Free-living Nitrogen-fixing Bacteria Research Articles

Influence of minimization of tillage methods and direct seeding on soil biogenicity and development of nitrogen bacterium in soil and climatic conditions of the south-east of the Central chernozem region

In long-term studies of soil biogenicity and the development of nitrogen bacteria, conducted in order to study changes in soil processes while minimizing tillage and direct sowing, it was shown that in the soil and climatic conditions of the south-east of the Central chernozem region in the grain crop rotation, there was a decrease in soil biogenicity and an increase in its dependence on weather conditions. The most favorable conditions for the development of azotobacter were formed when plowing to a depth of 20–22 cm, with an average annual number of 445 CFT/50 g of soil in a layer of 0–20 cm. Minimization of tillage led to deterioration of the soil environment conditions for the development of azotobacter, which increased with the duration of its use. Glyphosate-containing herbicides with zero tillage and prolonged use had a depressing effect on the development of free-living nitrogen-fixing bacteria of the genus nitrogen bacteria. The use of mineral fertilizers N60P60K60 with zero tillage reduced the negative effect of glyphosate-containing preparations on microflora and nitrogen bacteria in ordinary chernozem.

EFFECT OF MAGNETITE AND CHITOSAN-MAGNETITE ADDITION ON BACTERIAL LEVELS AND NH3-N (FREE-LIVING N2-FIXING BACTERIA CULTURE)

Free-living N2-fixing bacteria are essential in the soil because they provide a source of nitrogen in the form of ammonium needed by plants to be used in building protein blocks. The fixation of free N2 needs to be increased by adding nanomaterials such as magnetite (Fe3O4), which has an active group and can be a source of nitrogenase enzyme cofactor. In this study, increased N2 fixation used N2-fixing bacteria in Burks medium. This increase was determined by measuring NH3 levels using the Phenate method formed after Burks medium was treated with Fe3O4 and chitosan-magnetite (CS-Fe3O4). The study found that the number of bacteria can be well decreased. This research showed that using Fe3O4 and CS-Fe3O4 increased NH3-N levels in cultures of free-living nitrogen-fixing bacteria by 15.40% and 75.54%. For future development, it can be in the form of optimization, the effect of adding the same material to plant secondary metabolites, and the mechanism of bacteria in using the material.

Isolation and Biochemical Identification of N2 Fixing Bacteria (Azospirillium Sp.) From Saurashtra Region

Azospirillium species are widely used as Biofertilizer to increase crop yield and are free-living nitrogen-fixing bacteria, one of the best-studied plant growth-promoting Rhizobacteria. It is commonly found along with the roots of many different plant species. The present study included the isolation of Azospirillium species from roots and soils in Rhizospheric regions. 50 isolates were isolated from fields in different districts of Saurashtra region in Gujarat against NFB Medium. Significant isolates were isolated from the root surface and root internal tissues. These 50 were morphologically identified and biochemically characterized isolates included the techniques documented in Bergey's Textbook of Identified Bacteria 9th edition (TSI- Triple Sugar Iron, GPB- Glucose Phosphate Broth, MR- Methyl Red VP- Voges Proskauer, TRP-Tryptophan, PNB- Peptone Nitrate Broth, Carbohydrate) out of which fifteen isolates were biochemically positive and were also capable of producing IAA (Indole Acetic Acid), and were also capable of producing IAA.

Codon usage behavior distinguishes pathogenic Clostridium species from the non-pathogenic species

Genus Clostridium is of the largest genus in class Clostridia. It is comprised of spore-forming, anaerobic, gram-positive organisms. The members of this genus include human pathogens to free-living nitrogen fixing bacteria. In the present study, we have performed a comparison of the choice of preferred codons, codon usage patterns, dinucleotide and amino acid usage pattern of 76 species of Genus Clostridium. We found the pathogenic clostridium species to have smaller AT-rich genomes as compared to opportunistic and non-pathogenic clostridium species. The choice of preferred and optimal codons was also influenced by genomic GC/AT content of the respective clostridium species. The pathogenic clostridium species displayed a strict bias in the codon usage, employing 35 of the 61 codons encoding for 20 amino acids. Comparison of amino acid usage revealed an increased usage of amino acids with lower biosynthetic cost by pathogenic clostridium species as compared to opportunistic and non-pathogenic clostridium species. Smaller genome, strict codon usage bias and amino acid usage lead to lower protein energetic cost for the clostridial pathogens. Overall, we found the pathogenic members of genus Clostridium to prefer small, AT-rich codons to reduce biosynthetic costs and match the cellular environment of its AT-rich human host.

