title: Conserved S-Layer-Associated Proteins Revealed by Exoproteomic Survey of S-Layer-Forming Lactobacilli.
abstract: The Lactobacillus acidophilus homology group comprises Gram-positive species that include L. acidophilus, L. helveticus, L. crispatus, L. amylovorus, L. gallinarum, L. delbrueckii subsp. bulgaricus, L. gasseri, and L. johnsonii. While these bacteria are closely related, they have varied ecological lifestyles as dairy and food fermenters, allochthonous probiotics, or autochthonous commensals of the host gastrointestinal tract. Bacterial cell surface components play a critical role in the molecular dialogue between bacteria and interaction signaling with the intestinal mucosa. Notably, the L. acidophilus complex is distinguished in two clades by the presence or absence of S-layers, which are semiporous crystalline arrays of self-assembling proteinaceous subunits found as the outermost layer of the bacterial cell wall. In this study, S-layer-associated proteins (SLAPs) in the exoproteomes of various S-layer-forming Lactobacillus species were proteomically identified, genomically compared, and transcriptionally analyzed. Four gene regions encoding six putative SLAPs were conserved in the S-layer-forming Lactobacillus species but not identified in the extracts of the closely related progenitor, L. delbrueckii subsp. bulgaricus, which does not produce an S-layer. Therefore, the presence or absence of an S-layer has a clear impact on the exoproteomic composition of Lactobacillus species. This proteomic complexity and differences in the cell surface properties between S-layer- and non-S-layer-forming lactobacilli reveal the potential for SLAPs to mediate intimate probiotic interactions and signaling with the host intestinal mucosa.
authors.affiliation: Graduate Program in Microbiology, College of Agriculture and Life Sciences, North Carolina State University, Raleigh, North Carolina, USA Department of Food, Bioprocessing, and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina, USA.
authors.forename: Brant R
authors.initials: BR
authors.lastname: Johnson
authors.affiliation: Department of Food, Bioprocessing, and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina, USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Hymes
authors.affiliation: Department of Food, Bioprocessing, and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina, USA.
authors.forename: Rosemary
authors.initials: R
authors.lastname: Sanozky-Dawes
authors.affiliation: Department of Food, Bioprocessing, and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina, USA.
authors.forename: Emily DeCrescenzo
authors.initials: ED
authors.lastname: Henriksen
authors.affiliation: Graduate Program in Microbiology, College of Agriculture and Life Sciences, North Carolina State University, Raleigh, North Carolina, USA Department of Food, Bioprocessing, and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina, USA.
authors.forename: Rodolphe
authors.identifier: http://orcid.org/0000-0002-0648-3504
authors.initials: R
authors.lastname: Barrangou
authors.affiliation: Graduate Program in Microbiology, College of Agriculture and Life Sciences, North Carolina State University, Raleigh, North Carolina, USA Department of Food, Bioprocessing, and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina, USA klaenhammer@ncsu.edu.
authors.forename: Todd R
authors.initials: TR
authors.lastname: Klaenhammer
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D007778:Lactobacillus / Q000737:chemistry / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D007779:Lactobacillus acidophilus / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D040901:Proteomics
chemical_list: D001426:Bacterial Proteins; D008562:Membrane Glycoproteins; C055764:S-layer proteins