Molecular Characterization
and Functional Analysis
of Outer Membrane Vesicles from the Antarctic Bacterium Pseudomonas
syringae Suggest a Possible Response to Environmental Conditions
posted on 2014-03-07, 00:00authored byHeramb
M. Kulkarni, Ch. V. B. Swamy, Medicharla V. Jagannadham
Outer membrane vesicles (OMVs) of
Gram-negative bacteria form an
important aspect of bacterial physiology as they are involved in various
functions essential for their survival. The OMVs of the Antarctic
bacterium Pseudomonas syringae Lz4W were isolated,
and the proteins and lipids they contain were identified. The matrix-assisted
laser desorption/ionization time of flight (MALDI-TOF/TOF) analysis
revealed that phosphatidylethanolamines and phosphatidylglycerols
are the main lipid components. The proteins of these vesicles were
identified by separating them by one-dimensional gel electrophoresis
and liquid chromatography coupled to electrospray ionization tandem
mass spectrometry (ESI–MS/MS). They are composed of outer membrane
and periplasmic proteins according to the subcellular localization
predictions by Psortb v.3 and Cello V2.5. The functional annotation
and gene ontology of these proteins provided hints for various functions
attributed to OMVs and suggested a potential mechanism to respond
to the extracellular environmental changes. The OMVs were found to
protect the producer organism against the membrane active antibiotics
colistin and melittin but not from streptomycin. The 1-N-phenylnapthylamine (NPN)-uptake assay revealed that the OMVs protect
the bacterium from membrane active antibiotics by scavenging them
and also showed that membrane and protein packing of the OMVs was
similar to the parent bacterium. The sequestering depends on the composition
and organization of lipids and proteins in the OMVs.