scholarly journals Nitrogen Fixing Azotobacter Species as Potential Soil Biological Enhancers for Crop Nutrition and Yield Stability

2021 ◽  
Vol 12 ◽  
Author(s):  
Abderrahim Aasfar ◽  
Adnane Bargaz ◽  
Kaoutar Yaakoubi ◽  
Abderraouf Hilali ◽  
Iman Bennis ◽  
...  
Keyword(s):  
Plant Nutrition ◽  
Nutrient Use Efficiency ◽  
Cyst Formation ◽  
Plant Roots ◽  
N Fixation ◽  
Bacterial Cells ◽  
Nutrient Deficiencies ◽  
Free Living ◽  
Beneficial Traits ◽  
Agronomic Features

Biological nitrogen fixation (BNF) refers to a microbial mediated process based upon an enzymatic “Nitrogenase” conversion of atmospheric nitrogen (N2) into ammonium readily absorbable by roots. N2-fixing microorganisms collectively termed as “diazotrophs” are able to fix biologically N2 in association with plant roots. Specifically, the symbiotic rhizobacteria induce structural and physiological modifications of bacterial cells and plant roots into specialized structures called nodules. Other N2-fixing bacteria are free-living fixers that are highly diverse and globally widespread in cropland. They represent key natural source of nitrogen (N) in natural and agricultural ecosystems lacking symbiotic N fixation (SNF). In this review, the importance of Azotobacter species was highlighted as both important free-living N2-fixing bacteria and potential bacterial biofertilizer with proven efficacy for plant nutrition and biological soil fertility. In addition, we described Azotobacter beneficial plant promoting traits (e.g., nutrient use efficiency, protection against phytopathogens, phytohormone biosynthesis, etc.). We shed light also on the agronomic features of Azotobacter that are likely an effective component of integrated plant nutrition strategy, which contributes positively to sustainable agricultural production. We pointed out Azotobacter based-biofertilizers, which possess unique characteristics such as cyst formation conferring resistance to environmental stresses. Such beneficial traits can be explored profoundly for the utmost aim to research and develop specific formulations based on inoculant Azotobacter cysts. Furthermore, Azotobacter species still need to be wisely exploited in order to address specific agricultural challenges (e.g., nutrient deficiencies, biotic and abiotic constraints) taking into consideration several variables including their biological functions, synergies and multi-trophic interactions, and biogeography and abundance distribution.

scholarly journals Diversity of Free-Living and Attached Bacteria in Offshore Western Mediterranean Waters as Depicted by Analysis of Genes Encoding 16S rRNA

1999 ◽  
Vol 65 (2) ◽  
pp. 514-522 ◽  
Author(s):  
Silvia G. Acinas ◽  
Josefa Antón ◽  
Francisco Rodríguez-Valera
Keyword(s):  
16S Rdna ◽  
Restriction Analysis ◽  
Western Mediterranean ◽  
Bacterial Cells ◽  
Free Living ◽  
Attached Bacteria ◽  
Genes Encoding ◽  
Community Fingerprinting ◽  
Close Relatives ◽  
Alteromonas Macleodii

ABSTRACT In a previous study (S. G. Acinas, F. Rodrı́guez-Valera, and C. Pedrós-Alió, FEMS Microbiol. Ecol. 24:27–40, 1997), community fingerprinting by 16S rDNA restriction analysis applied to Mediterranean offshore waters showed that the free-living pelagic bacterial community was very different from the bacterial cells aggregated or attached to particles of more than about 8 μm. Here we have studied both assemblages at three depths (5, 50, and 400 m) by cloning and sequencing the 16S rDNA obtained from the same samples, and we have also studied the samples by scanning electron microscopy to detect morphology patterns. As expected, the sequences retrieved from the assemblages were very different. The subsample of attached bacteria contained very little diversity, with close relatives of a well-known species of marine bacteria, Alteromonas macleodii, representing the vast majority of the clones at every depth. On the other hand, the free-living assemblage was highly diverse and varied with depth. At 400 m, close relatives of cultivated γProteobacteria predominated, but as shown by other authors, near the surface most clones were related to phylotypes described only by sequence, in which the α Proteobacteria of the SAR11 cluster predominated. The new technique of rDNA internal spacer analysis has been utilized, confirming these results. Clones representative of the A. macleodii cluster have been completely sequenced, producing a picture that fits well with the idea that they could represent a genus with at least two species and with a characteristic depth distribution.

scholarly journals Customized Fertilizers- All in One a Review

2020 ◽  
pp. 27-39
Author(s):  
S. K. Choudhary ◽  
Rajesh Kumar ◽  
Arun Kumar ◽  
Rakesh Deo Ranjan
Keyword(s):  
Crop Yields ◽  
Nutrient Use Efficiency ◽  
Soil Health ◽  
Micronutrient Deficiencies ◽  
Nutrient Deficiencies ◽  
Eligibility Criteria ◽  
Long Run ◽  
Nutrient Use ◽  
Fertilizer Recommendations ◽  
Use Efficiency

