HERA: a web server for host element reference-based aligner

Abstract

Plasmids play a central role in bacterial adaptation and in the dissemination of antimicrobial resistance, driving a growing need for accessible tools that support their comparative analysis without requiring local computational infrastructure. Although several circular genome visualization platforms exist, most are designed for general bacterial genome analysis rather than focused on plasmid comparison. Host element reference-based aligner (HERA) is a web server for intuitive visualization and comparison of plasmids and other circular molecules through BLAST alignment against reference sequences. Built on interactive circular genome visualization, HERA simplifies comparative genomics by providing an accessible interface for exploring sequence similarity, identifying conserved regions, and analyzing genetic elements without the complexity of traditional local tools. HERA includes a plasmid-oriented annotation pipeline covering replicon and mobility typing, antimicrobial resistance detection, mobile element identification, and homology search against the PLSDB plasmid database. HERA also provides an automatic selection of the reference which is the most appropriate from the uploaded sequences. The web server is available without login or any restriction at https://web.ccb.uni-saarland.de/hera/.