Growth Promotion of Guava “Pear” (Psidium guajava cv.) by Sinorhizobium mexicanum in Southern Mexican Agricultural Fields

Biofertilizers formulated with nitrogen-fixing bacteria represent an alternative to chemical fertilizers because they increase soil fertility and protect the environment. Therefore, the objective of this study was to analyze the effects on the growth of guava “pear” (Psidium guajava cv.) after inoculation with a nitrogen fixing bacterium Sinorhizobium mexicanum ITTG-R7T. The study was carried out in an agricultural rural area of Chiapas, Mexico, where farmers do not have programs of regenerative agriculture. First, the agricultural soil was subjected to physicochemical and metagenomic analysis in order to determine the soil quality and its bacterial community composition. Likewise, multifunctional biochemical tests and plant inoculation assays were evaluated to determine the potential of S. mexicanum ITTG-R7T as plant-growth-promoting bacteria (PGPB). The site was rain fed and had silty clay loam soil with abundant Bacillaceae. S. mexicanum ITTG-R7T showed different properties as PGPB such as the production of indole compounds, synthesis of extracellular enzymes, phosphate solubilization, synthesis of siderophores, ACC (1-aminocyclopropane-1-carboxylate) deaminase, and nitrogenase activity (ARA). When the strain ITTG-R7 T was combined with chemical nutrients, it had the highest positive effect on the growth and development of guava plants. Guava biofertilization with ITTG-R7T had a significant influence (p < 0.05) mainly on the total plant height (368.83 cm), number of flowers (36.0) and the amount of chlorophyll (2.81 mg mL−1) in comparison with the other treatments evaluated. ITTG-R7T is a promising strain for improving the guava crop yield

Growth Promotion of Guava “Pear” (<i>Psidium guajava</i> cv.) by <i>Sinorhizobium mexicanum</i> in Southern Mexican Agricultural Fields

Biofertilizers formulated with nitrogen-fixing bacteria represent an alternative to chemical fertilizers because they increase soil fertility and protect the environment. Therefore, the objective of this study was to analyze the effects on the growth of guava “pear” (Psidium guajava cv.) after inoculation with a nitrogen fixing bacterium Sinorhizobium mexicanum ITTG-R7T. The study was carried out in an agricultural rural area of Chiapas, Mexico, where farmers do not have programs of regenerative agriculture. First, the agricultural soil was subjected to physicochemical and metagenomic analysis in order to determine the soil quality and its bacterial community composition. Likewise, multifunctional biochemical tests and plant inoculation assays were evaluated to determine the potential of S. mexicanum ITTG-R7T as plant-growth-promoting bacteria (PGPB). The site was rain fed and had silty clay loam soil with abundant Bacillaceae. S. mexicanum ITTG-R7T showed different properties as PGPB such as the production of indole compounds, synthesis of extracellular enzymes, phosphate solubilization, synthesis of siderophores, ACC (1-aminocyclopropane-1-carboxylate) deaminase, and nitrogenase activity (ARA). When the strain ITTG-R7 T was combined with chemical nutrients, it had the highest positive effect on the growth and development of guava plants. Guava biofertilization with ITTG-R7T had a significant influence (p −1) in comparison with the other treatments evaluated. ITTG-R7T is a promising strain for improving the guava crop yield

Bacterial Community with Plant Growth-Promoting Potential Associated to Pioneer Plants from an Active Mexican Volcanic Complex