Blanket fertilizer recommendations for different crops have caused poor nutrient supply, low nutrient use efficiency and limited crop response. Customized fertilizers may help to sustain soil health by ensuring appropriate fertilization. Hence, specific customized fertilizers should be promoted to counteract the problem of expanding multi-nutrient deficiencies in soils. In India, among the nutrients, NPK remain the major ones for increased and sustained productivity. However, the development of high yielding systems will likely exacerbate the problem of secondary and micronutrient deficiencies, not only because larger amounts are removed, but also because the application of large amounts of N, P and K to achieve higher yield targets, as a result in the intensive systems there is every possibility to build up of negative balance and deficiency of secondary and micronutrients. To attain high future targets, customized fertilizers will play a very important role. The development of site and crop specific readymade customized fertilizers based on scientific principles may prove to be more effective to meet the plant requirement and enhance nutrient use efficiency. Such an approach is also likely to boost crop yields and arrest soil fertility decline in a long-run. Thus, this article discusses the manufacturing methodologies, eligibility criteria, success in Indian fertilizer industry, adoption of fertilizer recommendations and problems in marketing of customized fertilizer.

scholarly journals Extracellular Electron Transfer Powers Enterococcus faecalis Biofilm Metabolism

2017 ◽  
Author(s):  
Damien Keogh ◽  
Ling Ning Lam ◽  
Lucinda E. Doyle ◽  
Artur Matysik ◽  
Shruti Pavagadhi ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Enterococcus Faecalis ◽  
Bacterial Biofilm ◽  
Extracellular Electron Transfer ◽  
Bacterial Cells ◽  
Free Living ◽  
Biofilm Growth ◽  
Metabolic Versatility ◽  
Tract Infections ◽  
Biofilm Matrix

AbstractEnterococci are important human commensals and significant opportunistic pathogens associated with endocarditis, urinary tract infections, wound and surgical site infections, and medical device associated infections. These infections often become chronic upon the formation of biofilm. The biofilm matrix establishes properties that distinguish this state from free-living bacterial cells and increase tolerance to antimicrobial interventions. The metabolic versatility of the Enterococci is reflected in the diversity and complexity of environments and communities in which they thrive. Understanding metabolic factors governing colonization and persistence in different host niches can reveal factors influencing the transition from commensal to opportunistic pathogen. Here, we report a new form of iron-dependent metabolism for Enterococcus faecalis where, in the absence of heme, respiration components can be utilised for extracellular electron transfer (EET). Iron augments E. faecalis biofilm growth and generates alterations in biofilm matrix, cell spatial distribution, and biofilm matrix properties. We identify the genes involved in iron-augmented biofilm growth and show that it occurs by promoting EET to iron within biofilm.SignificanceBacterial metabolic versatility is often key in dictating the outcome of host-pathogen interactions, yet determinants of metabolic shifts are difficult to resolve. The bacterial biofilm matrix provides the structural and functional support that distinguishes this state from free-living bacterial cells. Here, we show that the biofilm matrix provides access to resources necessary for metabolism and growth which are otherwise inaccessible in the planktonic state. Our data shows that in the absence of heme, components of Enterococcus faecalis respiration (l-lactate dehydrogenase and acetaldehyde dehydrogenase) may function as initiators of EET through the cytoplasmic membrane quinone pool and utilize matrix-associated iron to carry out EET. The presence of iron resources within the biofilm matrix leads to enhanced biofilm growth.

scholarly journals EFFECT OF INTEGRATED NUTRIENT MANAGEMENT ON NUTRIENT USE EFFICIENCY OF MAJOR NUTRIENTS: A REVIEW

2021 ◽  
Vol 21 (No 1) ◽  
Author(s):  
Barkha . ◽  
Ananya Chakraborty
Keyword(s):  
Crop Production ◽  
Nutrient Management ◽  
Nutrient Use Efficiency ◽  
Mineral Fertilizer ◽  
Utilization Efficiency ◽  
Nutrient Deficiencies ◽  
Nutrient Sources ◽  
Organic Nutrient ◽  
Nutrient Use ◽  
Use Efficiency

