Generalized gene transfer by virus-like particles from marine bacteria

Abstract

Spontaneous VLP (virus-like particle) production and VLP-mediated gene transfer into Escherichia coli AB1157 as recipient was demonstrated. Five marine isolates (Alc 096, Alc 233, Alc 252, Agrobacterium kieliense and Flavobacterium sp. 11604) were investigated for their potential to produce VLP as well as for the gene transfer capability of these VLPs to the E. col1 recipient. These strains are classified as ubiquinone-10-possessing marine bacteria (QIOMB) in the 16s-rRNA Superfamily IV VLPs were obtained from 100 h cultured broth of all strains examined. VLP-host ratio after 100 h growth culture was: Alc 233, 1.54; Alc 252, 1.26; Alc 096, 1.06; Flavobacterjum sp. 11604, 0.69; and A. kieliense, 0.06. These ratios were smaller than those found in the marine environment. However, the spontaneously produced VLP number can be considered as high because the reported numbers are relatively low from coliphage h (0.005) and phage Mu (-0.0001). VLP-mediated gene transfer was examined using an auxotrophic mutant of E. coli (AB1157) with 4 amino acid deficiencies (leu, pro, his, arg) as recipient at multiplicity of infection (MOI) of 0.1. Through this treatment, VLPs showed lethal effect on the recipient. The survival rate of control was: Alc 096, 7%; Alc 252, 8%; A. kieliense, 17%; Flavobacterium sp. 11604,31%; and Alc 233,40%. At the same time, all the purified VLPs derived from these 5 strains successfully transferred genes to rescue genetlc defects of the recipi.ent. Overall average efficiency of VLP-mediated gene transfer at MO1 of 0.1 was estimated to be between 2.62 X' 10-3 and 3.58 X 10-'per VLP particle. Loci of employed genetic markers were dispersed on the E. coli chromosome with mutual distance of 121, 1154, 1397 and 364 kb between them. Since VLPs from different sources showed similar gene transfer efficiency in respect to the genet~c marker rescued, it is suggested that VLPs from QlOMB transferred genes as generalized transduction. These results indicate that the VLPs produced by certain marine bacteria may be an important element for both non-specific generalzed horizontal gene transfer towards a broad range of bacterial hosts and population control in the marine environment.