Microorganisms in extreme volcanic environments play an important role in the development of plants on newly exposed substrates. In this work, we studied the structure and diversity of a bacterial community associated to Andropogon glomeratus and Cheilanthes aemula at El Chich&oacute;n volcano. The genetic diversity of the strains was revealed by genomic fingerprints and by 16S rDNA gene sequencing. Furthermore, a metagenomic analysis of the rhizosphere samples was carried out for pioneer plants growing inside and outside the volcano. Multifunctional biochemical tests and plant inoculation assays were evaluated to determine their potential as plant growth-promoting bacteria (PGPB). Through metagenomic analysis, a total of 33 bacterial phyla were identified from A. glomeratus and C. aemula rhizosphere samples collected inside the volcano, and outside the volcano 23 bacterial phyla were identified. For both rhizosphere samples, proteobacteria was the most abundant phylum. With a cultivable approach, 174 bacterial strains were isolated from the rhizosphere and tissue of plants growing outside the volcanic complex. Isolates were classified within the genera Acinetobacter, Arthrobacter, Bacillus, Burkholderia, Cupriavidus, Enterobacter, Klebsiella, Lysinibacillus, Pantoea, Pseudomonas, Serratia, Stenotrophomonas and Pandoraea. The evaluated strains were able to produce indole compounds, solubilize phosphate, synthesize siderophores, showed ACC deaminase and nitrogenase activity, and they had a positive effect on the growth and development of Capsicum chinense. The wide diversity of bacteria associated to pioneer plants at El Chich&oacute;n volcano with PGPB qualities represent an alternative for the recovery of eroded environments, and they can be used efficiently as biofertilizers for agricultural crops growing under adverse conditions

Biostimulation and Bioaugmentation of Soils Contaminated with Decachlorobiphenyl (PCB-209) Using Native Bacterial Strains Individually and in Consortia

Historically, microorganisms have proven to be efficient alternatives for the removal of PCBs, since these contaminants continue to be a major problem for human health and the environment. In this work, the removal of decachlorobiphenyl (PCB-209) was evaluated using native bacterial strains individually and in consortia through biostimulation and bioaugmentation processes. Bacillus sp. DCB13, Staphylococcus sp. DCB28, and Acinetobacter sp. DCB104 were biostimulated in a minimal medium that initially contained biphenyl and later PCB-209 for adaptation as a carbon source. The removal potential of PCB-209 by bacterial strains was evaluated in a bioaugmentation process under aerobic conditions. Using a completely randomized design, ten different treatments were evaluated. Finally, the bacterial growth (CFU/g of soil) and the chemical characteristics of the bioaugmented soil were determined, as was the content of PCB-209 removed by gas chromatography&ndash;mass spectrometry. Strains DCB13, DCB28, and DCB104 showed cell growth (&gt;3.4 &times; 105 CFU/mL) during 120 h of biostimulation, with a marked difference between treatments with biphenyl compared with those where PCB-209 was added. Strains DCB13 and DCB104 (3.4 &times; 105 CFU/mL and 2.0 &times; 106 CFU/mL, respectively) grew better with PCB-209, while DCB28 grew better with biphenyl (4.5 &times; 106 CFU/mL). In bioaugmented soils contaminated with PCB-209, the strains showed maximum growth when inoculated in a consortium (&gt;2.0 &times; 104 CFU/g). The results showe that the range of the bacterial elimination of PCB-209 in the treatments was from 9.58 to 17.33 mg/kg. The highest elimination potential of PCB-209 was obtained when the bacterial strains were inoculated in a consortium. These findings open a wide perspective for the use of native bacteria for the cleaning and restoration of soils contaminated by toxic chemicals

Biostimulation and Bioaugmentation of Soils Contaminated with Decachlorobiphenyl (PCB-209) Using Native Bacterial Strains Individually and in Consortia

Historically, microorganisms have proven to be efficient alternatives for the removal of PCBs, since these contaminants continue to be a major problem for human health and the environment. In this work, the removal of decachlorobiphenyl (PCB-209) was evaluated using native bacterial strains individually and in consortia through biostimulation and bioaugmentation processes. Bacillus sp. DCB13, Staphylococcus sp. DCB28, and Acinetobacter sp. DCB104 were biostimulated in a minimal medium that initially contained biphenyl and later PCB-209 for adaptation as a carbon source. The removal potential of PCB-209 by bacterial strains was evaluated in a bioaugmentation process under aerobic conditions. Using a completely randomized design, ten different treatments were evaluated. Finally, the bacterial growth (CFU/g of soil) and the chemical characteristics of the bioaugmented soil were determined, as was the content of PCB-209 removed by gas chromatography–mass spectrometry. Strains DCB13, DCB28, and DCB104 showed cell growth (>3.4 × 105 CFU/mL) during 120 h of biostimulation, with a marked difference between treatments with biphenyl compared with those where PCB-209 was added. Strains DCB13 and DCB104 (3.4 × 105 CFU/mL and 2.0 × 106 CFU/mL, respectively) grew better with PCB-209, while DCB28 grew better with biphenyl (4.5 × 106 CFU/mL). In bioaugmented soils contaminated with PCB-209, the strains showed maximum growth when inoculated in a consortium (>2.0 × 104 CFU/g). The results showe that the range of the bacterial elimination of PCB-209 in the treatments was from 9.58 to 17.33 mg/kg. The highest elimination potential of PCB-209 was obtained when the bacterial strains were inoculated in a consortium. These findings open a wide perspective for the use of native bacteria for the cleaning and restoration of soils contaminated by toxic chemicals

