a pot experiment to investigate the effects of inoculation with the PGPB Bacillus sp. SL-413 and Enterobacter sp. VY-1 on sorghum growth and Cd accumulation under conditions of combined cadmium (Cd) and polyethylene (PE) pollution. Cd+PE composite contamination led to a significant reduction in sorghum length and biomass due to increased toxicity. Inoculation with Bacillus sp. SL-413 and Enterobacter sp. VY-1 alleviated the stress caused by Cd+PE complex pollution, and the dry weight of sorghum increased by 25.7% to 46.1% aboveground and by 12.3% to 45.3% belowground. Bacillus sp. SL-413 and Enterobacter sp. VY-1 inoculation increased the Cd content and accumulation in sorghum and improved the phytoremediation efficiency of Cd. The inoculation treatment effectively alleviated the nutrient stress caused by the reduction in soil mineral nutrients due to Cd+PE composite pollution. The composition of the soil bacterial communities was also affected by the Cd, Cd+PE and bacterial inoculation treatments, which affected the diversity of the soil bacterial communities. Network analyses indicated that bacterial inoculation regulated the interaction of rhizospheric microorganisms and increased the stability of soil bacterial communities. The Mantel test showed that the changes in the soil bacterial community and function due to inoculation with Bacillus sp. SL-413 and Enterobacter sp. VY-1 were important factors influencing sorghum growth and Cd remediation efficiency. The results of this study will provide new evidence for the research on joint plantmicrobe remediation of heavy metal and microplastic composite pollution.

Synergistic effect of biochar and plant growth promoting bacteria improve the growth and phytostabilization potential of Sorghum bicolor in Cd and Zn contaminated soils

The synergetic effect of biochar (BC) and plant growth promoting bacteria (PGPB) on phytoremediation potential of plants in heavy metal (HM) contaminated soils was not well understood. A pot experiment was carried out to evaluate the effects of banana pith derived BC (0, 2.5 and 5%, w/w) as soil amendment together with inoculation of PGPB Bacillus thuringiensis SE1C2 on the growth, physiological response and phytoremediation potential of Sorghum bicolor (L.) Moench in Cd and Zn contaminated soils. Combined treatment of BC 5% and SE1C2 increased plant shoot length, root length, fresh weight and dry weight but decreased Cd and Zn accumulation as compared to other treatments. The BC 5% treatment also increased SE1C2 colonization in rhizosphere soils and tissue interior of S. bicolor even under HM stress. In addition, the plants treated with BC 5% and SE1C2 also had increased chlorophyll, carotenoid and antioxidant enzymes while lower leaf malondialdehyde and proline contents which suggest their potential in improving HM stress tolerance in plants. Similarly, the combined BC 5% and SE1C2 treatment considerably improved enzymatic activities (acid phosphatases, alkaline phosphatases, β-glucosidase and urease) in HM contaminated soils. Thus, this study concludes that the combined treatment of Bacillus thuringiensis SE1C2 and banana pith BC could be exploited as an effective strategy for improving the plant growth and phytostabilization potential in HM contaminated soils.

Three rhizobacteria differentially change endogenous hormones and yield in four rice cultivars

Four Thai rice cultivars Pathum Thani 1, RD41, RD57, and RD85 were investigated to observe their responses to Plant Growth Promoting Bacteria Bacillus sp. N7 (N7), Lysinibacillus sp. N5 (N5), and Bacillus thuringiensis B20 (B20). A pot experiment with 5 plants pot−1 and four replicates was used. This study reported that the combination of plant growth promoting bacteria and optimized fertilization play role in crop yield enhancement by modulating endogenous levels of indole-3-acetic acid, salicylic acid, and tryptophan. Endogenous levels of indole-3-acetic acid, salicylic acid, tryptophan, and grain-yield-related components and grain yield of four Thai rice cultivars Pathum Thani 1, RD41, RD57, and RD85 were measured. Significant (p < 0.05) increase in grain yield observed at PTT1, RD41, and RD85 (40.13–51.18 g pot−1, 43.33–54.05 g pot−1, 47.80–69.08 g pot−1, respectively), but no significant (p > 0.05) grain yield increase in RD57 (48.75–51.75 g pot−1) when compared to uninoculated conditions. Significant (p < 0.05) endogenous indole-3-acetic acid, salicylic acid, and tryptophan level changes compared to the uninoculated control were observed across four Thai rice cultivars. Consortia development to enhance the plant growth promoting bacteria capability and larger field trials will be performed in the future to further investigate the efficacy of the bacteria in the real-field application.

