Alejandro Lopez Cortes | Centro de Investigaciones Biologicas (CIB) (original) (raw)

Papers by Alejandro Lopez Cortes

Microorganisms, 2023

Knowledge regarding the diversity of methanogenic archaeal communities in hypersaline environment... more Knowledge regarding the diversity of methanogenic archaeal communities in hypersaline environments is limited because of the lack of efficient cultivation efforts as well as their low abun- dance and metabolic activities. In this study, we explored the microbial communities in hypersaline microbial mats. Bioinformatic analyses showed significant differences among the archaeal com- munity structures for each studied site. Taxonomic assignment based on 16S rRNA and methyl coenzyme-M reductase (mcrA) gene sequences, as well as metagenomic analysis, corroborated the presence of Methanosarcinales. Furthermore, this study also provided evidence for the presence of Methanobacteriales, Methanomicrobiales, Methanomassiliicoccales, Candidatus Methanofastidiosales, Methanocellales, Methanococcales and Methanopyrales, although some of these were found in ex- tremely low relative abundances. Several mcrA environmental sequences were significantly different from those previously reported and did not match with any known methanogenic archaea, suggesting the presence of specific environmental clusters of methanogenic archaea in Guerrero Negro. Based on functional inference and the detection of specific genes in the metagenome, we hypothesised that all four methanogenic pathways were able to occur in these environments. This study allowed the detection of extremely low-abundance methanogenic archaea, which were highly diverse and with unknown physiology, evidencing the presence of all methanogenic metabolic pathways rather than the sheer existence of exclusively methylotrophic methanogenic archaea in hypersaline environments.

En esencia, la clonación, es decir, la reproducción de …, 1998

RESUMEN El presente artículo describe algunos aspectos biológicos, eco-lógicos y biotecnológicos ... more RESUMEN El presente artículo describe algunos aspectos biológicos, eco-lógicos y biotecnológicos del conocimiento y utilización de las comunidades microbianas laminadas (tapetes microbianos y oncolitos) y de sus miembros, arqueobacterias y cianobac-terias, ...

Two proteins were purified and preliminarily characterized from the soluble extract of cells (310... more Two proteins were purified and preliminarily characterized from the soluble extract of cells (310 g, wet weight) of the aminolytic and peptidolytic sulfate-reducing bacterium Desulfovibrio (D.) aminophilus DSM 12254. The iron-sulfur flavoenzyme adenylylsulfate (adenosine 5"-phosphosulfate, APS) reductase, a key enzyme in the microbial dissimilatory sulfate reduction, has been purified in three chromatographic steps (DEAE-Biogel A, Source 15, and Superdex 200 columns). It contains two different subunits with molecular masses of 75 and 18 kDa. The fraction after the last purification step had a purity index (A278 ,m/A388 nm) of 5.34, which was used for further EPR spectroscopic studies. The D. aminophilus APS reductase is very similar to the homologous enzymes isolated from D. gigas and D. desulfuricans ATCC 27774. A tetraheme cytochrome c3 (His-heme iron-His) has been purified in three chromatographic steps (DEAE-Biogel A, Source 15, and Biogel-HTP columns) and preliminarily characterized. It has a purity index ([A.s.s3 nm" A570 nm]rcd/m280nm ox) of 2.9 and a molecular mass of around 15 kDa, and its spectroscopic characterization (NMR and EPR) has been carried out. This hemoprotein presents similarities with the tetraheme cytochrome c3 from Desulfomicrobium (Des.) norvegicurn (NMR spectra, and N-terminal amino acid sequence).

Current Microbiology

The bacterial strain 42Xb2 T was isolated from a female adult krill Nyctiphanes simplex infected ... more The bacterial strain 42Xb2 T was isolated from a female adult krill Nyctiphanes simplex infected with the apostome parasitoid ciliate Pseudocollinia brintoni in January 2007 in the Gulf of California. The strain has the morphological, phenotypic, and molecular characteristics of the bacteria of the family Vibrionaceae. The 16S rRNA gene sequence has a similarity of 97.7% with Enterovibrio pacificus SW014 T and 96.1% similarity with Enterovibrio norvegicus LMG 19839 T. A phylogenomic and a multilocus sequence analyses placed this strain close to the genera Enterovibrio, Grimontia, and Salinivibrio, but clearly forming a separate branch from these bacterial genera. Genomic analyses presented further support this result. A novel genus Veronia gen. nov. and a species Veronia nyctiphanis sp. nov. is here described with CAIM 600 T (= DSM 24592 T = CECT 7578 T) as the type strain. Morphological, physiological, and genetic evidence presented here support the unification of Enterovibrio pacificus and Veronia nyctiphanis in the new genus Veronia. Enterovibrio pacificus is reclassified as Veronia pacifica. V. pacifica is assigned as the type species of the new genus Veronia.Genome Sequencing Data The GenBank/EMBL/DDBJ accession numbers for the genome sequence of Veronia nyctiphanis CAIM 600 T is PEIB01 and of Enterovibrio pacificus CAIM 1920 T is LYBM01. The 16S rRNA gene sequence of V. nyctiphanis CAIM 600 T is JX129353.

