pH-effects on chitosan stability control whether cellular dynamics are characteristic of planktonic or biofilm phenotypes in artificial S. epidermidis RP62A biofilms.
(a) Mean squared displacement, 〈Δx2(t)〉, of planktonic S. epidermidis RP62A bacteria and bacteria in high (pH = 4.3) and low (pH = 5.3) cellular density S. epidermidis RP62A constructs compared with biofilm 〈Δx2(t)〉 inferred from ref. 7. (b) 〈Δx2(t)〉 of high cellular density constructs before (pH = 4.3) and after (pH = 7.3) pH is increased and low cellular density constructs before (pH = 5.3) and after (pH = 4.4) pH is decreased. (c) J(t), at t = 1 s, of high and low-density constructs before and after pH changes; arrows indicate the direction of pH change. The upper dotted line is the creep compliance, J(t), of planktonic cells. The dotted dashed lines bound the J(t) observed for S. epidermidis RP62A biofilms7. (d) CLSM image of cells and 0.05 wt. % chitosan at pH = 5.3. (e) CLSM image of cells and 0.3 wt. % chitosan at pH = 4.3. (f) 0.05 wt. % chitosan in tryptic soy broth with 1 wt. % added glucose (TSBG). (g) 0.3 wt. % chitosan in TSBG. Scale bars, 10 μm (d–g).