Sensor histidine kinase is a β-lactam receptor and induces resistance to β-lactam antibiotics

beta-Lactams disrupt bacterial cell wall synthesis, and these agents are the most widely used antibiotics. One of the principle mechanisms by which bacteria resist the action of beta-lactams is by producing beta-lactamases, enzymes that degrade beta-lactams. In Gram-negative bacteria, production of beta-lactamases is often induced in response to the antibiotic-associated damage to the cell wall. Here, we have identified a previously unidentified mechanism that governs beta-lactamase production. In the Gram-negative enteric pathogen Vibrio parahaemolyticus, we found a histidine kinase/response regulator pair (VbrK/VbrR) that controls expression of a beta-lactamase. Mutants lacking either VbrK or VbrR do not produce the beta-lactamase and are no longer resistant to beta-lactam antibiotics. Notably, VbrK autophosphorylation is activated by beta-lactam antibiotics, but not by other lactams. However, single amino acid substitutions in the putative periplasmic binding pocket of VbrK leads its phosphorylation in response to both beta-lactam and other lactams, suggesting that this kinase is a beta-lactam receptor that can directly detect beta-lactam antibiotics instead of detecting the damage to cell wall resulting from beta-lactams. In strong support of this idea, we found that purified periplasmic sensor domain of VbrK binds penicillin, and that such binding is critical for VbrK autophosphorylation and beta-lactamase production. Direct recognition of beta-lactam antibiotics by a histidine kinase receptor may represent an evolutionarily favorable mechanism to defend against beta-lactam antibiotics.