Enterococci and Bacilli from surface water: assessment of their resistance to copper and antibiotics

Abstract

Heavy metal-resistant bacteria can be efficient bioremediators of metals and might provide an alternative method for metal removal in contaminated environments. The present study aims to isolate bacteria from the aquatic environment and evaluate their potential tolerance to copper metal, aiming at bioremediation processes. Also, compare co-resistance to heavy metal and antibiotics. The morphology of isolates was observed, and sequence analysis (16S ribosomal DNA) revealed that isolated strains were closely related to species belonging to the genera Enterococcus and Bacillus. Bacterial isolates were resistant to CuSO4, with a minimum inhibitory concentration of 0.78 mg ml-1. Enterococcus lactis was resistant to a combination of copper and tetracycline. The other tested isolates were sensitive to the tested antimicrobials. The metal removal ability of these isolates was assayed using atomic absorption spectroscopy, and the strains 27, 23, and E. lactis were best at removing heavy metals, at 87.7%. Enterococcus casseliflavus EC55 was 62%, followed by Bacillus aerius (18.4%), E. casseliflavus EC70 (10%) and Bacillus licheniformis (10%). Based on our findings, Enterococcus sp and Bacillus sp. have potential applications in enhanced remediation of contaminated environments.

Potential probiotic strains with heavy metals and mycotoxins bioremoval capacity for application in foodstuffs

“…They observed that Cr removal was through the cell membrane. Maia et al (2021) investigated the potential tolerance of Enterococcus to Cu. The results showed the maximum removal by Ent.…”

“…Heavy metals bioremoval by using Bacillus strains has been observed and Cd reduction by B. coagulans was reported (Majlesi et al, 2017). Maia et al (2021) measured Bacillus strains ability in Cu biodegradation. The removal process was evaluated by using atomic adsorption spectroscopy.…”

“…Temperature is one of the main parameters in bioremoval (Dixit et al, 2015). Temperature is an important parameter in the bioremoval of metals because it changes the adsorption rate (Maia et al, 2021). The optimum metals (Pb, Cd and Hg) bioremoval by S. cerevisiae at 25°C was reported (Massoud, Hadiani, et al, 2019).…”