Interaction of Sewage Bacteria with Heavy Metals, Antibiotics and Plants

Abstract

Environment pollution of toxic heavy metals and antibiotics is widespread due of massive industrialization and overuse of antibiotics. Moreover, metal contamination can function as a selective agent in the spread of antibiotic resistance, affecting both animals and plant species. Isolation, identification and characterization of three heavy metal resistant bacterial strains from sewage pipes of Lahore city was carried out in this study. On the basis of morphology and 16S ribosomal RNA (rRNA) gene sequencing, the isolates were identified as Escherichia coli strain MHR-1, Bacillus subtilis strain MHR-2, Exiguobacterium aurantiacum strain MHR-3. These isolates were resistant to Cadmium (Cd) at (< 100 µg/mL), Chromium (Cr) (< 500 µg/mL), Lead (Pb) (< 400 µg/mL) and Arsenic (As) (< 200 µg/mL). Moreover, the isolates tolerated a combined stress of 50 µg/mL for all the heavy metals tested. Antibiotic susceptibility of the bacteria towards the 9 antibiotics revealed: MHR-1 was resistant to 66%, intermediate to 12% and susceptible to 22%; MHR-2 was resistant 66%, intermediate to 22% and susceptible to 12%; MHR-3 was resistant to 22%, intermediate to 33% and susceptible to 45%. For antibiotic-heavy metal co-stress, about 78% of antibiotics showed synergistic effects while 11% showed antagonistic effects along with a stress of 50 µg/mL of all heavy metals tested. Test of isolates for their ability to affect seed growth with and without heavy metal stress, showed no significant interaction with plants to tolerate the heavy metal stress. This study proposes an effective approach to target antibiotic resistant bacteria with combine stress of heavy metals, and further investigation will lead in to better insight in devising an effective treatment for targeting resistant pathogens. Key Words: , , , , .