Effect of formulated biochar on nodule production, dry matter and grain yield of black soybean (Glycine max (L.) Merr) in Indonesia

Biochar is an important material for soil mineral supply and amendment. Root nodule formation in leguminous plants is also stimulated by biochar. Biochar contains carbon which can be used as an energy source by microbes and contains pores which are suitable for microbial habitat, and it temporarily increases activity of free-living nitrogen-fixing bacteria. Coconut shell biochar can be used as an ameliorant, but the use of single coconut shell biochar can cause a problem such as the use of high dose that will lead into high cost. One of the solutions to solve the problem is to improved coconut shell biochar into formulated biochar (FB) by managing the composition and enrich it with chemical fertilizer’s such as dolomite, organic fertilizer compost of sugarcane bagasse and guano. Mixture of formulated biochar (FB) gave better results than single biochar alone on black soybean. When this FB is applied in the field, it can make efficient use of an organic fertilizers in increasing grain yields. This research was conducted to determine the effect of Formulated Biochar (FB) on nodule production, dry matter and productivity of black soybean seeds. The study was conducted for one season in an experiment field in Winaya Mukti University, Sumedang-Indonesia at 850 m above sea level (m ASL). Detam I seed cultivar was used because it has a wide adaptability in Indonesia and has high nutrient composition and yield potential. The experiment was arranged in a randomized block design consisting of 5 treatment doses of FB (0, 0.5, 1.0, 1.5, 2.0 tons ha-1) and replicated 5 times. The responses observed were the number of effective nodules, growth characteristics, production components and productivity of black soybeans. The results showed that the application of FB had a significant effect on increasing the effectiveness of nodule production, dry matter, and productivity of black soybean seeds. The formulated biochar dose of 2.0 tons ha-1 increased the effectiveness of nodule production up to 100% and 44.87% of soybean productivity, while the formulated biochar dose of 1.5 tons ha-1 increased soybean productivity by 38.46% compared to the control. It is therefore concluded that formulated biochar as soil conditioner and soil booster could be used to improve the growth and grain yield of black soybean. Key words: Black soybean, coconut shell biochar, component yield, dry mater, formulated biochar, grain yield, growth, nodulation

Bulk and Spatially Resolved Extracellular Metabolome of Free-Living Nitrogen Fixation

ABSTRACTSoil nitrogen (N) transformations constrain terrestrial net primary productivity and are driven by the activity of soil microorganisms. Free-living N fixation (FLNF) is an important soil N transformation and key N input to terrestrial systems, but the forms of N contributed to soil by FLNF are poorly understood. To address this knowledge gap, a focus on microorganisms and microbial scale processes is needed that links N-fixing bacteria and their contributed N sources to FLNF process rates. However, studying the activity of soil microorganisms in situ poses inherent challenges, including differences in sampling scale between microorganism and process rates, which can be addressed with culture-based studies and an emphasis on microbial-scale measurements. Culture conditions can differ significantly from soil conditions, so it also important that such studies include multiple culture conditions like liquid and solid media as proxies for soil environments like soil pore water and soil aggregate surfaces. Here we characterized extracellular N-containing metabolites produced by two common, diazotrophic soil bacteria in liquid and solid media, with or without N, across two sampling scales (bulk via GC-MS and spatially resolved via MALDI mass spec imaging). We found extracellular production of inorganic and organic N during FLNF, indicating terrestrial N contributions from FLNF occur in multiple forms not only as ammonium as previously thought. Extracellular metabolite profiles differed between liquid and solid media supporting previous work indicating environmental structure influences microbial function. Metabolite profiles also differed between sampling scales underscoring the need to quantify microbial scale conditions to accurately interpret microbial function.IMPORTANCE Free-living nitrogen-fixing bacteria contribute significantly to terrestrial nitrogen availability; however, the forms of nitrogen contributed by this process are poorly understood. This is in part because of inherent challenges to studying soil microorganisms in situ, such as vast differences in scale between microorganism and ecosystem and complexities of the soil system (e.g., opacity, chemical complexity). Thus, upscaling important ecosystem processes driven by soil microorganisms, like free-living nitrogen fixation, requires microbial-scale measurements in controlled systems. Our work generated bulk and spatially resolved measurements of nitrogen released during free-living nitrogen fixation under two contrasting growth conditions analogous to soil pores and aggregates. This work allowed us to determine that diverse forms of nitrogen are likely contributed to terrestrial systems by free-living nitrogen bacteria. We also demonstrated that microbial habitat (e.g., liquid versus solid media) alters microbial activity and that measurement of microbial activity is altered by sampling scale (e.g., bulk versus spatially resolved) highlighting the critical importance of quantifying microbial-scale processes to upscaling of ecosystem function.

