Two novel regulators of N‐acetyl‐galactosamine utilization pathway and distinct roles in bacterial infections

Abstract

Bacterial pathogens can exploit metabolic pathways to facilitate their successful infection cycles, but little is known about roles of d‐galactosamine (GalN)/N‐acetyl‐d‐galactosamine (GalNAc) catabolism pathway in bacterial pathogenesis. Here, we report the genomic reconstruction of GalN/GalNAc utilization pathway in Streptococci and the diversified aga regulons. We delineated two new paralogous AgaR regulators for the GalN/GalNAc catabolism pathway. The electrophoretic mobility shift assays experiment demonstrated that AgaR2 (AgaR1) binds the predicted palindromes, and the combined in vivo data from reverse transcription quantitative polymerase chain reaction and RNA‐seq suggested that AgaR2 (not AgaR1) can effectively repress the transcription of the target genes. Removal of agaR2 (not agaR1) from Streptococcus suis 05ZYH33 augments significantly the abilities of both adherence to Hep‐2 cells and anti‐phagocytosis against RAW264.7 macrophage. As anticipated, the dysfunction in AgaR2‐mediated regulation of S. suis impairs its pathogenicity in experimental models of both mice and piglets. Our finding discovered two novel regulators specific for GalN/GalNAc catabolism and assigned them distinct roles into bacterial infections. To the best of our knowledge, it might represent a first paradigm that links the GalN/GalNAc catabolism pathway to bacterial pathogenesis.

An ancient deletion in the ABO gene affects the composition of the porcine microbiome by altering intestinal N-acetyl-galactosamine concentrations

“…Closer examination of the structure of the most complete GalNAc gene clusters in the studied MAGs (Fig. 6C) Erysipelotrichaceae are not endowed with the capacity to sense GalNAc concentrations in the medium and only induce expression of the genes and proteins necessary for GalNAc utilization when needed (Leyn et al, 2012;Biddart et al, 2014;Zhang et al, 2015), but may rather express their GalNAc-related genes constitutively. The GalNAc gene cluster as seen in the OTU476-like strains is a possible evolutionary intermediate towards the formation of a genuine regulon as seen in E.Coli, already facilitating horizontal transmission of a "selfish" functional gene ensemble even if not yet adaptively coregulated (Lawrence, 1999 (Fig.…”

“…While some bacteria may have both GH and TR/CP for specific monosaccharides, other may only have the GH ("donors") or the TR/CP ("acceptors") (Ravcheev & Thiele, 2017). We compiled a list of 24 genes (with corresponding KEGG ontology number) implicated in GalNAc utilization (TR/CP) from the literature (Brinkkötter et al, 2000;Rodionov et al, 2010;Leyn et al, 2012;Hu et al, 2012;Biddart et al, 2014;Zhang et al, 2015;Ravcheev & Thiele, 2017, Zuniga et al, 2018. These encode (i) 11 components of one of three GalNAc transporter systems (AgaPTS: agaE, agaF, agaV, agaW; TonB dependent transporter: omp, agaP, agaK; GnbPTS: gnbA, gnbB, gnbC, gnbD), (ii) two GalNAc-6P deacetylases (agaA, nagA), (iii) two galactosamine-6P (GalN-6P) isomerase and/or deaminases (agaI, agaS), (iv) three tagatose-6P kinases (pfka, lacC, fruK), (v) four tagatose-1,6-PP aldolases or aldolase subunits (gatY-kbaY, gatZ-kbaZ, lacD, fba), and (vi) two regulon repressors (agaR, gntR), for a total of six essential pathway constituents (Suppl.…”

N-acetylgalatosamine-Mediated Regulation of the aga Operon by AgaR in Streptococcus pneumoniae

“…The genes encoding galactosamine/NAGa pathways were recognized in 16 genomes signifying four families; Streptococcaceae, Lactobacillaceae, Enterobacteraceae , and Carnobacteriaceae . Lactobacillus helveticus and Streptococcus pyogenes possess the minimal number of genes in the reconstructed regulons (Zhang et al, 2015 ). It is very likely that these organisms cannot utilize NAGa as only one or two genes from the NAGa utilization pathway were found in these organisms.…”

“…Streptococcus gordonii and Streptococcus mitis have the minimal gene set that allows them to utilize NAGa. These genes include transcriptional regulator ( agaR ), galactosamine-6-phosphate deaminase/isomerase ( agaS ), glycoside hydrolase ( bgaC ) and PTS ( gadVWEF ) (Zhang et al, 2015 ). The gene for the tagatose-1,6-diphosphate aldolase ( agaY ) is present in some other well-studied Streptococcal genomes.…”

“…The gene for the tagatose-1,6-diphosphate aldolase ( agaY ) is present in some other well-studied Streptococcal genomes. On the contrary, all the investigated Lactobacilli lack agaY , but have the gene for N-acetylgalactosamine-phosphate deacetylase ( agaA ) (Zhang et al, 2015 ). agaA was recognized only in the Streptococcus suis genome among Streptococcaceae .…”