our results predict that all viunalikeviruses are likely to be capable of highly efficient horizontal gene transfer between their cognate bacterial hosts . this capacity could be exploited for use in fundamental research in bacterial functional genomics , and biotechnologically , for genetic engineering in chemical biology and synthetic biology applications . however , phages that show efficient horizontal gene transfer capacity could present biosafety implications for manipulation of bacterial pathogens . obviously , the transduction capabilities of viunalikeviruses should encourage a cautious reconsideration of their appropriateness for phage therapy in human , animal or plant pathology .
bacteriophages have been used as natural biocontrol and therapeutic agents , but also as biotechnological tools for bacterial engineering . 
 we showed recently that the transducing bacteriophage mam1 is a vii - like phage and a member of the new genus , 
 viunalikevirus ' . here 
 , we show that four additional vii - like phages and three new environmentally isolated viunalikeviruses , all infecting plant and human pathogens , are very efficient generalised transducers capable of transducing chromosomal markers at frequencies of up to 104 transductants per plaque - forming unit . 
 we also demonstrate the interstrain transduction of plasmids and chromosomal markers , including genes involved in anabolism , genes for virulence and genes encoding secondary metabolites involved in biocontrol . 
 we propose that all viunalikeviruses are likely to perform efficient horizontal gene transfer . 
 viunalikeviruses therefore represent useful agents for functional genomics and bacterial engineering , and for chemical and synthetic biology studies , but could be viewed as inappropriate choices for phage therapy .