Piyush Pandey

Rhizosphere Competent Pseudomonas aeruginosa GRC1 Produces Characteristic Siderophore and Enhances Growth of Indian Mustard (Brassica campestris)

Pseudomonas aeruginosa GRC1, an isolate of potato rhizosphere, was known to have several plant growth–promoting activities, including production of phytohormone and antibiotic substance. The isolate was found to have prolific production ability of hydroxamate siderophore in iron-deficient conditions. The siderophore of GRC1 was purified and characterized. The purified siderophore appeared to be of pyoverdin type with typical amino acid composition. In field trials, P. aeruginosa GRC1 enhanced the growth of Brassica campestris var Pusa Gold (Indian mustard). Significant increase in root and shoot weight, length, grain yield per plant, and total grain yield was recorded. Root colonization was studied with Tn5-induced streptomycin-resistant transconjugants of spontaneous rifampicin-resistant GRC1 (designated GRC1rif+strep+) after different durations. The strain was significantly rhizopheric competent and stabilized in the rhizosphere, without disturbing the normal indigenous bacterial population.

Bioremediation of polyaromatic hydrocarbons (PAHs) using rhizosphere technology

The remediation of polluted sites has become a priority for society because of increase in quality of life standards and the awareness of environmental issues. Over the past few decades there has been avid interest in developing in situ strategies for remediation of environmental contaminants, because of the high economic cost of physicochemical strategies, the biological tools for remediation of these persistent pollutants is the better option. Major foci have been considered on persistent organic chemicals i.e. polyaromatic hydrocarbons (PAHs) due to their ubiquitous occurrence, recalcitrance, bioaccumulation potential and carcinogenic activity. Rhizoremediation, a specific type of phytoremediation that involves both plants and their associated rhizospheric microbes is the creative biotechnological approach that has been explored in this review. Moreover, in this review we showed the significance of rhizoremediation of PAHs from other bioremediation strategies i.e. natural attenuation, bioaugmentation and phytoremediation and also analyze certain environmental factor that may influence the rhizoremediation technique. Numerous bacterial species were reported to degrade variety of PAHs and most of them are isolated from contaminated soil, however few reports are available from non contaminated soil. Pseudomonas aeruginosa , Pseudomons fluoresens , Mycobacterium spp., Haemophilus spp., Rhodococcus spp., Paenibacillus spp. are some of the commonly studied PAH-degrading bacteria. Finally, exploring the molecular communication between plants and microbes, and exploiting this communication to achieve better results in the elimination of contaminants, is a fascinating area of research for future perspective.

Emerging Role of Plant Growth Promoting Rhizobacteria in Agrobiology

Plant growth promoting rhizobacteria (PGPR) colonize rhizosphere and reside in harmony with plants. These introduced or naturally occurring bacteria are known to enhance plant growth and yield components. Therefore, their potential has been exploited extensively to reduce the indiscriminate use of synthetic chemicals such as inorganic fertilizers, fungicides, and pesticides and prevent the accumulation of toxic, health hazardous chemicals in soil and water resources. Biological control of plant diseases and plant growth promotion approach becomes a prime focus of recent biotechnological trends in agro-ecosystem. Considerable research has been performed globally to exploit the functioning of beneficial bacterial communities in agro-industries. Further, advanced and better understanding of rhizobacteria will facilitate maintenance of natural soil structure, pure water resources, and increased productivity of agro- and forest-based industries to achieve their commercial success in sustainable ecosystems.

Volatile Organic Compounds from Native Potato-associated Pseudomonas as Potential Anti-oomycete Agents.

The plant kingdom represents a prominent biodiversity island for microbes that associate with the below- or aboveground organs of vegetal species. Both the root and the leaf represent interfaces where dynamic biological interactions influence plant life. Beside well-studied communication strategies based on soluble compounds and protein effectors, bacteria were recently shown to interact both with host plants and other microbial species through the emissions of volatile organic compounds (VOCs). Focusing on the potato late blight-causing agent Phytophthora infestans, this work addresses the potential role of the bacterial volatilome in suppressing plant diseases. In a previous study, we isolated and identified a large collection of strains with anti-Phytophthora potential from both the phyllosphere and the rhizosphere of potato. Here we report the characterization and quantification of their emissions of biogenic volatiles, comparing 16 Pseudomonas strains differing in (i) origin of isolation (phyllosphere vs. rhizosphere), (ii) in vitro inhibition of P. infestans growth and sporulation behavior, and (iii) protective effects against late blight on potato leaf disks. We systematically tested the pharmacological inhibitory activity of core and strain-specific single compounds against P. infestans mycelial growth and sporangial behavior in order to identify key effective candidate molecules present in the complex natural VOCs blends. We envisage the plant bacterial microbiome as a reservoir for functional VOCs and establish the basis for finding the primary enzymatic toolset that enables the production of active components of the volatile bouquet in plant-associated bacteria. Comprehension of these functional interspecies interactions will open perspectives for the sustainable control of plant diseases in forthcoming agriculture.

Shape dependent physical mutilation and lethal effects of silver nanoparticles on bacteria

In this report, spherical silver nanoparticle (AgNP-sp) and rod-shaped silver nanoparticle (AgNR) were prepared by chemical reduction method and their antibacterial activity against various Gram-positive and Gram-negative bacteria had been evaluated for their efficiency. Minimal inhibitory concentration (MIC) tests were conducted to study the antibacterial properties, and substantiated with killing kinetics of silver nanoparticles (AgNPs). The study revealed that both AgNP-sp and AgNRs are good antibacterial candidates. Bacterial sensitivity to nanoparticles (NPs) was found to vary depending on microbial species. Disc diffusion studies revealed the greater effectiveness of AgNP-sp and AgNR against Klebsiella pneumoniae AWD5 at the doses of 249 and 392 µg. The dose dependent activities of prepared NPs were also observed on the batch studies of disc diffusion and MIC with various strains. The optical and morphological structures of NPs were analyzed by UV-visible, XRD, FE-SEM and TEM. Further, FESEM of bacterial culture treated with AgNPs confirmed antibacterial activity of NPs by showing rupture of bacterial cell wall. Also, the genome of test organism was found to have CusCFBA and CusRS operons. The killing kinetics confirmed that the death rate of K. pneumoniae was higher against AgNP-sp as compared to AgNR.