Plant Growth-Promoting Traits and Genetic Diversity of Free-Living Nitrogen-Fixing Bacteria Isolated from Soils in North of Iran

Plant Growth-Promoting Traits and Genetic Diversity of Free-Living Nitrogen-Fixing Bacteria Isolated from Soils in North of Iran

IMPORTANCE OF BIO FERTILIZERS AS ALTERNATIVE SOIL FERTILITY AMENDMENTS

There is a current interest in agrarian sustainability with soil microorganisms instead of agro-chemicals. Key constraints in the use of bio fertilizers are; inadequate awareness about bio inoculants and lack of promotion network and publicity among the end users. This review discusses current technical information a way of creating awareness in order to promote the use of bio fertilizers. Publon, Google Scholar, Science Direct and Microsoft Academic data bases were used for the review 2021. Research and review articles published from 2019 onwards were considered as current information for the review. The findings of the review are that; both primary and secondary macronutrients can be provided by bio fertilizers. Potential microbes are; free-living nitrogen fixing bacteria and cyanobacteria, symbiotic nitrogen-fixing bacteria and fungi such as mycorrhiza. Other important functions of bacteria are; conferring to plants the ability for salt tolerance, lignin degradation and remediation of heavy metals from the soil. Bio Compost, vermicompost and termite soil with their rich microorganism content can be used as bio fertilizers for soil nutrient increase. In order to reap maximum benefit from bio fertilizers there is need to formulate them in appropriate materials. Apart from addition of nutrients to the soil, bio fertilizers play an important role in plant health, conclusion. This paper has brought to the fore the need to improve rhizosphere management in a sustainable way particularly at this point in time when there are strong indications that it has deteriorated in the face of continued use of chemical fertilizers.

Piriformospora indica and Azotobacter chroococcum Consortium Facilitates Higher Acquisition of N, P with Improved Carbon Allocation and Enhanced Plant Growth in Oryza sativa.

The soil microbiome contributes to nutrient acquisition and plant adaptation to numerous biotic and abiotic stresses. Numerous studies have been conducted over the past decade showing that plants take up nutrients better when associated with fungi and additional beneficial bacteria that promote plant growth, but the mechanisms by which the plant host benefits from this tripartite association are not yet fully understood. In this article, we report on a synergistic interaction between rice (Oryza sativa), Piriformospora indica (an endophytic fungus colonizing the rice roots), and Azotobacter chroococcum strain W5, a free-living nitrogen-fixing bacterium. On the basis of mRNA expression analysis and enzymatic activity, we found that co-inoculation of plant roots with the fungus and the rhizobacterium leads to enhanced plant growth and improved nutrient uptake compared to inoculation with either of the two microbes individually. Proteome analysis of O. sativa further revealed that proteins involved in nitrogen and phosphorus metabolism are upregulated and improve nitrogen and phosphate uptake. Our results also show that A. chroococcum supports colonization of rice roots by P. indica, and consequentially, the plants are more resistant to biotic stress upon co-colonization. Our research provides detailed insights into the mechanisms by which microbial partners synergistically promote each other in the interaction while being associated with the host plant.

Molecular Characterization of Free Living N2 Fixing Bacteria Isolated from Agricultural Soils of North Gujarat, India

Background: Molecular identification of a wide range of organisms capable of carrying out biological nitrogen fixation (BNF) are diverse in nature and significantly improves plant growth. Biological N2 fixation reflects the activity of a phylogenetically diverse list of microorganisms. Molecular characterization provides efficient means to identify organisms with the potential of N2 fixation. Applying these techniques in an array of environments has considerably broadened our understanding of the suite of organisms that can carry out BNF. Methods: Thirty-four strains of free living N2 fixing bacterial strains were isolated from diverse plants cultivated in North Gujarat, including wheat, cotton, castor and pearl millet, using a nitrogen-free selective medium. Acetylene reduction assay was used to check the ability of all bacteria to fix nitrogen. Hybridization with nifH probe derived from Azotobacter vinelandii with isolated free-living nitrogen-fixing bacteria showed a positive result. The selected strains were characterized by molecular analysis like; ARDRA and 16S rDNA sequencing. Result: Based on molecular characterization 17 strains to known groups of nitrogen-fixing bacteria, including organisms from the genus Azotobacter, Pseudomonas, Enterobacter, Arthrobacter, Bacillus, Variovorax, Nocardiodies, Rhodococcus, Mycobacterium, Planococcus, Microbacterium have been identified. One of the strains was identified as unknown bacteria. The potential strains were identified by 16srDNA analysis and also corroborated by morphological and biochemical characterization.

