Tolerancia a ciprofloxacino y capacidad de biotransformación en bacterias aisladas de bahías subantárticas.
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Date
2026
Journal Title
Journal ISSN
Volume Title
Publisher
Universidad de Concepción
Abstract
El ciprofloxacino (CIP) es un antibiótico de la familia de las fluoroquinolonas ampliamente utilizado en medicina humana y veterinaria, reconocido por su recalcitrancia, baja biodegradabilidad relativa y persistencia de actividad antimicrobiana en distintas matrices. Debido a estas características, constituye un contaminante emergente de interés para estudiar respuestas microbianas asociadas a tolerancia, transformación parcial y potenciales aplicaciones biotecnológicas. El objetivo de esta tesis fue evaluar bacterias cultivables aisladas desde agua de mar y sedimento de dos bahías subantárticas para determinar su capacidad de tolerar CIP y promover su biotransformación parcial mediante procesos co-metabólicos dependientes de la disponibilidad de carbono. Para ello, se obtuvieron aislados bacterianos desde las bahías subantárticas, Dos Lobos (DL) y Puesto Pomar (PP), sitios seleccionados por presentar señales locales de intervención antrópica. Las cepas fueron caracterizadas mediante ensayos de susceptibilidad antimicrobiana, concentración mínima inhibitoria de CIP, crecimiento en medio mínimo M9 suplementado con glucosa o acetato de sodio, bioensayos de actividad antimicrobiana residual y análisis genómicos de aislados seleccionados. Los resultados evidenciaron perfiles heterogéneos de no susceptibilidad antimicrobiana, principalmente frente a ampicilina, cefuroxima y cloranfenicol. La tolerancia a CIP se restringió a un subconjunto de aislados y dependió del contexto metabólico del cultivo. En medio mínimo, el crecimiento en presencia de CIP ocurrió principalmente cuando se incorporó acetato de sodio como fuente adicional de carbono, mientras que CIP por sí solo no sostuvo crecimiento detectable. La actividad antimicrobiana residual se mantuvo durante el ensayo, sin una disminución temporal consistente atribuible a la incubación bacteriana, por lo que no se obtuvo evidencia funcional suficiente para demostrar la biotransformación parcial del antibiótico. A nivel genómico, no se identificaron genes clásicos de resistencia a quinolonas ni sustituciones en la región determinante de resistencia a quinolonas (QRDR) asociadas a fluoroquinolonas. En conjunto, la hipótesis fue respaldada parcialmente, ya que los aislados toleraron CIP bajo condiciones dependientes de carbono, aunque no promovieron una biotransformación funcionalmente detectable. Desde una perspectiva biotecnológica, estos resultados destacan el valor de los aislados ambientales subantárticos como modelos para estudiar respuestas fisiológicas frente a antibióticos en ambientes fríos y orientar estrategias de bioprospección centradas en tolerancia, co-sustratos y biotransformación de contaminantes emergentes.
Ciprofloxacin (CIP) is a fluoroquinolone widely used in human and veterinary medicine, recognized for its recalcitrance, relatively low biodegradability, and persistence of antimicrobial activity in different matrices. These characteristics make CIP an emerging contaminant of interest for studying microbial responses associated with tolerance partial transformation, and potential biotechnological applications. The aim of this thesis was to evaluate culturable bacteria isolated from seawater and sediment from two subantarctic bays to determine their capacity to tolerate CIP and promote its partial transformation through co-metabolic processes dependent on carbon availability. For this purpose, bacterial isolates were obtained from Dos Lobos (DL) and Puesto Pomar (PP) bays, sites selected based on local signs of anthropogenic intervention. The strains were characterized by antimicrobial susceptibility assays, minimum inhibitory concentration of CIP, growth in M9 minimal medium supplemented with glucose or sodium acetate, residual antimicrobial activity bioassays, and genomic analyses of selected isolates. The results showed heterogeneous antimicrobial non-susceptibility profiles, mainly against ampicillin, cefuroxime, and chloramphenicol. CIP tolerance was restricted to a subset of isolates and depended on the metabolic context of the culture. In minimal medium, growth in the presence of CIP occurred mainly when sodium acetate was incorporated as an additional carbon source, whereas CIP alone did not sustain detectable growth. Residual antimicrobial activity was maintained throughout the assay, without a consistent temporal decree attributable to bacterial incubation; therefore, there was insufficient functional evidence to demonstrate partial biotransformation of the antibiotic. At the genomic level, no classical quinolone resistance genes or substitutions in the quinolone resistance-determining region (QRDR) associated with fluoroquinolones resistance were identified. Overall, the hypothesis was partially supported, as the isolate s tolerated CIP under carbon-dependent conditions, although they did not promote functionally detectable biotransformation. From a biotechnological perspective, these results highlight the value of subantarctic environmental isolates as models for studying physiological responses to antibiotics in cold environments for guiding bioprospecting strategies focused on tolerance, co-substates, and biotransformation of emerging contaminants.
Ciprofloxacin (CIP) is a fluoroquinolone widely used in human and veterinary medicine, recognized for its recalcitrance, relatively low biodegradability, and persistence of antimicrobial activity in different matrices. These characteristics make CIP an emerging contaminant of interest for studying microbial responses associated with tolerance partial transformation, and potential biotechnological applications. The aim of this thesis was to evaluate culturable bacteria isolated from seawater and sediment from two subantarctic bays to determine their capacity to tolerate CIP and promote its partial transformation through co-metabolic processes dependent on carbon availability. For this purpose, bacterial isolates were obtained from Dos Lobos (DL) and Puesto Pomar (PP) bays, sites selected based on local signs of anthropogenic intervention. The strains were characterized by antimicrobial susceptibility assays, minimum inhibitory concentration of CIP, growth in M9 minimal medium supplemented with glucose or sodium acetate, residual antimicrobial activity bioassays, and genomic analyses of selected isolates. The results showed heterogeneous antimicrobial non-susceptibility profiles, mainly against ampicillin, cefuroxime, and chloramphenicol. CIP tolerance was restricted to a subset of isolates and depended on the metabolic context of the culture. In minimal medium, growth in the presence of CIP occurred mainly when sodium acetate was incorporated as an additional carbon source, whereas CIP alone did not sustain detectable growth. Residual antimicrobial activity was maintained throughout the assay, without a consistent temporal decree attributable to bacterial incubation; therefore, there was insufficient functional evidence to demonstrate partial biotransformation of the antibiotic. At the genomic level, no classical quinolone resistance genes or substitutions in the quinolone resistance-determining region (QRDR) associated with fluoroquinolones resistance were identified. Overall, the hypothesis was partially supported, as the isolate s tolerated CIP under carbon-dependent conditions, although they did not promote functionally detectable biotransformation. From a biotechnological perspective, these results highlight the value of subantarctic environmental isolates as models for studying physiological responses to antibiotics in cold environments for guiding bioprospecting strategies focused on tolerance, co-substates, and biotransformation of emerging contaminants.
Description
Tesis presentada para optar al grado de Doctor/a en Biotecnología Molecular.
Keywords
Antibióticos, Ciprofloxacino, Bacterias, Sedimentos marinos, Biotecnología