Archaea kill bacteria, at least on occasion. The molecular underpinnings of these lethal interactions are barely understood. Here, we describe cinquedea, an /{beta} hydrolase secreted by the halophilic archaeon Haloferax larsenii s5a-1. Cinquedea exhibits bactericidal activity in the nanomolar range, killing halophilic Pontibacillus bacteria. Bacterial death is accompanied by gross morphological abnormalities, indicative of severe damage to the cell envelope. We predict, and confirm in vitro, that cinquedea is a phospholipase, with structural similarities to a phospholipase A1 enzyme isolated from hornet venom. Exposing lipids extracted from a cinquedea-sensitive Pontibacillus strain to the enzyme leads to accumulation of lysophosphatidylglycerol, a cleavage product of phospholipase A activity, supporting direct activity of cinquedea against the Pontibacillus membrane, which is chiefly composed of phosphatidylglycerol. Following the recent discovery that some archaea encode bactericidal peptidoglycan hydrolases, these findings suggest that archaea can kill bacteria in mechanistically diverse ways. Our work provides a template for future experimental discovery and characterization of bactericidal proteins of archaeal origin and reinforces an emerging view that archaea represent a substantial reservoir for the discovery of new antibacterial compounds.
Taissir, C., Strock, R., Wang, Y., Guffick, C., Misson, P., Soo, V. W., Hocher, A., Montoya, A., Shliaha, P. V., Oksanen, H. M., Bolla, J. R., Warnecke, T.
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