رسائل ماجيستير
English
2023
Bioaccumulation of Heavy Metals and Their Resistance Genes in E. coli Isolated from Carp Fish Cultured in Dukan Lake
إيمان ظاهر عارف, جيا عمر عثمان, زيد خلف خض
كلية الطب البيطري-جامعة السليمانية · العراق
Due to its toxicity, persistence, bioaccumulation, and biomagnification characteristics, heavy metal pollution is a significant environmental issue. Fish take heavy metals through GIT or gills as they grow, and they are unable to expel these heavy metals. When people eat polluted fish, the heavy metals in it concentrate and become more enriched in the body, harming their health. The study aimed to perform a microbiological evaluation of fish muscle, an estimate of heavy metal accumulation, including nickel, copper, lead, cadmium, and cobalt, in fish muscles, and find the relation between heavy metal accumulation in fish and heavy metal resistance genes in E. coliresiding in the fish. A total of 180 fish samples (Cyprinus carpio) were taken from three distinct areas of Dukan Lake, sixty samples for each of the fishing areas (the center of Dukan Lake, Ranya, and Qaladze) in the winter and spring. The microbiological evaluation of fish muscle was determined by the total bacterial count and total coliform. The total bacterialcounts for fish samples from Dukan, Ranya, and Qaladaza were 9.6985×104, 1.5437×104, and 1.2403×104 respectively. On the other hand, the total coliforms for fish samples from Dukan, Ranya, and Qaladaza were 4.912×103, 1.005×103,and 0.722×103 respectively. The descending order of the mean values for the metals found in fish muscles was Cu > Pb > Cd > Ni > Co. Except for cadmium, whose result (0.136 mg/kg) was higher than the 0.05 mg/kg threshold set by the European Union and government, all of the identified heavy metals were within the authorized FAO levels .The location, sex, and season of the fish that were caught had an impact on the concentration of Co, whereas the sex of the fish had an impact on the concentrations of Cu and Ni, for the lead neitherlocation, sex and season have effects on it. The isolation and identification of E. coliwere performed using culturing and molecular methods. Of the 180 fish samples, 116 (64.4%) were positive for E. coli by culture. The molecular detection showed that 92 (51.1%) samples were positive for the 16S ribosomal RNA gene and 12 (6.7%) were positive for the copA gene, while boththe czcA and nccgenes were not detected in any samples. The E. coligene 16S rRNA has been sequenced and assigned accession number ON385541 under the name "E. coli isolate 2022 mabao" in NCBI GenBank. The phylogenetic analysis of 16S rRNA gene sequences revealed that E. colistrains were related to other E. colibacteria from other countries, with the maximum identity being 99.61 percent. In conclusion, for both microbiological evaluation and heavy metal concentrations in fish muscle, consuming such fish poses no dangers to humans except cadmium. For the heavy metal resistance genes, small numbers of E. coli isolated from common carp in three distinct areas of Dukan Lake have the copA gene. Additionally, the 16S rRNA gene sequence analysis in this study revealed that the conserved region of this gene only had a few minor nucleotide changes.