Predation structures food webs, influences energy flow, and alters rates
and pathways of nutrient cycling through ecosystems, effects that are well documented
for macroscopic predators. In the microbial world, predatory bacteria are
common, yet little is known about their rates of growth and roles in energy flows
through microbial food webs, in part because these are difficult to quantify. Here,
we show that growth and carbon uptake were higher in predatory bacteria compared
to nonpredatory bacteria, a finding across 15 sites, synthesizing 82 experiments
and over 100,000 taxon-specific measurements of element flow into newly
synthesized bacterial DNA. Obligate predatory bacteria grew 36% faster and assimilated
carbon at rates 211% higher than nonpredatory bacteria. These differences
were less pronounced for facultative predators (6% higher growth rates, 17% higher
carbon assimilation rates), though high growth and carbon assimilation rates were
observed for some facultative predators, such as members of the genera Lysobacter
and Cytophaga, both capable of gliding motility and wolf-pack hunting behavior.
Added carbon substrates disproportionately stimulated growth of obligate predators,
with responses 63% higher than those of nonpredators for the Bdellovibrionales and
81% higher for the Vampirovibrionales, whereas responses of facultative predators to
substrate addition were no different from those of nonpredators. This finding supports
the ecological theory that higher productivity increases predator control of
lower trophic levels. These findings also indicate that the functional significance of
bacterial predators increases with energy flow and that predatory bacteria influence
element flow through microbial food webs.
Published: July 18, 2021
Citation
Hungate B., J.C. Marks, M.E. Power, E. Schwartz, K. van Groenigen, S.J. Blazewicz, and P. Chuckran, et al. 2021.The Functional Significance of Bacterial Predators.mBio 12, no. 2:Article No. e00466-21.PNNL-SA-161233.doi:10.1128/mBio.00466-21