N-Acetyl-l-Cysteine Affects Growth, Extracellular Polysaccharide Production, and Bacterial Biofilm Formation on Solid Surfaces

Effect of NAC on EPS production. Bacteria were grown in 20% LB overnight in the presence or absence of NAC and then starved in PS for 48 h. Open columns, no NAC; cross-hatched columns, 0.25 mg of NAC ml⁻¹; grey columns, 0.5 mg of NAC ml⁻¹. The bars indicate the standard deviations of the means for four experiments. Abbreviations: K.p, K. pneumoniae; A.b, A. baumannii; B.m, B. megaterium; B.s, B. subtilis; B.c, B. cereus; A.l, A. lwoffii; P.m, P. mendocina; E.c, E. cloacae; S.w, S. warneri; B, Bacillus sp. NM, not measured.

Effect of NAC on EPS production by starving bacteria. Bacteria were grown in 20% LB overnight in the absence of NAC, washed, and subsequently exposed to 0.5 mg of NAC ml⁻¹ in PS for 48 h. Open columns, no NAC; cross-hatched columns, 0.5 mg of NAC ml⁻¹. The bars indicate the standard deviations of the means for three experiments. Abbreviations: B.c, B. cereus; A.l, A. lwoffii; P.m, P. mendocina; S.w, S. warneri; B, Bacillus sp.

Effect of NAC on degradation of EPS. Isolated EPS from K. pneumoniae, B. megaterium, B. subtilis, B. cereus, E. cloacae, and P. mendocina, as well as dextran, were incubated in the presence or absence of 0.5 mg of NAC ml⁻¹ for 1 h at room temperature. Open columns, no NAC; cross-hatched columns, 0.5 mg of NAC ml⁻¹. The bars indicate the standard deviations of the means for three experiments. The values for dextran (0.5 mg ml⁻¹) were not affected by NAC (the values were too small to show). Abbreviations: K.p, K. pneumoniae; B.m, B. megaterium; B.s, B. subtilis; B.c, B. cereus; E.c, E. cloacae; P.m, P. mendocina.

Numbers of cells that adhered to stainless steel surfaces after 24, 48, and 72 h of incubation in 20% LB. The seven-member multispecies community comprised A. baumannii, A. lwoffii, Bacillus sp., E. cloacae, K. pneumoniae, P. mendocina, and S. warneri. Open columns, no NAC; cross-hatched columns, 0.5 mg of NAC ml^−1. The bars indicate the standard deviations of the means for three experiments. Abbreviations: K.p, K. pneumoniae; E.c, E. cloacae; mix, multispecies community.

Numbers of cells that adhered to stainless steel surfaces after 24, 48, and 72 h of incubation in process water. The seven-member multispecies community comprised A. baumannii, A. lwoffii, Bacillus sp., E. cloacae, K. pneumoniae, P. mendocina, and S. warneri. Open columns, no NAC; cross-hatched columns, 0.5 mg of NAC ml⁻¹. The bars indicate the standard deviations of the means for three experiments.

Acridine orange-stained K. pneumoniae attached to stainless steel surfaces after 72 h of incubation in 20% LB. (a) No NAC in the medium; (b) 0.5 mg of NAC ml⁻¹ in the medium.