Nutrient use efficiency (NUE) is an important concept in the evaluation of crop production systems. With emerging nutrient deficiencies under intensive agriculture, there is a need to improve NUE. One of the approaches to enhance it is by judicious use of fertilizers (adequate rate, effective source, methods and time of application) as well as inclusion of organic manures. Organic nutrient sources are very effective but as their availability is not sufficient to meet the nutrient demand, we have to integrate both organic and inorganic sources of nutrients together in order to achieve higher NUE. Common measures of NUE include Partial Factor Productivity (PFP), Agronomic Efficiency (AE), Apparent Recovery Efficiency (RE), Physiological Efficiency (PE) and Internal Utilization Efficiency (IE). Mineral Fertilizer Equivalent (MFE) is another parameter that can be used to assess short term release of nutrients (mainly nitrogen) from organic nutrient sources

scholarly journals Role of Probiotic Bacilli in Developing Synbiotic Food: Challenges and Opportunities

2021 ◽  
Vol 12 ◽  
Author(s):  
Carolina Szlufman ◽  
Moshe Shemesh
Keyword(s):  
Bacterial Cells ◽  
Free Living ◽  
Commensal Microbiota ◽  
Adaptive Immune ◽  
Symbiotic Interactions ◽  
Normal Microbiota ◽  
Challenges And Opportunities ◽  
Successful Establishment ◽  
Food Challenges

The human body is inhabited by a vast diversity of probiotic microorganisms that could positively affect human physiology. Besides, prebiotic food substances may induce symbiotic relationship among probiotic species through the successful establishment of commensal microbiota, whose connections with the host are multifaceted and multidirectional. As deliberated throughout this review, prebiotic and synbiotic foods contain the capability to stimulate numerous health characteristics in host organisms through various means. Predominantly, the normal microbiota fosters the digestion of food and may boost the innate and adaptive immune system’s functionalities. Therefore, live probiotic bacteria, for instance, probiotic Bacilli obtained together with prebiotic food, can help stimulate healthiness in humans. Thus, we discuss how certain dietary fibers may preserve the probiotic efficacy by serving as the scaffold for probiotic Bacilli to colonize them through forming symbiotic interactions. The fibers can essentially promote protection by encapsulating probiotic Bacilli against various environmental and physical stresses that might kill the free-living bacterial cells. Besides, these fibers would serve as prebiotic substances that would eventually be utilized for the proliferation of probiotic cells. It is believed that applying this conceptual idea will provide a novel platform toward developing probiotic and synbiotic foods, as discussed in this review.

scholarly journals Evolutionary origins and diversification of proteobacterial mutualists

2014 ◽  
Vol 281 (1775) ◽  
pp. 20132146 ◽  
Author(s):  
Joel L. Sachs ◽  
Ryan G. Skophammer ◽  
Nidhanjali Bansal ◽  
Jason E. Stajich
Keyword(s):  
Diversification Rate ◽  
Ancestral State ◽  
Free Living ◽  
Evolutionary Diversification ◽  
Evolutionary Conservatism ◽  
Evolutionary Origins ◽  
Eukaryotic Species ◽  
Beneficial Traits ◽  
Bacterial Lineages

Mutualistic bacteria infect most eukaryotic species in nearly every biome. Nonetheless, two dilemmas remain unresolved about bacterial–eukaryote mutualisms: how do mutualist phenotypes originate in bacterial lineages and to what degree do mutualists traits drive or hinder bacterial diversification? Here, we reconstructed the phylogeny of the hyperdiverse phylum Proteobacteria to investigate the origins and evolutionary diversification of mutualistic bacterial phenotypes. Our ancestral state reconstructions (ASRs) inferred a range of 34–39 independent origins of mutualist phenotypes in Proteobacteria, revealing the surprising frequency with which host-beneficial traits have evolved in this phylum. We found proteobacterial mutualists to be more often derived from parasitic than from free-living ancestors, consistent with the untested paradigm that bacterial mutualists most often evolve from pathogens. Strikingly, we inferred that mutualists exhibit a negative net diversification rate (speciation minus extinction), which suggests that mutualism evolves primarily via transitions from other states rather than diversification within mutualist taxa. Moreover, our ASRs infer that proteobacterial mutualist lineages exhibit a paucity of reversals to parasitism or to free-living status. This evolutionary conservatism of mutualism is contrary to long-standing theory, which predicts that selection should often favour mutants in microbial mutualist populations that exploit or abandon more slowly evolving eukaryotic hosts.

scholarly journals Quantitative root ecology as element of soil fertility theory.

