The Mediterranean fruit fly (medfly) (Ceratitis capitata) lays eggs in fruits, where larvae subsequently develop, causing large-scale agricultural damage. Within its digestive tract, the fly supports an extended bacterial community that is composed of multiple strains of a variety of enterobacterial species. Most of these bacteria appear to be functionally redundant, with most strains sustaining diazotrophy and/or pectinolysis. At least some of these bacteria were shown to be vertically inherited, but colonization, structural, and metabolic aspects of the community's dynamics have not been investigated. We used fluorescentin situhybridization, metabolic profiling, plate cultures, and pyrosequencing to show that an initial, egg-borne, diverse community expands throughout the fly's life cycle. While keeping “core” diazotrophic and pectinolytic functions, it also harbors diverse and fluctuating populations that express varied metabolic capabilities. We suggest that the metabolic and compositional plasticity of the fly's microbiota provides potential adaptive advantages to the medfly host and that its acquisition and dynamics are affected by mixed processes that include stochastic effects, host behavior, and molecular barriers.

Standard aquaculture generates large-scale pollution and strains water resources. In aquaculture using zero discharge systems (ZDS), highly efficient

Significance: In obligate bacterial predators such as Bdellovibrio bacteriovorus the cell-replication cycle is tightly coupled to the predatory act. Using a novel growth system, in which the content of emptied prey cells is manipulated, we show that B. bacteriovorus uses two spatially and temporally separated prey-derived cues to regulate the steps from prey recognition to predatory cell growth through differential gene expression. A previously unidentified cell-cycle checkpoint is uncovered, during which prey quality, as defined by nutrient availability, may be assessed.

Bacterial soft rot diseases caused by Pectobacterium spp. and Dickeya spp. are among the most important plant diseases caused by bacteria. Among other crops, they inflict large-scale damage to potatoes. As of today, farmers have few options to control them. The bacteria Bdellovibrio and like organisms (BALOs) are obligate predators of bacteria. We tested their potential to prey on Pectobacterium spp. and Dickeya spp. and to protect potato. We show that different BALOs can prey on soft rot-causing bacteria and prevent their growth in situ , precluding tissue maceration. Dead predators and the supernatant of BALO cultures did not significantly prevent maceration, showing that the effect is due to predation. Soft rot control by the predators was concentration dependent and was higher when the predator was inoculated ahead of the prey. As residual prey remained, we investigated what determines their level and found that initial prey and predator population parameters affect prey response to predation.

A fundamental question in community ecology is the role of predator–prey interactions in food-web stability and species coexistence. Although microbial microcosms offer powerful systems to investigate it, interrogating the environment is much more arduous. Here, we show in a 1-year survey that the obligate predators Bdellovibrio and like organisms (BALOs) can regulate prey populations, possibly in a density-dependent manner, in the naturally complex, species-rich environments of wastewater treatment plants. Abundant as well as rarer prey populations are affected, leading to an oscillating predatory landscape shifting at various temporal scales in which the total population remains stable. Shifts, along with differential prey range, explain co-existence of the numerous predators through niche partitioning. We validate these sequence-based findings using single-cell sorting combined with fluorescent hybridization and community sequencing. Our approach should be applicable for deciphering community interactions in other systems.