2.4. Determination of the minimum inhibitory concentration
The tolerance experiments were carried out in 250 mL conical
flasks, each containing 45 mL of YA broth. Approximately equal
numbers of cells from the four isolated strains were used and the
bacterial mixtures with an initial cell density of 1 × 108 cells/mL for
each ofthe isolated strains. All cultures were incubated at 30 ◦C and
agitated at 200 rpm. To study the influence of heavy metals on bacterial
growth, bacterial mixtures were exposed to a mix of heavy
metals with individual concentrations ranging from 0 to 10 mM.