Current Microbiology

This study investigated the intestinal microbial community structure of Litopenaeus vannamei at s... more This study investigated the intestinal microbial community structure of Litopenaeus vannamei at six different stages during shrimp farming. Our goal was to elucidate the bacterial profile and the changes in the relative abundance of taxa during an atypical massive mortality event in Sonora, Mexico. High-throughput sequencing of the 16S rRNA gene and denaturing gradient gel electrophoresis showed that Vibrionaceae was persistent with high relative abundances in the intestine from cultivated shrimp during all the studied stages. The massive mortality observed at day 63 could be related to an overabundance of different Operational Taxonomic Units (OTUs) of Vibrio, Shewanella and Clostridium. Principal coordinate analysis (PCoA) showed variations in microbial structure at different culture times. These findings suggest that OTUs of different taxa contributed to the community switch from healthy to diseased individuals, questioning the hypothesis that single bacterial species is the cause of disease outbreaks. This study provided data to improve the understanding of disease outbreaks during shrimp farming.

Extremophiles

Bacterial and archaeal community structure of five microbial communities, developing at different... more Bacterial and archaeal community structure of five microbial communities, developing at different salinities in Baja California Sur, Mexico, were characterized by 16S rRNA sequencing. The response of the microbial community to artificial changes in salinity–sulfate concentrations and to addition of trimethylamine was also evaluated in microcosm experiments. Ordination analyses of the microbial community structure showed that microbial composition was distinctive for each hypersaline site. Members of bacteria were dominated by Bacteroidetes and Proteobacteria phyla, while Halobacteria of the Euryarchaeota phylum was the most represented class of archaea for all the environmental samples. At a higher phylogenetic resolution, methanogenic communities were dominated by members of the Methanosarcinales, Methanobacteriales and Methanococcales orders. Incubation experiments showed that putative hydrogenotrophic methanogens of the Methanomicrobiales increased in abundance only under lowest salinity and sulfate concentrations. Trimethylamine addition effectively increased the abundance of methylotrophic members from the Methanosarcinales, but also increased the relative abundance of the Thermoplasmata class, suggesting the potential capability of these microorganisms to use trimethylamine in hypersaline environments. These results contribute to the knowledge of microbial diversity in hypersaline environments from Baja California Sur, Mexico, and expand upon the available information for uncultured methanogenic archaea in these ecosystems.

Revista, vol, 1979

Nas comunidades rurais, o transporte escolar é fundamental no acesso à unidade de ensino, porém o... more Nas comunidades rurais, o transporte escolar é fundamental no acesso à unidade de ensino, porém o tempo que os estudantes permanecem no veículo até as escolas acaba sendo muito longo, o que acarreta no cansaço e desgaste dos alunos e, consequentemente, influencia no seu rendimento escolar. Um exemplo desta situação acontece no Instituto Federal de Roraima/campus Novo Paraíso, localizado na zona rural de Caracaraí-RR, onde o tempo de deslocamento até a escola é maior que o recomendado e o desempenho dos alunos no Exame Nacional do Ensino Médio nos últimos dois anos foi abaixo da média nacional. Para minimizar esse problema, é necessário, além de um melhor planejamento das rotas do transporte rural, políticas públicas para melhorar as vias rurais e um plano pedagógico de ensino que seja mais atrativo e retrate a realidade dos alunos do campo. Transporte escolar rural. Desempenho escolar. Tempo de deslocamento.

Australian Journal of Agricultural Research, 2002

The salt tolerance of 25 cowpea genotypes (Vigna unguiculata L. Walp.) was studied during early v... more The salt tolerance of 25 cowpea genotypes (Vigna unguiculata L. Walp.) was studied during early vegetative growth. Salinity treatments were applied by irrigating with a nutrient solution containing 0, 85, and 170 mmol NaCl/L. Seedling survival decreased linearly as salinity increased, but this enabled cowpea genotypes to be ranked for salinity tolerance according to the magnitudes of slopes of regression of survival percentage on salinity. Sodium concentration was higher in roots than in shoots in all genotypes, and increased significantly in both roots and shoots as salinity increased. Chloride concentration in both roots and shoots increased with increasing salinity in all genotypes, and was higher in shoots than in roots at 85 and 170 mmol NaCl/L. In some cases, Ca, Mg, K, and P concentrations were reduced by an increase in salinity, but none of the genotypes appeared to suffer any nutrient deficiency. We observed wide differences in responses to salinity, and our results suggest...

