Query: Bacteria affect on plant growth

title: Isolation and Characterization of Antagonistic Bacteria Paenibacillus jamilae HS 26 and Their Effects on Plant Growth
abstract: Soilborne pathogens affect plant growth and food production worldwide. The application of chemical fertilizers and pesticides to control plant diseases has harmful effects; fortunately, plant growth promoting rhizobacteria can be used as a potential alternative strategy. Here, Paenibacillus jamilae HS 26 was selected for its highly antagonistic activity against several soilborne pathogens. The bacterium synthesized hydrolytic enzymes and released extracellular antifungal metabolites and volatile organic compounds primarily, N, N diethyl 1, 4 phenylenediamine, which was detected by gas chromatography mass spectrometry and shown to inhibit fungal mycelial growth. Furthermore, HS 26 was useful for nitrogen fixation, phosphate and potassium solubilization, and siderophore and indoleacetic acid production. In vitro tests and pot experiments revealed that HS 26 considerably increased plant biometric parameters. Illumina MiSeq sequencing data showed a significant reduction in soilborne pathogens and increase in beneficial bacteria in the wheat rhizosphere after treatment with strain HS 26.

title: Endophytic bacteria affect sugarcane physiology without changing plant growth
abstract: The aim of this study was to evaluate if endophytic bacteria inoculants would be beneficial to the sugarcane varieties IACSP94 2094 and IACSP95 5000, promoting changes in photosynthesis and plant growth. The plants, obtained from mini stalks with one bud, were treated with two bacteria mixtures (inoculum I or II) or did not receive any inoculum (control plants) The inocula did not affect shoot and root dry matter accumulation as compared to the control condition (plants with native endophytic bacteria) However, photosynthesis and electron transport rate (ETR) increased in IACSP94 2094 treated with the inoculum II, whereas the inoculum I enhanced photosynthesis and stomatal conductance in IACSP95 5000. The inoculum II caused increase in leaf sucrose concentration of IACSP94 2094 and decrease in IACSP95 5000 leaves. Leaf nitrogen concentration was not affected by treatments, but bacteria inoculation increased nitrate reductase activity in IACSP95 5000, and the highest activity was found in plants treated with the inoculum II. We can conclude that bacteria inoculation changed sugarcane physiology, improving photosynthesis and nitrate reduction in a genotype dependent manner, without promoting plant growth under non limiting conditions.

title: Under saline stress plant growth promoting bacteria affect growth, photosynthesis and antioxidant activities in paddy
abstract: Inoculation of plant growth promoting bacteria (PGPB) was found to be more promising to induce growth of paddy plants under lower and moderate salinity levels. PGPB protects the plants from salinity injury by increasing biomass content, photo synthetic activity and antioxidant enzymes acid phosphatase and glutathione reductase. This study also states that PGPB helps in decrement of lipid peroxidation, plays an important role in regulation of growth for posi tive adaptation of plants to salt stress. However with increase in soil salinity the glutathione reductase activity decreased in non inoculated plants. The present study shows that inoculation of paddy (Oryza sativa) with root associated bacteria could provide salt tolerant ability to paddy plants as these isolates also remain associated with root and root is the plant part affected first by salinity, so it serve as a useful tool for alleviating salinity stress.

title: Plant growth promoting bacteria improve leaf antioxidant metabolism of drought stressed Neotropical trees
abstract: Plant growth promoting bacteria association improved the enzymatic and non enzymatic antioxidant pathways in Neotropical trees under drought, which led to lower oxidative damage and enhanced drought tolerance in these trees.  Water deficit is associated with oxidative stress in plant cells and may, thus, negatively affect the establishment of tree seedlings in reforestation areas. The association with plant growth promoting bacteria (PGPB) is known to enhance the antioxidant response of crops, but this strategy has not been tested in seedlings of Neotropical trees. We evaluated the effects of inoculation with two PGPB Azospirillum brasilense and Bacillus sp. on the antioxidant metabolism of Cecropia pachystachya and Cariniana estrellensis seedlings submitted to drought. We measured the activity of antioxidant enzymes and the content of non enzymatic antioxidants in leaves, and biometrical parameters of the seedlings. In both tree species, drought decreased the activity of antioxidant enzymes and the content of non enzymatic antioxidant compounds. For C. pachystachya, the enzymatic and non enzymatic pathways were mostly influenced by A. brasilense inoculation, which enhanced ascorbate peroxidase (APX) and superoxide dismutase activities and positively affected the level of non enzymatic antioxidant compounds. In C. estrellensis A. brasilense inoculation enhanced APX activity. However, A. brasilense and Bacillus sp. inoculation had more influence on the non enzymatic pathway, as both bacteria induced a greater accumulation of secondary compounds (such as chlorogenic acid, gallic acid, rutin and synapic acid) compared to that in non inoculated plants under drought. For both species, PGPB improved biometrical parameters related to drought tolerance, as specific leaf area and leaf area ratio. Our results demonstrate that PGPB induced antioxidant mechanisms in drought stressed Neotropical trees, increasing drought tolerance. Thus, PGPB inoculation provides a biotechnological alternative to improve the success of reforestation programmes.

