Lactobacillus fermentum AGR1487 cell surface structures and supernatant increase paracellular permeability through different pathways

Abstract

Lactobacillus fermentum is commonly found in food products, and some strains are known to have beneficial effects on human health. However, our previous research indicated that L. fermentum AGR1487 decreases in vitro intestinal barrier integrity. The hypothesis was that cell surface structures of AGR1487 are responsible for the observed in vitro effect. AGR1487 was compared to another human oral L. fermentum strain, AGR1485, which does not cause the same effect. The examination of phenotypic traits associated with the composition of cell surface structures showed that compared to AGR1485, AGR1487 had a smaller genome, utilized different sugars, and had greater tolerance to acid and bile. The effect of the two strains on intestinal barrier integrity was determined using two independent measures of paracellular permeability of the intestinal epithelial Caco-2 cell line. The transepithelial electrical resistance (TEER) assay specifically measures ion permeability, whereas the mannitol flux assay measures the passage of uncharged molecules. Both live and UV-inactivated AGR1487 decreased TEER across Caco-2 cells implicating the cell surfaces structures in the effect. However, only live AGR1487, and not UV-inactivated AGR1487, increased the rate of passage of mannitol, implying that a secreted component(s) is responsible for this effect. These differences in barrier integrity results are likely due to the TEER and mannitol flux assays measuring different characteristics of the epithelial barrier, and therefore imply that there are multiple mechanisms involved in the effect of AGR1487 on barrier integrity.

Complete Genome Sequence of Lactobacillus fermentum Strain AGR1485, a Human Oral Isolate

“…The in silico restriction digest fragment pattern and fragment sizes closely resembled previously published pulsed-field gel electrophoresis results of the same genome using a commercial I-Ceul restriction enzyme ( Fig. 1 ) ( 6 ).…”

“… Lactobacillus fermentum is commonly found in food products ( 1 , 2 ) and is used as a probiotic therapeutic agent for the treatment of intestinal and vaginal pathogens ( 3 – 5 ). L. fermentum AGR1485 increases the barrier integrity of Caco-2 monolayers but does not induce colonic inflammation in germfree mice ( 6 , 7 ). L. fermentum AGR1485 has genetic similarities to other known probiotic L. fermentum strains, but little is known about the probiotic mechanisms of action of these strains.…”

“…The values given are the sizes (kb) of the DNA fragments from the bacterial strains. Image and caption adapted from Sengupta et al ( 6 ) under a CC BY-NC 4.0 license. (B) In silico digest results of the AGR1485 genome assembly using I-Ceul restriction sites processed by UGENE ( 17 ) and presented as the range from one restriction site to the next (fragment sizes are in base pairs and kilobase pairs).…”

Human oral isolate Lactobacillus fermentum AGR1487 induces a pro-inflammatory response in germ-free rat colons

“…A greater number of AGR1487 bacterial cells were present in the in the rat ileum, caecum and colon than AGR1485. This was expected based on previous in vitro studies showing AGR1487 had increased tolerance to gastrointestinal conditions (bile salts and low pH) 22 . It is unlikely that the increased pro-inflammatory response to AGR1487 in the colon was solely due to the fact that more bacterial cells were present because histological signs of inflammation were not observed in the caecum where AGR1487 was present in greater numbers compared to the colon.…”

Complete Annotated Genome Sequence of Limosilactobacillus fermentum AGR1487

“…In humans, strains of L. fermentum have been shown to improve the ratio of beneficial microorganisms of the large intestine and have been used as probiotic treatments for intestinal and vaginal diseases ( 1 – 3 ). However, L. fermentum AGR1487 has been found to increase colon inflammation in germfree mice and decreased the barrier integrity of Caco-2 monolayers ( 4 , 5 ). L. fermentum AGR1487 was isolated from an oral swab of a healthy human and identified using 16S rRNA gene sequencing ( 6 ).…”