Phylogenetic Analysis of Species of the meso-Diaminopimelic Acid-Containing Genera Brevibacterium and Dermabacter

This study performed 16S rRNA gene sequencing on Dermabacter hominis and four meso-diaminopimelic acid-containing Brevibacterium species to clarify their phylogenetic relationships within high-guanine-plus-cytosine-containing gram-positive bacteria. The researchers extracted chromosomal DNA, amplified and sequenced 16S rRNA genes, then constructed phylogenetic trees using neighbor-joining methods. Results showed that all four Brevibacterium species (B. casei, B. epidermidis, B. iodinum, and B. linens) were highly similar to each other (97-99% sequence similarity) and formed a distinct phylogenetic lineage with no close relationship to other examined organisms. In contrast, Dermabacter hominis showed high sequence similarity to organisms in the Arthrobacter/Micrococcus subline, particularly Arthrobacter globiformis (93.0%), Micrococcus luteus (93.1%), and Renibacterium salmoninarum (91.5%). However, the association was not particularly close phylogenetically. The findings support Brevibacterium as a separate genus and confirm Dermabacter hominis as a distinct genus, despite its unusual wall chemistry of meso-diaminopimelic acid rather than the lysine found in related Arthrobacter and Micrococcus species.

Key findings

• All four Brevibacterium species form a distinct phylogenetic lineage with 97-99% sequence similarity to each other and show no specific affinity with other actinomycetes examined.
• Dermabacter hominis shares highest 16S rRNA sequence similarity with Arthrobacter globiformis (93.0%), Micrococcus luteus (93.1%), and Renibacterium salmoninarum (91.5%), placing it in the Arthrobacter/Micrococcus subline.
• Despite phylogenetic affinity to lysine-containing Arthrobacter and Micrococcus, Dermabacter hominis contains meso-diaminopimelic acid in its cell wall, making its genetic distinctness sufficient to justify separate generic status.
• Sequence analysis of 1,320 nucleotides from each organism provided evidence that Brevibacterium represents an individual line of descent at phylogenetic distances excluding close genus-level relationships with reference actinomycetes.