title: Plant growth promoting bacteria as potential bio inoculants and biocontrol agents to promote black pepper plant cultivation.
abstract: Black pepper production in Malaysia was restricted by various diseases. Hazardous chemical products appear to be the best solution to control diseases in black pepper cultivation. However, persistence of chemical residues in peppercorns could affect the quality of exports and consumptions. Application of fertilizers is crucial to sustain pepper growth and high yield. But, continuous use of chemical fertilizers could affect the soil ecosystem and eventually restrict nutrient uptake by pepper roots. Therefore, we propose biological approaches as an alternative solution instead of chemical products to sustain pepper cultivation in Malaysia. In this study, we have isolated a total of seven indigenous rhizobacteria antagonistic to soil borne Fusarium solani, the causal fungus of slow decline, the most serious debilitating disease of black pepper in Malaysia. The isolated bacteria were identified as Bacillus subtilis, Bacillus siamensis, Brevibacillus gelatini, Pseudomonas geniculata, Pseudomonas beteli, Burkholderia ubonensis and Burkholderia territorii. These bacteria were effective in production of antifungal siderophore with the amount of 53.4 73.5 per 0.5 mL of cell free supernatants. The bacteria also produced appreciable amount of chitinase with chitinolytic index was ranged from 1.19 to 1.76. The bacteria have shown phosphate solubilizing index within 1.61 to 2.01. They were also efficient in ACC deaminase (0.52 mM 0.62 mM) and ammonia (60.3 mM 75.3 mM) production. The isolated antagonists were efficacious in stimulation of black pepper plant growth and root development through IAA (10.5 mg/mL 42.6 mg/mL) secretion. In conclusion, the isolated rhizobacteria are potent to be developed not only as biocontrol agents to minimize the utilization of hazardous chemicals in black pepper disease management, but also developed as bio fertilizers to improve black pepper plant growth due to their capabilities in plant growth promotion.

title: Beneficial features of plant growth promoting rhizobacteria for improving plant growth and health in challenging conditions: A methodical review.
abstract: New eco friendly approaches are required to improve plant biomass production. Beneficial plant growth promoting (PGP) bacteria may be exploited as excellent and efficient biotechnological tools to improve plant growth in various including stressful environments. We present an overview of bacterial mechanisms which contribute to plant health, growth, and development. Plant growth promoting rhizobacteria (PGPR) can interact with plants directly by increasing the availability of essential nutrients (e.g. nitrogen, phosphorus, iron) production and regulation of compounds involved in plant growth (e.g. phytohormones) and stress hormonal status (e.g. ethylene levels by ACC deaminase) They can also indirectly affect plants by protecting them against diseases via competition with pathogens for highly limited nutrients, biocontrol of pathogens through production of aseptic activity compounds, synthesis of fungal cell wall lysing enzymes, and induction of systemic responses in host plants. The potential of PGPR to facilitate plant growth is of fundamental importance, especially in case of abiotic stress, where bacteria can support plant fitness, stress tolerance, and/or even assist in remediation of pollutants. Providing additional evidence and better understanding of bacterial traits underlying plant growth promotion can inspire and stir up the development of innovative solutions exploiting PGPR in times of highly variable environmental and climatological conditions.

