PsrA is a novel regulator contributes to antibiotic synthesis, bacterial virulence, cell motility and extracellular polysaccharides production in Serratia marcescens

Abstract

Serratia marcescens is a Gram-negative bacterium of the Enterobacteriaceae family that can produce numbers of biologically active secondary metabolites. However, our understanding of the regulatory mechanisms behind secondary metabolites biosynthesis in S. marcescens remains limited. In this study, we identified an uncharacterized LysR family transcriptional regulator, encoding gene BVG90_12635, here we named psrA, that positively controlled prodigiosin synthesis in S. marcescens. This phenotype corresponded to PsrA positive control of transcriptional of the prodigiosin-associated pig operon by directly binding to a regulatory binding site (RBS) and an activating binding site (ABS) in the promoter region of the pig operon. We demonstrated that L-proline is an effector for the PsrA, which enhances the binding affinity of PsrA to its target promoters. Using transcriptomics and further experiments, we show that PsrA indirectly regulates pleiotropic phenotypes, including serrawettin W1 biosynthesis, extracellular polysaccharide production, biofilm formation, swarming motility and T6SS-mediated antibacterial activity in S. marcescens. Collectively, this study proposes that PsrA is a novel regulator that contributes to antibiotic synthesis, bacterial virulence, cell motility and extracellular polysaccharides production in S. marcescens and provides important clues for future studies exploring the function of the PsrA and PsrA-like proteins which are widely present in many other bacteria.

Improving prodigiosin production by transcription factor engineering and promoter engineering in Serratia marcescens

“…In recent years, transcription factor engineering has gained much attention due to its efficient application in altering gene transcription and improve the yield of target product ( Li et al, 2018 , 2021 ; Deng et al, 2021 ). PsrA ( Pan et al, 2022 ) and OmpR are two prodigiosin synthesis activators in strain JNB5-1 we have identified by Tn5G transposon insertion mutation. To efficiently production of prodigiosin, psrA and ompR genes, driven by its own promoter, were cloned into pUCP18 plasmid, and transformed into strain JNB5-1 to construct strain PG-1 and PG-2, respectively.…”

“…Among them, prodigiosin has received widespread attention due to its antimalarial, antibacterial, antifungal, antiprotozoal and immunosuppressant activities ( Williamson et al, 2006a ). Besides the well-studied pigA (encoding acyl-CoA dehydrogenase PigA), pigB (encoding FAD-dependent oxidoreductase PigB), pigC (encoding PEP-utilizing enzyme PigC), pigD (encoding prodigiosin biosynthesis protein PigD), pigE (encoding aminotransferase PigE), pigF (encoding O-methyl transferase PigF), pigG (encoding peptidyl carrier protein PigG), pigH (encoding aminotransferase PigH), pigI (encoding L-prolyl-AMP ligase PigI), pigJ (encoding beta-ketomyristol-ACP synthase PigJ), pigK (encoding prodigiosin biosynthesis protein PigK), pigL (encoding 4′-phosphopantetheinyl transferase PigL), pigM (encoding prodigiosin biosynthesis protein PigM), and pigN (encoding oxidoreductase PigN) genes involved in the metabolic pathway of the prodigiosin ( Williamson et al, 2006a ), lots of transcriptional regulator-encoding genes that play important roles in prodigiosin synthesis in S. marcescens have also been investigated, such as negative regulators MetR ( Pan et al, 2020 ), SpnR ( Horng et al, 2002 ), CopA ( Williamson et al, 2006b ), CRP ( Stella and Shanks, 2014 ), RssB ( Horng et al, 2010 ), RcsB ( Brothers et al, 2019 ; Pan et al, 2021 ), CpxR ( Sun et al, 2020 ) and SmaR ( Coulthurst et al, 2006 ), and positive regulators EepR ( Shanks et al, 2017 ), PigP ( Shanks et al, 2013 ), GumB ( Stella et al, 2018 ), RbsR ( Lee et al, 2017 ), RpoS ( Qin et al, 2020 ), and PsrA ( Pan et al, 2022 ). However, our understanding of the regulatory mechanisms behind prodigiosin synthesis in S. marcescens is still limited.…”

“…Due to its efficient application in altering gene transcription to obtain beneficial cellular phenotype, transcription factor engineering has also been used to improve the yield of the target product in recent years ( Zhang et al, 2015 ; Li et al, 2018 ; Deng et al, 2021 ). And in our previous studies, we have identified that the pig gene cluster essential for prodigiosin synthesis is positively regulated by transcription factor PsrA in S. marcescens ( Pan et al, 2022 ). Therefore, it probably can be improving the prodigiosin production in S. marcescens strains through transcription factor engineering and promoter engineering.…”

“…And compared with the traditional chemical methods, the production of prodigiosin by microbial fermentation is more economical and environmentally friendly and hence has recently attracted lots of interest. However, although many studies have been used to dissect the biosynthetic pathways and regulatory network of prodigiosin production in S. marcescens ( Horng et al, 2002 , 2010 ; Coulthurst et al, 2006 ; Williamson et al, 2006b ; Shanks et al, 2013 , 2017 ; Stella and Shanks, 2014 ; Lee et al, 2017 ; Stella et al, 2018 ; Brothers et al, 2019 ; Pan et al, 2020 , 2021 , 2022 ), few studies have been used to improve the efficiency of prodigiosin synthesis through metabolic engineering in this strain.…”

BysR, a LysR-type Pleiotropic Regulator, Controls Production of Occidiofungin by Activating the LuxR-type transcriptional regulator AmbR1 in Burkholderia sp. JP2-270

“…BysR is identified as a member in the LysR-type transcription regulators (LTTRs) family. As global regulators, LTTRs are the most widespread in prokaryotes and can regulate the expression of genes involved various cellular processes in different microorganisms, such as the control of carbon catabolism, amino acid metabolism, antibiotic resistance and motility (11,(33)(34)(35)(36)(37). Here, we explored the RNA-seq and DAP-seq data, and the genes and associated pathways directly or indirectly regulated by BysR in JP2-270 were identified.…”