Phytoremediation of soils contaminated with crude and weathered oil using two rice varieties (Oryza sativa L.)

Objective: To evaluate the potential for soil phytoremediation with new and weathered hydrocarbons with two rice varieties (Oryza sativa L.). Materials and Methods: The assessed treatments were 150 mg kg-1 (control soil), 30,000; 60,000 and 90,000 mg kg-1 of new oil and 79,457 mg kg-1 of weathered oil 1 and 42,000 of mg kg-1 of weathered oil 2; they were established in a completely randomized design with 6 x 3 factorial, with four repetitions each. The evaluated variables were populations of total bacteria (colony forming units CFU per grams of dry soil), free-living nitrogen-fixing bacteria (CFU), total fungi (CFU), and total dry biomass (g). Total bacteria and fungi were quantified at the beginning of the experiment at 90 and 145 days. Results: The highest total petroleum hydrocarbons (HTP) degradation was 73 and 72 % in the 79,457 and 42,000 mg kg-1 concentrations of weathered HTP 1 and 2, in the rhizosphere of rice silver line 21. The total dry biomass reported significant differences (p ≤ 0.05), evidencing a lower effect in the 60,000 mg kg-1 concentration in new oil, which caused a 33 % reduction compared to the control. Results/Conclusions: The rice variety line 21 has a greater potential to phytoremediate soils contaminated with crude and weathered oil in field conditions in tropical areas.

Low Frequency of Plants Associated with Symbiotic Nitrogen-Fixers Exhibits High Frequency of Free-Living Nitrogen Fixing Bacteria: A Study in Karst Shrub Ecosystems of Southwest China

Plants associated with symbiotic nitrogen-fixers and soil free-living nitrogen-fixing bacteria are good indicators for detecting the source of nitrogen in natural ecosystems. However, the community composition and diversity of plants associated with symbiotic nitrogen-fixers and soil free-living nitrogen-fixing bacteria in karst shrub ecosystems remain poorly known. The community composition and diversity of soil free-living nitrogen-fixing bacteria and plants, as well as the soil physical–chemical properties were investigated in 21 shrub plots (including different topographies and plant types). The frequency of plants associated with symbiotic nitrogen-fixers was found to be low in the 21 shrub plots. The soil free-living nitrogen-fixing bacterial community structure varied among the 21 shrub soils. Based on a variance partitioning analysis, topography, plant type, and soil pH explained 48.5% of the observed variation in bacterial community structure. Plant type had a predominant effect on community structure, and topography (aspect and ascent) and soil pH had minor effects. A negative correlation between the abundance of the soil free-living nitrogen-fixing bacterial community and the richness index for plants associated with symbiotic nitrogen-fixers was observed. The result of the low frequency of plants associated with symbiotic nitrogen-fixers highlights the importance of sources of fixed nitrogen by soil free-living nitrogen-fixing bacteria in the nitrogen limitation shrub ecosystem of the karst regions.

ISOLATION, MOLECULAR CHARACTERIZATION OF DIAZOTROPIC BACTERIA FROM VIRGIN SOIL FROM ARAKU VALLEY AND ASSESSMENT OF OF AMMONIA ACCUMULATION AT SALINE CONDITIONS

Nitrogen-fixing bacteria are widely distributed in nature where they reduce atmospheric nitrogen in soil or in association with plant. They have been found in a wide variety of terrestrial and aquatic habitats in both temperate and tropical regions of the word. Nitrogen-fixing bacteria are found in symbiotic associations with plants free living in soil. The objective of the present research was to isolate free living Nitrogen fixing bacteria from virgin soil samples in araku valley and assessment of their ammonia accumulation at saline conditions. 10 soil samples were collected in different place from virgin areas. For isolation of the free living nitrogen fixing bacteria, Nitrogen free media like Jensens Medium and Azotobacter Agar were used. Serially diluted soil samples were spread on the agar media and incubated for 48 hours. Eleven morphologically different bacteria were separated on made pure colonies on nutrient agar media. All bacteria were under go biochemical characterization which reveals that all these bacteria related to Azospirillum, Azotobacter and Clostridium. High ammonia liberating isolate MGN-10 was molecular characterizes as Azotobacter chroococcum and this soil application increase the plant growth in terms of growth parameters.