World Journal of …, 2010

Page 1. ORIGINAL PAPER Characterization of polyhydroxyalkanoate and the phaC gene of Paracoccus s... more Page 1. ORIGINAL PAPER Characterization of polyhydroxyalkanoate and the phaC gene of Paracoccus seriniphilus E71 strain isolated from a polluted marine microbial mat Alejandro López-Cortés Æ Oliverio Rodrıguez-Fernández ...

In this work, the characterization of poly(3-hydroxybutyrate) PHB produced by Halomonas salina is... more In this work, the characterization of poly(3-hydroxybutyrate) PHB produced by Halomonas salina isolated from a hypersaline microbial mat from Guerrero Negro, Baja California Sur, Mexico, is reported. The bacterial strain was able to produce isotactic PHB biopolymer with glucose (1%) as a single carbon source. The chemical structure of the polymer obtained was confirmed by Fourier-transform infrared (FTIR) and Nuclear magnetic resonance (NMR) spectroscopy. The polymer was thermally stable up to 225 °C and Differential scanning calorimetry (DSC) analysis showed a melting temperature (T m) of 173.6 °C. The obtained polymer presented a lower degree of crystallinity (39.3%) in comparison with PHB produced by other bacteria and polyhydroxyalkanoate co-polymers. Thus, the PHB biopolymer obtained in this study, could be recognized as more suitable for practical use, contributing to the repertoire of available bioplastics for further potential biotechnological applications, in which elastic polymers are needed.

The bacterial strain 42Xb2 T was isolated from a female adult krill Nyctiphanes simplex infected ... more The bacterial strain 42Xb2 T was isolated from a female adult krill Nyctiphanes simplex infected with the apostome parasitoid ciliate Pseudocollinia brintoni in January 2007 in the Gulf of California. The strain has the morphological, phenotypic, and molecular characteristics of the bacteria of the family Vibrionaceae. The 16S rRNA gene sequence has a similarity of 97.7% with Enterovibrio pacificus SW014 T and 96.1% similarity with Enterovibrio norvegicus LMG 19839 T. A phylogenomic and a multilocus sequence analyses placed this strain close to the genera Enterovibrio, Grimontia, and Salinivibrio, but clearly forming a separate branch from these bacterial genera. Genomic analyses presented further support this result. A novel genus Veronia gen. nov. and a species Veronia nyctiphanis sp. nov. is here described with CAIM 600 T (= DSM 24592 T = CECT 7578 T) as the type strain. Morphological, physiological, and genetic evidence presented here support the unification of Enterovibrio pacificus and Veronia nyctiphanis in the new genus Veronia. Enterovibrio pacificus is reclassified as Veronia pacifica. V. pacifica is assigned as the type species of the new genus Veronia. Genome Sequencing Data The GenBank/EMBL/DDBJ accession numbers for the genome sequence of Veronia nyctiphanis CAIM 600 T is PEIB01 and of Enterovibrio pacificus CAIM 1920 T is LYBM01. The 16S rRNA gene sequence of V. nyctiphanis CAIM 600 T is JX129353.

... 1 / 1 Seleccione referencia / Select reference. Signatura : F/631.58 C5. Autor : Alejandro Ló... more ... 1 / 1 Seleccione referencia / Select reference. Signatura : F/631.58 C5. Autor : Alejandro López Cortés, Yolanda Maya Delgado, Enrique Troyo Diéguez, Luis Landa Hernández. Aut. Analit.: López Cortés, Alejandro Maya Delgado, Yolanda coaut. Troyo Diéguez, Enrique coaut. ...