Inoculation with the pH Lowering Plant Growth Promoting Bacterium Bacillus sp. ZV6 Enhances Ni Phytoextraction by Salix alba from a Ni-Polluted Soil Receiving Effluents from Ni Electroplating Industry

Soil contamination with Ni poses serious ecological risks to the environment. Several members of the Salix genus have the ability to accumulate high concentrations of Ni in their aerial parts, and thus can be used for the remediation of Ni-contaminated soils. Interestingly, the efficacy of Ni phytoextraction by Salix may be improved by the acidification of rhizosphere with rhizosphere acidifying bacterial strains. Therefore, the aim of this study was to assess the efficacy of bacterial strain Bacillus sp. ZV6 in the presence of animal manure (AM) and leaf manure (LM) for enhancing the bioavailability of Ni in the rhizosphere of Salix alba via reducing the pH of rhizosphere and resultantly, enhanced phytoextraction of Ni. Inoculation of Ni-contaminated soil with strain ZV6 significantly increased plant growth as well as Ni uptake by alba. It was found that the addition of AM and LM resulted into a significant increase in plant growth and Ni uptake by alba in Ni-contaminated soil inoculated with ZV6 stain. However, the highest improvements in diethylene triamine penta-acetic acid (DTPA) extractable Ni (10%), Ni removal from soil (54%), Ni bioconcentration factor (26%) and Ni translocation factor (13%) were detected in the soil inoculated with ZV6 along with the addition of LM, compared to control. Similarly, the enhancements in microbial biomass (92%), bacterial count (348%), organic carbon (organic C) (57%) and various enzymatic activities such as urease (56%), dehydrogenase (32%), β-glucosidase (53%), peroxidase (26%) and acid phosphatase (38%) were also significantly higher in the soil inoculated with ZV6 along with the addition of LM. The findings of this study suggest that the inoculation of Ni-contaminated soils with rhizosphere acidifying bacteria can effectively improve Ni phytoextraction and, in parallel, enhance soil health.

Potential role of plant growth-promoting bacteria in Miscanthus x giganteus phytotechnology applied to the trace elements contaminated soils

The second-generation energy crop Miscanthus x giganteus (M. xgiganteus) is a perspective plant for phytoremediation of contaminated lands and the production of biomass. The excellent quality biomass can be ensured by adding soil amendments or inoculation of the plant by plant growth-promoting bacteria (PGPB). The main goal of the current study was to research the influence of PGPB Bacillus altitudinis strain KP-14 isolated from the post-mining aged contaminated soil in Všebořice dump, Ústí nad Labem to the phytoremediation parameters and biomass production of M. xgiganteus. The experiment was done in the greenhouse conditions using the initial aged soil contaminated by the following trace elements (TEs): V, Cr, Mn, Ni, Cu, Zn, Sr, Pb and the same aged soil, additionally artificially contaminated by Pb. The results showed that PGPB treatment increased the growth process and leaves, stems, and roots biomass at harvest by 49%, 86%, and 76%, respectively. In the presence of B. altitudinis strain KP-14, the translocation factor decreased, the uptake index of TEs remained low and the process can be classified as phytostabilization. The finding showed that the application of PGPB strain could be used in the sustainable production of M. xgiganteus at the TEs contaminated soil.

Bacillus toyonensis COPE52 Modifies Lipid and Fatty Acid Composition, Exhibits Antifungal Activity, and Stimulates Growth of Tomato Plants Under Saline Conditions.

Salinity is one of the most important factors that limit the productivity of agricultural soils. Certain plant growth-promoting bacteria (PGPB) have the ability to stimulate the growth of crop plants even under salt stress. In the present study, we analysed the potential of PGPB Bacillus toyonensis COPE52 to improve the growth of tomato plants and its capacity to modify its membrane lipid and fatty acid composition under salt stress. Thus, strain COPE52 increased the relative amount of branched chain fatty acids (15:0i and 16:1∆9) and accumulation of an unknown membrane lipid, while phosphatidylethanolamine (PE) levels decreased during growth with 100 and 200mM NaCl. Importantly, direct and indirect plant growth-promoting (PGP) mechanisms of B. toyonensis COPE52, such as indole-3-acetic acid (IAA), protease activity, biofilm formation, and antifungal activity against Botrytis cinerea, remained unchanged in the presence of NaCl in vitro, compared to controls without salt. In a greenhouse experiment, tomato plants (Lycopersicon esculentum 'Saladette') showed increased shoot and root length, higher dry biomass, and chlorophyll content when inoculated with B. toyonensis COPE52 at 0 and 100mM NaCl. In summary, these results indicate that Bacillus toyonensis COPE52 can modify cell membrane lipid components as a potential protecting mechanism to maintain PGP traits under saline-soil conditions.

