Fig. 4

Susceptibility of planktonic and attached cells to alkaline pH and Fe³⁺ after 1 h of attachment. The planktonic and attached cells were collected after 1 h of attachment and were added to physiological saline with the pH adjusted to 8 and 9 by adding NaOH and 1 × 10^− 4 M ferric iron for another hour. The number of viable cells was measured by dilution plating. The y-axis in the graph represents the proportion of viable cells after the addition of stimuli to the initial sample. Different letters indicate significant differences