Cost-Effective Cultivation of Native PGPB <i>Sinorhizobium</i> Strains in a Homemade Bioreactor for Enhanced Plant Growth

The implementation of bioreactor systems for the production of bacterial inoculants as biofertilizers has become very important in recent decades. However, it is essential to know the bacterial growth optimal conditions to optimize the production and efficiency of bioinoculants. The aim of this work was to identify the best nutriment and mixing conditions to improve the specific cell growth rates (µ) of two PGPB (plant growth-promoting bacteria) rhizobial strains at the bioreactor level. For this purpose, the strains Sinorhizobium mexicanum ITTG-R7T and Sinorhizobium chiapanecum ITTG-S70T were previously reactivated in a PY-Ca2+ (peptone casein, yeast extract, and calcium) culture medium. Afterward, a master cell bank (MCB) was made in order to maintain the viability and quality of the strains. The kinetic characterization of each bacterial strain was carried out in s shaken flask. Then, the effect of the carbon and nitrogen sources and mechanical agitation was evaluated through a factorial design and response surface methodology (RSM) for cell growth optimization, where µ was considered a response variable. The efficiency of biomass production was determined in a homemade bioreactor, taking into account the optimal conditions obtained during the experiment conducted at the shaken flask stage. In order to evaluate the biological quality of the product obtained in the bioreactor, the bacterial strains were inoculated in common bean (Phaseolus vulgaris var. Jamapa) plants under bioclimatic chamber conditions. The maximum cell growth rate in both PGPB strains was obtained using a Y-Ca2+ (yeast extract and calcium) medium and stirred at 200 and 300 rpm. Under these growth conditions, the Sinorhizobium strains exhibited a high nitrogen-fixing capacity, which had a significant (p < 0.05) impact on the growth of the test plants. The bioreactor system was found to be an efficient alternative for the large-scale production of PGPB rhizobial bacteria, which are intended for use as biofertilizers in agriculture

Evaluation of Metabolomic Profile and Growth of Moringa oleifera L. Cultivated with Vermicompost under Different Soil Types

Moringa oleifera is a highly versatile plant with potential use in the agro-food and biochemical industry. The goals of this study were to evaluate the effect of chemical fertilization and vermicompost on plant growth, and to analyze the metabolomic profile of M. oleifera crops cultivated over agricultural and native soils. The extracts were obtained from 90-day-old leaves via extraction with a hydroalcoholic mixture. Multivariate data analyses, such as principal component analysis (PCA) and partial least square-discriminant analysis (PLS-DA), were used to differentiate the distribution of leaf metabolites according to the soils or types of fertilizers used for the cultivation of Moringa oleifera. The results indicated that there was no significant effect on parameters such as plant height, root length and dry weight of leaves (p &lt; 0.05). UPLC-ESI-MS/MS analysis of leaf extracts revealed a wide range of flavonoids, alkaloids and organic acids. The results of PCA and PLS-DA confirmed that the type of fertilizer had an effect on the metabolomic profile of M. oleifera leaves. The application of vermicompost induced changes in the metabolomic profile, but not in the morphometric variables of Moringa oleifera. These results are important for metabolite production via organic cultures and over different soil types in the industrialization of Moringa