Publications

• YdgG (TqsA) controls biofilm formation in Escherichia coli K-12 through autoinducer 2 transport.

  Herzberg M., Kaye I.K., Peti W., Wood T.K.

  YdgG is an uncharacterized protein that is induced in Escherichia coli biofilms. Here it is shown that deletion of ydgG decreased extracellular and increased intracellular concentrations of autoinducer 2 (AI-2); hence, YdgG enhances transport of AI-2. Consistent with this hypothesis, deletion of y ... >> More

  YdgG is an uncharacterized protein that is induced in Escherichia coli biofilms. Here it is shown that deletion of ydgG decreased extracellular and increased intracellular concentrations of autoinducer 2 (AI-2); hence, YdgG enhances transport of AI-2. Consistent with this hypothesis, deletion of ydgG resulted in a 7,000-fold increase in biofilm thickness and 574-fold increase in biomass in flow cells. Also consistent with the hypothesis, deletion of ydgG increased cell motility by increasing transcription of flagellar genes (genes induced by AI-2). By expressing ydgG in trans, the wild-type phenotypes for extracellular AI-2 activity, motility, and biofilm formation were restored. YdgG is also predicted to be a membrane-spanning protein that is conserved in many bacteria, and it influences resistance to several antimicrobials, including crystal violet and streptomycin (this phenotype could also be complemented). Deletion of ydgG also caused 31% of the bacterial chromosome to be differentially expressed in biofilms, as expected, since AI-2 controls hundreds of genes. YdgG was found to negatively modulate expression of flagellum- and motility-related genes, as well as other known products essential for biofilm formation, including operons for type 1 fimbriae, autotransporter protein Ag43, curli production, colanic acid production, and production of polysaccharide adhesin. Eighty genes not previously related to biofilm formation were also identified, including those that encode transport proteins (yihN and yihP), polysialic acid production (gutM and gutQ), CP4-57 prophage functions (yfjR and alpA), methionine biosynthesis (metR), biotin and thiamine biosynthesis (bioF and thiDFH), anaerobic metabolism (focB, hyfACDR, ttdA, and fumB), and proteins with unknown function (ybfG, yceO, yjhQ, and yjbE); 10 of these genes were verified through mutation to decrease biofilm formation by 40% or more (yfjR, bioF, yccW, yjbE, yceO, ttdA, fumB, yjiP, gutQ, and yihR). Hence, it appears YdgG controls the transport of the quorum-sensing signal AI-2, and so we suggest the gene name tqsA. << Less

  J. Bacteriol. 188:587-598(2006) [PubMed] [EuropePMC]

• The autoinducer-2 exporter superfamily.

  Rettner R.E., Saier M.H. Jr.

  The TqsA (YdgG) protein of Escherichia coli has been shown to export the autoinducer-2 (AI-2) molecule, a furanosyl borate diester that bears little resemblance to previously characterized biological molecules. TqsA belongs to a large superfamily, the AI-2 exporter (AI-2E) superfamily, of putative ... >> More

  The TqsA (YdgG) protein of Escherichia coli has been shown to export the autoinducer-2 (AI-2) molecule, a furanosyl borate diester that bears little resemblance to previously characterized biological molecules. TqsA belongs to a large superfamily, the AI-2 exporter (AI-2E) superfamily, of putative transporters with no other functionally characterized members. These proteins derive exclusively from bacteria. Many different bacterial kingdoms contain them, although several kingdoms do not. These proteins exhibit a uniform topology with 8 putative transmembrane segments (TMSs) which we show probably arose from a 4-TMS precursor in a process that involved at least one and possibly two intragenic duplication event(s). The first halves of these proteins are more diverse in sequence than the second halves, suggesting that the first halves may serve substrate-specific functions while the second halves serve family-specific functions. Conserved residues and motifs in these proteins are identified. Some homologues include extra catalytic domains including those involved in purine nucleotide biosynthesis, ATP and GTP binding, and molecular signaling. The results presented provide guides for future functional studies on members of this superfamily of bacterial transporters. << Less

  J. Mol. Microbiol. Biotechnol. 18:195-205(2010) [PubMed] [EuropePMC]