Abhinav Aeron

Mineral Release Dynamics of Tricalcium Phosphate and Waste Muscovite by Mineral-Solubilizing Rhizobacteria Isolated from Indo-Gangetic Plain of India

ABSTRACT The aim of the present investigation was to evaluate the mineral release abilities of ten rhizobacterial strains isolated from rhizosphere of various crops growing in the Indo-Gangetic Plain (IGP) of India. Their abilities to solubilize inorganic phosphorus (P) and potassium (K) minerals from insoluble tricalcium phosphate (TCP) and waste muscovite (WM) revealed that rhizobacteria significantly solubilized different levels of inorganic P and fixed K, respectively. Some of the rhizobacterial stains have the ability to produce ammonia, indole-3-acetic acid (IAA), and hydrogen cyanide (HCN). The identification based on the 16S rDNA gene sequencing of selected mineral-solubilizing rhizobacteria (MSR) having greater potential to serve as bioagents were identified as Bacillus subtilis (BRHU01, BRHU03, and BHU20), Bacillus tequilensis (BRHU02), Bacillus licheniformis (BRHU04), Bacillus pumilus (BRHU05), Bacillus flexus (BHU02), Brevibacillus formosus (BHU16), Bacillus methylotrophicus (BHU29), and Bacillus amyloliquefaciens (BHU30). Interestingly, inorganic P and K solubilization by these strains belonging to genera Bacillus and Brevibacillus showed significant variations from 0.52 to 14.49 and from 1.62 to 8.60 µg mL−1, respectively. However, generally, pH values of culture media decreased from near neutral (6.43) to acidic (3.83) with increasing incubation period, and this was inversely correlated with quantities of K solubilized by these rhizobacterial strains. Meanwhile, the electrical conductivity (EC) of broth culture increased from 0.09 to 0.23 dS m−1 with increasing incubation period. Principal component analysis (PCA) of the MSR revealed three clusters, which exhibited high variance with respect to nutrient release. Taken together, these results suggest that Bacillus and Brevibacillus sp. identified in this study solubilized varying levels of inorganic P and fixed K from insoluble TCP and WM by acidolysis mechanisms.

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.

Bacteria in Agrobiology: Crop Productivity

No wonder you activities are, reading will be always needed. It is not only to fulfil the duties that you need to finish in deadline time. Reading will encourage your mind and thoughts. Of course, reading will greatly develop your experiences about everything. Reading bacteria in agrobiology crop productivity is also a way as one of the collective books that gives many advantages. The advantages are not only for you, but for the other peoples with those meaningful benefits.

Enterobacter : Role in Plant Growth Promotion

It is believed that inoculation with rhizobacteria containing plant growth promoting (PGP) characteristics consequently promote root and shoot growth. Further evaluation of these bacteria exhibiting multiple PGP traits on soil–plant system is needed to uncover their efficacy as effective PGP rhizobacteria (PGPR) or PGP bacteria (PGPB) depending upon their nature. The genera within the family Enterobacteriaceae that feature members described as PGPB are Citrobacter, Enterobacter, Erwinia, Klebsiella, Kluyvera, Pantoea and Serratia, although some of these genera also contain species reported to be plant pathogens. Genus Enterobacter is a Gram-negative, straight rod which is motile with peritrichous flagella and is facultatively anaerobic. Enterobacter spp. are known to have a wide range of PGP characteristics involving in nitrogen fixation, soil phosphorus solubilisation, production of antibiotics, having ability to secrete siderophore produce, chitinase, ACC deaminase, hydrolytic enzymes besides exopolysaccharides and in the enhancement of soil porosity. Numerous Enterobacter strains express these activities which promote plant growth and suppress soilborne plant pathogens. These PGP abilities of Enterobacter can make them a potential candidate suitable for plant growth and development. Due to their multifarious role in crop growth, a number of these strains have been developed commercially as plant growth promoters and biocontrol agents.

Root nodule bacteria from Clitoria ternatea L. are putative invasive nonrhizobial endophytes.

In this study, bacteria (8 species and 5 genera) belonging to the classes Betaproteobacteria, Gammaproteobacteria, and Sphingobacteria were isolated from root nodules of the multipurpose legume Clitoria ternatea L. and identified on the basis of partial 16S rRNA sequencing. The root nodule bacteria were subjected to phenotypic clustering and diversity studies using biochemical kits, including Hi-Media Carbokit™, Enterobacteriaceae™ identification kit, ERIC-PCR, and 16S ARDRA. All the strains showed growth on Ashbys N-free media over 7 generations, indicative of presumptive nitrogen fixation and further confirmed by amplification of the nifH gene. None of the strains showed the capability to renodulate the host plant, neither alone nor in combination with standard rhizobial strains, which was further confirmed by the absence of nodC bands in PCR assay. The results clearly indicate the common existence of nonrhizobial microflora inside the root nodules of legumes, which were thought to be colonized only by rhizobia and were responsible for N2 fixation in leguminous crops. However, with the recent discovery of nodule endophytes from a variety of legumes, as also observed here, it can be assumed that symbiotic rhizobia are not all alone and that these invasive endophytes belonging to various bacterial genera are more than just opportunistic colonizers of specialized nodule niche.

