A bistable prokaryotic differentiation system underlying development of conjugative transfer competence

Area of Science:

• Microbiology
• Genetics
• Molecular Biology

Background:

• Horizontal gene transfer (HGT) is vital for prokaryotic adaptation, yet the lifestyle of mobile elements driving HGT remains poorly understood.
• Integrative and conjugative elements (ICEs) are key mediators of HGT, often carrying genes for antibiotic resistance and xenobiotic metabolism.
• Understanding ICE lifestyle is critical for deciphering their transfer fitness and impact on bacterial populations.

Purpose of the Study:

• To elucidate the complete regulon governing the lifestyle of a specific ICE in the genus Pseudomonas.
• To identify the regulatory network and gene clusters involved in ICE activation and transfer competence.
• To characterize the cellular dynamics and population fraction responsible for ICE-mediated gene transfer.

Main Methods:

• Single-cell time-lapse microscopy with fluorescent reporters.
• RNA sequencing to analyze gene expression patterns.
• Mutant analysis to determine the function of regulatory factors and gene clusters.

Main Results:

• A comprehensive regulon comprising at least three regulatory nodes and five to six gene clusters was described.
• Expression of key regulatory nodes (bisR and alpA-bisDC) preceded other cluster expressions.
• ICE transfer was confined to a small subpopulation (1.7-4%) of cells exhibiting a dedicated transfer competence program.

Conclusions:

• ICEs impose a specific program for transfer competence, executed by a differentiated subpopulation of cells.
• The identified regulon and conserved transfer components highlight the selected fitness of these mobile elements.
• This study provides a detailed mechanistic understanding of ICE lifestyle and its role in bacterial evolution and adaptation.