Biosorption of Malachite Green by Dry Cells of Isolated Free Living Nitrogen Fixing Bacteria

Contamination of water with Malachite green (MG) may threaten aquatic and human life. Nitrogen-fixing Azotobacter sp. is an efficient adsorbent for the removal of MG from dye solutions. The optimum pH for the biosorption process was determined. The maximum adsorption capacity and the effect of different adsorbate concentrations were detected. The kinetics and isotherm models for biosorption were constructed. Optimum adsorption of MG by Azotobacter sp. was obtained at pH 6.0, biomass concentration was 0.05%, initial dye concentration was 50 mg.L-1, and contact time was 600 mins. Dye adsorption exhibited an increase with contact time and initial malachite green concentration. The kinetics of the adsorption process was best followed by the pseudo-second-order kinetic model which confirms the chemisorption process. The adsorption equilibrium data fit well to the Langmuir model indicating a monolayer adsorption behavior onto a surface of Azotobacter sp. with a finite number of active sites. Maximum biosorption capacity was found to be 142.8 mg.g-1 of bacterial biomass. The dry biomass of Azotobacter sp. has proved to be an efficient biosorbent for the removal of synthetic dyes from actual industrial effluent that is contaminated with up to 400 mg.L-1 dye concentration.

Resource Allocation During the Transition to Diazotrophy in Klebsiella oxytoca

Free-living nitrogen-fixing bacteria can improve growth yields of some non-leguminous plants and, if enhanced through bioengineering approaches, have the potential to address major nutrient imbalances in global crop production by supplementing inorganic nitrogen fertilisers. However, nitrogen fixation is a highly resource-costly adaptation and is de-repressed only in environments in which sources of reduced nitrogen are scarce. Here we investigate nitrogen fixation (nif) gene expression and nitrogen starvation response signaling in the model diazotroph Klebsiella oxytoca (Ko) M5a1 during ammonium depletion and the transition to growth on atmospheric N2. Exploratory RNA-sequencing revealed that over 50% of genes were differentially expressed under diazotrophic conditions, among which the nif genes are among the most highly expressed and highly upregulated. Isotopically labelled QconCAT standards were designed for multiplexed, absolute quantification of Nif and nitrogen-stress proteins via multiple reaction monitoring mass spectrometry (MRM-MS). Time-resolved Nif protein concentrations were indicative of bifurcation in the accumulation rates of nitrogenase subunits (NifHDK) and accessory proteins. We estimate that the nitrogenase may account for more than 40% of cell protein during diazotrophic growth and occupy approximately half the active ribosome complement. The concentrations of free amino acids in nitrogen-starved cells were insufficient to support the observed rates of Nif protein expression. Total Nif protein accumulation was reduced 10-fold when the NifK protein was truncated and nitrogenase catalysis lost (nifK1–1203), implying that reinvestment of de novo fixed nitrogen is essential for further nif expression and a complete diazotrophy transition. Several amino acids accumulated in non-fixing ΔnifLA and nifK1–1203 mutants, while the rest remained highly stable despite prolonged N starvation. Monitoring post-translational uridylylation of the PII-type signaling proteins GlnB and GlnK revealed distinct nitrogen regulatory roles in Ko M5a1. GlnK uridylylation was persistent throughout the diazotrophy transition while a ΔglnK mutant exhibited significantly reduced Nif expression and nitrogen fixation activity. Altogether, these findings highlight quantitatively the scale of resource allocation required to enable the nitrogen fixation adaptation to take place once underlying signaling processes are fulfilled. Our work also provides an omics-level framework with which to model nitrogen fixation in free-living diazotrophs and inform rational engineering strategies.

Effect of Predation by Colpoda sp. in Nitrogen Fixation Rate of Two Free-Living Bacteria.

