Plesiomonas was moved to which bacterial family?

• A. Brucellaceae
• B. Enterobacteriaceae
• C. Legionellaceae
• D. Vibrionaceae

Answer: (B)

Taxonomy and molecular phylogeny guide how bacteria are grouped into families. When classification changes, it’s because genetic data, especially 16S rRNA gene sequences and genome analyses, reveal evolutionary relationships that better reflect true lineages.

Plesiomonas was moved into the Enterobacteriaceae family because molecular analyses place it within the Enterobacterales, clustering with Enterobacteriaceae members rather than with the other families listed. This genetic relationship indicates a closer common ancestry with Enterobacteriaceae than with Brucellaceae, Legionellaceae, or Vibrionaceae, even if some phenotypic traits might suggest otherwise. So, the best-fit family based on current phylogenetic data is Enterobacteriaceae.