LOS MAESTROS ALEJANDRO LOPEZ CORTES, DE LA FACULTAD DE CIENCIAS (FCYA), Y ANTONIO LAZCANO ARAUJO,... more LOS MAESTROS ALEJANDRO LOPEZ CORTES, DE LA FACULTAD DE CIENCIAS (FCYA), Y ANTONIO LAZCANO ARAUJO, DEL INSTITUTO DE ASTRONOMIA (IA) DE LA UNAM, AL COMPARAR LOS DIFERENTES METABOLISMOS DE MICROORGANISMO ANAEROBIOS CONTEMPORANEOS, HAN PODIDO DEMOSTRAR QUE EN LA TIERRA PRIMITIVA SE DIO RAPIDAMENTE UN PROCESO DE DIVERSIFICACION QUE LLEVO A LA UTILIZACION DE DIFERENTES SUSTANCIAS EN LA FERMENTACION, QUE ES EL METABOLISMO MAS SIMPLE QUE EXISTE. LOS INVESTIGADORES BASAN SUS INVESTIGACIONES EN LA TEORIA OPARIN-HALDANE.

Recursos Naturales y Sociedad

El presente artículo describe algunos aspectos biológicos, ecológicos y biotecnológicos de microo... more El presente artículo describe algunos aspectos biológicos, ecológicos y biotecnológicos de microorganismos de la Península de Baja California, con el propósito de difundir su uso e importancia y promover la protección de áreas naturales que poseen este patrimonio biológico. Especial énfasis es dado a los tapetes microbianos laminados, a las bacterias promotoras de crecimiento en plantas y su participación en la remediación de aguas residuales y de suelos contaminados. También se incluyen resultados de los beneficios de la composta como agente mejorador de suelos de ambientes desérticos.

PeerJ, 2018

Hypersaline microbial mats develop through seasonal and diel fluctuations, as well as under sever... more Hypersaline microbial mats develop through seasonal and diel fluctuations, as well as under several physicochemical variables. Hence, resident microorganisms commonly employ strategies such as the synthesis of polyhydroxyalkanoates (PHAs) in order to resist changing and stressful conditions. However, the knowledge of bacterial PHA production in hypersaline microbial mats has been limited to date, particularly in regard to medium-chain length PHAs (mcl-PHAs), which have biotechnological applications due to their plastic properties. The aim of this study was to obtain evidence for PHA production in two hypersaline microbial mats of Guerrero Negro, Mexico by searching for PHA granules and PHA synthase genes in isolated bacterial strains and environmental samples. Six PHA-producing strains were identified by 16S rRNA gene sequencing; three of them corresponded to a sp. In addition, sp., sp. and sp. were also identified as PHA producers. Presumptive PHA granules and PHA synthases genes w...

Australian Journal of Experimental Agriculture, 2001

Current Microbiology, 2020

This study investigated the intestinal microbial community structure of Litopenaeus vannamei at s... more This study investigated the intestinal microbial community structure of Litopenaeus vannamei at six different stages during shrimp farming. Our goal was to elucidate the bacterial profile and the changes in the relative abundance of taxa during an atypical massive mortality event in Sonora, Mexico. High-throughput sequencing of the 16S rRNA gene and denaturing gradient gel electrophoresis showed that Vibrionaceae was persistent with high relative abundances in the intestine from cultivated shrimp during all the studied stages. The massive mortality observed at day 63 could be related to an overabundance of different Operational Taxonomic Units (OTUs) of Vibrio, Shewanella and Clostridium. Principal coordinate analysis (PCoA) showed variations in microbial structure at different culture times. These findings suggest that OTUs of different taxa contributed to the community switch from healthy to diseased individuals, questioning the hypothesis that single bacterial species is the caus...

Journal of Polymers and the Environment

In this work, the characterization of poly(3-hydroxybutyrate) PHB produced by Halomonas salina is... more In this work, the characterization of poly(3-hydroxybutyrate) PHB produced by Halomonas salina isolated from a hypersa-line microbial mat from Guerrero Negro, Baja California Sur, Mexico, is reported. The bacterial strain was able to produce isotactic PHB biopolymer with glucose (1%) as a single carbon source. The chemical structure of the polymer obtained was confirmed by Fourier-transform infrared (FTIR) and Nuclear magnetic resonance (NMR) spectroscopy. The polymer was thermally stable up to 225 °C and Differential scanning calorimetry (DSC) analysis showed a melting temperature (T m) of 173.6 °C. The obtained polymer presented a lower degree of crystallinity (39.3%) in comparison with PHB produced by other bacteria and polyhydroxyalkanoate co-polymers. Thus, the PHB biopolymer obtained in this study, could be recognized as more suitable for practical use, contributing to the repertoire of available bioplastics for further potential biotechnological applications, in which elastic polymers are needed.

Geomicrobiology …, 1994

The presence of extremely halophilic archaebacteria in NaCl solution increased the number and siz... more The presence of extremely halophilic archaebacteria in NaCl solution increased the number and size of cubic crystals of halite formed and also yielded dendritic crystals. Various dissolved and suspended materials such as glucose, glycerol, casein hy-drolysate, amino acids, ...