Biological nitrogen fixation is limited to several groups of prokaryotes, some of them reduce nitrogen as free-living nitrogen-fixing bacteria. Protozoa predation on these latter releases sequestered nitrogen that may enhance the formation of new bacterial biomass and possibly increase nitrogen fixation within soil microbial communities. We aim to evaluate the predation effect of Colpoda sp. on two nitrogen fixers: Azospirillum lipoferum and Stenotrophomonas sp. during their lag, early exponential, and exponential phases. The kinetics of bacterial population growth was determined in the predators' presence or absence and the effect of predation on the rate of N fixation was evaluated through the reduction of acetylene to ethylene technique. Colpoda sp. showed a non-significant difference in preferences between the two species offered as prey. Consequently, the abundance of A. lipoferum and Stenotrophomonas sp. decreased significantly due to predator's pressure and both species responded by increasing their specific growth rate. Likewise, predation promoted greater nitrogen fixation rate by CFU during the lag phase in A. lipoferum (0.20nM/CFU with predation vs 0.09nM/CFU without predation) and Stenotrophomonas sp. (0.22nM/CFU vs 0.09nM/CFU respectively). During early exponential phase (29h), the rate diminished to 0.13 and 0.05nM/CFU in A. lipoferum and to 0.09nM/CFU and 0.05nM/CFU in Stenotrophomonas sp. Finally, during the exponential phase (52h), only A. lipoferum without predation produced 0.003nM/CFU of ethylene. Thus, the nitrogenase activity was higher in the lag and the early exponential phases when predator activity was involved.

Yield and Rhizosphere - microflora of Cowpea in Response to Magnesium Fertilization in Lateritic Soils of Kerala

Background: Magnesium deficiency has become a major nutritional disorder in lateritic soils of Kerala. Appropriate magnesium fertilization is the best strategy to combat deficiency issues. Apart from correcting nutritional deficiency, magnesium fertilization has an influence on the growth of beneficial microbes such as nitrogen fixing bacterias and arbuscular mycorrhizal fungi. The experiment aimed to investigate the effect of magnesium fertilization on crop yield and population rhizosphere micoflora of cowpea in lateritic soils of Kerala.Methods: A pot culture experiment was conducted with a gradient of magnesium additions ranging from 5 mg kg-1 to 80 mg kg-1 of soil along with recommended dose of fertilizers. Population of rhizobium, free living nitrogen fixing bacteria, spore count of arbuscular mycorrhizal fungi and per cent root colonization of arbuscular mycorrhizal fungi were studied during flowering. The available magnesium and magnesium uptake were also worked out during harvest. Yield and yield contributing characteristics of cowpea were measured during harvest stage.Result: Magnesium addition produced significant variations in population of rhizobium and free- living nitrogen fixing bacteria whereas spore count of AMF and per cent root colonization of AMF did not vary according to the added doses of magnesium. A higher population of rhizobium, free living nitrogen fixers, root nodules, magnesium uptake, plant height and yield were obtained in the treatment where magnesium was applied @ 10 mg kg-1 soil.

Formation of phthalates during the degradation of N-phenyl-2-naphthylamine by soil bacteria

N-phenyl-2-naphthylamine (N-PNA) and phthalates are classified as antibiotic substances. The appearance and accumulation of these substances in the biosphere is associated with their technogenic and biogenic origin (metabolites of plants and bacteria). In this article, we compare the degrading action of such soil bacteria as Rhizobium leguminosarum bv. viceae, Bradyrhizobium japonicum, Pseudomonas syringae pv. pisi, Clavibacter michiganensis sps. Sepedonicus and Azotobacter chroococcum against N-PNA. These bacteria differ in their interaction with pea plants (Pisum sativum L.) synthesising N-PNA. The degradation products were studied using gas chromatography-mass spectrometry in ethyl acetate extracts obtained from culture liquid media, in which N-PNA at a concentration of 10 μM and the bacteria under study were introduced. The decrease in the N-PNA concentration in the extracts obtained using ethyl acetate from culture media, in which N-PNA had been added to a concentration of 100 μM, was monitored following two days of bacterial growth using the methods of high-performance liquid chromatography. It was shown that all the studied bacterial species are capable of degrading N-PNA with the formation of phthalates. The Rhizobium bacteria, endosymbionts of pea plants synthesising N-PNA, and free-living nitrogen-fixing bacteria of the Azotobacter genus showed the highest degrading activity. It was found that N-PNA reduced the viability of all types of bacteria, although to a varying degree. N-PNA had the most negative effect on the viability of the Azotobacter genus, although these bacteria showed a high degrading action against N-PNA. The dependence between the negative effect of NPNA on bacterial viability and the N-PNA concentration was mildly pronounced for Rhizobium and Pseudomonas, although being significant for Bradyrhizobium and Clavibacter.

