A conserved bacterial signature characterizes plant microbiome responses to drought

Plant-associated microbes contribute to host resilience under stress, yet the extent to which microbial responses to drought generalize across hosts and environments remains unclear.

Here, we performed a meta-analysis of 13 studies including more than 3,000 root and bulk soil samples from 52 plant hosts to identify bacterial taxa consistently affected by drought and link them to inoculation outcomes. Using a standardized processing workflow and differential abundance analysis, we derived a "drought signature" of taxa differentially abundant under water limitation across the endosphere, rhizosphere, and bulk soil.

The signature is dominated by Gram-positive Actinobacteria enriched under drought, including Kribella, and by Gram-negative taxa depleted under drought, such as Ramilbacter. Comparison with four independent inoculation experiments revealed limited overlap between drought and inoculation responses, with only Nitrospira depleted in both contexts.

Studies reporting improved plant performance under inoculation also exhibited stronger and more extensive microbial shifts, suggesting that the magnitude of community restructuring may be characteristic of successful inoculation outcomes. This work provides the fi rst genus-level meta-analysis of microbial responses under drought and inoculation, across hosts and experimental conditions, and delivers a unifi ed root and soil microbiome dataset.