비교 유전체학을 통한 S-layer와 관계된 락토바실러스의 분석

Abstract

Background: Surface layers (S-layers) are two-dimensional crystalline proteinaceous envelope represented at the outermost surface of the cell wall in Gram-positive and Gram-negative bacteria. S-layers have an important role in adhesion to the gastrointestinal mucosa, interaction with the host and its immune system. The Lactobacillus acidophilus complex is gram-positive, facultative anaerobic bacteria and include many species that are closely related and have a diverse ecological lifestyle as probiotics and dairy fermenters. This complex can be divided into two groups, whether S-layer is present or not. In order to characterize functional differences and identify the S-layer-associated proteins, S-layer present group and S-layer absent group were analyzed based on comparative genomics approaches. Results: The phylogenetic analysis of strains of two groups revealed three distinct clusters of S-layer present group and two species of S-layer absent group and L. bulgaricus of S-layer absent group. In S-layer present group, carbohydrates and nucleotides metabolisms were significantly identified. Lysine biosynthesis is to strain-specific. Cytochrom bd complex were found in L. gasseri and L. johnsonii of S-layer absent group but, other species have another type of mechanisms against oxidative stress. L. bulgaricus is unique species that showed genetic functions found in only this species thus does not clustered with other S-layer absent group and have some similar genetic patterns with ones of S-layer present strains. The conserved genetic region composed of S-layer proteins, N-acetylmuramidase and amidase is found in all members of S-layer present group. Conclusion: The identification of functional differences between S-layer present and absent lactobacilli provides insight of their biological needs for making and maintaining S-layer and furthermore, the characterization of strain-specific mechanisms reveals its potential for probiotics.