Jesús Muñoz-Rojas

Agricultural Plant Science, Biotechnology, Microbiology

Doctor en Ciencias
19.90

Publications

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    Full-text · Article · Dec 2015
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    ABSTRACT: It has been established that a decrease in the population of Gluconacetobacter diazotrophicus associated with sugarcane occurs after nitrogen fertilization. This fact could be due to a direct influence of NH4NO3 on bacterial cells or to changes in plant physiology after fertilizer addition, affecting bacterial establishment. In this work, we observed that survival of G. diazotrophicus was directly influenced when 44.8mM of NH4NO3 (640mgN/plant) was used for in vitro experiments. Furthermore, micropropagated sugarcane plantlets were inoculated with G. diazotrophicus and used for split root experiments, in which both ends of the system were fertilized with a basal level of NH4NO3 (0.35mM; 10mgN/plant). Twenty days post inoculation (dpi) one half of the plants were fertilized with a high dose of NH4NO3 (6.3mM; 180mgN/plant) on one end of the system. This nitrogen level was lower than that directly affecting G. diazotrophicus cells; however, it caused a decrease in the bacterial population in comparison with control plants fertilized with basal nitrogen levels. The decrease in the population of G. diazotrophicus was higher in pots fertilized with a basal nitrogen level when compared with the corresponding end supplied with high levels of NH4NO3 (100dpi; 80 days post fertilization) of the same plant system. These observations suggest that the high nitrogen level added to the plants induce systemic physiological changes that affect the establishment of G. diazotrophicus.
    Full-text · Article · Dec 2015 · Revista Argentina de microbiología
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    ABSTRACT: The aim of this study was to identify the chemical properties and bactericidal activity of Rosmarinus officinalis and Origanum x majoricum in relation to the compounds detected by gas chromatographic analysis. Proceeded to wash samples Rosmarinus officinalis and Origanum x majoricum and were referred to a mashing process for seven days at room temperature with ethanol, filtering the ethanol extracts. The extracts obtained were analyzed by a gas chromatography system equipped with a mass spectrometer. Staphylococcus aureus (ATCC 25923) was used to evaluate the activity antiomicrobial extracts of Rosmarinus officinalis and Origanum x majoricum by the Kirby-Bauer method modified and quantified with the software Image J. Rosmarinus officinalis were detected alcohol, terpene and cetone compounds noted for their abundance and absence of compounds thymol and carvacol. Origanum x majoricum were identified for a considerable percentage of alcohol, acids and esters compounds, highlighting the carvacol as one of the most abundant, and linolenic acid and paeonol was detected. Antimicrobial activity of Rosmarinus officinalis extracts showed greater antimicrobial activity against Staphylococcus aureus, with respect to extract Origanum x majoricum. http://www.arpnjournals.com/jabs/research_papers/rp_2015/jabs_1015_756.pdf
    No preview · Article · Oct 2015
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    ABSTRACT: The PctC chemoreceptor of Pseudomonas aeruginosa mediates chemotaxis with high specificity to gamma-aminobutyric acid (GABA). This compound is present everywhere in nature and has multiple functions, including being a human neurotransmitter or plant signaling compound. Because P. aeruginosa is ubiquitously distributed in nature and able to infect and colonize different hosts, the physiological relevance of GABA taxis is unclear, but it has been suggested that bacterial attraction to neurotransmitters may enhance virulence. We report the identification of McpG as a specific GABA chemoreceptor in non-pathogenic P. putida KT2440. As with PctC, GABA was found to bind McpG tightly. The analysis of chimeras comprising the PctC and McpG ligand-binding domains fused to the Tar signaling domain showed very high GABA sensitivities. We also show that PctC inactivation does not alter virulence in Caenorhabditis elegans. Significant amounts of GABA were detected in tomato root exudates, and deletion of mcpG reduced root colonization that requires chemotaxis through agar. The C. elegans data and the detection of a GABA receptor in non-pathogenic species indicate that GABA taxis may not be related to virulence in animal systems but may be of importance in the context of colonization and infection of plant roots by soil-dwelling pseudomonads. This article is protected by copyright. All rights reserved.
