ABSTRACT
The mechanisms of tolerance to heavy metals used by some microorganisms identified by bioprospection processes are useful for the development and implementation of bioremediation strategies for contaminated environments with high toxic load caused by heavy metals. A total of seven native microbial isolates were obtained from wastewater bodies from an industrial zone in the municipality of Girardota, Antioquia, Colombia. Subsequently, they were selected to evaluate their lead tolerance capacity at different concentrations. In addition, some parameters were determined, such as the capacity to produce exopolysaccharides and their biosorption to understand potential mechanisms associated to lead tolerance. According to the biocehemical test (Vitek) and the molecular analysis of sequences of 16S rDNA, bacterial were identified as Pseudomonas aeruginosa, Pseudomonas nitroreducens, and Pseudomonas alcaligenes. We determined that the seven isolates had the capacity to tolerate concentrations higher than 50 mg/ml of lead, and that the concentration and exposure time (40 h) to this metal significantly affect the Pseudomonas spp. isolates. Statistically significant differences were detected (p < 0.05) in the production of the exopolysaccharide (EPS) among the isolates. P. aeruginosa (P16) was the strain with the maximum absorbance exopolysaccharide measured. We evidenced that P. aeruginosa (P14) and P. nitroreducens (P20) have 80% capacity to biosorber lead using live mass (minimum range from 80.9% to 87%). It is suggested that the tolerance to lead exhibited by the environmental isolates of Pseudomonas spp. can be attributed to the production of exopolysaccharides and biosorption, which are protection factors for its survival in contaminated places. Finally, it was determined that the adsorption measured from dead biomass was significant (p < 0.05) from 40 h of exposure to metal (Average 182.2 ± 7). We generated new knowledge about the potential use of the Pseudomonas spp. genus to bioremediate affluent contaminated with heavy metals.
ABSTRACT
Aedes aegypti is one of the vectors responsible for transmitting the viruses that cause dengue, Zika and chikungunya in the human population. Mosquitoes have bacterial communities in different organs, mainly in the midgut, but to a lesser extent in their reproductive organs, such as the ovaries, where replication and vertical transmission is decisive for dengue virus. These bacteria also influence metabolic and physiological processes such as ingestion and digestion of blood. In this study, aerobic bacterial communities associated with ovaries of A. aegypti Rockefeller strain were determined, describing their potential function during ovocitary development. The groups of mosquitoes were separated into three treatments: diet with 10% sugar solution, diet with blood supply, and blood feeding combined with tetracycline. The ovaries were extracted from the mosquitoes, and then put in enriched culture media (blood and nutritive agar) by direct inoculation, for subsequent isolation and macroscopic and microscopic characterization of the colonies. The taxonomic determination of bacterial isolates was achieved by sequence analysis of the 16S rRNA gene. A higher bacterial load was observed in the sugar feeding group (6 × 10³ CFU/ml) in contrast to the group fed only with blood, with and without an antibiotic (4.03-4.04 × 10³CFU/ml; 4.85-5.04 × 10³CFU/ml). As a result, a total of 35 colonies were isolated, of which 80% were gram-negative and 20% gram-positive; 72% were lactose negative and 8% lactose positive. Of the total bacteria, 83% had gamma hemolysis, 17% alpha hemolysis, and none presented beta hemolysis. After phenotypic and biochemical characterization, 17 isolates were selected for molecular identification. Only phyla Actinobacteria and Proteobacteria were found. Bacteria associated with ovaries of A. aegypti were mainly identified as belonging to the Serratia and Klebsiella genera. Some bacteria (Serratia marcescens, Pantoea dispersa and Klebsiella oxytoca) have wide biotechnological potential due to their entomopathogenic power and their bioactivity against different pathogens.
