Available online at www.sciencedirect.com Colloids and Surfaces B: Biointerfaces 62 (2008) 91–96 Adhesion of Pseudomonas putida NCIB 9816-4 to a naphthalene-contaminated soil Geelsu Hwang a , Young-Min Ban a , Chang-Ha Lee a , Chan-Hwa Chung b , Ik-Sung Ahn a,∗ a Department of Chemical Engineering, Yonsei University, Seoul 120-749, South Korea b Department of Chemical Engineering, Sungkyunkwan University, Suwon 440-746, South Korea Received 9 August 2006; received in revised form 12 September 2007; accepted 17 September 2007 Available online 21 September 2007 Abstract The effect of a soil contaminant on the initial adhesion to the soil of a contaminant-degrading soil microorganism in the exponential phase was investigated using naphthalene as the soil contaminant and Pseudomonas putida strain NCIB 9816-4 as the naphthalene-degrading bacteria. P. putida strain DK-1, which is not capable of degrading naphthalene, was used as a control. P. putida NCIB 9816-4 in the exponential phase showed the more adhesion to the soil than that in the stationary phase. In contrast, P. putida DK-1 showed the increased adhesion to the soil when it was in the stationary phase. P. putida NCIB 9816-4 in the exponential phase showed the preferred adhesion to the naphthalene-contaminated soil, whereas the adhesion of P. putida DK-1 was not affected by naphthalene. From the data of surface hydrophobicities of the cells and the soil, the microbial adhesion, especially the initial adhesion to the naphthalene-contaminated soil, takes place through the hydrophobic interaction. We suspect that the surface hydrophobicity of P. putida NCIB 9816-4 in the exponential phase might be increased during the uptake of naphthalene, which caused the preferred adhesion to the naphthalene-contaminated soil. © 2007 Elsevier B.V. All rights reserved. Keywords: Adhesion; Hydrophobic interaction; Naphthalene; Pseudomonas putida; Soil 1. Introduction Polycyclic aromatic hydrocarbons (PAHs) are introduced into the soil through contamination by crude oil or refinery prod- ucts. Although many of these PAH compounds may undergo photolysis, chemical oxidation or volatilization, some may per- sist and, as result, accumulate in the environment, causing toxic, mutagenic, or carcinogenic effects [1,2]. Hence, the presence of PAHs in soil and groundwater is of widespread environmental concern. Microbial degradation of PAHs has long been recognized as the major process affecting their persistence and fate in the environment. Biological processes frequently bring about a com- plete conversion of PAHs to CO 2 and H 2 O, and the major agents causing this biological transformation in soil are the microorganisms that inhabit the soil [3]. Numerous soil con- taminants, including PAHs, have been studied with respect to ∗ Corresponding author. Fax: +82 2 312 6401. E-mail address: iahn@yonsei.ac.kr (I.-S. Ahn). their sorption/desorption behaviors in soil, and various studies have also identified the microbial strains capable of degrad- ing these compounds and have elucidated the biodegradation pathways involved. In addition to knowledge about the biodegra- dation and the transport of the contaminants in the soil, it is also necessary to know about microbial transport through the soil matrix in order to predict the fate of these contaminants and to monitor the progress of soil bioremediation, especially in-situ bioremediation [4]. For example, biological clogging is known to occur during in-situ bioremediation, which inhibits the biodegradation of contaminants due to the retarded trans- port of oxygen [5]. Bio-clogging has been reported to be caused by liquid porosity reduction due to biofilm growth, by the formation of biomass aggregates plugging pore necks, by the production of extracellular polymers that fill the pores, by the formation of gas bubbles that prevent liquid flow, and by an increase in the pore channel friction factor [5]. Therefore, a thorough understanding of the interactions between microorgan- isms and the surface of contaminated soil is needed, especially with respect to the initial adhesion of cells to the soil surface [6–9]. 0927-7765/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfb.2007.09.014