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.

Ecofriendly Management of Charcoal Rot and Fusarium Wilt Diseases in Sesame (Sesamum indicum L.)

Sesame (Sesamum indicum L.) is one of the most ancient oil seed crop cultivated in tropical and sub-tropical countries. Irrespective of the agro-climate conditions, sesame is liable to be infected by various pathogenic fungi. Among the fungal diseases, charcoal rot of sesame caused by Macrophomina phaseolina (Tasi) Goid is the most devastating, causing up to 50% or more disease incidence in field resulting in heavy yield losses. The pathogen survives as sclerotia in the soil and in host tissue for varying periods. Due to its soil-borne nature, practically no effective field control is available so far. The second most drastic disease is caused by Fusarium oxysporum f. sp. sesami (Zaprometoff) Castellani sesame wilt which causes drastic decline in sesame production. Management of Fusarium wilt is mainly through chemical soil fumigation and using resistant varieties. The broad-spectrum biocides used to fumigate the soil before planting also have negative impact on soil biota. Moreover, adverse effects of different groups of chemicals have been observed on sesame. Thus, development and use of resistant cultivars is effective, economical and eco-friendly for disease control. However, variable responses with cultivation conditions have been a matter of concern. Soil health has become a cause of concern for sustainable agricultural production in the new millennium. For an environmental friendly and economically viable agriculture to meet the rising oil demand from a limited production area and ecofriendly and sustainable management of charcoal rot and Fusarium wilt, biological control with application of plant-growth-promoting rhizobacteria (PGPRs) offers a potential non-chemical means for disease management. Several strains have been widely reported as microbial inoculants for biofertilization, phytostimulation, biopesticides and effective biocontrol agents for disease complexes including charcoal rot and wilt of sesame.

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.

Sustainable Approaches for Biological Control of Fusarium Wilt in Pigeon Pea (Cajanus cajan L. Millspaugh)

Cajanus cajan (Pigeon pea) is an important crop of Indian subcontinent and African countries, cultivated in the tropics and subtropics. Fusarium wilt is one of the major yield and growth-limiting factors of pigeon pea. Along with nematodes such as Meloidogyne incognita and Heterodera cajani, F. udum result in highly destructive wilt disease complex, which is a major constraint for the successful cultivation of pigeon pea. F. udum from the same or different geographical origin have shown that the fungus is highly variable in cultural characteristics and pathogenicity. Although development and use of resistant cultivars is effec tive, economical, and environmentally sound strategy for disease control, still variable responses with cultivation conditions had been a matter of concern. For an eco-friendly and sustainable management of fusarium wilt, biological control with the application of PGPR offers a potential nonchemical means for disease management. Several strains of Pseudomonas and Bacillus have been widely reported as effective biocontrol agents for pigeon pea wilt, though combination of several organisms have been proved more effective in field conditions.

Ghost probiotics with a combined regimen: a novel therapeutic approach against the Zika virus, an emerging world threat

Abstract The Zika virus (ZIKV) used to be an obscure flavivirus closely related to dengue virus (DENV). Transmission of this epidemic pathogen occurs mainly via mosquitoes, but it is also capable of placental and sexual transmission. Although the characteristics of these viruses are well defined, infections are unpredictable in terms of disease severity, unusual clinical manifestations, unexpected methods of transmission, long-term persistence, and the development of new strains. Recently, ZIKV has gained huge medical attention following the large-scale epidemics around the world, and reported cases of congenital abnormalities associated with Zika virus infections which have created a public health emergency of international concern. Despite continuous research on ZIKV, no specific treatment or vaccine has been developed, excepting a preventive strategy for congenital ZIKV infection. Probiotics, known as GRAS, are bacteria that confer various health beneficial effects, and have been shown to be effective at curing a number of viral diseases by modulating the immune system. Furthermore, probiotic preparations consisting of dead cells and cellular metabolites, so-called “Ghost probiotics”, can also act as biological response modifiers. Here, we review available information on the epidemiology, transmission, and clinical features of ZIKV, and on treatment and prevention strategies. In addition, we emphasize the use of probiotics and plant-based natural remedies and describe their action mechanisms, and the green technologies for microbial conversion, which could contribute to the development of novel therapies that may reduce the pathogenicity of ZIKV. Accordingly, we draw attention to new findings, unanswered questions, unresolved issues, and controversies regarding ZIKV.