1986 ◽  
Vol 34 (3) ◽  
pp. 273-281 ◽  
Author(s):  
M. van Noordwijk ◽  
P. de Willigen
Keyword(s):  
Soil Fertility ◽  
Soil Properties ◽  
Special Reference ◽  
Plant Nutrition ◽  
Nutrient Use Efficiency ◽  
Plant System ◽  
Nutrient Use ◽  
Root Ecology ◽  
Use Efficiency

Nutrient use efficiency with special reference to the soil/plant system, soil fertility theory relating to fertilizers, plant nutrition, soil properties and root ecology and aspects of quantitative root ecology are considered and an approach to modelling the relation of root ecology to soil fertility theory is outlined. (Abstract retrieved from CAB Abstracts by CABI’s permission)

scholarly journals Deficiency of phyto-available sulphur, zinc, boron, iron, copper and manganese in soils of India

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Arvind Kumar Shukla ◽  
Sanjib Kumar Behera ◽  
Chandra Prakash ◽  
Ajay Tripathi ◽  
Ashok Kumar Patra ◽  
...  
Keyword(s):  
Nutritional Quality ◽  
Crop Production ◽  
Agricultural Soils ◽  
Nutrient Use Efficiency ◽  
Management Strategies ◽  
Soil Health ◽  
Crop Productivity ◽  
Nutrient Deficiencies ◽  
Agricultural Produce ◽  
Nutrient Use

AbstractNutrient deficiencies in soil–crop contexts and inappropriate managements are the important reasons for low crop productivity, reduced nutritional quality of agricultural produce and animal/human malnutrition, across the world. The present investigation was carried out to evaluate nutrient deficiencies of sulphur (S) and micronutrients [zinc (Zn), boron (B), iron (Fe), copper (Cu) and manganese (Mn)] in agricultural soils of India for devising effective management strategies to achieve sustainable crop production, improved nutritional quality in crops and better animal/human health. A total of 2,42,827 surface (0–15 cm depth) soil samples were collected from agriculture fields of 615 districts lying in 28 states of India and were analysed for available S and micronutrients concentration. The study was carried out under the aegis of All India Coordinated Research Project on Micro- and Secondary-Nutrients and Pollutant Elements in Soils and Plants. The mean concentrations were 27.0 ± 29.9 mg kg−1 for available S, 1.40 ± 1.60 mg kg−1 for available Zn and 1.40 ± 4.70 mg kg−1 for available B, 31.0 ± 52.2 mg kg−1 for available Fe, 2.30 ± 3.50 mg kg−1 for available Cu and 17.5 ± 21.4 mg kg−1 for available Mn. There were variable and widespread deficiencies of S and micronutrients in different states. The deficiencies (acute deficient + deficient + latent deficiency) of S (58.6% of soils), Zn (51.2% of soils) and B (44.7% of soils) were higher compared to the deficiencies of Fe (19.2% of soils), Cu (11.4% of soils) and Mn (17.4% of soils). Out of 615 districts, > 50% of soils in 101, 131 and 86 districts were deficient in available S, available Zn and available B, respectively. Whereas, > 25% of soils in 83, 5 and 41 districts had deficiencies of available Fe, available Cu and available Mn, respectively. There were occurrences of 2-nutrients deficiencies such S + Zn (9.30% of soils), Zn + B (8.70% of soils), S + B (7.00% of soils) and Zn + Fe (5.80% of soils) to a greater extent compared to the deficiencies of Zn + Mn (3.40% of soils), S + Fe (3.30% of soils), Zn + Cu (2.80% of soils) and Fe + B (2.70% of soils). Relatively lower % of soils were deficient in 3-nutrients (namely S + Zn + B, S + Zn + B and Zn + Fe + B), 4-nutrients (namely Zn + Fe + Cu + Mn) and 5-nutrients (namely Zn + Fe + Cu + Mn + B) simultaneously. The information regarding the distribution of deficiencies of S and micronutrients (both single and multi-nutrients) could be used by various stakeholders for production, supply and application of right kind of fertilizers in different districts, states and agro-ecological regions of India for better crop production, crop nutritional quality, nutrient use efficiency, soil health and for tackling human and animal malnutrition.

Responses of agronomically important crops to inoculation with Azospirillum

2001 ◽  
Vol 28 (9) ◽  
pp. 871 ◽  
Author(s):  
Sofie Dobbelaere ◽  
Anja Croonenborghs ◽  
Amber Thys ◽  
David Ptacek ◽  
Jos Vanderleyden ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Plant Growth ◽  
Root Development ◽  
Physiological Responses ◽  
Plant Roots ◽  
Mineral Uptake ◽  
Free Living ◽  
Plant Growth Promoting ◽  
Promote Plant Growth ◽  
Growth Promoting

This paper originates from an address at the 8th International Symposium on Nitrogen Fixation with Non-Legumes, Sydney, NSW, December 2000 Azospirilla are free-living rhizobacteria that are able to promote plant growth and increase yields in many crops of agronomic importance. It is assumed that the bacteria affect plant growth mainly by the production of plant growth promoting substances, which leads to an improvement in root development and an increase in the rate of water and mineral uptake. In the present review, we discuss the physiological responses of the plant roots to inoculation with Azospirillum, and report on field and greenhouse experiments carried out with these bacteria during 1994–2001 in Belgium, Uruguay, Mexico and Israel.

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