title: Bacterial cell surface properties: role of loosely bound extracellular polymeric substances (LB-EPS).
abstract: This study investigated the effect of loosely bound extracellular polymeric substances (LB-EPS) on the comprehensive surface properties of four bacteria (Bacillus subtilis, Streptococcus suis, Escherichia coli and Pseudomonas putida). The removal of LB-EPS from bacterial surfaces by high-speed centrifugation (12,000×g) was confirmed by SEM images. Viability tests showed that the percentages of viable cells ranged from 95.9% to 98.0%, and no significant difference was found after treatment (P>0.05). FTIR spectra revealed the presence of phosphodiester, carboxylic, phosphate, and amino functional groups on bacteria surfaces, and the removal of LB-EPS did not alter the types of cell surface functional groups. Potentiometric titration results suggested the total site concentrations on the intact bacteria were higher than those on LB-EPS free bacteria. Most of the acidity constants (pKa) were almost identical, except the increased pKa values of phosphodiester groups on LB-EPS free S. suis and E. coli surfaces. The electrophoretic mobilities and hydrodynamic diameters of the intact and LB-EPS free bacteria were statistically unchanged (P>0.05), indicating LB-EPS had no influence on the net surface charges and size distribution of bacteria. However, LB-ESP could enhance cell aggregation processes. The four LB-EPS free bacteria all exhibited fewer hydrophobicity values (26.1-65.0%) as compared to the intact cells (47.4-69.3%), suggesting the removal of uncharged nonpolar compounds (e.g., carbohydrates) in LB-EPS. These findings improve our understanding of the changes in cell surface characterizations induced by LB-EPS, and have important implications for assessing the role of LB-EPS in bacterial adhesion and transport behaviors.
authors: State Key Laboratory of Agricultural Microbiology, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors: Wenqiang
authors: W
authors: Zhao
authors: State Key Laboratory of Agricultural Microbiology, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors: Shanshan
authors: S
authors: Yang
authors: State Key Laboratory of Agricultural Microbiology, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors: Qiaoyun
authors: Q
authors: Huang
authors: State Key Laboratory of Agricultural Microbiology, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China. Electronic address: cp@mail.hzau.edu.cn.
authors: Peng
authors: P
authors: Cai
mesh_terms: D001412:Bacillus subtilis / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure; D001422:Bacterial Adhesion; D001704:Biopolymers / Q000737:chemistry* / Q000302:isolation & purification; D002462:Cell Membrane / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure; D004586:Electrophoresis; D004926:Escherichia coli / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure; D057927:Hydrophobic and Hydrophilic Interactions; D050296:Microbial Viability; D016958:Pseudomonas putida / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure; D017011:Streptococcus suis / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure; D013499:Surface Properties
chemical_list: D001704:Biopolymers
keywords: Bacteria; Functional group; Hydrophobicity; LB-EPS; Surface charge