2nd Edition of Preventive Medicine World Conference 2026

Abstract

A proteomic and molecular genetic approach was used to identify novel targets of the AlgT regulon. AlgT/U or Sigma 22 is an ECF Sigma Factor (Extra cytoplasmic function sigma factor. belonging to the Sigma 70 sub-family). Using this approach, two novel targets, pDsbA-1 and PA5178, were identified. PA5178 is robustly regulated by the alternative sigma factor AlgT, under mucoid conditions. This study examines the biology of PA5178. Recently, Dr Ohman’s group reidentified PA5178 as being regulated by AlgT using an alternative molecular genetic approach. 

PA5178 ORF encodes a hitherto uncharacterised protein in P. aeruginosa. The putative amino acid sequence of the protein suggests the presence of a bon and lysM domain.  Using a part of the PA5178 deduced protein sequence as a search query in a BLAST search, we identified an E. coli protein YgaU or KbP as one of the top hits, suggesting it’s an ortholog. It is very similar in protein sequence, and has a bon and lysM domain too. KbP is better characterised than PA5178. A PA5178 deletion mutant ORF exhibited no growth deficit with respect to the wild type strain.

Additionally, the mutant strain did not exhibit a reduction in alginate production with respect to wild type mucoid strain. To understand the increased expression under mucoid conditions (AlgT++ activity), we used a primer extension analysis to probe the putative promoter upstream of PA5178 ORF. We identified novel transcripts under mucoid conditions emanating from the presumptive promoter region upstream of the PA5178 ORF.  Recently, an NMR study proposed a 3D structure for YgaU, now called Kbp. The study shows the ability of Kbp to bind potassium ions. We performed a pairwise alignment of Kbp and PA5178 encoded ORF. Amino acid residues involved in K+ ion binding in Kbp were also found seen the PA5178 ORF. Greater than 90% of these were identical to the corresponding residues found in Kbp.

This finding at the level of bioinformatics suggests a potassium-binding role for the PA5178-encoded protein. The unique aspect of the PA5178 protein is highlighted in this poster study.