Site, Fertilization and Season Structure the Soil Microbiome and Its Interactions With Bdellovibrio and Like Organisms Predators.

The contribution of predation between bacteria to microbial community dynamics in agricultural soil has hardly been investigated. Here, dynamics of general prokaryotes (GEP) and the predatory Bdellovibrionales (Bd) and Bacteriovoracales (Bac) (Bdellovibrio-and-Like Organisms, BALOs) were studied in two agricultural fields differing in organic and mineral inputs for 1 year. Season, but not fertilization, affected absolute sizes of GEP and of BALO communities. 16S rRNA gene analysis identified numerous previously undetected Bd and Bac lineages, with none of the BALOs related to characterized isolates. A few dominant BALO amplicon sequence variants (ASVs) persisted year-round, whereas others showed seasonal or treatment specific responses. Alpha diversity of the GEP, Bd and Bac communities was influenced by season, with some changes due to fertilization observed for Bd and Bac. Seasonal variation, site and fertilization regime also significantly influenced beta diversity and the structure of BALO-gram-negative bacterial association networks, revealing distinct community associations under different environmental conditions. Accordingly, we suggest that environmental variation and agricultural practice influence bacterial community structure and are associated with corresponding changes in BALO communities and their potential associations with gram-negative bacteria. These dynamics may be harnessed to manipulate the soil microbiome to benefit sustainable environmental and agricultural outcomes.