Exploring the Impact of Climate Change on Bacteria-Phage Interactions: Insights from Temperature-Dependent Lifecycle Modeling

Effect of High Temperatures on Bacterial Infection by Phage

We studied how the phage AMP1 infects B. thailandensis E264 at high temperatures (≥ 37°C). Our findings, detailed in Figure 1 and Table S2, show that AMP1 performs well within temperatures from 37°C to 39°C. However, its effectiveness drops significantly at higher temperatures, decreasing by over 1000 times at 40°C. No infection occurred at 41°C—a situation where we only saw some bacterial lysis when using a concentrated phage sample. Notably, B. thailandensis still thrived on all plates. These results imply that AMP1 cannot destroy bacteria above 40°C, suggesting this temperature (approximately 40°C) is critical for infection cessation.

Our experiment also indicates a sudden shift from infection to non-infection occurs within about 1.5°C. This suggests we can model the halt of infection at high temperatures using a specific sigmoid function, similar to modeling transitions in infection cycles at lower temperatures.

This figure shows the efficiency of AMP1 phage on bacterial lawns after 24 hours at various temperatures. Each row indicates a different dilution level.

Temperature and UV Index Trends in Thailand

This figure illustrates historical and forecasted temperatures and UV index for Nakhon Phanom, Thailand. It covers daily max/min temperatures and average UV index from 2009 to 2044.

Analysis of weather data from 2009 to 2020 shows rising average temperatures and UV indices across several provinces in Thailand. Interestingly, global temperature anomalies reported since 2000 have shifted, with notable drops in 2021 and 2022.

Our seasonal assessment reveals a clear cycle in temperatures and UV index, showing peaks usually in April and May. Similar patterns were observed across other provinces. The forecast for 2024-2044 predicts continual increases in both temperature and UV index, impacting the environment significantly.

Modeling Bacteria-Phage Dynamics from 2009 to 2023

We used historical data to simulate bacteria and phage dynamics in Thailand. Figure 3 depicts annual averages of the populations over 15 years. Notably, bacterial densities showed noticeable fluctuations related to temperature and UV exposure. High levels of bacteria without phages appeared in 2013-2016 and again in 2018-2019, while the lowest count was in 2022. This fluctuation correlates with temperature patterns, UV index variations, and total hot hours.

This figure charts simulated bacteria-phage dynamics across eight provinces in Thailand for 2009-2023.

Typical seasonal patterns of bacterial-phage interactions are highlighted, particularly in Nakhon Phanom, where high incidents of bacteria occur during peak agricultural seasons. Our model predicts significant daily variations, suggesting heightened infection risks during specific times—especially in the evenings when bacteria density peaks.

This figure illustrates the seasonal variation in the bacteria-phage system for Nakhon Phanom over three selected years.

Predictions for future bacteria-phage interactions from 2024 onwards were also examined, taking into account various scenarios for UV index changes and their implications for bacterial densities. The forecast highlights the need to consider both temperature increases and UV exposure for understanding future dynamics.

Impacts of Agrochemicals on Bacteria-Phage Dynamics

Some agrochemicals, especially those rich in iron, can significantly reduce phage populations. Our research examines the effects of these phage-killing substances on infection risks in fluctuating weather conditions. The study models the impact of phage removal and predicts differing outcomes based on the timing and conditions of agrochemical application.

This figure displays the dynamics of bacteria and phage before and after the application of phage-killing agrochemicals in Nakhon Phanom.

Our simulations found that the impact of phage removal varies based on environmental conditions. For instance, during cooler periods, eliminating phages had limited effects, whereas, in hotter conditions, it resulted in significant bacterial population increases. Therefore, the application of such agrochemicals is not advisable during high-temperature periods.

Exploring Vertical Spatial Dynamics

We also investigated bacteria-phage interactions in soil layers, highlighting how spatial factors affect microbial dynamics. Our model predicts how vertical temperature gradients in the soil can create different environments for bacterial types and phage interactions.

This figure shows the predicted densities of bacteria and phages in soil across different depths from 2009-2023.

Our results indicate a dual peak in vulnerable bacterial populations, influenced by both daily and annual temperature shifts. The dynamics of these populations in soil contrast with those observed in surface water, as phage populations are sustained under warmer soil conditions.

This figure illustrates the forecasted annual density distributions of bacteria and phages in soil for the years 2024-2044.

In conclusion, our study highlights the importance of understanding bacterial and phage interactions within the context of climate change, agricultural practices, and spatial environments. These insights are crucial for accurately predicting microbial dynamics and potential disease risks in agricultural settings.