The gene transfer agent-like particle of the marine phototrophic bacterium Rhodovulum sulfidophilum

Abstract

Gene transfer agents (GTAs) are shaped like bacteriophage particles but have many properties that distinguish them from bacteriophages. GTAs play a role in horizontal gene transfer in nature and thus affect the evolution of prokaryotic genomes. In the course of studies on the extracellular production of designed RNAs using the marine bacterium Rhodovulum sulfidophilum, we found that this bacterium produces a GTA-like particle. The particle contains DNA fragments of 4.5 kb, which consist of randomly fragmented genomic DNA from the bacterium. This 4.5-kb DNA production was prevented while quorum sensing was inhibited. Direct observation of the particle by transmission electron microscopy revealed that the particle resembles a tailed phage and has a head diameter of about 40 nm and a tail length of about 60 nm. We also identified the structural genes for the GTA in the genome. Translated amino acid sequences and gene positions are closely related to those of the genes that encode the Rhodobacter capsulatus GTA. This is the first report of a GTA-like particle from the genus Rhodovulum. However, gene transfer activity of this particle has not yet been confirmed. The differences between this particle and other GTAs are discussed.

Involvement of the response regulator CtrA in the extracellular DNA production of the marine bacterium <i>Rhodovulum sulfidophilum</i>

“…We also mentioned that the particle production is also controlled by the gene ctrA (Nagao et al, 2015b). Although the relationship between the extracellular soluble DNA and the GTA-like particle of this organism is not clear at present, both may be used for genetic exchange between cells.…”

“…2, lane WT). These may be the genome fragments which would be incorporated in, or have leaked from, the GTA-like particles (Nagao et al, 2015b). The band of 4.5 kb is visible in lane T of Fig.…”

“…In a previous paper (Nagao et al, 2015b), we reported that R. sulfidophilum produces the GTA-like particle which is thought to be involved in genetic exchange between host cells. We also mentioned that the particle production is also controlled by the gene ctrA (Nagao et al, 2015b).…”

“…During the course of this study, we also found that R. sulfidophilum produces a gene transfer agent-like particle (GTA-like particle) (Nagao et al, 2015b). Gene transfer agents (GTAs) were first discovered in Rhodobacter capsulatus (basionym Rhodopseudomonas capsulata) by Marrs (1974), but have now been described from various prokaryotic species Beatty, 2007, 2010).…”

“…capsulatus is not essential and is not involved in the cell cycle (Mercer et al, 2010). In a previous paper, we reported that R. sulfidophilum produces GTA-like particles and that this production is controlled by the gene ctrA (Nagao et al, 2015b). Here, we further considered that not only the GTAlike particles, but also the extracellular soluble nucleic acid production, may be controlled by CtrA.…”