Predation by BALOs also releases nutrients ( Martínez et al., 2013), affecting biogeochemical cycling and production in nutrient-limited environments, similar to the effects of phage ( Fuhrman, 1999 Brussaard et al., 2008). Conversely, generalist predators have more influence over the diversity and dynamics of their aggregate prey community.īdellovibrionales and like organisms (BALOs) are an order of predatory δ-proteobacteria that prey exclusively on other bacteria, including many known pathogens ( Schoeffield and Williams, 1990). Specialists' predation via viral infections drives an evolutionary arms race within their specific prey population and can destroy entire clonal blooms of phytoplankton ( Martínez et al., 2007). Both specialist and generalist predatory strategies impact ecological communities by shifting community composition and abundance, but through different mechanisms. Although top-down control via predation is known to structure many animal communities ( Baum and Worm, 2009), the role of predation by bacteria on the structure of microbial communities is less well studied. In addition to their interactions with an animal host, host-associated microbes simultaneously compete and cooperate with one another, and alterations to these interactions can affect holobiont function ( De Boer et al., 2007). Host–microbe relationships are so important for the health of many plants and animals that the term ‘holobiont’ has been coined to describe the sum of a host and its symbionts ( Hosokawa et al., 2006). Thus, animal microbiomes can harbor active bacterial predators, which may regulate microbiome structure and protect the host by consuming potential pathogens. Co-occurrence network analysis showed that Halobacteriovorax’s interactions with other bacteria are influenced by temperature and inorganic nutrient concentration, and further suggested that this bacterial predator’s abundance may be driven by prey availability. Cultured Halobacteriovorax from Porites asteroides corals tested positive for predation on the putative coral pathogens Vibrio corallyticus and Vibrio harveyii. Across a library of 198 16S rRNA samples spanning three coral genera, 79% were positive for carriage of Halobacteriovorax. Here we show that predatory bacteria of the genus Halobacteriovorax are prevalent and active predators on the surface of several genera of reef-building corals.
Although predation has been extensively explored in animals and microbial eukaryotes, predation by bacteria is less well understood. In many ecological communities, predation has a key role in regulating community structure or function.
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