Deletion of Lipoteichoic Acid Synthase Impacts Expression of Genes Encoding Cell Surface Proteins in Lactobacillus acidophilus

Abstract

Lactobacillus acidophilus NCFM is a well-characterized probiotic microorganism, supported by a decade of genomic and functional phenotypic investigations. L. acidophilus deficient in lipoteichoic acid (LTA), a major immunostimulant in Gram-positive bacteria, has been shown to shift immune system responses in animal disease models. However, the pleiotropic effects of removing LTA from the cell surface in lactobacilli are unknown. In this study, we surveyed the global transcriptional and extracellular protein profiles of two strains of L. acidophilus deficient in LTA. Twenty-four differentially expressed genes specific to the LTA-deficient strains were identified, including a predicted heavy metal resistance operon and several putative peptidoglycan hydrolases. Cell morphology and manganese sensitivity phenotypes were assessed in relation to the putative functions of differentially expressed genes. LTA-deficient L. acidophilus exhibited elongated cellular morphology and their growth was severely inhibited by elevated manganese concentrations. Exoproteomic surveys revealed distinct changes in the composition and relative abundances of several extracellular proteins and showed a bias of intracellular proteins in LTA-deficient strains of L. acidophilus. Taken together, these results elucidate the impact of ltaS deletion on the transcriptome and extracellular proteins of L. acidophilus, suggesting roles of LTA in cell morphology and ion homeostasis as a structural component of the Gram positive cell wall.

Lipoteichoic acid depletion in Lactobacillus impacts cell morphology and stress response but does not abolish mercury surface binding

“…However, differences in the cell morphology were evidenced between both L. plantarum mutant strains. The morphology of the L. plantarum WCFS1 ltaS mutant was similar to that described for L. acidophilus (Selle et al, 2017) and L. gasseri (Selle et al, 2014) strains lacking LTA, while the Lpp+ ltaS strain was characterized by a non-rod morphology with an irregular surface. A rough surface with protrusions has also been observed in the cells of tagO mutants from S. aureus unable to synthesize WTA, compared to the smooth surface of wild-type cells (Koprivnjak et al, 2008).…”

“…Part of these effects had been previously observed in lactobacilli of L. acidophilus NCFM and Lactobacillus gasseri ATCC 33323 lacking the ltaS counterparts LBA0447 and LGAS_1586, respectively. Light microscopy inspection of these mutants revealed elongated cells twice as long as the wild type cells, and exhibiting bending and curving (Selle et al, 2017;Selle et al, 2014). However, contrarily to L. plantarum, and ltaS mutants of other species (Mamou et al, 2017;Oku et al, 2009;Schirner et al, 2009), no relevant growth defect was observed in L. acidophilus NCFM upon ltaS mutation (Mohamadzadeh et al, 2011).…”

“…L. plantarum strains lacking ltaS showed increased sensitivity to Hg cations. In B. subtilis (Schirner et al, 2009) and L. acidophilus (Selle et al, 2017), ltaS mutants are more susceptible to the toxic effects of Mn 2+ and a B. subtilis ltaS deletion strain had reduced requirements of Mg 2+ in minimal medium (Schirner et al, 2009). It is assumed that the loss of LTA-cations interactions at the cell wall allows better cation access to the membrane, which results in increased toxicity (Mn 2+ ) or lower requirements (Mg 2+ ) for cations (Schirner et al, 2009).…”

A Quorum Sensing-Regulated Protein Binds Cell Wall Components and Enhances Lysozyme Resistance in Streptococcus pyogenes

“…In Gram-positive bacteria, S-layer proteins noncovalently bind to components of the cell wall (39). For example, the S-layer protein of Lactobacillus acidophilus, SlpA, contains a C-terminal domain (SAC) that is required for the protein to associate with lipoteichoic acid for surface association (40). Like StcA, the SAC domain has many positively charged residues, and binding of the protein is severely reduced in the presence of salt concentrations greater than 250 mM NaCl (30).…”

Deletion of S-Layer Associated Ig-Like Domain Protein Disrupts the Lactobacillus acidophilus Cell Surface

“…Increased Slp shedding by igdA suggests not only a function in S-layer formation, but also a probable relationship with LTA, though notably, ltaS expression was unaffected by the deletion. However, like igdA, an LTA-deficient strain of L. acidophilus exhibited elongated cells mediated through aberrant cell division and attributed to the upregulation of peptidoglycan turnover genes such as lysin (Selle et al, 2017). Similarly, L. acidophilus with an insertionally inactivated cell division protein, cdpA, also developed elongated cells, salt sensitivity, and an altered cell wall structure (Altermann et al, 2004).…”