title: Improved growth and nutrient acquisition of wheat genotypes in phosphorus deficient soils by plant growth promoting rhizospheric and endophytic bacteria
abstract: In this study, two bacterial strains were isolated from the rhizosphere and inside the roots of wheat (Triticum aestivum L. plants growing in wheat land of Iran. Based on the 16s rRNA gene sequences, strains R185 and E240 were identified as Pseudomonas sp. (rhizospheric isolate) and Pseudomonas mosselii (endophytic isolate) respectively. Isolates were tested for traits that affect plant growth such as indole 3 acetic acid, siderophore, hydrogen cyanide production, and phosphate solubilization ability. Then the effect of strains on growth promotion, protein, nutrients of grains, and soil enzyme activity was investigated using a low phosphorous soil under greenhouse conditions. Results revealed that significantly higher biomass accumulation and micronutrient assimilation were obtained in all the pots treated with bacterial strains as compared to the control. Co inoculation of rhizospheric and endophytic bacteria improved the protein of grain by 11.3% (Marvdasht) and 9% (Roshan) Microbial inoculation had a positive effect on the concentration of P, Zn, and Fe in wheat grains. While inoculating wheat genotypes with a single rhizospheric strain increased dehydrogenase activity by 53.4% this effect became stronger with increasing endophytic strain: up to 72% increase in soil dehydrogenase activity was observed in bacterial consortium treatment. Taken together, inoculation by rhizospheric endophytic mix strains with multi plant growth promoting traits could be a promising option to promote cereal quality.

title: Impact of soil salinity on the plant growth promoting and biological control abilities of root associated bacteria
abstract: The effectiveness of plant growth promoting bacteria is variable under different biotic and abiotic conditions. Abiotic factors may negatively affect the beneficial properties and efficiency of the introduced PGPR inoculants. The aim of this study was to evaluate the effect of plant growth promoting rhizobacteria on plant growth and on the control of foot and root rot of tomatoes caused by Fusarium solani under different soil salinity conditions. Among the five tested strains, only Pseudomonas chlororaphis TSAU13, and Pseudomonas extremorientalis TSAU20 were able to stimulate plant growth and act as biological controls of foot and root rot disease of tomato. The soil salinity did not negatively affect the beneficial impacts of these strains, as they were able to colonize and survive on the roots of tomato plants under both saline and non saline soil conditions. The improved plant height and fruit yield of tomato was also observed for plants inoculated with P. extremorientalis TSAU20. Our results indicated that, saline condition is not crucial factor in obtaining good performance with respect to the plant growth stimulating and biocontrol abilities of PGPR strains. The bacterial inoculant also enhanced antioxidant enzymes activities thereby preventing ROS induced oxidative damage in plants, and the proline concentrations in plant tissue that play an important role in plant stress tolerance.

title: Diversity, Plant Growth Promoting Attributes, and Agricultural Applications of Rhizospheric Microbes
abstract: Rhizosphere harbors potential microbiomes which play a pivotal role in nutrient cycling, enhancing soil fertility, maintaining plant health and productivity. Specific microbiomes that are assembled near roots are considered to be some of the most complex ecosystems on the Earth. Heterogeneous microbial communities of rhizospheric microbiomes considerably vary by soil type, land use pattern, plant species, and host genotype. It is demonstrated that root exudates act as substrates and signaling molecules which are required for establishing plant rhizobacterial interactions. The present chapter focused on the rhizosphere microbiomes of different agricultural crops, their functions, and possible biotechnological applications for increasing crop production in a sustainable manner. Further, the plant growth promoting mechanisms of rhizobacteria were highlighted. Although much work has been done on the biocontrol characteristics of rhizospheric bacteria, it has to be considered that soil type, plant species, and the pathogen affect altogether influence the biocontrol efficiency of strain applied against a soil borne pathogen.

title: Enhanced performance of the microalga Chlorella sorokiniana remotely induced by the plant growth promoting bacteria Azospirillum brasilense and Bacillus pumilus
abstract: Remote effects (occurring without physical contact) of two plant growth promoting bacteria (PGPB) Azospirillum brasilense Cd and Bacilus pumilus ES4 on growth of the green microalga Chlorella sorokiniana UTEX 2714 were studied. The two PGPB remotely enhanced the growth of the microalga, up to six fold, and its cell volume by about three fold. In addition to phenotypic changes, both bacteria remotely induced increases in the amounts of total lipids, total carbohydrates, and chlorophyll a in the cells of the microalga, indicating an alteration of the microalga's physiology. The two bacteria produced large amounts of volatile compounds, including CO2, and the known plant growth promoting volatile 2,3 butanediol and acetoin. Several other volatiles having biological functions in other organisms, as well as numerous volatile compounds with undefined biological roles, were detected. Together, these bacteria derived volatiles can positively affect growth and metabolic parameters in green microalgae without physical attachment of the bacteria to the microalgae. This is a new paradigm on how PGPB promote growth of microalgae which may serve to improve performance of Chlorella spp. for biotechnological applications.