Identification of Bacterial Communities in Surface Waters of Rio Bravo/Rio Grande Through 16S rRNA Gene Metabarcoding

The Rio Bravo/Grande River is a binational water resource between Mexico and the United States and supports diverse anthropogenic activities. However, limited studies on its microbiological composition focus on molecular techniques. Therefore, the aim of this study was to characterize the bacteriome and identify potentially pathogenic bacteria in surface waters of the Rio Bravo/Grande in northeastern Tamaulipas, Mexico, using the 16S rRNA gene metabarcoding technique. Surface water samples were collected from the localities of Diaz Ordaz, Reynosa, and Matamoros between 2016 and 2017. DNA extraction and sequencing were performed, focusing on the V3–V4 region of the 16S rRNA gene. A taxonomic analysis revealed the presence of 13 bacterial phyla, with Proteobacteria (40%), Firmicutes (28%), and Actinobacteria (10.2%) being the most abundant. At the genus level, Bacillus, Pseudomonas, and Acinetobacter were predominant, while 16 potentially pathogenic species, including Acinetobacter baumannii and Vibrio vulnificus, were identified. Alpha and beta diversity analyses highlighted significant differences in the bacterial diversity among the sampling sites, indicating that the river has some capacity to recover from anthropogenic and environmental disturbances. This study underscores the need for the continuous monitoring of the Rio Bravo/Grande to protect public health and maintain the water quality in the face of increasing anthropogenic pressures.