Draft Genome Sequence of Klebsiella pneumoniae AWD5

ABSTRACT Here, we report the draft genome sequence of Klebsiella pneumoniae strain AWD5, isolated from an automobile workshop in India. The de novo assembly resulted in a 4,807,409 bp genome containing 25 rRNA genes, 81 tRNAs, and 4,636 coding sequences (CDS). It carries important genes for polyaromatic hydrocarbon degradation and benzoate degradation.

Consortium of Plant-Growth-Promoting Bacteria: Future Perspective in Agriculture

The term “plant-growth-promoting rhizobacteria” (PGPR) include soil bacteria that colonize the roots of plants following inoculation onto seed and enhance plant growth. The bacteria useful to plants were proposed to be characterized in two general types: bacteria forming a symbiotic relationship with the plant and another the free-living ones found in the soil but are often found near, on, or even within the plant tissues. The PGPR are known to enhance growth by several direct mechanisms—like biofertilizers fix nitrogen, phytostimulators directly promote the growth of plants by the production of hormones, and several other metabolites like siderophore, ACC deaminase, etc., are produced by PGPR strains for plant growth enhancement. Also, biocontrol agents that are able to protect plants from soilborne infection by deleterious microorganisms also offer environment-friendly strategy for pest control. Recently, application of two or more PGPR as consortium is taking gain in field application worldwide. This offers multifarious approach of promoting plant growth and improve yield. In this review, the various strategies for consortium formulation are described. In fact, use of rhizobia with free-living nitrogen fixers or with phosphate solubilizers including VAM fungi has been widely reported. Also, application of biocontrol agents along with direct growth promoters is also observed as holistic approach for sustainable agriculture. Further, tailor-made consortium is sometimes designed to include other benefits like improving soil health.

The Endophytic Symbiont—Pseudomonas aeruginosa Stimulates the Antioxidant Activity and Growth of Achyranthes aspera L.

A plant growth promoting bacterial endophyte designated as AL2-14B isolated from the leaves of Achyranthes aspera L. was identified as Pseudomonas aeruginosa based on its phenotypic and physiological features, and 16S rRNA gene sequence analysis. AL2-14B had plant growth stimulating attributes including siderophore and indole acetic acid release, inorganic phosphate solubilization, along with nitrogenase, ammonification, and protease activities. It also exhibited antifungal property against Rhizoctonia solani. The plantlets grown in germ-free condition were inoculated with AL2-14B and studied for the colonization of endophyte. Significant increase in population of AL2-14B between 3rd and 5th days after inoculation was recorded. The treatment of plants with endophytic P. aeruginosa AL2-14B increased nitrogen, phosphorus, potassium (NPK) contents in plant by 3.8, 12.59, and 19.15%, respectively. Significant enhancement of shoot and root length, dry leaf, dry shoot and dry root weight, and leaf surface area as compared to control (P < 0.05) was recorded in AL2-14B inoculated plants. The antioxidant activities increased in plants grown in germ-free conditions and inoculated with AL2-14B. The present study emphasizes on the role of diazotrophic endophyte P. aeruginosa AL2-14B in stimulating growth of A. aspera L. and improvement of its medicinal properties. Significant increase in growth and antioxidant content of P. aeruginosa AL2-14B treated plants suggests the possibility of an economical and eco-friendly mean of achieving antioxidants rich, healthier A. aspera plants.

Bacilli and Agrobiotechnology

Development of value-added products from renewable supplies is attracting more and more attention due to the fossil fuel resource depletion and environmental concerns. Bacillus species show distinctive benefits as hosts for production of industrially important enzymes and biochemical compounds. They are also improved through metabolic engineering techniques for efficient production of fuels, microbial enzymes, and fine and bulk chemicals. In this chapter, recent findings about Bacillus spp. and their usage as microbial factories are summarized.

Rhizosphere mediated nutrient management in Allium hookeri Thwaites by using phosphate solubilizing rhizobacteria and tricalcium phosphate amended soil

ABSTRACT This work describes integrated nutrient management for cultivation of Allium hookeri by using phosphate solubilizing bacteria (PSB) applied in rhizosphere, along with tricalcium phosphate (TCP). Arthrobacter luteolus S4C7, Enterobacter asburiae S5C7, Klebsiella pneumoniae S4C9, S4C10 and S6C1, and K. quasipneumoniae S6C2, were isolated from rhizosphere of Allium hookeri Thwaites, and were found to release substantial amount of soluble phosphate (124.8–266.4 μg/mL) from TCP in vitro conditions. These isolates were experimented for plant growth promoting attributes, including IAA, siderophore, and nitrogen-fixation. Treatment with PSB resulted in enhanced growth of A. hookeri Th., which was even better with TCP amendment with PSB. K.quasipneumoniae S6C2 resulted in 39.1% and 533.3% increase (p ≤ 0.05) of root length and weight respectively. The treatment with these isolates, in TCP amended soil also resulted in 200–250% increase in available P in soil, which was maximum for K. quasipneumoniae (1.866 mg/g).