broadhostrange

Broad-host range refers to the ability of an organism, often a virus or a mobile genetic element, to infect, replicate in, or be maintained across a wide array of host species or strains. It contrasts with a narrow host range, where infection or maintenance is limited to a single species or a few closely related strains.

In bacteriophages and viruses, broad host range is determined by factors such as the availability of cellular receptors, adsorption machinery, and the ability to overcome host defense systems like CRISPR and restriction-modification. Receptor-binding proteins, tail fibers, and baseplate structures influence which hosts can be infected. Environmental conditions and genetic variability can shift host range over time.

For plasmids and gene delivery vectors, broad-host range refers to replication and maintenance across diverse bacterial hosts. Replication origins, partition systems, and appropriate regulatory elements enable stable inheritance in multiple species. Classic examples include IncP plasmids (RP4, RK2) that replicate in many Gram-negative bacteria, and vectors based on pBBR1, used to extend cloning capacity across diverse hosts. The practical use requires compatibility with host replication and selection systems, and sometimes host range is constrained by restriction-modification or compatibility with existing plasmids.

Applications and implications: in phage therapy and biocontrol, broad-host-range phages can target multiple pathogens but may raise biosafety concerns due to horizontal gene transfer. In genetic engineering, broad-host-range plasmids facilitate shuttle vectors between species, enabling comparative studies and multi-host pathways. Limitations include ecological relevance, potential for unintended gene transfer, and maintenance burden in some hosts.