Evolutionary Principles of Bacterial Signaling Capacity and Complexity

Area of Science:

• Microbiology
• Evolutionary Biology
• Systems Biology

Background:

• Bacteria utilize signal transduction systems to adapt to environmental changes, but the evolutionary trajectory of these networks remains unclear.
• Niche adaptation influences bacterial signaling repertoires, yet systematic studies on the temporal evolution of signaling complexity are lacking.
• Understanding how bacterial signaling networks transition from simple to complex, or vice versa, is crucial for comprehending genome evolution.

Purpose of the Study:

• To investigate the evolutionary processes of major signal transduction systems in the bacterial phylum Campylobacterota.
• To elucidate the mechanisms driving the increase or decrease in complexity of bacterial signaling networks over time.
• To identify general principles governing the evolution of cellular signaling networks and genome evolution in bacteria.

Main Methods:

• Comparative genomic analysis of signal transduction systems across diverse Campylobacterota species.
• Phylogenetic reconstruction to infer evolutionary histories and identify gene transfer events.
• Analysis of network architecture, including component interactions and pathway rewiring.

Main Results:

• Chemosensory systems gain complexity primarily through horizontal gene transfer (HGT) of entire classes, with limited component mixing.
• Two-component systems evolve complexity via fused histidine kinases and receiver domains, enabling multistep or branched signaling.
• The presence and complexity of cyclic di-GMP (c-di-GMP) mediated systems correlate with overall network size and exhibit high rewiring potential.
• Signaling capacity and complexity in Campylobacterota fluctuate together, influenced by sensory demands, genetic resources, and genomic context.

Conclusions:

• Bacterial signaling network evolution is characterized by gains and losses of complexity, driven by factors like HGT and pathway rewiring.
• The evolution of signaling capacity in Campylobacterota follows general principles applicable to other bacterial phyla and cellular networks.
• This study provides insights into the dynamic evolution of bacterial signaling, bridging the gap between highly complex and streamlined networks, and informing genetic circuit design.