Microorganisms, 2023

Knowledge regarding the diversity of methanogenic archaeal communities in hypersaline environment... more Knowledge regarding the diversity of methanogenic archaeal communities in hypersaline environments is limited because of the lack of efficient cultivation efforts as well as their low abun- dance and metabolic activities. In this study, we explored the microbial communities in hypersaline microbial mats. Bioinformatic analyses showed significant differences among the archaeal com- munity structures for each studied site. Taxonomic assignment based on 16S rRNA and methyl coenzyme-M reductase (mcrA) gene sequences, as well as metagenomic analysis, corroborated the presence of Methanosarcinales. Furthermore, this study also provided evidence for the presence of Methanobacteriales, Methanomicrobiales, Methanomassiliicoccales, Candidatus Methanofastidiosales, Methanocellales, Methanococcales and Methanopyrales, although some of these were found in ex- tremely low relative abundances. Several mcrA environmental sequences were significantly different from those previously reported and did not match with any known methanogenic archaea, suggesting the presence of specific environmental clusters of methanogenic archaea in Guerrero Negro. Based on functional inference and the detection of specific genes in the metagenome, we hypothesised that all four methanogenic pathways were able to occur in these environments. This study allowed the detection of extremely low-abundance methanogenic archaea, which were highly diverse and with unknown physiology, evidencing the presence of all methanogenic metabolic pathways rather than the sheer existence of exclusively methylotrophic methanogenic archaea in hypersaline environments.

En esencia, la clonación, es decir, la reproducción de …, 1998

RESUMEN El presente artículo describe algunos aspectos biológicos, eco-lógicos y biotecnológicos ... more RESUMEN El presente artículo describe algunos aspectos biológicos, eco-lógicos y biotecnológicos del conocimiento y utilización de las comunidades microbianas laminadas (tapetes microbianos y oncolitos) y de sus miembros, arqueobacterias y cianobac-terias, ...

Two proteins were purified and preliminarily characterized from the soluble extract of cells (310... more Two proteins were purified and preliminarily characterized from the soluble extract of cells (310 g, wet weight) of the aminolytic and peptidolytic sulfate-reducing bacterium Desulfovibrio (D.) aminophilus DSM 12254. The iron-sulfur flavoenzyme adenylylsulfate (adenosine 5"-phosphosulfate, APS) reductase, a key enzyme in the microbial dissimilatory sulfate reduction, has been purified in three chromatographic steps (DEAE-Biogel A, Source 15, and Superdex 200 columns). It contains two different subunits with molecular masses of 75 and 18 kDa. The fraction after the last purification step had a purity index (A278 ,m/A388 nm) of 5.34, which was used for further EPR spectroscopic studies. The D. aminophilus APS reductase is very similar to the homologous enzymes isolated from D. gigas and D. desulfuricans ATCC 27774. A tetraheme cytochrome c3 (His-heme iron-His) has been purified in three chromatographic steps (DEAE-Biogel A, Source 15, and Biogel-HTP columns) and preliminarily characterized. It has a purity index ([A.s.s3 nm" A570 nm]rcd/m280nm ox) of 2.9 and a molecular mass of around 15 kDa, and its spectroscopic characterization (NMR and EPR) has been carried out. This hemoprotein presents similarities with the tetraheme cytochrome c3 from Desulfomicrobium (Des.) norvegicurn (NMR spectra, and N-terminal amino acid sequence).

Current Microbiology

The bacterial strain 42Xb2 T was isolated from a female adult krill Nyctiphanes simplex infected ... more The bacterial strain 42Xb2 T was isolated from a female adult krill Nyctiphanes simplex infected with the apostome parasitoid ciliate Pseudocollinia brintoni in January 2007 in the Gulf of California. The strain has the morphological, phenotypic, and molecular characteristics of the bacteria of the family Vibrionaceae. The 16S rRNA gene sequence has a similarity of 97.7% with Enterovibrio pacificus SW014 T and 96.1% similarity with Enterovibrio norvegicus LMG 19839 T. A phylogenomic and a multilocus sequence analyses placed this strain close to the genera Enterovibrio, Grimontia, and Salinivibrio, but clearly forming a separate branch from these bacterial genera. Genomic analyses presented further support this result. A novel genus Veronia gen. nov. and a species Veronia nyctiphanis sp. nov. is here described with CAIM 600 T (= DSM 24592 T = CECT 7578 T) as the type strain. Morphological, physiological, and genetic evidence presented here support the unification of Enterovibrio pacificus and Veronia nyctiphanis in the new genus Veronia. Enterovibrio pacificus is reclassified as Veronia pacifica. V. pacifica is assigned as the type species of the new genus Veronia.Genome Sequencing Data The GenBank/EMBL/DDBJ accession numbers for the genome sequence of Veronia nyctiphanis CAIM 600 T is PEIB01 and of Enterovibrio pacificus CAIM 1920 T is LYBM01. The 16S rRNA gene sequence of V. nyctiphanis CAIM 600 T is JX129353.

