# Frenemy: adaptive temperate phage_SAP_1432 supports Staphylococcus aureus survival in changing temperatures

## TL;DR

A heat-resistant phage helps Staphylococcus aureus survive better at high temperatures, showing how phages can benefit bacteria during climate change.

## Contribution

This study reveals that a temperate phage can enhance bacterial survival and thermal performance in changing temperature conditions.

## Key findings

- Phage_SAP_1432 increased the maximal growth rate of Staphylococcus aureus Q1432 by 41.2% at specific temperatures.
- The presence of phage_SAP_1432 shifted the optimal growth temperature of the host from 41.0°C to 44.1°C.
- Bacteria co-cultured with phage_SAP_1432 survived at temperatures up to 80°C, compared to 51°C without the phage.

## Abstract

It is important to understand how the presence of pathogens could benefit the survival of their hosts during climate change. In this study, we investigated the influence of the heat-resistant temperate phage phage_SAP_1432 on its bacterial host Staphylococcus aureus Q1432 at different temperatures. Thermal host performance curves at a multiplicity of infection of 0.001 showed that the phage killed the bacterium efficiently from 20 to 39°C and from 47 to 50°C. However, the phage resulted in a 41.2% increase in the maximal growth rate for the host bacterium from 1.53 (95% confidence interval [CI]: 1.42–1.63) in the absence of phage_SAP_1432 to 2.16 (95% CI: 2.02–2.37) in its presence, along with a shift in the optimum temperature from 41.0°C to 44.1°C. In the absence of phage, the maximum survival temperature of S. aureus Q1432 was 51°C, but after co-culture with phage_SAP_1432, a few bacteria survived at 55°C–80°C. Lysogenesis occurred more easily at lower temperatures; the percentage of lysogenesis increased with phage concentration, while the maximum growth rate of the host decreased. Our findings provide new evidence that heat-resistant temperate phages can benefit the survival of their bacterial host at specific temperatures, giving a new perspective on the effects of co-evolution of heat-resistant temperate phages and bacterial hosts in an era of global climate change.

Understanding pathogen–host interactions is crucial for predicting climate change impacts on microbial ecosystems. This study examined the heat-resistant temperate phage_SAP_1432 and its effects on Staphylococcus aureus Q1432 at various temperatures. Phage_SAP_1432 enhanced the thermal performance and survival at high temperatures of its host at a low MOI. This mutual benefit demonstrates the adaptive advantages phages provide in changing thermal environments. As global temperatures rise, such phage–host interactions may play a critical role in microbial survival and evolution. Our research highlights the potential for phages to act as allies, offering a new perspective on the co-evolution of heat-resistant temperate phages and their bacterial hosts.