Effects of rhamnolipids and shear on initial attachment of Pseudomonas aeruginosa PAO1 in glass flow chambers.
OBJECTIVE
Solid surfaces in contact with water have been found to be biofouled due to the attachment of various organisms. For better understanding of the biofilm formation, the important initial stage of bacterial attachment was investigated with Pseudomonas aeruginosa PAO1 as a model microorganism. Effects of the biosurfactant rhamnolipids and the shear conditions were particularly examined.


METHODS
A highly reproducible procedure was employed. The procedure involved monitoring and counting the number of attached cells on glass walls of the flow chambers, through which a PAO1 suspension was circulated and, subsequently, a saline solution was passed for washing. The experiments were made under different circulation rates (exerting different shear on the bacteria) and rhamnolipid concentrations.


CONCLUSIONS
Reproducibility of the procedure was confirmed. The velocity profiles near the flow chamber wall were determined. Rhamnolipids, even at a very low concentration of 13 mg/l, were found to deter the bacterial attachment substantially. Prewashing the cells with a 100 mg/l rhamnolipid solution, however, did not affect the attachment significantly. As for the effect of shear, the PAO1 attachment showed an increasing-then-decreasing trend in the range investigated, i.e., 1.0 to 26 mN/m(2) shear stresses at the chamber wall. The diffusion-limited transport of cells to the chamber wall might have contributed to, but could not fully explain, the increasing attachment observed in the very low shear range (up to 3.5-5.0 mN/m(2)).


CONCLUSIONS
As compared to static systems, the flow chamber systems significantly improved the reproducibility of initial attachment results. Flow chamber systems were more suitable for experimental investigations of bacterial attachment to surfaces. Rhamnolipids were found to be potent antifoulants for PAO1 attachment on glass. The initial cell attachment increased with increasing shear at the very low shear range (up to 3.5-5.0 mN/m(2)), but the attachment could be minimized with further increase of the shear.
Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, OH 44325-3906, USA.
Akhila
A
Raya
Maysam
M
Sodagari
Neissa M
NM
Pinzon
Xin
X
He
Bi-Min
BM
Zhang Newby
Lu-Kwang
LK
Ju
D018441:Biofilms / Q000187:drug effects; D057219:Biofouling / Q000517:prevention & control*; D005898:Glass / Q000737:chemistry*; D006017:Glycolipids / Q000737:chemistry / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000737:chemistry / Q000187:drug effects* / Q000502:physiology; D033081:Shear Strength / Q000187:drug effects
D006017:Glycolipids; C418382:rhamnolipid