Effect of Arbuscular Mycorrhizal Fungi (AMF) and Plant Growth-Promoting Bacteria (PGPR) Inoculations on Elaeagnus angustifolia L. in Saline Soil

Arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) are considered highly-efficient agents for conferring salt tolerance in host plants and improving soil fertility in rhizosphere. However, information about the inoculation of beneficial microbes on halophytes in arid and semi-arid regions remains inadequate. The objective of this study was to evaluate the influence of AMF (Glomus mosseae) inoculation, alone or in combination with PGPR (Bacillus amyloliquefaciens), on biomass accumulation, morphological characteristics, photosynthetic capacity, and rhizospheric soil enzyme activities of Elaeagnus angustifolia L., a typical halophyte in the northwest of China. The results indicate that, for one-year-old seedlings of Elaeagnus angustifolia L., AMF significantly promoted biomass accumulation in aboveground organs, increased the numbers of leaves and branches, and improved the leaf areas, stem diameters and plant height. AMF-mediated morphological characteristics of aboveground organs favored light interception and absorption and maximized the capacities for photosynthesis, transpiration, carbon dioxide assimilation and gas exchange of Elaeagnus angustifolia L. seedlings in saline soil. AMF also promoted root growth, modified root architecture, and enhanced soil enzyme activities. Elaeagnus angustifolia L. was more responsive to specific inoculation by AMF than by a combination of AMF and PGPR or by solely PGPR in saline soils. Therefore, we suggest that G. mosseae can be used in saline soil to enhance Elaeagnus angustifolia L. seedlings growth and improve soil nutrient uptake. This represents a biological technique to aid in restoration of saline-degraded areas.

Combined application of photo-selective mulching films and beneficial microbes affects crop yield and irrigation water productivity in intensive farming systems

Cultivation of vegetables under plastic tunnels is a steadily growing farming system, nevertheless there are concerns about its environmental sustainability. This work tests a new cultivation system based on the application of photo-selective mulching films to the soil combined with beneficial microbes to improve crop yield, save irrigation water and enhance crop irrigation water productivity. A two-year project was carried out in three farms of southern Italy that practice cultivation in greenhouses with different soil characteristics. Photo-selective mulching films (PS) were used alone or in combination with microbial consortia (M) containing beneficial microbes (i.e. antagonistic fungi of the genus Trichoderma, mycorrhizal fungi of the genus Glomus and the plant growth promoting bacterium Bacillus subtilis) and compared with black plastic mulching (B). Soil temperature, soil water content, and irrigation water volumes were continuously monitored for eight cropping cycles including tomato, sweet pepper, lettuce, melon, and kohlrabi. Crop yields were assessed at the end of each cycle. PS films in combination with M significantly increased crop yields with respect to control, with the most positive effects on winter crops. Soil temperature under PS was consistently lower than that under B mulch. All mulching films allowed the saving of irrigation water compared with untreated control, but no difference was detected between PS and B. However, PS increases crop irrigation water productivity (CIWP) compared with B film in 25% of the experimental cases. In conclusion, our results indicate that combining PS films with beneficial microbes in cultivation under plastic tunnel greenhouses promotes crop yield and increases CIWP compared with control in 87.5% and 75% of the study cases, respectively.

Mitigation Effect of Drought Stress by Plant Growth-promoting Bacterium Bacillus sp. SB19 on Kale Seedlings in Greenhouse

Mitigation Effect of Drought Stress by Plant Growth-promoting Bacterium Bacillus sp. SB19 on Kale Seedlings in Greenhouse

Varieties of lima bean shows different growth responses when inoculated with Bacillus sp., a plant growth-promoting bacteria

Plant growth-promoting bacteria (PGPB) comprise of soil microorganisms that cause positive effects on plant growth. The hypothesis according to which the inoculation of lima bean with PGPB Bacillus stimulates vegetative growth, which may result in a higher plant productivity, was tested. Thus, this study aimed to evaluate the effects of inoculation of two varieties of lima bean (branca and boca de moca) with Bacillus sp., UFPEDA 472 strain, based on plant growth responses. The experiment was conducted in a greenhouse using a completely randomized design. Three treatments were applied separately to each lima bean variety: the first used inoculation with Bacillus , one was submitted to nitrogen supplementation, and one was the absolute control (non-inoculated plants). The following variables were evaluated: absolute and relative growth rate, root length, stem diameter, fresh and dry mass of shoots and roots, shoot:root ratio and total chlorophyll. The results showed that lima bean displayed better growth responses when inoculated with Bacillus sp. UFPEDA 472 in relation to the treatment with nitrogen and/or non-inoculated plants. When inoculated with PGPB Bacillus , the lima bean var. branca was superior to boca de moca in terms of root length and root dry mass. The lima bean var. boca de moca inoculated with Bacillus sp. UFPEDA 472 was superior to branca in terms of absolute growth rate, stem diameter, fresh and dry mass of shoot, shoot:root ratio and total chlorophyll. In general, the lima bean var. boca de moca inoculated with Bacillus shows a better growth performance. Our results suggest that growth responses of lima bean varieties branca and boca de moca are related with a positive interaction with the PGPB Bacillus .