Cells and Materials


The aim of this study was to examine the effect of serial passaging in liquid medium on physico-chemical and structural surface characteristics of two lactobacillus strains. To this end, starting cultures (p = 1) of urogenital isolate L. acidophilus RC 14 and poultry isolate L. fermentum B54 were serially passaged in liquid medium up to 20 times (p = 20). In both strains, similar physico-chemical and structural changes were observed following serial passaging. According to water contact angle measurements , cells in p = 20 cultures became less hydrophobic. Microelectrophoresis showed that isoelectric points shifted towards the acidic region upon serial passaging. Jn addition, the strains had become heterogeneous with respect to the pH dependence of their zeta potentials. According to FTIR and XPS, the surfaces of p = 20 cultures of both strains showed decreasing amounts of proteinaceous material and increasing amounts of polysaccharide-like substances as compared to p = 1 cultures. Heterogeneity of p = 20 strains was also reflected in structural features of the cell surface at the electron microscopic level. In p = 1 cultures of both strains, all cells had a stained layer: in contrast , in p = 20 cultures about half of the cells became devoid of this layer. The study clearly showed that surface characteristics of lactobacilli may change following serial passaging in liquid medium. Knowledge of these changes is of importance because these microorganisms are considered for use in biomedical applications like the restoration of a healthy vaginal microflora by cell seeding.