AUTHOR=Harrison Mark A. , Kaur Harparkash , Wren Brendan W. , Dawson Lisa F. 

TITLE=Production of p-cresol by Decarboxylation of p-HPA by All Five Lineages of Clostridioides difficile Provides a Growth Advantage

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=11

YEAR=2021

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2021.757599

DOI=10.3389/fcimb.2021.757599

ISSN=2235-2988

ABSTRACT=<p><italic>Clostridioides difficile</italic> is the leading cause of antibiotic-associated diarrhea and is capable of causing severe symptoms, such as pseudomembranous colitis and toxic megacolon. An unusual feature of <italic>C. difficile</italic> is the distinctive production of high levels of the antimicrobial compound <italic>para</italic>-cresol. <italic>p</italic>-Cresol production provides <italic>C. difficile</italic> with a competitive colonization advantage over gut commensal species, in particular, Gram-negative species. <italic>p</italic>-Cresol is produced by the conversion of <italic>para</italic>-hydroxyphenylacetic acid (<italic>p</italic>-HPA) <italic>via</italic> the actions of HpdBCA decarboxylase coded by the <italic>hpdBCA</italic> operon. Host cells and certain bacterial species produce <italic>p</italic>-HPA; however, the effects of <italic>p</italic>-HPA on the viability of <italic>C. difficile</italic> and other gut microbiota are unknown. Here we show that representative strains from all five <italic>C. difficile</italic> clades are able to produce <italic>p</italic>-cresol by two distinct mechanisms: (i) <italic>via</italic> fermentation of <italic>p</italic>-tyrosine and (ii) <italic>via</italic> uptake and turnover of exogenous <italic>p</italic>-HPA. We observed strain-specific differences in <italic>p</italic>-cresol production, resulting from differential efficiency of <italic>p-</italic>tyrosine fermentation; representatives of clade 3 (CD305) and clade 5 (M120) produced the highest levels of <italic>p</italic>-cresol <italic>via</italic> tyrosine metabolism, whereas the toxin A-/B+ isolate from clade 4 (M68) produced the lowest level of <italic>p</italic>-cresol. All five lineages share at least 97.3% homology across the <italic>hpdBCA</italic> operon, responsible for decarboxylation of <italic>p</italic>-HPA to <italic>p</italic>-cresol, suggesting that the limiting step in <italic>p</italic>-cresol production may result from tyrosine to <italic>p</italic>-HPA conversion. We identified that elevated intracellular <italic>p</italic>-HPA, modulated indirectly <italic>via</italic> CodY, controls <italic>p</italic>-cresol production <italic>via</italic> inducing the expression of HpdBCA decarboxylase ubiquitously in <italic>C. difficile</italic> populations. Efficient turnover of <italic>p</italic>-HPA is advantageous to <italic>C. difficile</italic> as <italic>p</italic>-HPA has a deleterious effect on the growth of <italic>C. difficile</italic> and other representative Gram-negative gut bacteria, transduced potentially by the disruption of membrane permeability and release of intracellular phosphate. This study provides insights into the importance of HpdBCA decarboxylase in <italic>C. difficile</italic> pathogenesis, both in terms of <italic>p</italic>-cresol production and detoxification of <italic>p</italic>-HPA, highlighting its importance to cell survival and as a highly specific therapeutic target for the inhibition of <italic>p</italic>-cresol production across <italic>C. difficile</italic> species.</p>