ABSTRACT
There is no single family in the δ class of the phylum Proteobacteria that has had a greater impact on medicine and public health, molecular genetics and phylogeny, pathogenesis, gene structure, regulation, and function, or microbial ecology than the Enterobacteriaceae. The family currently consists of more than 65 validated genera including over 350 species (https://www.bacterio.net). About 25% of current genera consist of a single species (e.g., Plesiomonas) while other genera contain more than 20 species (e.g., Erwinia, Xenorhabdus). The metamorphosis of the family over the past few decades and the logarithmic explosion in the number of recognized taxa is due to pioneering studies conducted by the Centers for Disease Control and Prevention and the Pasteur Institute (French: Institut Pasteur) and the upsurge in phylogenetic investigations employing molecular chronometers such as digital DNA-DNA hybridization, 16S rDNA and rpoB gene sequencing, matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF), amino acid sequence identity, multilocus sequence analysis (MLST), average nucleotide identity, and genome-to-genome distance calculator. 1 These investigations have led to dramatic classification changes within some important members of the family with some genera, such as Enterobacter, experiencing marked attrition in the number of valid species within the taxon. The latest proposed additions to the family Enterobacteriaceae include the genera Metakosakonia, Pluralibacter, 2 and Mixta. 3
