Bacterias asimbióticas fijadoras de nitrógeno presentes en suelos agrícolas de la comuna de Chillán, región de Ñuble
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Date
2025
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Universidad de Concepción
Abstract
El objetivo de este trabajo fue evaluar la presencia de bacterias no simbióticas con capacidad de fijación de nitrógeno en el suelo de dos cultivos agrícolas presentes en la universidad de concepción campus Chillán, ya que estos microorganismos pueden ser utilizados como biofertilizantes mejorando la fertilidad del suelo sin necesidad de fertilizantes sintéticos a través de un proceso denominado Fijación Biológica de Nitrógeno, este se lleva a cabo mediante el uso de un complejo enzimático llamado nitrogenasa que le permite la reducción de compuestos nitrogenados a nitrógeno asimilable que puede ser captado y usado por las plantas. Para encontrar estas bacterias se utilizó el método de muestreo al azar en disposición de zigzag en donde se determinaron cinco puntos de muestreo y a partir de ellos se generó una muestra compuesta en cada cultivo, a partir de esta muestra se realizó el método de diluciones seriadas en el laboratorio para hacer crecer dichas nitrógeno, a las colonias emergidas se les realizó el conteo de UFC/g y posteriormente fueron aisladas, caracterizadas y se realizaron comparaciones morfológicas con bacterias obtenidas de otros estudios sobre diazótrofos en revisiones bibliográficas. Aparentemente se obtuvieron 11 cepas diferentes de bacterias entre las que destacan especies como Azotobacter, Beijerinckia, Azomonas y algunos Actinomicetos. Se determinó que hubo un decrecimiento poblacional en ambos cultivos de alfalfa y maíz debido posiblemente a influencias climáticas y condiciones del suelo, sin embargo, es recomendable ampliar el periodo de estudio para encontrar la causa de estas diferencias en las cinéticas de crecimiento de estas bacterias.
The objective of this study was to evaluate the presence of non-symbiotic nitrogen-fixing bacteria in the soil of two agricultural crops located at the University of Concepción, Chillán campus, as these microorganisms can be used as biofertilizers to improve soil fertility without the need for synthetic fertilizers, through a process known as Biological Nitrogen Fixation. This process is carried out by means of an enzymatic complex called nitrogenase, which enables the reduction of nitrogen compounds to assimilable nitrogen that can be taken up and used by plants. To isolate these bacteria, a random zigzag sampling method was employed, determining five sampling points from which a composite sample was generated for each crop. From these composite samples, the serial dilution method was applied in the laboratory to cultivate the bacteria on plates using Burk’s medium, specific for nitrogen-fixing microorganisms. The emerging colonies were quantified in CFU/g, subsequently isolated, characterized, and morphologically compared with bacteria reported in previous bibliographic reviews on diazotrophs.A total of 11 different bacterial strains were apparently obtained, among which species such as Azotobacter, Beijerinckia, Azomonas, and some actinomycetes were identified. It was determined that there was a population decline in both alfalfa and maize crops, possibly due to climatic influences and soil conditions. However, it is recommended to extend the study period to identify the causes of these differences in the growth kinetics of these bacteria.
The objective of this study was to evaluate the presence of non-symbiotic nitrogen-fixing bacteria in the soil of two agricultural crops located at the University of Concepción, Chillán campus, as these microorganisms can be used as biofertilizers to improve soil fertility without the need for synthetic fertilizers, through a process known as Biological Nitrogen Fixation. This process is carried out by means of an enzymatic complex called nitrogenase, which enables the reduction of nitrogen compounds to assimilable nitrogen that can be taken up and used by plants. To isolate these bacteria, a random zigzag sampling method was employed, determining five sampling points from which a composite sample was generated for each crop. From these composite samples, the serial dilution method was applied in the laboratory to cultivate the bacteria on plates using Burk’s medium, specific for nitrogen-fixing microorganisms. The emerging colonies were quantified in CFU/g, subsequently isolated, characterized, and morphologically compared with bacteria reported in previous bibliographic reviews on diazotrophs.A total of 11 different bacterial strains were apparently obtained, among which species such as Azotobacter, Beijerinckia, Azomonas, and some actinomycetes were identified. It was determined that there was a population decline in both alfalfa and maize crops, possibly due to climatic influences and soil conditions. However, it is recommended to extend the study period to identify the causes of these differences in the growth kinetics of these bacteria.
Description
Tesis presentada para optar al título de Ingeniero Ambiental
Keywords
Cultivos agrícolas -- Chile, Biofertilizantes, Cinéticas de crecimiento