@article{klotz_goh_o'flaherty_johnson_barrangou_2020, title={Deletion of S-Layer Associated Ig-Like Domain Protein Disrupts the Lactobacillus acidophilus Cell Surface}, volume={11}, ISSN={["1664-302X"]}, DOI={10.3389/fmicb.2020.00345}, abstractNote={Bacterial surface-layers (S-layers) are crystalline arrays of repeating proteinaceous subunits that coat the exterior of many cell envelopes. S-layers have demonstrated diverse functions in growth and survival, maintenance of cell integrity, and mediation of host interactions. Additionally, S-layers can act as scaffolds for the outward display of auxiliary proteins and glycoproteins. These non-covalently bound S-layer associated proteins (SLAPs) have characterized roles in cell division, adherence to intestinal cells, and modulation of the host immune response. Recently, IgdA (LBA0695), a Lactobacillus acidophilus SLAP that possesses a Group 3 immunoglobulin (Ig)-like domain and GW (Gly-Tryp) dipeptide surface anchor, was recognized for its high conservation among S-layer-forming lactobacilli, constitutive expression, and surface localization. These findings prompted its selection for examination within the present study. Although IgdA and corresponding orthologs were shown to be unique to host-adapted lactobacilli, the Ig domain itself was specific to vertebrate-adapted species suggesting a role in vertebrate adaptation. Using a counterselective gene replacement system, igdA was deleted from the L. acidophilus NCFM chromosome. The resultant mutant, NCK2532, exhibited a visibly disrupted cell surface which likely contributed to its higher salt sensitivity, severely reduced adhesive capacity, and altered immunogenicity profile. Transcriptomic analyses revealed the induction of several stress response genes and secondary surface proteins. Due to the broad impact of IgdA on the cellular physiology and probiotic attributes of L. acidophilus, identification of similar proteins in alternative bacterial species may help pinpoint next-generation host-adapted probiotic candidates.}, journal={FRONTIERS IN MICROBIOLOGY}, author={Klotz, Courtney and Goh, Yong Jun and O'Flaherty, Sarah and Johnson, Brant and Barrangou, Rodolphe}, year={2020}, month={Mar} }
 @article{selle_goh_johnson_sarah_andersen_barrangou_klaenhammer_2017, title={Deletion of Lipoteichoic Acid Synthase Impacts Expression of Genes Encoding Cell Surface Proteins in Lactobacillus acidophilus}, volume={8}, DOI={10.3389/fmicb.2017.00553}, abstractNote={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.}, journal={Frontiers in Microbiology}, publisher={Frontiers Media SA}, author={Selle, Kurt and Goh, Yong J. and Johnson, Brant R. and Sarah, O’Flaherty and Andersen, Joakim M. and Barrangou, Rodolphe and Klaenhammer, Todd R.}, year={2017}, month={Apr} }
 @article{johnson_o'flaherty_goh_carroll_barrangou_klaenhammer_2017, title={The S-layer Associated Serine Protease Homolog PrtX Impacts Cell Surface-Mediated Microbe-Host Interactions of Lactobacillus acidophilus NCFM}, volume={8}, ISSN={["1664-302X"]}, DOI={10.3389/fmicb.2017.01185}, abstractNote={Health-promoting aspects attributed to probiotic microorganisms, including adhesion to intestinal epithelia and modulation of the host mucosal immune system, are mediated by proteins found on the bacterial cell surface. Notably, certain probiotic and commensal bacteria contain a surface (S-) layer as the outermost stratum of the cell wall. S-layers are non-covalently bound semi-porous, crystalline arrays of self-assembling, proteinaceous subunits called S-layer proteins (SLPs). Recent evidence has shown that multiple proteins are non-covalently co-localized within the S-layer, designated S-layer associated proteins (SLAPs). In Lactobacillus acidophilus NCFM, SLP and SLAPs have been implicated in both mucosal immunomodulation and adhesion to the host intestinal epithelium. In this study, a S-layer associated serine protease homolog, PrtX (prtX, lba1578), was deleted from the chromosome of L. acidophilus NCFM. Compared to the parent strain, the PrtX-deficient strain (ΔprtX) demonstrated increased autoaggregation, an altered cellular morphology, and pleiotropic increases in adhesion to mucin and fibronectin, in vitro. Furthermore, ΔprtX demonstrated increased in vitro immune stimulation of IL-6, IL-12, and IL-10 compared to wild-type, when exposed to mouse dendritic cells. Finally, in vivo colonization of germ-free mice with ΔprtX led to an increase in epithelial barrier integrity. The absence of PrtX within the exoproteome of a ΔprtX strain caused morphological changes, resulting in a pleiotropic increase of the organisms’ immunomodulatory properties and interactions with some intestinal epithelial cell components.}, journal={FRONTIERS IN MICROBIOLOGY}, publisher={Frontiers Media SA}, author={Johnson, Brant R. and O'Flaherty, Sarah and Goh, Yong Jun and Carroll, Ian and Barrangou, Rodolphe and Klaenhammer, Todd R.}, year={2017}, month={Jun} }