Current Microbiology

This study investigated the intestinal microbial community structure of Litopenaeus vannamei at s... more This study investigated the intestinal microbial community structure of Litopenaeus vannamei at six different stages during shrimp farming. Our goal was to elucidate the bacterial profile and the changes in the relative abundance of taxa during an atypical massive mortality event in Sonora, Mexico. High-throughput sequencing of the 16S rRNA gene and denaturing gradient gel electrophoresis showed that Vibrionaceae was persistent with high relative abundances in the intestine from cultivated shrimp during all the studied stages. The massive mortality observed at day 63 could be related to an overabundance of different Operational Taxonomic Units (OTUs) of Vibrio, Shewanella and Clostridium. Principal coordinate analysis (PCoA) showed variations in microbial structure at different culture times. These findings suggest that OTUs of different taxa contributed to the community switch from healthy to diseased individuals, questioning the hypothesis that single bacterial species is the cause of disease outbreaks. This study provided data to improve the understanding of disease outbreaks during shrimp farming.

Extremophiles

Bacterial and archaeal community structure of five microbial communities, developing at different... more Bacterial and archaeal community structure of five microbial communities, developing at different salinities in Baja California Sur, Mexico, were characterized by 16S rRNA sequencing. The response of the microbial community to artificial changes in salinity–sulfate concentrations and to addition of trimethylamine was also evaluated in microcosm experiments. Ordination analyses of the microbial community structure showed that microbial composition was distinctive for each hypersaline site. Members of bacteria were dominated by Bacteroidetes and Proteobacteria phyla, while Halobacteria of the Euryarchaeota phylum was the most represented class of archaea for all the environmental samples. At a higher phylogenetic resolution, methanogenic communities were dominated by members of the Methanosarcinales, Methanobacteriales and Methanococcales orders. Incubation experiments showed that putative hydrogenotrophic methanogens of the Methanomicrobiales increased in abundance only under lowest salinity and sulfate concentrations. Trimethylamine addition effectively increased the abundance of methylotrophic members from the Methanosarcinales, but also increased the relative abundance of the Thermoplasmata class, suggesting the potential capability of these microorganisms to use trimethylamine in hypersaline environments. These results contribute to the knowledge of microbial diversity in hypersaline environments from Baja California Sur, Mexico, and expand upon the available information for uncultured methanogenic archaea in these ecosystems.

Revista, vol, 1979

Nas comunidades rurais, o transporte escolar é fundamental no acesso à unidade de ensino, porém o... more Nas comunidades rurais, o transporte escolar é fundamental no acesso à unidade de ensino, porém o tempo que os estudantes permanecem no veículo até as escolas acaba sendo muito longo, o que acarreta no cansaço e desgaste dos alunos e, consequentemente, influencia no seu rendimento escolar. Um exemplo desta situação acontece no Instituto Federal de Roraima/campus Novo Paraíso, localizado na zona rural de Caracaraí-RR, onde o tempo de deslocamento até a escola é maior que o recomendado e o desempenho dos alunos no Exame Nacional do Ensino Médio nos últimos dois anos foi abaixo da média nacional. Para minimizar esse problema, é necessário, além de um melhor planejamento das rotas do transporte rural, políticas públicas para melhorar as vias rurais e um plano pedagógico de ensino que seja mais atrativo e retrate a realidade dos alunos do campo. Transporte escolar rural. Desempenho escolar. Tempo de deslocamento.

Australian Journal of Agricultural Research, 2002

The salt tolerance of 25 cowpea genotypes (Vigna unguiculata L. Walp.) was studied during early v... more The salt tolerance of 25 cowpea genotypes (Vigna unguiculata L. Walp.) was studied during early vegetative growth. Salinity treatments were applied by irrigating with a nutrient solution containing 0, 85, and 170 mmol NaCl/L. Seedling survival decreased linearly as salinity increased, but this enabled cowpea genotypes to be ranked for salinity tolerance according to the magnitudes of slopes of regression of survival percentage on salinity. Sodium concentration was higher in roots than in shoots in all genotypes, and increased significantly in both roots and shoots as salinity increased. Chloride concentration in both roots and shoots increased with increasing salinity in all genotypes, and was higher in shoots than in roots at 85 and 170 mmol NaCl/L. In some cases, Ca, Mg, K, and P concentrations were reduced by an increase in salinity, but none of the genotypes appeared to suffer any nutrient deficiency. We observed wide differences in responses to salinity, and our results suggest...