    Full-text · Article · Apr 2015 · Molecular Microbiology
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    ABSTRACT: The microbial antagonism is deleterious or negative association; is the inhibition, damage or death of a microorganism by another action. The objective of the study was to determine the antagonistic effects of different isolates of indigenous microbiota grown in greenhouse tomato and corn of the State of Puebla, against the bacteria Burkholderia cepacia (H1A). Fifteen strains were used, thirteen came from red tomato (Lycopersicum esculentum Mill) and two came from corn (Zea mays), none of them showed antagonism against B. cepacia for the tests about simultaneous inhibition, agar discussion and detection with sensi-disc. Regarding the test of double layer, 26.6% of the strains (all of them isolated from red tomato), were able to inhibit B. cepacia growth; these strains belong to the genres coming from: Pseudomonas (2S3B, 2H4B), Sphingomonas (2S1A) and Chromobacterium (2S1C). ISSN 2334-2501
    Full-text · Article · Aug 2014
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    ABSTRACT: In an attempt to quantify the number of bacteria present in a high number of samples, routine procedures are usually very time-consuming. During this period of time, bacterial population could be modified. In this work, an alternative for a mas-sive, quick and economic method was evaluated in order to count viable bacteria, consisting in the sealing or stamping of serial dilutions performed in samples from different origins. The time required to prepare 22 samples for plate stamping is only 15 minutes. The quantification was based in performing serial dilutions (10-fold) of the original liquid samples contai-ned in a multiwell plate using a multichannel micropipette. Afterwards, using a replicator, the same volume of each sample (approximately 1,65 μl) was recovered from each well, and then it was inoculated and sealed in a solid growth media of interest. Plates were incubated as needed, colonies were counted in the quantifiable dilution and Colony Forming Units per milliliter (CFU/ml) was calculated for each sample. We called this method “Massive Stamping Drop Plate” (MSDP) and it has been successfully applied to count bacteria from different lab samples, including liquid cultures, clinical samples (exudates and secretions) and bacteria recovered from the rhizosphere of corn plants. However, MSDP could also be applied to mas-sively count bacteria from any other source.
    Full-text · Article · Dec 2012
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    ABSTRACT: Pineapple is the second most important tropical fruit in international trade and Mexico ranks ninth in world production. Pink disease is asymptomatic in the field and is characterized by the production of dark discoloration (amber-reddish brown) and its initial effects are not recognized until the fruits are cored and canned. Hence pink disease is considered a major problem in the pineapple canning industry.Four hundred and eighty isolates of pineapple were tested for antagonistic activity vs. Tatumella, causal agent of pink disease, and strain UAPS07070 was selected for further assays.Population dynamics were explored in co-inoculation in vitro and in planta with strain UAPS07070 and T. ptyseos UAPS07007. The population of UAPS07007, the producer strain of the disease severely declined in comparison with the controls.This work contributes to the knowledge of the ecology of pink disease in pineapple, as well as to the comprehension of the interactions between microorganisms colonizing the habitat of the plant.Highlights► We determined the antagonism of B. gladioli on a pink disease causative agent. ► We detected inhibition of T. ptyseos by B. gladioli in in vitro experiments. ► We detected inhibition of T. ptyseos by B. gladioli in in planta experiments. ► We detected pigmentation decline by cultivating T. ptyseos with B. gladioli.
    Full-text · Article · Oct 2012 · Applied Soil Ecology
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    ABSTRACT: The rhizospheric soil interacts with substances of low molecular weight such as carboxylic acids, among other substances, whose sorption dynamics of mineral particle surface is unknown. Adsorption of water and volatile carboxylic acids from plants and bacteria (methane, ethane, propane and butane) was determined by the chromatographic method in an agricultural soil in San Juan Atenco, Puebla, Mexico. The soil under study was characterized by their physical, chemical, biological and surface properties. Porosity was determined by the method of N2 adsorption at its boiling point (76 K). Specific surface area values were determined using the method of Brunauer-Emmett-Teller (BET); pore volume was obtained using the Gursvitch rule and pore size distribution was studied by the Barrett-Joyner-Halenda (BJH) approach. The adsorption of the adsorbates was determined in the temperature range 423-523 K using gas chromatography with thermal conductivity detector and using helium as carrier gas. The Freundlich and Langmuir equations were applied to all cases. The results showed that the adsorption of water and volatile carboxylic acids, derived from biological metabolism in soil, is a function of the differential structure of molecules that impact the degree of interaction with the porous soil system.
    Full-text · Article · Aug 2012
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    ABSTRACT: Bacteria have been found in all niches explored on Earth, their ubiquity derives from their enormous metabolic diversity and their capacity to adapt to changes in the environment. Some bacterial strains are able to thrive in the presence of high concentrations of toxic organic chemicals, such as aromatic compounds, aliphatic alcohols and solvents. The extrusion of these toxic compounds from the cell to the external medium represents the most relevant aspect in the solvent tolerance of bacteria, however, solvent tolerance is a multifactorial process that involves a wide range of genetic and physiological changes to overcome solvent damage. These additional elements include reduced membrane permeabilization, implementation of a stress response programme, and in some cases degradation of the toxic compound. We discuss the recent advances in our understanding of the mechanisms involved in solvent tolerance.
