Mediterranean seasonality and the halophyte Arthrocnemum macrostachyum determine the bacterial community in salt marsh soils in Southwest Spain

Perennial halophytes dominate coastal ecosystems, but little is known about how the biotic and abiotic factors alter their microbial community. This study compares the bacterial diversity associated with the rhizosphere, with respect to adjacent soil, for the halophyte Arthrocnemum macrostachyum in high salt marshes in Southern Spain, in dry and wet seasons (July and October, respectively) using metagenomics coupled with High-Throughput Sequencing. The read-based analysis revealed that seven phyla (Proteobacteria, Actinobacteria, Bacteroidetes, Gemmatimonadetes, Chloroflexi, Firmicutes and Acidobacteria) accounted for the 90% of the diversity and 94% of the abundance and that, seasonal and spatial variations in soil salinity were the main determinants of the bacterial community diversity in these marshes, compared to the apparent no effect of the plant. However, at A. macrostachyum flowering stage, the bacterial community associated with the rhizosphere was comparatively more diverse than that inhabiting adjacent bulk soil, suggesting a more intensive plant-microbe interaction during this period.