World Journal of …, 2010

Page 1. ORIGINAL PAPER Characterization of polyhydroxyalkanoate and the phaC gene of Paracoccus s... more Page 1. ORIGINAL PAPER Characterization of polyhydroxyalkanoate and the phaC gene of Paracoccus seriniphilus E71 strain isolated from a polluted marine microbial mat Alejandro López-Cortés Æ Oliverio Rodrıguez-Fernández ...

In this work, the characterization of poly(3-hydroxybutyrate) PHB produced by Halomonas salina is... more In this work, the characterization of poly(3-hydroxybutyrate) PHB produced by Halomonas salina isolated from a hypersaline microbial mat from Guerrero Negro, Baja California Sur, Mexico, is reported. The bacterial strain was able to produce isotactic PHB biopolymer with glucose (1%) as a single carbon source. The chemical structure of the polymer obtained was confirmed by Fourier-transform infrared (FTIR) and Nuclear magnetic resonance (NMR) spectroscopy. The polymer was thermally stable up to 225 °C and Differential scanning calorimetry (DSC) analysis showed a melting temperature (T m) of 173.6 °C. The obtained polymer presented a lower degree of crystallinity (39.3%) in comparison with PHB produced by other bacteria and polyhydroxyalkanoate co-polymers. Thus, the PHB biopolymer obtained in this study, could be recognized as more suitable for practical use, contributing to the repertoire of available bioplastics for further potential biotechnological applications, in which elastic polymers are needed.

The bacterial strain 42Xb2 T was isolated from a female adult krill Nyctiphanes simplex infected ... more The bacterial strain 42Xb2 T was isolated from a female adult krill Nyctiphanes simplex infected with the apostome parasitoid ciliate Pseudocollinia brintoni in January 2007 in the Gulf of California. The strain has the morphological, phenotypic, and molecular characteristics of the bacteria of the family Vibrionaceae. The 16S rRNA gene sequence has a similarity of 97.7% with Enterovibrio pacificus SW014 T and 96.1% similarity with Enterovibrio norvegicus LMG 19839 T. A phylogenomic and a multilocus sequence analyses placed this strain close to the genera Enterovibrio, Grimontia, and Salinivibrio, but clearly forming a separate branch from these bacterial genera. Genomic analyses presented further support this result. A novel genus Veronia gen. nov. and a species Veronia nyctiphanis sp. nov. is here described with CAIM 600 T (= DSM 24592 T = CECT 7578 T) as the type strain. Morphological, physiological, and genetic evidence presented here support the unification of Enterovibrio pacificus and Veronia nyctiphanis in the new genus Veronia. Enterovibrio pacificus is reclassified as Veronia pacifica. V. pacifica is assigned as the type species of the new genus Veronia. Genome Sequencing Data The GenBank/EMBL/DDBJ accession numbers for the genome sequence of Veronia nyctiphanis CAIM 600 T is PEIB01 and of Enterovibrio pacificus CAIM 1920 T is LYBM01. The 16S rRNA gene sequence of V. nyctiphanis CAIM 600 T is JX129353.

... 1 / 1 Seleccione referencia / Select reference. Signatura : F/631.58 C5. Autor : Alejandro Ló... more ... 1 / 1 Seleccione referencia / Select reference. Signatura : F/631.58 C5. Autor : Alejandro López Cortés, Yolanda Maya Delgado, Enrique Troyo Diéguez, Luis Landa Hernández. Aut. Analit.: López Cortés, Alejandro Maya Delgado, Yolanda coaut. Troyo Diéguez, Enrique coaut. ...

LOS MAESTROS ALEJANDRO LOPEZ CORTES, DE LA FACULTAD DE CIENCIAS (FCYA), Y ANTONIO LAZCANO ARAUJO,... more LOS MAESTROS ALEJANDRO LOPEZ CORTES, DE LA FACULTAD DE CIENCIAS (FCYA), Y ANTONIO LAZCANO ARAUJO, DEL INSTITUTO DE ASTRONOMIA (IA) DE LA UNAM, AL COMPARAR LOS DIFERENTES METABOLISMOS DE MICROORGANISMO ANAEROBIOS CONTEMPORANEOS, HAN PODIDO DEMOSTRAR QUE EN LA TIERRA PRIMITIVA SE DIO RAPIDAMENTE UN PROCESO DE DIVERSIFICACION QUE LLEVO A LA UTILIZACION DE DIFERENTES SUSTANCIAS EN LA FERMENTACION, QUE ES EL METABOLISMO MAS SIMPLE QUE EXISTE. LOS INVESTIGADORES BASAN SUS INVESTIGACIONES EN LA TEORIA OPARIN-HALDANE.

