Phage strategies facilitate bacterial coexistence under environmental variability

Area of Science:

• Microbial ecology
• Theoretical ecology
• Mathematical biology

Background:

• Bacterial communities face resource variability impacting coexistence.
• Bacteriophages are key drivers of bacterial mortality and population dynamics.
• Phage infection strategies (lytic, lysogenic, PtL, PtW) influence host-phage interactions.

Purpose of the Study:

• To investigate how different phage strategies (lytic, PtL, PtW) affect bacterial coexistence under varying resource conditions.
• To evaluate the response of these phage strategies to environmental variability, specifically fluctuating resource inflow.
• To understand the mechanisms by which phages maintain bacterial diversity in constant and fluctuating environments.

Main Methods:

• Developed a microbial trophic network model using ordinary differential equations (ODEs).
• Performed 'in silico' experiments to simulate phage infection cycles and resource dynamics.
• Modified lysis rates and employed density-dependent switching points to model transitions between lysogenic and lytic cycles.

Main Results:

• The viral shunt (nutrient release post-lysis) enriches the system, enabling bacterial coexistence at lower resource levels.
• A purely lytic phage model ensures stable bacterial coexistence despite resource fluctuations.
• PtW shows stable coexistence within a narrow resource range and is sensitive to fluctuations; PtL facilitates coexistence across a broad range of stable and fluctuating resources.

Conclusions:

• Temperate phage strategies (PtL, PtW) offer distinct mechanisms for coping with environmental variability.
• Phage strategies are crucial for maintaining bacterial coexistence in both stable and fluctuating environments.
• PtL and lytic strategies enhance resilience to resource variability with increased bacterial growth rates.