Autoinducer-2 Quorum Sensing Contributes to Regulation of Microcin PDI in .
Journal:
Frontiers in microbiology
Published Date:
Dec 22, 2017
Abstract
The 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 25 was used to generate Δ, Δ (Δ), and Δ 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 (Δ) and -uptake negative strain (Δ) were >1,000-fold less inhibitory to susceptible bacteria ( < 0.05). With complementation of , the AI-2 deficient mutant reduced the susceptible 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 25 showed a 5-fold reduction in transcription with an average 2-h delay in McpM synthesis. Furthermore, overexpression of sRNA and (both involved in porin protein regulation) was correlated with regulation, consistent with a possible link between QS and regulation. This is the direct first evidence that microcin regulation can be linked to quorum sensing in a Gram-negative bacterium.
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