Surface of Lactic Acid Bacteria: Relationships between Chemical Composition and Physicochemical Properties

Abstract

The surface chemical composition and physicochemical properties (hydrophobicity and zeta potential) of two lactic acid bacteria, Lactococcus lactis subsp. lactis bv. diacetilactis and Lactobacillus helveticus, have been investigated using cells harvested in exponential or stationary growth phase. The surface composition determined by X-ray photoelectron spectroscopy (XPS) was converted into a molecular composition in terms of proteins, polysaccharides, and hydrocarbonlike compounds. The concentration of the last was always below 15% (wt/wt), which is related to the hydrophilic character revealed by water contact angles of less than 30°. The surfaces of L. lactis cells had a polysaccharide concentration about twice that of proteins. The S-layer of L. helveticus was either interrupted or crossed by polysaccharide-rich compounds; the concentration of the latter was higher in the stationary growth phase than in the exponential growth phase. Further progress was made in the interpretation of XPS data in terms of chemical functions by showing that the oxygen component at 531.2 eV contains a contribution of phosphate in addition to the main contribution of the peptide link. The isoelectric points were around 2 and 3, and the electrophoretic mobilities above pH 5 (ionic strength, 1 mM) were about ؊3.0 ؋ 10 ؊8 and ؊0.6 ؋ 10 ؊8 m 2 s ؊1 V ؊1 for L. lactis and L. helveticus, respectively. The electrokinetic properties of the latter reveal the influence of carboxyl groups, while the difference between the two strains is related to a difference between N/P surface concentration ratios, reflecting the relative exposure of proteins and phosphate groups at the surface.In many instances, the behavior of lactic acid bacteria is dependent on interfacial processes and thus on cell surface physicochemical properties and chemical composition. A better knowledge of these aspects would allow a deeper understanding of the autolysis of lactic acid bacteria (29, 36) and the production of texturing exopolysaccharides (4). It would help in controlling the sedimentation of starters for commercial production (7) and in understanding the roles of specific and nonspecific interactions in phage attachment (7,46,56).In dairy product manufacturing, adhesion of lactic bacteria to a material may be the first step leading to biofilm formation, which can be either deleterious (contamination, taste alteration, and biofouling on heat exchangers) (17, 25) or beneficial (continuous inoculation in yogurt or cheese making) (5). The adhesion behavior of microbial cells has been shown to depend on the balance of electrostatic and van der Waals interactions and on the hydrophobic character of the surfaces involved (38,42,53,54), pointing to the possible influence of the respective zeta potentials and surface hydrophobicities. Moreover, the production of extracellular substances either at the cell surface or in the surrounding medium has been shown to influence adhesion (14, 55).The surface hydrophobicity and composition of lactic acid bacteria have been studie...

Article

“…Il a été proposé d'expliquer les propriétés adhésives des bactéries par les propriétés physicochimiques globales de la surface des cellules [4]. Il a été établi que la surface lactococcale se compose principalement de protéines et de polysaccharides, et possède un caractère hydrophile [3]. Le rôle exact de chaque composant moléculaire de la surface des lactocoques dans l'adhésion et la formation d'un biofilm n'a pas encore été clairement établi.…”

Conditioning materials with biomacromolecules: Composition of the adlayer and influence on cleanability

“…Chemical compounds present in food and pharmaceutical mixtures may influence interactions with surfaces and adhesion processes (Speranza et al, 2004). Proteins at the outer surface of bacteria are known to play an important role in the initial attachment to solid surfaces in water (Dufrêne et al, 1996;Flint et al, 1997;Caccavo, 1999;Boonaert and Rouxhet, 2000;Lower et al, 2005;Mercier-Bonin et al, 2009). In a work devoted to soiling by starch suspension, it was reported (Detry et al, 2011) that the presence of macromolecules, mainly polysaccharides, which were adsorbed from the liquid phase or carried by the retracting water film and deposited at the granulesubstrate interface, acted as an adhesive joint, the properties of which seemed to be influenced by the detailed history of drying and subsequent exposure to humidity.…”

Cell surface acid-base properties of the cyanobacterium Synechococcus : Influences of nitrogen source, growth phase and N:P ratios

“…Bruinsma et al (2001) observed that Pseudomonas aeruginosa grown to mid-exponential phase possessed greater concentrations of nitrogen-rich cell surface components and adhered better to hydrophobic and hydrophilic substrata than cells in the early stationary growth phase. Boonaert and Rouxhet (2000) reported that Lactobacillus helveticus contained more polysaccharide-rich compounds in stationary phase than during exponential growth. In contrast, other research indicated that bacterial surface compositions remain unchanged in response to growth phase.…”

“…For example, Mozes et al (1988) showed that there was a direct correlation between the cell surface N:P atomic concentration ratio and the cell's electrostatic charge; the presence of phosphate groups mainly determined the anionic surface charges, while nitrogenous groups were linked to increased positive charges. Boonaert and Rouxhet (2000) suggested that the difference in electrokinetic properties between Lactococcus lactis and Lactobacillus helveticus is related to N:P surface concentration ratios, which reflects the relative exposure of proteins and phosphate groups at the surface. However, there is still a scarcity of information linking the alteration of N:P ratios to changes in bacteria cell wall composition or surface properties.…”