Limousia bacteria encode mucinolysome for mucin utilization in animal gut microbiomes

Area of Science:

• Microbiology and Gut Microbiome Research
• Molecular Biology and Biochemistry
• Bioinformatics and Genomics

Background:

• Mucins form a crucial physical barrier protecting host tissues from pathogens.
• The mechanisms by which gut microbes degrade mucins are not fully understood.
• Understanding mucin degradation is key to comprehending host-microbe interactions.

Purpose of the Study:

• To identify and characterize novel mechanisms of mucin degradation in the gut microbiome.
• To investigate the role of a newly identified bacterial genus, Limousia, in mucin metabolism.
• To explore the prevalence and abundance of Limousia in different animal hosts.

Main Methods:

• Bioinformatic analysis of metagenome-assembled genomes (MAGs) to predict mucinolysome presence.
• Cultivation of Limousia strain ET540 using mucins as a sole carbon source.
• Gene expression analysis of mucinolysome-related genes.
• Protein structure modeling using AlphaFold3 to predict mucinolysome assembly.
• Metagenomic read mapping to assess Limousia abundance and prevalence in diverse cohorts.

Main Results:

• Discovery of mucinolysomes, novel cellulosome-like complexes for mucin degradation.
• Prediction of mucinolysomes in multiple Limousia genomes, including human gut samples.
• Validation that Limousia utilizes mucins for growth and upregulates mucinolysome genes.
• Modeling of mucinolysome assembly through predicted cohesin-dockerin interactions.
• Higher abundance and prevalence of Limousia in farm animals compared to humans.

Conclusions:

• The novel gut bacteria genus Limousia employs a unique, highly organized mucin glycan degradation mechanism via mucinolysomes.
• This discovery expands the known repertoire of mucin-degrading bacteria in mammalian gut ecosystems.
• Limousia's distinct molecular strategy offers new insights into microbe-host interactions across various animal hosts, including humans.