An RpoHI-Dependent Response Promotes Outgrowth after Extended Stationary Phase in the Alphaproteobacterium...

Area of Science:

• Microbiology
• Bacterial Physiology
• Gene Regulation

Background:

• Bacteria enter a non-replicating stationary phase under unfavorable conditions.
• Efficient resumption of growth (outgrowth) is vital for bacterial survival in fluctuating environments.
• Understanding outgrowth mechanisms is crucial for microbial ecology and biotechnology.

Purpose of the Study:

• To investigate the regulatory mechanisms governing bacterial outgrowth after stationary phase.
• To analyze the impact of stationary phase duration on gene expression during outgrowth.
• To identify key genetic factors involved in enabling bacterial regrowth.

Main Methods:

• Global transcriptome analysis of Rhodobacter sphaeroides at different growth phases (exponential, short stationary, long stationary, outgrowth).
• Differential gene expression analysis to identify genes with altered expression levels.
• Growth experiments using mutant strains lacking specific sigma factors (RpoHI, RpoHII).

Main Results:

• The majority of genes showed stable expression across growth phases.
• Outgrowth gene expression is significantly influenced by the preceding stationary phase length.
• A longer stationary phase induced a larger set of genes during outgrowth, many associated with stress responses.
• Alternative sigma factors RpoHI and RpoHII play a critical role in outgrowth after prolonged stationary phases.

Conclusions:

• The duration of the stationary phase profoundly impacts the transcriptome during bacterial outgrowth.
• RpoHI and RpoHII are key regulators enabling efficient outgrowth following extended periods of nutrient limitation or stress.
• This study provides novel insights into the molecular mechanisms facilitating bacterial recovery and regrowth.