Behaviour of Bdellovibrio bacteriovorus in the presence of Gram-positive Staphylococcus aureus.

: The present study aimed to characterize the behavior of Bdellovibrio bacteriovorus in the presence of Staphylococcus aureus. B. bacteriovorus was co-cultured with S. aureus or Pseudomonas aeruginosa or Streptococcus mutans, in planktonic and sessile conditions. Co-cultures were studied by Field-Emission Scanning Electron Microscopy (FESEM), Scanning Transmission Electron Microscopy (STEM), turbidimetry, quantitative PCR (qPCR), and sequencing of gene Bd0108 of B. bacteriovorus. Results indicated that B. bacteriovorus comparably inhibited planktonic growth of P. aeruginosa and S. aureus, but not of S. mutans. FESEM and STEM showed that B. bacteriovorus interacts with S. aureus affecting its cell wall and membrane. Sequencing of gene Bd0108 did not reveal any of the mutations that can arise from the host-interaction (hit) locus. Although some Gram-negative species are reported to be B. bacteriovorus prey, it seems that in case of nutrient deficiency this predatory bacterium can also take advantage of some Gram-positive species. B. bacteriovorus behaviour in the presence of S. aureus is relevant for its possible therapeutic use in several pathologies, like cystic fibrosis in which S. aureus and P. aeruginosa frequently coexist as infectious agents.