Guillermo Liendo Aguirre | Universidad Peruana Cayetano Heredia (original) (raw)
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UPB - Universidad Pontificia Bolivariana - Medellín
Universidad Michoacana de San Nicolás de Hidalgo
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Papers by Guillermo Liendo Aguirre
In situ transfer of a self-transmissible, antibiotic-multiresistant plasmid RP4 from a laboratory... more In situ transfer of a self-transmissible, antibiotic-multiresistant plasmid RP4 from a laboratory Escherichia coli strain C600 to indigenous activated sludge bacteria was investigated using filter mating. The transfer frequency of RP4 from the donor E. coli to the bacteria that was sampled from two wastewater treatment plants was 5.1×10 -2 to 7.5×10 -1 and 4.6×10 -3 to 1.3×10 -2 /potential recipient. The isolated transconjugants showed resistance to Ap, Km, and Tc and the presence of a plasmid with a similar size to RP4. The traG gene on RP4 was also detected from all transconjugants. Reverse-transfer experiments from the transconjugants to E. coli HB101 indicated that RP4 maintained self-transmissibility in the transconjugants. The transconjugant strains were dominant bacteria in activated sludge including Pseudomonas fluorescens, P. putida, and Ochrobactrum anthropi and minor populations of enteric bacterial strains including Citrobacter freundii, E. coli, Enterobacter cloacae, E. asburiae, and Klebsiella pneumoniae ssp. pneumoniae. The transconjugant strains K. pneumoniae ssp. pneumonia, E. cloacae, and E. asburiae had several naturally occurring plasmids. These results suggest that in situ transfer of plasmids and the exchange of antibiotic-resistant genes can occur between released and indigenous bacteria in activated sludge.
During tiatin of conjugative transfer of DNA containing the transfer origin (onTiT) of the promis... more During tiatin of conjugative transfer of DNA containing the transfer origin (onTiT) of the promiscuous plasmid RP4, the proteins TraI, TraJ, and Trai interact and assemble a specialized nucleoprotein complex (the relaxosome) at onT. The structure can be visualized on electron micrographs. Siteand strand-specific nicking at the transfer origin in vitro is dependent on the proteins TraIl and TraJ and on Mg2+ ions. Substrate specificity is directed exclusively towards the cognate transfer origin: the RP4-specifled TraJ protein cannot recognize the closely related onT of plasmid R751. After nicking, TraI protein remains attached to the 5'-terminal 2'-deoxycytidyl residue at the nic site [
The emergence and spread of antibiotic resistance among pathogenic bacteria has been a rising pro... more The emergence and spread of antibiotic resistance among pathogenic bacteria has been a rising problem for public health in recent decades. It is becoming increasingly recognized that not only antibiotic resistance genes (ARGs) encountered in clinical pathogens are of relevance, but rather, all pathogenic, commensal as well as environmental bacteria-and also mobile genetic elements and bacteriophages-form a reservoir of ARGs (the resistome) from which pathogenic bacteria can acquire resistance via horizontal gene transfer (HGT). HGT has caused antibiotic resistance to spread from commensal and environmental species to pathogenic ones, as has been shown for some clinically important ARGs. Of the three canonical mechanisms of HGT, conjugation is thought to have the greatest influence on the dissemination of ARGs. While transformation and transduction are deemed less important, recent discoveries suggest their role may be larger than previously thought. Understanding the extent of the resistome and how its mobilization to pathogenic bacteria takes place is essential for efforts to control the dissemination of these genes. Here, we will discuss the concept of the resistome, provide examples of HGT of clinically relevant ARGs and present an overview of the current knowledge of the contributions the various HGT mechanisms make to the spread of antibiotic resistance.
Leaves from three different Arabidopsis lines with different expression levels of PsbS protein sh... more Leaves from three different Arabidopsis lines with different expression levels of PsbS protein showed
different levels of non-photochemical quenching. The PsbS deficient plant npq4 showed remarkable
reduction of electron transport rate, while the other two lines with a moderate amount (wild type) or an
overexpression of PsbS (L17) presented unchanged electron transport rates under the same range of high
light intensities. Biochemical investigation revealed that the plant with the highest PsbS content (L17) sustained
the highest level of stable PSII–LHCII supercomplex structure, and displayed the smallest fluorescence
quenching in the thylakoid membranes, the most efficient linear electron transport and the smallest
cyclic electron transport. Based on these observations, it is proposed that the remodeling of PSII–LHCII
supercomplexes affected by PsbS plays important roles in regulating the energy balance in thylakoid
membrane and in ensuring the sophisticated coordination between energy excitation and dissipation.
