# Climate history modulates stress responses of common soil bacteria under experimental drought

## TL;DR

This study shows that soil bacteria from different climates respond differently to drought stress, with semi-arid bacteria showing stronger metabolic responses.

## Contribution

The study reveals that climate history influences bacterial stress responses, beyond phylogenetic similarity.

## Key findings

- Semi-arid bacteria showed stronger metabolic responses to osmotic stress compared to tropical forest isolates.
- Matric stress led to increased production of carbohydrate stress compounds like glycine betaine and trehalose.
- Phylogenetically similar bacteria exhibited different stress responses based on their climate history.

## Abstract

Soil drying challenges microbial viability and survival, with bacteria employing various mechanisms to respond to shifts in osmolarity, including dormancy or metabolic upregulation of osmoprotectants. However, the extent to which these responses are shaped by an organism’s phylogeny, or the climate history of a given environment is poorly understood. This study examines the responses of phylogenetically similar bacteria from semi-arid and humid tropical forest soils to osmotic and matric stress using synchrotron radiation-based Fourier Transform Infrared spectromicroscopy. This non-destructive approach depicts the biochemical phenotype for whole cells under control and stress conditions. We observed that, under osmotic stress, bacteria upregulated cell-signaling pathways, rapidly turned over lipid-storage compounds, and increased osmolyte production. In contrast, matric stress induced a more muted response, typically elevating the production of carbohydrate stress compounds, such as glycine betaine and trehalose. Whereas phylogenetically similar bacteria showed comparable biochemistry under control conditions, climate history played an important role in regulating responses to stress, whereby a stronger metabolic response was observed from semi-arid relative to tropical forest isolates. We conclude that bacterial stress response to drought can be more diverse than previously observed and regulated by both phylogeny and climate history.