Metal-resistance encoding gene-fingerprints in some bacteria isolated from wastewaters of selected printeries in Ibadan, South-western Nigeria

Abstract

Several studies have reported the occurrence of metal-resistant bacteria and their genes in different wastewater, but there is a dearth of information on wastewater generated from printing operations as a probable source. This study aimed at fingerprinting metal-resistance encoding genes in bacteria recovered from wastewaters of selected printeries in Ibadan, Nigeria. Wastewaters from 10 selected printeries in Ibadan were collected monthly for 12 months. The metal composition of wastewater was determined using Atomic Absorption Spectrophotometry. Metal-resistant bacteria were isolated on metal-supplemented nutrient medium, and characterized using 16S rRNA gene sequencing. Metal-resistance genes were detected using specific primers and the presence of plasmids was determined using alkaline-lysis method. Forty metal-resistant bacteria belonging to six genera; Bacillus, Klebsiella, Pseudomonas, Citrobacter, Providencia and Proteus were identified. cusCBA, encoding resistance to copper and silver was detected in nine bacteria, while pbrA (encoding lead resistance) was detected in seven Pseudomonas aeruginosa isolates. chrA, encoding resistance to chromate ions, was detected in Proteus mirabilis PW3a and two isolates of Pseudomonas aeruginosa, while chrB was detected in Providencia vermicola PWAP3 and Proteus mirabilis PW4c. Bacillus stratosphericus PW1b possessed the copper-resistance genes, pcoA and pcoR. Thirty-six bacteria (90%) of the total bacteria possessed plasmids larger than 10 Kb in size. In conclusion, wastewater generated from printing operations could be a potential source of metal-resistant bacteria and their genes.

Keywords

• printing wastewater
• printeries
• metal-resistance genes
• metal-resistant bacteria
• plasmids
• nigeria