Proteomic Characterization of the Outer Membrane Vesicle of Pseudomonas putida KT2440

Outer membrane vesicles (OMVs) are
produced by various pathogenic
Gram-negative bacteria such as Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii. In this study, we isolated
OMVs from a representative soil bacterium, Pseudomonas
putida KT2440, which has a biodegradative activity
toward various aromatic compounds. Proteomic analysis identified the
outer membrane proteins (OMPs) OprC, OprD, OprE, OprF, OprH, OprG,
and OprW as major components of the OMV of P. putida KT2440. The production of OMVs was dependent on the nutrient availability
in the culture media, and the up- or down-regulation of specific OMPs
was observed according to the culture conditions. In particular, porins
(e.g., benzoate-specific porin, BenF-like porin) and enzymes (e.g.,
catechol 1,2-dioxygenase, benzoate dioxygenase) for benzoate degradation
were uniquely found in OMVs prepared from P. putida KT2440 that were cultured in media containing benzoate as the energy
source. OMVs of P. putida KT2440 showed
low pathological activity toward cultured cells that originated from
human lung cells, which suggests their potential as adjuvants or OMV
vaccine carriers. Our results suggest that the protein composition
of the OMVs of P. putida KT2440 reflects
the characteristics of the total proteome of P. putida KT2440.