Characterisation of novel functionality within the Blastocystis tryptophanase gene

Area of Science:

• Microbiology
• Gastroenterology
• Parasitology

Background:

• The human gut microbiome's role in host health is increasingly recognized, involving complex host-microbiota interactions.
• Blastocystis, a common single-cell eukaryotic parasite, has a debated role in gut health and disease.
• Understanding molecular cross-talk, including horizontally acquired genes, is crucial for gastrointestinal condition research.

Purpose of the Study:

• To investigate the function of the Blastocystis tryptophanase gene (BhTnaA), acquired via horizontal gene transfer.
• To compare the enzymatic activity of BhTnaA with bacterial tryptophanase homologs.
• To explore the implications of BhTnaA function for tryptophan metabolism in the gut.

Main Methods:

• Bioinformatic analysis and phylogenetic reconstruction of the BhTnaA gene.
• Enzymatic assays to determine the catalytic activity of BhTnaA on tryptophan and indole.
• Co-culture experiments with Blastocystis and Escherichia coli to assess tryptophan metabolism.

Main Results:

• BhTnaA shows distinct divergence from bacterial tryptophanase homologs despite high homology to E. coli's gene.
• Blastocystis does not efficiently convert tryptophan to indole; instead, BhTnaA preferentially catalyzes indole to tryptophan conversion.
• In the presence of E. coli, Blastocystis ST7 exhibits reduced ability to metabolize indole to tryptophan.

Conclusions:

• Horizontally acquired genes can exhibit functional variation compared to their original counterparts.
• Blastocystis possesses a unique tryptophanase activity, potentially contributing to tryptophan production in the gut.
• This study sheds light on the functional adaptation of horizontally transferred genes and their impact on host-microbe interactions.