d‐Alanyl ester depletion of teichoic acids in Lactobacillus reuteri 100‐23 results in impaired colonization of the mouse gastrointestinal tract

Abstract

The dlt operon of Gram-positive bacteria encodes proteins required for the incorporation of D-alanine esters into cell wall-associated teichoic acids (TA). D-alanylation of TA has been shown to be important for acid tolerance, resistance to antimicrobial peptides, adhesion, biofilm formation, and virulence of a variety of pathogenic organisms. The aim of this study was to determine the importance of D-alanylation for colonization of the gastrointestinal tract by Lactobacillus reuteri 100-23. Insertional inactivation of the dltA gene resulted in complete depletion of D-alanine substitution of lipoteichoic acids. The dlt mutant had similar growth characteristics as the wild type under standard in vitro conditions, but formed lower population sizes in the gastrointestinal tract of ex-Lactobacillus-free mice, and was almost eliminated from the habitat in competition experiments with the parental strain. In contrast to the wild type, the dlt mutant was unable to form a biofilm on the forestomach epithelium during gut colonization. Transmission electron microscope observations showed evidence of cell wall damage of mutant bacteria present in the forestomach. The dlt mutant had impaired growth under acidic culture conditions and increased susceptibility to the cationic peptide nisin relative to the wild type. Ex vivo adherence of the dlt mutant to the forestomach epithelium was not impaired. This study showed that D-alanylation is an important cell function of L. reuteri that seems to protect this commensal organism against the hostile conditions prevailing in the murine forestomach.

Functional genomics of Lactobacillus casei establishment in the gut

“…A mature cell wall, particularly proper biosynthesis and branching of the lipoteichoic acid, is a crucial element during L. casei establishment in the gut. This result is consistent with another contribution (32), which showed that a Lactobacillus reuteri dltA mutant was not competitive when newly introduced in the gastrointestinal tract of previously Lactobacillus-free mice. Our screening also reports the importance of one penicillin-binding protein (PBP): LSEI_0221, a D-alanyl-Dalanine carboxypeptidase that removes the last amino acid of the peptide bridge allowing the transpeptidation between two strands of peptidoglycan, is essential for gut establishment.…”

“…Alteration of the cell wall structure may decrease the bacteria's sensing of its environment and resistance to the environment's harsh components (49). The consequences may encompass an increase in cellular permeability to environmental compounds and to protons (50), a decrease in resistance to autolysis (32), and a modification of surface properties and hence an enhanced susceptibility to bacteriocins and antimicrobial peptides. Also, some ABC transporters can be involved in resistance to antimicrobial or peptides by excluding these compounds.…”

Diversification of the gut symbiont Lactobacillus reuteri as a result of host-driven evolution

“…In rodents, pigs and chickens, L. reuteri is one of the dominant species in the GIT (Leser et al, 2002;Salzman et al, 2002;Brooks et al, 2003;Abbas Hilmi et al, 2007). In these animals, L. reuteri colonizes the surfaces of the stratified squamous epithelial lining of the proximal regions of the digestive tract (Tannock, 1992;Walter et al, 2007). The ecology of L. reuteri in the human gut is less clear and the organism is only detected in some subjects (Walter, 2008).…”

Characterization of surface molecules from bacterial cells involved in the potential probiotic activity of natural lactobacilli isolates

“…Kod soja Lb. reuteri 100-23 LTA omogućava kolonizaciju mišijeg GIT-a (Walter et al, 2007). Pokazano je da i egzopolisaharidi (EPS) koje produkuju bakterije imaju funkciju adhezije za ECM komponente.…”