Atomic Force Microscopy Study of the Effect of Lipopolysaccharides and Extracellular Polymers on Adhesion of Pseudomonas aeruginosa

Abstract

The roles of lipopolysaccharides (LPS) and extracellular polymers (ECP) on the adhesion of Pseudomonas aeruginosa PAO1 (expresses the A-band and B-band of O antigen) and AK1401 (expresses the A-band but not the B-band) to silicon were investigated with atomic force microscopy (AFM) and related to biopolymer physical properties. Measurement of macroscopic properties showed that strain AK1401 is more negatively charged and slightly more hydrophobic than strain PAO1 is. Microscopic AFM investigations of individual bacteria showed differences in how the biopolymers interacted with silicon. PAO1 showed larger decay lengths in AFM approach cycles, suggesting that the longer polymers on PAO1 caused greater steric repulsion with the AFM tip. For both bacterial strains, the long-range interactions we observed (hundreds of nanometers) were inconsistent with the small sizes of LPS, suggesting that they were also influenced by ECP, especially polysaccharides. The AFM retraction profiles provide information on the adhesion strength of the biopolymers to silicon (F adh ). For AK1401, the adhesion forces were only slightly lower (F adh ‫؍‬ 0.51 nN compared to 0.56 nN for PAO1), but the adhesion events were concentrated over shorter distances. More than 90% of adhesion events for AK1401 were at distances of <600 nm, while >50% of adhesion events for PAO1 were at distances of >600 nm. The sizes of the observed molecules suggest that the adhesion of P. aeruginosa to silicon was controlled by ECP, in addition to LPS. Steric and electrostatic forces each contributed to the interfacial interactions between P. aeruginosa and the silicon surface.

Relating the Physical Properties of Pseudomonas aeruginosa Lipopolysaccharides to Virulence by Atomic Force Microscopy

“…Ten force cycles were recorded for at least five different cells of each strain examined. Raw AFM data were processed in Microsoft Excel and MATLAB (MathWorks, Natick, MA) by using a procedure we previously described, which is based on a method developed by Ducker et al (3,15). A steric repulsion model was applied to individual force curves using nonlinear curve fitting in TableCurve 2D (Systat Software Inc., Chicago, IL) to obtain the equilibrium length of the polymer brush, its compressibility, and the spacing between the LPS molecules (see Fig.…”

“…The O antigen protrudes into the environment and allows the bacterium to interact with its surroundings. There are 20 serotypes of P. aeruginosa (27), and 14 of those groups also produce the Aband saccharide known as common antigen, which is composed of D-rhamnose sugar polymer and consists of about 23 repeating units (6,47).LPS physical properties such as three-dimensional structure and number of repeating units contribute to bacterial adhesion (3,37,40). P. aeruginosa uses complicated biosynthetic mechanisms for assembly of LPS O antigen; this has been described extensively elsewhere (24).…”

“…LPS physical properties such as three-dimensional structure and number of repeating units contribute to bacterial adhesion (3,37,40). P. aeruginosa uses complicated biosynthetic mechanisms for assembly of LPS O antigen; this has been described extensively elsewhere (24).…”

Bacteriophage-derived enzyme that depolymerizes the alginic acid capsule associated with cystic fibrosis isolates ofPseudomonas aeruginosa

“…These bacteria convert to a mucoid phenotype and produce copious amounts of O-acetylated alginic acids: exopolysaccharides comprising b-d-mannuronic acid and its C5 epimer a-l-guluronic acid (Wong et al 2000). Alginates may mediate attachment to tracheal epithelium, enabling the bacteria to grow as a genetically heterogeneous, antibiotic refractory population within alginate biofilms (Costerton et al 1999;Mah et al 2003;Atabek and Camesano 2007).…”

Differential Lipopolysaccharide Core Capping Leads to Quantitative and Correlated Modifications of Mechanical and Structural Properties in Pseudomonas aeruginosa Biofilms

“…Accurate measurement of adhesion is therefore essential for monitoring the tendency of bacteria to attach to surfaces and to switch from a planktonic lifestyle to a biofilm lifestyle. Data accumulated in previous studies suggest that LPS is involved in bacterial cell adhesion to both abiotic (2,8,20,32,35,54,56) and biotic (17,38,49,56,57) surfaces. Moreover, environmental factors, such as growth temperature, pH, ionic strength, nutrient availability, and oxygen levels, may influence cell adhesion via modification of LPS expression and conformation (16,36,46,47,53).…”