    Full-text · Article · Dec 2011 · Current Opinion in Biotechnology
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    ABSTRACT: A maize rhizosphere isolate was phenotypically and genotypically characterized and identified as Enterobacter spp. bacterium. Germinated seeds were inoculated, the plantlets were sown in vermiculite and in soil and grown under laboratory and field conditions, respectively. The adherence, colonization and plant growth promotion capability of Enterobacter sp. UAPS03001 was evaluated in "Rojo-Criollo" maize under laboratory conditions. Twenty days after inoculation, the treated plantlets showed larger biomass than non-inoculated ones. In field grown plants, the kernel biomass was also greater in inoculated than in non-inoculated plants. The inoculation of maize sprouts with plant growth- promoting bacteria before their sowing in the field would be an alternative practice for achieving successful yield in temporal agriculture.
    Full-text · Article · Oct 2011 · Revista Argentina de microbiología
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    ABSTRACT: Forty soil samples were collected from four rural communities in the Municipality of Huauchinango (Puebla, Mexico), a region with endemic dermatomycoses. Classical and molecular approaches allowed the identification of 30 different species, including several agents of superficial, subcutaneous and opportunistic mycoses. The most prevalent pathogenic agents identified by micro-morphological characteristics were: Trichophyton mentagrophytes (12.5%), T. rubrum (7.5%), and Aspergillus flavus (7.5%). A lower number of isolates was obtained in soils having acidic pH (5.19). Fungal diversity of Ascomycetes was also found in the studied area by sequence analysis of the ITS1-5.8S-ITS2 rDNA region. Our results showed a high prevalence of pathogenic and potential agents of mycoses, as well as the importance of molecular tools to identify microbial populations in soil.
    Full-text · Article · Jan 2011
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    ABSTRACT: Bacteria sustain life on earth, and even thought we only known around 1% of its diversity, several of them could result beneficial when used in different domains, including agriculture, biomedicine, bioremediation, and others. Nowadays, strong effort has been put into elucidating both new bacterial species and the function encoded in their genes; through mutagenesis and sequencing methods. Given the importance of working with bacteria from different sources, it is necessary to count on reliable methods to preserve bacteria successfully, allowing the researcher to use the precise same strain over his research. At the present work, we discuss several methodologies to preserve bacteria properly, while ensuring that they maintain a high viability as well as their phenotypic and genotypic characteristics. The improvement of these preserving techniques will ensure the conservation of the great biotechnological potential that bacteria contain in their genomes. Key words: Bacteria, preservation, freeze, freeze drying.
    Full-text · Article · May 2010
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    ABSTRACT: Pink disease is a major problem in the pineapple canning industry. Affected fruit acquire a brownish pigment after pasteurization and can contaminate non-affected fruit before they are released to the consumer. In the last few years, Pantoea citrea has been described as the causative agent of pink disease. In this study, over 300 bacterial isolates from pineapple plants, growing in Mexican commercial fields, and from soil close to plant roots were recovered. Over 250 isolates showed a very high similarity in their phenotypic and genotypic traits with Tatumella ptyseos, a close relative of Pantoea. These isolates exhibited typical pathogenicity reactions in pineapple juice tests, pineapple slices and fruit. On this basis, molecular identification procedures for the Tatumella isolates associated with pink disease were implemented. In affected fruit populations around 106 CFU/g of fresh tissue were recovered. This is first time that T. ptyseos is demonstrated as a causal agent of pink disease.
    Full-text · Article · Jan 2010 · Journal of Phytopathology
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    Full-text · Article · Jan 2010
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    Full-text · Article · Jan 2010
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    ABSTRACT: Bacterial isolates from maize plants showing a leaf spot disease were identified through molecular and phenotypic traits, showing that the isolates belong to Pantoea ananatis. Maize plants inoculated with those isolates showed a pathogenic reaction. This is the first report of a disease of Mexican maize caused by P. ananatis. Additional keywordsEnterobacteriaceae–Zea mays–phytopathogen
    Full-text · Article · Jan 2009 · Australasian Plant Disease Notes
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    ABSTRACT: We used a two-step enrichment approach to isolate root-colonizing hexachlorocyclohexane (HCH)-degrading microorganisms. The first step consists of the use of classical liquid enrichment to isolate γ-HCH degraders. The γ-HCH-degrading microbes were attached in mass to corn seeds sown in soil with γ-HCH, and after plant development we rescued bacteria growing on root tips. Bacteria were then subjected to a second enrichment round in which growth on liquid medium with γ-HCH and inoculation of corn seeds were repeated. We then isolated bacteria on M9 minimal medium with γ-HCH from root tips. We were able to isolate four Sphingomonas strains, all of which degraded α-, β-, γ- and δ-HCH. Two of the strains were particularly good colonizers of corn roots, reaching high cell density in vegetated soil and partly removing γ-HCH. In contrast, these bacteria performed poorly in unplanted soils. This study supports the hypothesis that the removal of persistent toxic chemicals can be accelerated by combinations of plants and bacteria, a process generally known as rhizoremediation.
