Effects of nonionic surfactants on the cell surface hydrophobicity and apparent Hamaker constant of a Sphingomonas sp

Derick G. Brown, Peter R. Jaffe

Research output: Contribution to journalArticle

57 Scopus citations

Abstract

Nonionic surfactants of the form CxEy, were studied for their ability to alter the cell surface hydrophobicity and apparent Hamaker constants of a Sphingomonas sp. Through contact angle measurements on hydrated and dried bacterial lawns, it was found that the cell surface hydrophobicity changed systematically with both the alkyl (x) and polyoxyethylene (y) chain lengths. While differences in contact angles were observed between hydrated and dried lawns, they could not be attributed to the mere presence or absence of water, suggesting that reorientation of cell surface components may occur during drying. All surfactants examined reduced the hydrophilicity of the bacterial cell surface, with one surfactant (C18E10) making the cells hydrophobic. Effective bacterial Hamaker constants for bacteria interacting across a vacuum (Abb) and water (Abwb) and bacteria interacting in water with quartz sand (Abws) were calculated from the contact angles. It was found that the surfactants have the potential to reduce the Hamaker constants, but that the overall effects differed between dried and hydrated lawns, indicating that lawn preparation method can have a significant impact in interpretation of cell surface properties. The results also indicate that the Abws value of 10-20 J, which is often assumed in bacterial attachment and transport studies, may be an order of magnitude higher than the actual value. Finally, the results suggest that alteration of bacterial adhesion due to the presence of surfactants cannot be attributed to a single cell surface property but is rather due to multiple interactions.

Original languageEnglish (US)
Pages (from-to)195-201
Number of pages7
JournalEnvironmental Science and Technology
Volume40
Issue number1
DOIs
StatePublished - Jan 1 2006

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Environmental Chemistry

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