Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2024

The effects of probiotic secretomes on human gut methanogen growth in-vitro provide new efficacy insights for functional constipation prophylaxis and/or therapy. (104588)

Yenkai Lim 1 2 , Abigail Tovey-Matthews 1 2 , Ahmed Sid-Ahmed 1 2 , Harley McRae 1 2 , Mark Morrison 1 2
  1. Frazer Institute, University of Queensland, Brisbane
  2. Translational Research Institute, Brisbane

Background:

Methane-producing archaea in the human distal gut have long been recognised as a metabolic sink for the hydrogen produced during microbial fermentation. However, recent studies also show an association between methane-positivity and slower intestinal transit in humans, and that “functional” constipation may be linked with methanogen “overgrowth”; and an early sign of more serious health conditions. In the clinical setting, Bifidobacteria probiotics have been successful in mitigating functional constipation, but the biology remains unexplained. Here, we examined how the secretomes from Bifidobacterium longum and B. infantis cultures affected the growth of Methanobrevibacter smithii strains PST and JC9 and Methanosphaera sp. DSMZ3091T and PA-5, which represent the two major lineages of human gut methanogens.

Methods:

The Bifidobacteria were cultured with MRS broth and their secretomes harvested via centrifugation and filter-sterilization, lyophilised, then resuspended to 1x and 5x their original concentrations with anaerobic water. Uninoculated MRS broth was similarly processed as a medium control. For the growth studies, aliquots (0.2 ml) of active methanogen cultures were mixed with either 1 ml of the 1x or 5x secretome preparations, uninoculated MRS broth, or sterile anaerobic water, then transferred into tubes containing 9 ml of a rumen fluid based medium with H2:CO2 (80:20) added to the headspace and methanol added to support growth of the Methanosphaera strains. These growth studies were repeated three times, with growth monitored by OD600 measurements over time and subjected to “area-under-curve” (AUC) analysis using the GrowthCurver package on RStudio. 

Results:

Compared to the cultures with the addition of anaerobic water, the uninoculated MRS and probiotic secretomes improved the growth kinetics of both Methanosphaera strains. In contrast, the growth of both M. smithii strains appeared to be reduced by the addition of the uninoculated MRS, and for M. smithii strain JC9, the probiotic secretomes further reduced the AUC values, primarily due to a greater lag time and reduced final yield of these cultures.

Conclusions:

Bifidobacteria secretomes appear to directly impose a metabolic burden on select strains of M. smithii that affects their growth, which may translate into a reduction in their persistence and abundance within distal gut.