Kamal Krishna Pal

Bio: Kamal Krishna Pal is an academic researcher from Directorate of Groundnut Research. The author has contributed to research in topics: Rhizobacteria & Collar rot. The author has an hindex of 10, co-authored 27 publications receiving 1510 citations.

Diversity of plant growth and soil health supporting bacteria

Abstract: The global necessity to increase agricultural production from a steadily decreasing and degrading land resource base has placed considerable strain on the fragile agro-ecosystems. Current strategies to maintain and improve agricultural productivity via high-input practices places considerable emphasis on 'fail-safe' techniques for each component of the production sequence with little consideration to the integration of these components in a holistic, systems approach. While the use of mineral fertilizers is considered the quickest and surest way of boosting crop production, their cost and other constraints deter farmers from using them in recommended quantities. In recent years, concepts of integrated plant nutrient management (IPNM) have been developed, which emphasize maintaining and increasing soil fertility by optimizing all possible sources (organic and inorganic) of plant nutrients required for crop growth and quality. This is done in an integrated manner appropriate to each cropping system and farming situation. Improvement in agricultural sustainability requires optimal use and management of soil fertility and soil physical properties, both of which rely on soil biological processes and soil biodiversity. An understanding of microbial diversity perspectives in agricultural context, is important and useful to arrive at measures that can act as indicators of soil quality and plant productivity. In this context, the long-lasting challenges in soil microbiology are development of effective methods to know the types of microorganisms present in soils, and to determine functions which the microbes perform in situ. This review describes some recent developments, particularly in India, to understand the relationship of soils and plants with the diversity of associated bacteria, and traces contributions of Indian scientists in isolating and defining the roles of plant growth promoting bacteria to evolve strategies for their better exploitation.

Haloarchaea Endowed with Phosphorus Solubilization Attribute Implicated in Phosphorus Cycle

Abstract: Archaea are unique microorganisms that are present in ecological niches of high temperature, pH and salinity. A total of 157 archaea were obtained from thirteen sediment, water and rhizospheric soil samples collected from Rann of Kutch, Gujarat, India. With an aim to screen phosphate solubilizing archaea, a new medium was designed as Haloarchaea P Solubilization (HPS) medium. The medium supported the growth and P solubilization activity of archaea. Employing the HPS medium, twenty isolates showed the P-solubilization. Phosphate solubilizing archaea were identified as seventeen distinct species of eleven genera namely Haloarcula, Halobacterium, Halococcus, Haloferax, Halolamina, Halosarcina, Halostagnicola, Haloterrigena, Natrialba, Natrinema and Natronoarchaeum. Natrinema sp. strain IARI-WRAB2 was identified as the most efficient P-solubilizer (134.61 mg/L) followed by Halococcus hamelinensis strain IARI-SNS2 (112.56 mg/L). HPLC analysis detected seven different kinds of organic acids, namely: gluconic acid, citric acid, formic acid, fumaric acid succinic acid, propionic acid and tartaric acid from the cultures of these isolates. These phosphate solubilizing halophilic archaea may play a role in P nutrition to vegetation growing in these hypersaline soils. This is the first report for these haloarchaea to solubilize considerable amount of P by production of organic acids and lowering of pH.

Diversity and phylogenetic profiling of niche-specific Bacilli from extreme environments of India

Abstract: The diversity of culturable, aerobic and heterotrophic Bacillus and Bacillus-derived genera (BBDG) was investigated in various extreme environments (including thermal springs, cold deserts, mangroves, salt lakes, arid regions, salt pans and acidic soils) of India. Heat treatment followed by enrichment in different media led to a total of 893 bacterial isolates. Amplified ribosomal DNA restriction analysis (ARDRA) using three restriction enzymes AluI, MspI and HaeIII led to the clustering of these isolates into 12–74 groups for the different sites at 75 % similarity index, adding up to 559 groups. Phylogenetic analysis based on 16S rRNA gene sequencing led to the identification of 392 bacilli, grouped in two families, Bacillaceae (89.03 %) and Paenibacillaceae (10.97 %), and included 13 different genera with 75 distinct species. It was found that among the thirteen genera, nine (Bacillus, Halobacillus, Lysinibacillus, Oceanobacillus, Pontibacillus, Salinibacillus, Sediminibacillus, Thalassobacillus and Virgibacillus) belonged to Bacillaceae and four (Ammoniphilus, Aneurinibacillus, Brevibacillus and Paenibacillus) belonged to Paenibacillaceae. Novel isolates tolerant to low and high pH and temperature, salt and low moisture were identified. The major outcome of the present investigation was the identification of niche-specific species and also the ubiquitous presence of selected species of BBDG, which illustrate the diversity and pervasive nature of BBDG in extreme environments.

Seasonal variations in culturable archaea and their plant growth promoting attributes to predict their role in establishment of vegetation in Rann of Kutch

Abstract: Archaea are unique microorganisms that are present in ecological niches of high temperature, pH and high salinity. Archaea may be present freely or associated with plant rhizosphere. The plant-microbe interactions may be implicit to plants adaptation to abiotic stress of hypersalinity. With an aim to look for population dynamics of archaea at different seasons of the year in hypersaline environments of Rann of Kutch, the rhizospheric, non-rhizospheric, water and sediment samples were collected during autumn, winter and summer. Sampling sites were selected on the basis of topography and vegetation which included barren land, salt pan and rhizosphere of monocot and dicot plants. Soil pH and salinity (mS cm−1) varied from 7.4–10.15 and 1.19–106.7 respectively. A total of 157 halophilic archaea were isolated using seven different selective media. The isolated archaeal were screened for abiotic stress and it has been found they show the wide range of in the tolerance to temperatures (25–65 °C), NaCl concentrations (0.86–5.48 M), water stresses (upto −0.75Mpa) and pH (4–10). The profiling of archaeal community using 16S rRNA gene sequencing and phylogenetic analysis revealed that all archaeal isolates belonged to a family halobacteriaceae of phylum euryarchaeota. Based on 16S rRNA gene sequencing the cultures were identified and belonged to twenty eight distinct species of 16 genera namely Haladaptatus, Haloarcula, Halobacterium, Halococcus, Haloferax, Halogeometricum, Halolamina, Halopenitus, Halorubrum, Halosarcina, Halostagnicola, Haloterrigena, Natrialba, Natrinema, Natronoarchaeum and Natronomonas. In the present study, seasonal and niche-specific archaea were reported and characterized from hypersaline environments. The haloarchaea with multifunctional plant growth promoting attributes, prevalent in the hypersaline environments must be colonizing the rhizosphere of plants and contributing to the growth and sustenance of plants.

