Center for Biofilm Engineering

Abstract:  

"Role of Alginate and Alginate O-Acetylation in the Formation of Pseudomonas aeruginosa Microcolonies and Biofilms" 

biofilms that absorbed IR-radiation near 1650 (amide I), 1550 (amide II), 1450 (CH2 deformation), 1400 (carboxylate symmetric stretch), 1240 (P-O stretch, C-O-C stretch, and/or amide III) and 1100 to 1000 cm-1 (C-O and P-O stretch).  The FRD1 biofilms produced spectra with an increase in relative absorbance at 1060 (C-OH stretch of alginate) and 1250 cm-1 (C-O-C stretch of alginate), as compared to biofilms of nonmucoid mutant strains. Dehydration of an 88 h FRD1 biofilm revealed other IR-bands that were also found in the spectrum of

purified FRD1 alginate. These results provide evidence that alginate was present within the FRD1 biofilms and at greater relative concentrations at depths exceeding 1 µm, the analysis range for the ATR/FT-IR technique. After 88 h, biofilms of the nonmucoid strains produced amide II absorbances that were 6 to 8 times as intense as those of the mucoid FRD1 parent strain. However, the cell densities in biofilms were similar, suggesting that FRD1 formed

biofilms with most cells at depths that exceeded the analysis range of the ATR/FT-IR technique. CSLM analysis confirmed this result, demonstrating that nonmucoid strains formed densely packed biofilms that were generally less than 6 µm in depth. In contrast, FRD1 produced microcolonies that were approximately 40 µm in depth. An algJ mutant strain that produced alginate lacking O-acetyl groups, gave an amide II signal approximately 5-fold less than that of FRD1, and produced small microcolonies. After 44 h, the algJ mutant switched to the nonmucoid phenotype, and formed uniform biofilms, similar to biofilms produced by the nonmucoid strains. These results demonstrate that alginate, although not required for P. aeruginosa biofilm development, plays a role in the biofilm structure and may act as intercellular material, required for microcolony formation. The results also demonstrate the importance of alginate O-acetylation in P. aeruginosa biofilm architecture.

Nivens, D.E., D.E. Ohman, J. Williams, and M.J. Franklin, "Role of Alginate and Alginate O-Acetylation in the Formation of Pseudomonas aeruginosa Microcolonies and Biofilms," J. Bacteriol. 183:1047-1057 (2001).