Characterisation of a novel extracellular structure produced by Xanthomonas citri and its relation with the Type IV pilus

Abstract

Gram-negative bacteria are capable of produce outer membrane vesicles (OMVs), the importance they play in interacting with other bacteria of the same or different species, with the host and with the its environment is increasingly gaining recognition. Being a process relevant to its growth and survival, and able to extend the interaction with its environment. In our observations of the phytopathogen Xanthomonas citri by transmission electron microscopy (TEM) we have identified extracellular structures that are compatible with vesicles; but, as a unique feature in relation to the vesicles most commonly described in the literature, which present an unique and isolated organization, those revealed in X. citri exhibit connections between them, forming a vesicle chains. TEM images also suggest that the connection between the vesicles can occur not only by the membrane, but also by the lumen, giving the chains of vesicles a tubular nature. In addition, we note that its production can be influenced by pilus type IV, since some mutants to components of this type increase the production of vesicles in relation to the wild type lineage. In addition, in preliminary tests, it was possible to verify in the vesicles the presence of DNA. Given the nanometric scale of these vesicles, it is interesting to use high capacity techniques for its visualization, such as electron microscopy and high resolution fluorescence microscopy. Our goals are also the standardization of a purification protocol for these structures, from which we will identify proteins and a possible associated genetic material; for this we intend to sequence the DNA and use MS / MS mass spectrometry to to identify the proteins present in the membranes.