GroEL of Lactobacillus johnsonii La1 (NCC 533) is cell surface associated: potential role in interactions with the host and the gastric pathogen Helicobacter pylori.

Heat shock proteins of the GroEL or Hsp60 class are highly conserved proteins essential to all living organisms. Even though GroEL proteins are classically considered intracellular proteins, they have been found at the surface of several mucosal pathogens and have been implicated in cell attachment and immune modulation. The purpose of the present study was to investigate the GroEL protein of a gram-positive probiotic bacterium, Lactobacillus johnsonii La1 (NCC 533). Its presence at the bacterial surface was demonstrated using a whole-cell enzyme-linked immunosorbent assay and could be detected in bacterial spent culture medium by immunoblotting. To assess binding of La1 GroEL to mucins and intestinal epithelial cells, the La1 GroEL protein was expressed in Escherichia coli. We report here that La1 recombinant GroEL (rGroEL) binds to mucins and epithelial cells and that this binding is pH dependent. Immunomodulation studies showed that La1 rGroEL stimulates interleukin-8 secretion in macrophages and HT29 cells in a CD14-dependent mechanism. This property is common to rGroEL from other gram-positive bacteria but not to the rGroEL of the gastric pathogen Helicobacter pylori. In addition, La1 rGroEL mediates the aggregation of H. pylori but not that of other intestinal pathogens. Our in vitro results suggest that GroEL proteins from La1 and other lactic acid bacteria might play a role in gastrointestinal homeostasis due to their ability to bind to components of the gastrointestinal mucosa and to aggregate H. pylori.

The complete genomes of Lactobacillus plantarum and Lactobacillus johnsonii reveal extensive differences in chromosome organization and gene content.

The first comprehensive comparative analysis of lactobacilli was done by comparing the genomes of Lactobacillus plantarum (3.3 Mb) and Lactobacillus johnsonii (2.0 Mb). L. johnsonii is predominantly found in the gastrointestinal tract, while L. plantarum is also found on plants and plant-derived material, and is used in a variety of industrial fermentations. The L. plantarum and L. johnsonii chromosomes have only 28 regions with conservation of gene order, totalling about 0.75 Mb; these regions are not co-linear, indicating major chromosomal rearrangements. Metabolic reconstruction indicates many differences between L. johnsonii and L. plantarum: numerous enzymes involved in sugar metabolism and in biosynthesis of amino acids, nucleotides, fatty acids and cofactors are lacking in L. johnsonii. Major differences were seen in the number and types of putative extracellular proteins, which are of interest because of their possible role in host-microbe interactions. The differences between L. plantarum and L. johnsonii, both in genome organization and gene content, are exceptionally large for two bacteria of the same genus, emphasizing the difficulty in taxonomic classification of lactobacilli.