Microbial decomposition of crustacean shell for production of bioactive metabolites and study of its fertilizing potential.

Crustacean shell waste disposal is considered as biggest problem in seafood processing centers. Incineration and landfilling are the commonest ways of disposal of the waste which causes environmental pollution. Microbial bio-conversion is one of the promising approaches to minimize the wastes by utilizing the same for deriving different value added metabolites. In this perspective, chitinase- and protease-producing bacterial strains were isolated from shrimp culture pond, and the potent isolate was subsequently identified as Alcaligenes faecalis SK10. Fermentative optimization of the production of chitinase (85.42 U/ml), protease (58.57 U/ml), and their catalytic products, viz., N-acetylaminosugar (84 μg/ml) and free amino acids (112 μg/ml), were carried out by utilizing shrimp and crab shell powder as principal substrate. The fermented hydrolysate (FH) was subsequently applied to evaluate its potential to be a candidate fertilizer for the growth of leguminous plant Pisum sativum and Cicer arietinum, and the results were compared with chitin, chitosan, and commercial biofertilizer amended group. The results revealed that FH have paramount potential to improve plants morpho-physiological parameters like stem and root length, chlorophyll, cellular RNA, protein content, and soil physico-chemical parameters like total nitrogen, magnesium, calcium, phosphorus, and potassium significantly (p < 0.05). Moreover, the application of FH also selectively encouraged the growth of free-living nitrogen-fixing bacteria, Rhizobium, phosphate-solubilizing bacteria in the soil by 4.82- and 5.27-, 5.57- and 4.71, and 7.64- and 6.92-fold, respectively, in the rhizosphere of P. sativum and C. arietinum, which collectively is a good sign for an ideal biofertilizer. Co-supplementation of FH with commercial PGPR-biofertilizer significantly influenced the morpho-physiological attributes of plant and physico-chemical and microbial attributes of soil. The study validated proficient and sustainable utilization of fermented hydrolysate of waste crustacean shell as biofertilizer.

Promoción del crecimiento de Agave potatorum Zucc. por bacterias fijadoras de nitrógeno de vida libre

Las bacterias f ijadoras de nitrógeno de vida libre (BFNVL) pueden ser una importante alternativa para reemplazar los fertilizantes nitrogenados en la agricultura. Agave potatorum Zucc, coloquialmente conocido como maguey tobalá, es una especie silvestre de la cual se obtiene un mezcal muy demandado debido a su alta calidad. Al ser una especie silvestre, no existe mucha información referente a su manejo agronómico. En este estudio se evaluó el efecto de BFNVL en el crecimiento y contenido de sólidos solubles totales (SST) en plantas de A. potatorum bajo condiciones semi-controladas. Bajo un diseño en bloques completamente al azar se evaluaron tres BFNVL (1) Burkholderia cepacia, (2) Flavobacterium sp., (3) Paenibacillus amylolyticus y un control (sin BFNVL). En total se tuvieron 4 bloques con 15 plantas de agave por bloque, dentro de cada bloque a cada planta de agave se le aplicó al azar una BFNVL diferente. Las variables de crecimiento vegetal evaluadas después de 48 semanas fueron: altura de la planta (AP), diámetro de roseta (DRO), diámetro del tallo (DT), número de hojas desplegadas (NHD), volumen radicular (VR), densidad de raíz (DR), biomasa seca del tallo (BST), biomasa total (BT), área foliar (AF) y, SST en el tallo (°Bx). El análisis de varianza y la prueba de comparación múltiple de medias (Tukey, P ≤ 0.05) revelaron que con respecto al control, B. cepacia incrementó 322.2% el VR, 42.6% el NHD y 72.9% los SST. P. amylolyticus incrementó 317.1% la BST. B. cepacia, Flavobacterium sp. y P. amylolyticus incrementaron aproximadamente 50.3% el DT, 48.6% el DRO, 127.2% el AF y 51.8% la AP. Flavobacterium sp. incrementó 164.8% la BT. Estos resultados sugieren que las BFNVL promueven el crecimiento de A. potatorum, por lo que pueden ser una tecnología ambientalmente amigable y económica para la producción de este agave.