A simulated mucus layer protects Lactobacillus reuteri from the inhibitory effects of linoleic acid

Abstract

Lactobacillus reuteri is a commensal, beneficial gut microbe that colonises the intestinal mucus layer, where it makes close contact with the human host and may significantly affect human health. Here, we investigated the capacity of linoleic acid (LA), the most common polyunsaturated fatty acid (PUFA) in a Western-style diet, to affect L. reuteri ATCC PTA 6475 prevalence and survival in a simulated mucus layer. Short-term (1 h) survival and mucin-agar adhesion assays of a log-phase L. reuteri suspension in intestinal water demonstrated that the simulated mucus layer protected L. reuteri against the inhibitory effects of LA by lowering its contact with the bacterial cell membrane. The protective effect of the simulated mucus layer was further evaluated using a more complex and dynamic model of the colon microbiota (SHIME®), in which L. reuteri survival was monitored during 6 days of daily exposure to LA in the absence (L-SHIME) and presence (M-SHIME) of a simulated mucus layer. After 6 days, luminal L- and M-SHIME L. reuteri plate counts had decreased by 3.1±0.5 and 2.6±0.9 log cfu/ml, respectively. Upon supplementation of 1.0 g/l LA, the decline in the luminal L. reuteri population started earlier than was observed for the control. In contrast, mucin-agar levels of L. reuteri (in the M-SHIME) remained unaffected throughout the experiment even in the presence of high concentrations of LA. Overall, the results of this study indicate the importance of the mucus layer as a protective environment for beneficial gut microbes to escape from stress by high loads of the antimicrobial PUFA LA to the colon, i.e. due to a Western-style diet.

Mucosa‐associated biohydrogenating microbes protect the simulated colon microbiome from stress associated with high concentrations of poly‐unsaturated fat

“…Following collection in Pyrex tubes, samples were stored at −80°C and freeze‐dried before extraction and methylation as described in De Weirdt et al . (). The sum of LA and its biohydrogenation products was calculated from the sum of LA, CLA, VA and SA (mg ml −1 ).…”

“…Devillard et al (2007) reported that LA increased the growth lag time of beneficial bacteria such as butyrate-producing and antiinflammatory Faecalibacterium prausnitzii, and lactic acid bacteria (LAB). Lactobacillus species were demonstrated to be highly sensitive to LA, as opposed to opportunistic pathogens such as Escherichia coli and Klebsiella pneumoniae (De Weirdt et al, 2013). However, survival of Lactobacillus reuteri upon LA exposure was improved when a mucosal environment was present (M-SHIME) (De Weirdt et al, 2013).…”

“…Lactobacillus species were demonstrated to be highly sensitive to LA, as opposed to opportunistic pathogens such as Escherichia coli and Klebsiella pneumoniae (De Weirdt et al, 2013). However, survival of Lactobacillus reuteri upon LA exposure was improved when a mucosal environment was present (M-SHIME) (De Weirdt et al, 2013). This protective effect may be partially attributed to mucins, which lowered the contact between LA and the bacterial membrane (De Weirdt et al, 2013).…”

“…However, survival of Lactobacillus reuteri upon LA exposure was improved when a mucosal environment was present (M-SHIME) (De Weirdt et al, 2013). This protective effect may be partially attributed to mucins, which lowered the contact between LA and the bacterial membrane (De Weirdt et al, 2013). In addition, LAbiohydrogenating bacteria inhabiting the mucosal layer may play a shielding role.…”

“…As a result, the survival of L. reuteri after in vitro exposure to high LA concentrations in the M-SHIME may also be promoted by the high abundance of mucin-associated, biohydrogenating Roseburia spp. (De Weirdt et al, 2013).…”