 @article{johnson_klaenhammer_2016, title={AcmB Is an S-Layer-Associated beta-N-Acetylglucosaminidase and Functional Autolysin in Lactobacillus acidophilus NCFM}, volume={82}, ISSN={["1098-5336"]}, DOI={10.1128/aem.02025-16}, abstractNote={ABSTRACT}, number={18}, journal={APPLIED AND ENVIRONMENTAL MICROBIOLOGY}, author={Johnson, Brant R. and Klaenhammer, Todd R.}, year={2016}, month={Sep}, pages={5687–5697} }
 @article{johnson_hymes_sanozky-dawes_henriksen_barrangou_klaenhammer_2016, title={Conserved S-Layer-Associated Proteins Revealed by Exoproteomic Survey of S-Layer-Forming Lactobacilli}, volume={82}, ISSN={["1098-5336"]}, url={https://doi.org/10.1128/AEM.01968-15}, DOI={10.1128/aem.01968-15}, abstractNote={ABSTRACT}, number={1}, journal={APPLIED AND ENVIRONMENTAL MICROBIOLOGY}, publisher={American Society for Microbiology}, author={Johnson, Brant R. and Hymes, Jeffrey and Sanozky-Dawes, Rosemary and Henriksen, Emily DeCrescenzo and Barrangou, Rodolphe and Klaenhammer, Todd R.}, editor={Nojiri, H.Editor}, year={2016}, month={Jan}, pages={134–145} }
 @article{hymes_johnson_barrangou_klaenhammer_2016, title={Functional Analysis of an S-Layer-Associated Fibronectin-Binding Protein in Lactobacillus acidophilus NCFM}, volume={82}, ISSN={["1098-5336"]}, DOI={10.1128/aem.00024-16}, abstractNote={ABSTRACT}, number={9}, journal={APPLIED AND ENVIRONMENTAL MICROBIOLOGY}, publisher={American Society for Microbiology}, author={Hymes, Jeffrey P. and Johnson, Brant R. and Barrangou, Rodolphe and Klaenhammer, Todd R.}, editor={Dudley, E. G.Editor}, year={2016}, month={May}, pages={2676–2685} }
 @misc{johnson_klaenhammer_2014, title={Impact of genomics on the field of probiotic research: historical perspectives to modern paradigms}, volume={106}, ISSN={["1572-9699"]}, DOI={10.1007/s10482-014-0171-y}, abstractNote={For thousands of years, humans have safely consumed microorganisms through fermented foods. Many of these bacteria are considered probiotics, which act through diverse mechanisms to confer a health benefit to the host. However, it was not until the availability of whole-genome sequencing and the era of genomics that mechanisms of probiotic efficacy could be discovered. In this review, we explore the history of the probiotic concept and the current standard of integrated genomic techniques to discern the complex, beneficial relationships between probiotic microbes and their hosts.}, number={1}, journal={ANTONIE VAN LEEUWENHOEK INTERNATIONAL JOURNAL OF GENERAL AND MOLECULAR MICROBIOLOGY}, author={Johnson, Brant R. and Klaenhammer, Todd R.}, year={2014}, month={Jul}, pages={141–156} }
 @article{johnson_selle_o'flaherty_goh_klaenhammer_2013, title={Identification of extracellular surface-layer associated proteins in Lactobacillus acidophilus NCFM}, volume={159}, ISSN={["1350-0872"]}, DOI={10.1099/mic.0.070755-0}, abstractNote={Bacterial surface (S-) layers are crystalline arrays of self-assembling, proteinaceous subunits called S-layer proteins (Slps), with molecular masses ranging from 40 to 200 kDa. The S-layer-forming bacterium Lactobacillus acidophilus NCFM expresses three major Slps: SlpA (46 kDa), SlpB (47 kDa) and SlpX (51 kDa). SlpA has a demonstrated role in adhesion to Caco-2 intestinal epithelial cells in vitro, and has been shown to modulate dendritic cell (DC) and T-cell functionalities with murine DCs. In this study, a modification of a standard lithium chloride S-layer extraction revealed 37 proteins were solubilized from the S-layer wash fraction. Of these, 30 have predicted cleavage sites for secretion, 24 are predicted to be extracellular, six are lipid-anchored, three have N-terminal hydrophobic membrane spanning regions and four are intracellular, potentially moonlighting proteins. Some of these proteins, designated S-layer associated proteins (SLAPs), may be loosely associated with or embedded within the bacterial S-layer complex. Lba-1029, a putative SLAP gene, was deleted from the chromosome of L. acidophilus. Phenotypic characterization of the deletion mutant demonstrated that the SLAP LBA1029 contributes to a pro-inflammatory TNF-α response from murine DCs. This study identified extracellular proteins and putative SLAPs of L. acidophilus NCFM using LC-MS/MS. SLAPs appear to impart important surface display features and immunological properties to microbes that are coated by S-layers.}, journal={MICROBIOLOGY-SGM}, author={Johnson, Brant and Selle, Kurt and O'Flaherty, Sarah and Goh, Yong Jun and Klaenhammer, Todd}, year={2013}, month={Nov}, pages={2269–2282} }