Plant Growth-Promoting Bacteria: Mechanisms and Applications

Abstract: The worldwide increases in both environmental damage and human population pressure have the unfortunate consequence that global food production may soon become insufficient to feed all of the world's people. It is therefore essential that agricultural productivity be significantly increased within the next few decades. To this end, agricultural practice is moving toward a more sustainable and environmentally friendly approach. This includes both the increasing use of transgenic plants and plant growth-promoting bacteria as a part of mainstream agricultural practice. Here, a number of the mechanisms utilized by plant growth-promoting bacteria are discussed and considered. It is envisioned that in the not too distant future, plant growth-promoting bacteria (PGPB) will begin to replace the use of chemicals in agriculture, horticulture, silviculture, and environmental cleanup strategies. While there may not be one simple strategy that can effectively promote the growth of all plants under all conditions, some of the strategies that are discussed already show great promise.

Plant growth-promoting rhizobacteria (PGPR): emergence in agriculture

Abstract: Plant growth-promoting rhizobacteria (PGPR) are the rhizosphere bacteria that can enhance plant growth by a wide variety of mechanisms like phosphate solubilization, siderophore production, biological nitrogen fixation, rhizosphere engineering, production of 1-Aminocyclopropane-1-carboxylate deaminase (ACC), quorum sensing (QS) signal interference and inhibition of biofilm formation, phytohormone production, exhibiting antifungal activity, production of volatile organic compounds (VOCs), induction of systemic resistance, promoting beneficial plant-microbe symbioses, interference with pathogen toxin production etc. The potentiality of PGPR in agriculture is steadily increased as it offers an attractive way to replace the use of chemical fertilizers, pesticides and other supplements. Growth promoting substances are likely to be produced in large quantities by these rhizosphere microorganisms that influence indirectly on the overall morphology of the plants. Recent progress in our understanding on the diversity of PGPR in the rhizosphere along with their colonization ability and mechanism of action should facilitate their application as a reliable component in the management of sustainable agricultural system. The progress to date in using the rhizosphere bacteria in a variety of applications related to agricultural improvement along with their mechanism of action with special reference to plant growth-promoting traits are summarized and discussed in this review.

Soil beneficial bacteria and their role in plant growth promotion: a review

Abstract: Soil bacteria are very important in biogeochemical cycles and have been used for crop production for decades. Plant–bacterial interactions in the rhizosphere are the determinants of plant health and soil fertility. Free-living soil bacteria beneficial to plant growth, usually referred to as plant growth promoting rhizobacteria (PGPR), are capable of promoting plant growth by colonizing the plant root. PGPR are also termed plant health promoting rhizobacteria (PHPR) or nodule promoting rhizobacteria (NPR). These are associated with the rhizosphere, which is an important soil ecological environment for plant–microbe interactions. Symbiotic nitrogen-fixing bacteria include the cyanobacteria of the genera Rhizobium, Bradyrhizobium, Azorhizobium, Allorhizobium, Sinorhizobium and Mesorhizobium. Free-living nitrogen-fixing bacteria or associative nitrogen fixers, for example bacteria belonging to the species Azospirillum, Enterobacter, Klebsiella and Pseudomonas, have been shown to attach to the root and efficiently colonize root surfaces. PGPR have the potential to contribute to sustainable plant growth promotion. Generally, PGPR function in three different ways: synthesizing particular compounds for the plants, facilitating the uptake of certain nutrients from the soil, and lessening or preventing the plants from diseases. Plant growth promotion and development can be facilitated both directly and indirectly. Indirect plant growth promotion includes the prevention of the deleterious effects of phytopathogenic organisms. This can be achieved by the production of siderophores, i.e. small metal-binding molecules. Biological control of soil-borne plant pathogens and the synthesis of antibiotics have also been reported in several bacterial species. Another mechanism by which PGPR can inhibit phytopathogens is the production of hydrogen cyanide (HCN) and/or fungal cell wall degrading enzymes, e.g., chitinase and s-1,3-glucanase. Direct plant growth promotion includes symbiotic and non-symbiotic PGPR which function through production of plant hormones such as auxins, cytokinins, gibberellins, ethylene and abscisic acid. Production of indole-3-ethanol or indole-3-acetic acid (IAA), the compounds belonging to auxins, have been reported for several bacterial genera. Some PGPR function as a sink for 1-aminocyclopropane-1-carboxylate (ACC), the immediate precursor of ethylene in higher plants, by hydrolyzing it into α-ketobutyrate and ammonia, and in this way promote root growth by lowering indigenous ethylene levels in the micro-rhizo environment. PGPR also help in solubilization of mineral phosphates and other nutrients, enhance resistance to stress, stabilize soil aggregates, and improve soil structure and organic matter content. PGPR retain more soil organic N, and other nutrients in the plant–soil system, thus reducing the need for fertilizer N and P and enhancing release of the nutrients.