B.bacteriovorus are small obligate predators of other gram negative bacteria. They are ubiquitously found in the environment and can affect the structure of microbial communities; as such, they can potentially be used as bio-control agents. B.bacteriovorus`s high swimming motility is essential for predation in liquid media. However, the effects of the heterogeneity of the soil/liquid/gaseous as well as those of particle size on predation are not understood. While water can be retained to enable pore connectivity under a large range of water content -thus enabling B.bacteriovorus swimming - pore size may limit motility. We demonstrate, that the predation pattern of B.bacteriovorus in the soil environment is different from that in free liquid, as the maximal concentration of Bdellovibrio in all soil types was one order of magnitude smaller than in free liquid, and predator growth was significantly slower. Furthermore, predation was significantly hampered at water contents below 20% for all soil types. Notably, at the lowest water contents B.bacteriovorus`s populations in coarse and fine sand were below detection level, while in middle-sized sand, the original inocula survived (5%) or even grew (10%). At 100% water content, complete pore saturation generally results in anoxic conditions. The ability of B.bacteriovorus to predate under anaerobic condition was tested. Bacterial predation only occurred in the presence of nitrate when glucose was provided for the prey bacterium to grow. Although B.bacteriovorus’s genome encodes for nitrite reductases, nitrite did not sustain B.bacteriovorus growth. Furthermore, these genes were similarly expressed under anaerobic and aerobic conditions.
