Preliminary Investigation of Iron Acquisition in Hypervirulent Klebsiella pneumoniae Mediated by Outer Membrane Vesicles.

Abstract

ObjectiveTo investigate the role of outer membrane vesicles (OMVs) and related proteins in iron acquisition of hypervirulent Klebsiella pneumoniae (HVKP) and classic Klebsiella pneumoniae (cKP).MethodsThe OMVs of HVKP and cKP under iron-deficient and iron-sufficient media were extracted and purified by ultracentrifugation. Transmission electron microscopy (TEM) was used to identify OMVs. The quantitative proteomics were performed based on mass spectrometry.ResultsFour OMVs samples secreted by HVKP and cKP under iron-deficient and iron-sufficient environment were isolated and collected (HVKP OMVs under iron-deficient environment (A1), HVKP OMVs under iron-sufficient environment (A2), cKP OMVs under iron-deficient environment (B1), cKP OMVs under iron-sufficient environment (B2)). The amount of OMVs released by HVKP in iron-deficient medium was significantly larger than that in iron-sufficient medium (P < 0.05). HVKP secreted more OMVs than cKP in iron-deficient medium (P < 0.05). A total of 1074 kinds of proteins were identified in four samples. A comparison between the iron-deficient vs iron-sufficient environment showed that 61 proteins in HVKP OMVs were identified with a significant change in abundance under iron-deficient environment. Among them, 17 proteins were related to iron acquisition and transportation systems. While in cKP OMVs, 62 proteins significantly changed under iron-deficient environment in which 5 proteins were related to iron acquisition and transportation systems. Upon comparison of the HVKP vs cKP OMVs under iron deficiency, 81 proteins were detected with a significant change in which 8 proteins were related to iron acquisition and transportation systems.ConclusionAbove all, the results of this study suggest a potential role for OMVs in iron acquisition of HVKP and provide evidence of potential connections between OMVs and strong iron-acquisition ability of HVKP during iron limitation.