    Full-text · Article · Jan 2008 · Microbial Biotechnology
  • Patricia Bernal · Jesús Muñoz-Rojas · Ana Hurtado · Juan L Ramos · Ana Segura
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    ABSTRACT: Biological membranes have evolved different mechanisms to modify their composition in response to chemical stimuli in a process called 'homeoviscous adaptation'. Among these mechanisms, modifications in the ratio of saturated/unsaturated fatty acids and in cis/trans fatty acid isomers, cyclopropanation and changes in the phospholipids head group composition have been observed. To further understand the role of phospholipid head groups in solvent stress adaptation, we knocked out the cls (cardiolipin synthase) gene in Pseudomonas putida DOT-T1E. As expected, cls mutant membranes contained less cardiolipin than those of the wild-type strain. Although no significant growth rate defect was observed in the cls mutant compared with the wild-type strain, mutant cells were significantly smaller than the wild-type cells. The cls mutant was more sensitive to toluene shocks and to several antibiotics than the parental strain, suggesting either that the RND efflux pumps involved in the extrusion of these drugs were not working efficiently or that membrane permeability was altered in the mutant. Membranes of the cls mutant strain seemed to be more rigid than those of the parental strain, as observed by measurements of fluorescence polarization using the DPH probe, which intercalates into the membranes. Ethidium bromide is pumped out in Pseudomonas putida by at least one RND efflux pump involved in antibiotic and solvent resistance, and the higher rate of accumulation of ethidium bromide inside mutant cells indicated that functioning of the efflux pumps was compromised as a consequence of the alteration in phospholipid head group composition.
    No preview · Article · Jun 2007 · Environmental Microbiology
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    ABSTRACT: Pseudomonas putida encodes 20 extracytoplasmic sigma factors (ECFs). In this study, we show that one of these ECFs, known as ECF-Pp12 (PP3006), plays a role in tolerance of toluene and other organic solvents. Based on this finding, we have called the gene that encodes this new ECF rpoT. The rpoT gene forms an operon with the preceding gene and with the gene located downstream. The translated gene product of the open reading frame PP3005 is an inner membrane protein, whereas the PP3007 protein is periplasmic. A nonpolar ΔrpoT mutant was generated by homologous recombination, and survival of the mutant was tested under various stress conditions. The mutant strain was hypersensitive to toluene and other solvents but just as tolerant as the wild type of stress imposed by heat, antibiotics, NaCl, paraquat, sodium dodecyl sulfate, H2O2, and benzoate. In the ΔrpoT mutant background, expression of around 50 transcriptional units was affected: 31 cistrons were upregulated, and 23 cistrons were downregulated. This indicates that about 1% of all P. putida genes are under the direct or indirect influence of RpoT. The rpoT gene controls the expression of a number of membrane proteins, including components of the respiratory chains, porins, transporters, and multidrug efflux pumps. Hypersensitivity of the P. putida RpoT-deficient mutant to organic solvents can be attributed to the fact that in the ΔrpoT strain, expression of the toluene efflux pump ttgGHI genes is severalfold lower than in the parental strain.
    Full-text · Article · Feb 2007 · Journal of Bacteriology
  • Y.E. Morales G. · Ma.C. Herrera · J. Muñoz Rojas
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    ABSTRACT: Chloramphenicol is a potent broad-spectrum antibiotic produced by diverse species of the Streptomyces genus. Because the chemical structure of this antibiotic is relatively simple, chloramphenicol was one of the first antibiotics to be chemically synthesized and produced on a commercial scale. Even though chloramphenicol is a toxic molecule, it is used as a systemic antibiotic in excepcional cases. In addition, due to its reduced size and apolar characteristics, chloramphenicol represents an alternative for the treatment of infections located in sites with difficult accessibility, such as the brain. This revision offers a global view of the knowledge related to chloramphenicol including: its biosynthesis, the mechanisms of action and the strategies that microorganisms have developed to avoid the effects of this antibiotic.
    No preview · Article · Jan 2007 · Revista Mexicana de Ciencias Farmaceuticas

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