In situ transfer of a self-transmissible, antibiotic-multiresistant plasmid RP4 from a laboratory... more In situ transfer of a self-transmissible, antibiotic-multiresistant plasmid RP4 from a laboratory Escherichia coli strain C600 to indigenous activated sludge bacteria was investigated using filter mating. The transfer frequency of RP4 from the donor E. coli to the bacteria that was sampled from two wastewater treatment plants was 5.1×10 -2 to 7.5×10 -1 and 4.6×10 -3 to 1.3×10 -2 /potential recipient. The isolated transconjugants showed resistance to Ap, Km, and Tc and the presence of a plasmid with a similar size to RP4. The traG gene on RP4 was also detected from all transconjugants. Reverse-transfer experiments from the transconjugants to E. coli HB101 indicated that RP4 maintained self-transmissibility in the transconjugants. The transconjugant strains were dominant bacteria in activated sludge including Pseudomonas fluorescens, P. putida, and Ochrobactrum anthropi and minor populations of enteric bacterial strains including Citrobacter freundii, E. coli, Enterobacter cloacae, E. asburiae, and Klebsiella pneumoniae ssp. pneumoniae. The transconjugant strains K. pneumoniae ssp. pneumonia, E. cloacae, and E. asburiae had several naturally occurring plasmids. These results suggest that in situ transfer of plasmids and the exchange of antibiotic-resistant genes can occur between released and indigenous bacteria in activated sludge.
During tiatin of conjugative transfer of DNA containing the transfer origin (onTiT) of the promis... more During tiatin of conjugative transfer of DNA containing the transfer origin (onTiT) of the promiscuous plasmid RP4, the proteins TraI, TraJ, and Trai interact and assemble a specialized nucleoprotein complex (the relaxosome) at onT. The structure can be visualized on electron micrographs. Siteand strand-specific nicking at the transfer origin in vitro is dependent on the proteins TraIl and TraJ and on Mg2+ ions. Substrate specificity is directed exclusively towards the cognate transfer origin: the RP4-specifled TraJ protein cannot recognize the closely related onT of plasmid R751. After nicking, TraI protein remains attached to the 5'-terminal 2'-deoxycytidyl residue at the nic site [
The emergence and spread of antibiotic resistance among pathogenic bacteria has been a rising pro... more The emergence and spread of antibiotic resistance among pathogenic bacteria has been a rising problem for public health in recent decades. It is becoming increasingly recognized that not only antibiotic resistance genes (ARGs) encountered in clinical pathogens are of relevance, but rather, all pathogenic, commensal as well as environmental bacteria-and also mobile genetic elements and bacteriophages-form a reservoir of ARGs (the resistome) from which pathogenic bacteria can acquire resistance via horizontal gene transfer (HGT). HGT has caused antibiotic resistance to spread from commensal and environmental species to pathogenic ones, as has been shown for some clinically important ARGs. Of the three canonical mechanisms of HGT, conjugation is thought to have the greatest influence on the dissemination of ARGs. While transformation and transduction are deemed less important, recent discoveries suggest their role may be larger than previously thought. Understanding the extent of the resistome and how its mobilization to pathogenic bacteria takes place is essential for efforts to control the dissemination of these genes. Here, we will discuss the concept of the resistome, provide examples of HGT of clinically relevant ARGs and present an overview of the current knowledge of the contributions the various HGT mechanisms make to the spread of antibiotic resistance.
Leaves from three different Arabidopsis lines with different expression levels of PsbS protein sh... more Leaves from three different Arabidopsis lines with different expression levels of PsbS protein showed
different levels of non-photochemical quenching. The PsbS deficient plant npq4 showed remarkable
reduction of electron transport rate, while the other two lines with a moderate amount (wild type) or an
overexpression of PsbS (L17) presented unchanged electron transport rates under the same range of high
light intensities. Biochemical investigation revealed that the plant with the highest PsbS content (L17) sustained
the highest level of stable PSII–LHCII supercomplex structure, and displayed the smallest fluorescence
quenching in the thylakoid membranes, the most efficient linear electron transport and the smallest
cyclic electron transport. Based on these observations, it is proposed that the remodeling of PSII–LHCII
supercomplexes affected by PsbS plays important roles in regulating the energy balance in thylakoid
membrane and in ensuring the sophisticated coordination between energy excitation and dissipation.