Gas gangrene-associated gliding motility is regulated by the Clostridium perfringens CpAL/VirSR system

Clostridium perfringens strains cause a wide variety of human and animal disease, including gas gangrene or myonecrosis. Production of toxins required for myonecrosis, PFO and CPA, is regulated by the C. perfringens Agr-like (CpAL) system via the VirSR two-component system. Myonecrosis begins at the site of infection from where bacteria migrate deep into the host tissue likely using a previously described gliding motility phenotype. We therefore assessed whether gliding motility was under the control of the CpAL/VirSR regulon. The migration rate of myonecrosis-causing C. perfringens strain 13 (S13) was investigated during a 96 h period, including an adaptation phase with bacterial migration (∼1.4 mm/day) followed by a gliding phase allowing bacteria faster migration (∼8.6 mm/day). Gliding required both an intact CpAL system, and signaling through VirSR. Mutants lacking ΔagrB, or ΔvirR, were impaired for onward gliding while a complemented strain S13ΔagrB/pTS1303 had the gliding phenotype restored. Gene expression studies revealed upregulated transcription of pili genes (pilA1, pilA2 and pilT) whose encoded proteins were previously found to be required for gliding motility and CpAL/VirSR-regulated pfoA and cpa toxin genes. Compared to S13, transcription of cpa and pfoA significantly decreased in S13ΔagrB, or S13ΔvirR, strains but not that of pili genes. Further experiments demonstrated that mutants S13ΔpfoA and S13Δcpa migrated at the same rate as S13 wt. We demonstrated that CpAL/VirSR regulates C. perfringens gliding motility and that gliding bacteria have an increased transcription of toxin genes involved in myonecrosis.