Recursos Naturales y Sociedad

El presente artículo describe algunos aspectos biológicos, ecológicos y biotecnológicos de microo... more El presente artículo describe algunos aspectos biológicos, ecológicos y biotecnológicos de microorganismos de la Península de Baja California, con el propósito de difundir su uso e importancia y promover la protección de áreas naturales que poseen este patrimonio biológico. Especial énfasis es dado a los tapetes microbianos laminados, a las bacterias promotoras de crecimiento en plantas y su participación en la remediación de aguas residuales y de suelos contaminados. También se incluyen resultados de los beneficios de la composta como agente mejorador de suelos de ambientes desérticos.

PeerJ, 2018

Hypersaline microbial mats develop through seasonal and diel fluctuations, as well as under sever... more Hypersaline microbial mats develop through seasonal and diel fluctuations, as well as under several physicochemical variables. Hence, resident microorganisms commonly employ strategies such as the synthesis of polyhydroxyalkanoates (PHAs) in order to resist changing and stressful conditions. However, the knowledge of bacterial PHA production in hypersaline microbial mats has been limited to date, particularly in regard to medium-chain length PHAs (mcl-PHAs), which have biotechnological applications due to their plastic properties. The aim of this study was to obtain evidence for PHA production in two hypersaline microbial mats of Guerrero Negro, Mexico by searching for PHA granules and PHA synthase genes in isolated bacterial strains and environmental samples. Six PHA-producing strains were identified by 16S rRNA gene sequencing; three of them corresponded to a sp. In addition, sp., sp. and sp. were also identified as PHA producers. Presumptive PHA granules and PHA synthases genes w...

Australian Journal of Experimental Agriculture, 2001

Current Microbiology, 2020

This study investigated the intestinal microbial community structure of Litopenaeus vannamei at s... more This study investigated the intestinal microbial community structure of Litopenaeus vannamei at six different stages during shrimp farming. Our goal was to elucidate the bacterial profile and the changes in the relative abundance of taxa during an atypical massive mortality event in Sonora, Mexico. High-throughput sequencing of the 16S rRNA gene and denaturing gradient gel electrophoresis showed that Vibrionaceae was persistent with high relative abundances in the intestine from cultivated shrimp during all the studied stages. The massive mortality observed at day 63 could be related to an overabundance of different Operational Taxonomic Units (OTUs) of Vibrio, Shewanella and Clostridium. Principal coordinate analysis (PCoA) showed variations in microbial structure at different culture times. These findings suggest that OTUs of different taxa contributed to the community switch from healthy to diseased individuals, questioning the hypothesis that single bacterial species is the caus...

Journal of Polymers and the Environment

In this work, the characterization of poly(3-hydroxybutyrate) PHB produced by Halomonas salina is... more In this work, the characterization of poly(3-hydroxybutyrate) PHB produced by Halomonas salina isolated from a hypersa-line microbial mat from Guerrero Negro, Baja California Sur, Mexico, is reported. The bacterial strain was able to produce isotactic PHB biopolymer with glucose (1%) as a single carbon source. The chemical structure of the polymer obtained was confirmed by Fourier-transform infrared (FTIR) and Nuclear magnetic resonance (NMR) spectroscopy. The polymer was thermally stable up to 225 °C and Differential scanning calorimetry (DSC) analysis showed a melting temperature (T m) of 173.6 °C. The obtained polymer presented a lower degree of crystallinity (39.3%) in comparison with PHB produced by other bacteria and polyhydroxyalkanoate co-polymers. Thus, the PHB biopolymer obtained in this study, could be recognized as more suitable for practical use, contributing to the repertoire of available bioplastics for further potential biotechnological applications, in which elastic polymers are needed.

Geomicrobiology …, 1994

The presence of extremely halophilic archaebacteria in NaCl solution increased the number and siz... more The presence of extremely halophilic archaebacteria in NaCl solution increased the number and size of cubic crystals of halite formed and also yielded dendritic crystals. Various dissolved and suspended materials such as glucose, glycerol, casein hy-drolysate, amino acids, ...