Sporulation and physiological profiles of bacterial communities of three Mediterranean soils affected by drying-rewetting or freezing-thawing cycles

- Drying-rewetting/freezing-thawing cycles affect community functions and sporulation.
- Basal respiration was negatively and systematically impacted after several cycles.
- Incubation at 40 °C induced function losses without any reliable biomass variation.
- Both the temperature and the soil origin can influence the sporulation/germination.

In the global change context, the basal respiration (BR), the estimated number of bacterial spores (SP) and the community level physiological profiles (CLPPs) were investigated in three different Mediterranean soils following different hydric and thermic stress scenarios. The treatments consisted in an increasing number (1, 2, 4, and 7) of drying-rewetting (DRWc) or freezing-thawing cycles (FTc) at 20, 40 or −20 °C. The results highlighted that the different soils responded differently to the same treatment and that the three variables considered were weakly related one to each another. In almost all soils and modalities, the BR increased significantly during the first cycles before decreasing during the last. With regards to SP, it appeared that, for a given soil, the capacity of microbial communities to sporulate and/or germinate can be considerably more influenced by the temperature rather than by the hydric stress. Finally, the CLPPs literally collapsed with the treatment at 40 °C, irrespective of the soil considered. This suggested a progressive replacement of the catabolically diversified original bacterial communities by another showing lower functional diversities.