Autoinducer-2 Quorum Sensing Contributes to Regulation of Microcin PDI in Escherichia coli

Abstract

The Escherichia coli quorum sensing (QS) signal molecule, autoinducer-2 (AI-2), reaches its maximum concentration during mid-to-late growth phase after which it quickly degrades during stationary phase. This pattern of AI-2 concentration coincides with the up- then down-regulation of a recently described microcin PDI (mccPDI) effector protein (McpM). To determine if there is a functional relationship between these systems, a prototypical mccPDI-expressing strain of E. coli 25 was used to generate ΔluxS, ΔlsrACDBFG (Δlsr), and ΔlsrR mutant strains that are deficient in AI-2 production, transportation, and AI-2 transport regulation, respectively. Trans-complementation, RT-qPCR, and western blot assays were used to detect changes of microcin expression and synthesis under co-culture and monoculture conditions. Compared to the wild-type strain, the AI-2-deficient strain (ΔluxS) and -uptake negative strain (Δlsr) were >1,000-fold less inhibitory to susceptible bacteria (P < 0.05). With in trans complementation of luxS, the AI-2 deficient mutant reduced the susceptible E. coli population by 4-log, which was within 1-log of the wild-type phenotype. RT-qPCR and western blot results for the AI-2 deficient E. coli 25 showed a 5-fold reduction in mcpM transcription with an average 2-h delay in McpM synthesis. Furthermore, overexpression of sRNA micC and micF (both involved in porin protein regulation) was correlated with mcpM regulation, consistent with a possible link between QS and mcpM regulation. This is the direct first evidence that microcin regulation can be linked to quorum sensing in a Gram-negative bacterium.

Microcin PDI Inhibits Antibiotic-Resistant Strains of Escherichia coli and Shigella through a Mechanism of Membrane Disruption and Protection by Homotrimer Self-Immunity

“…Data from multiple assays from the present study are consistent with the conclusion that the MccPDI precursor protein McpM kills susceptible strains via membrane disruption, and experiments here and elsewhere confirm that naturally susceptible strains are widespread (6)(7)(8)24). OmpF is the key ligand for susceptibility (8,42), but other genes have been identified that are requisite for susceptibility to MccPDI (ompR, atpA, atpF, atpE, atpH, dsbA, and dsbB [8]).…”

“…Microcin PDI inhibits Shigella strains and UTI E. coli strains. Previously validated coculture competition assays (5)(6)(7)(8)24) were employed to examine the sensitivity of the target bacteria to MccPDI. The coculture competition assays were conducted with E. coli strain 25 (MccPDI producer), six Shigella strains, and nine UTI E. coli strains that were resistant to between one and four classes of antibiotics ( Table 2 and Fig.…”

“…Unless otherwise stated, all strains described here (Table 1) were grown in LB Lennox (LB broth) medium (Difco Laboratories, Inc.) or in defined M9 minimal medium (6 g/liter Na 2 HPO 4 , 3 g/liter KH 2 PO 4 , 0.5 g/liter NaCl, 1 g/liter NH 4 Cl, 1 mM MgSO 4 , 0.1 mM CaCl 2 , and 0.2% glucose) supplemented with thiamine (1 mg/liter) and leucine (100 g/ml). Bacteria were cultured at 37°C on a shaker table (200 rpm) (24). When used, the following antibiotics were added to media: ampicillin (Amp) at 100 g/ml, tetracycline (Tet) at 50 g/ml, kanamycin (Kan) at 50 g/ml, nalidixic acid (Nal) at 30 g/ml, and chloramphenicol (Cm) at 32 g/ml.…”

Associations Between Nutrition, Gut Microbiome, and Health in A Novel Nonhuman Primate Model

“…Tetracycline resistance genes, in contrast, were elevated in the wild without an attendant significant upregulation of resistance. This pattern raises the possibility that the antibiotics pathways upregulated in captivity may be adapted for competition and virulence factor regulation (Balasubramanian et al 2011), whereas the pathways upregulated in the wild may play more of a quorum sensing role (Lu 2006).…”

Does quorum sensing interference affect the fitness of bacterial pathogens in the real world?

“…One of the earliest documented examples is the production of the antibiotic carbapenem in the plant pathogen Pectobacterium carotovorum (McGowan et al, 1995). Later reports have also documented quorum sensing regulation of carbapenem production in other bacteria, such as Serratia (Thomson et al, 2000), as well as quorum sensingregulated production of other antibacterials, including hydrogen cyanide (Pessi and Haas, 2000), bacteriocins (van der Ploeg, 2005), polyketide or peptide antibiotics (Duerkop et al, 2009) and microcin (Lu et al, 2017).…”