Catellicoccus marimammalium gen. nov., sp. nov., a novel Gram-positive, catalase-negative, coccus-shaped bacterium from porpoise and grey seal

Researchers characterized two Gram-positive, catalase-negative, coccus-shaped bacteria isolated from a dead harbour porpoise and grey seal found on Scottish coastlines. Using phenotypic, biochemical, and molecular phylogenetic methods, they determined these organisms possessed an unusual cell-wall murein type (L-Lys–Gly–D-Asp), 38 mol% DNA G+C content, and distinctive biochemical properties. Comparative 16S rRNA gene sequencing revealed the bacteria formed a distinct phylogenetic lineage closely related to, but sufficiently divergent from, known catalase-negative genera including Enterococcus, Vagococcus, and Melissococcus, with sequence divergence values exceeding 6% from recognized taxa. The organisms displayed unique characteristics including poor growth in conventional liquid media commonly used for similar bacteria and non-haemolytic colonies on blood agar. Based on comprehensive phenotypic and phylogenetic evidence demonstrating the bacteria represent a hitherto unrecognized genus, the authors propose classification as a novel genus and species: Catellicoccus marimammalium. The type strain M35/04/3T was recovered from multiple tissues of the deceased porpoise, which had suffered severe enteritis and peritonitis.

Key findings

• Two novel Gram-positive, catalase-negative cocci from marine mammal carcasses represent a distinct bacterial genus requiring new taxonomic classification as Catellicoccus marimammalium gen. nov., sp. nov.
• The novel organism possesses a rare cell-wall murein type L-Lys–Gly–D-Asp (type A4a) and DNA G+C content of 38 mol%, distinguishing it from closely related genera.
• Phylogenetic analysis by 16S rRNA gene sequencing showed greater than 6% sequence divergence from recognized genera, with the new species forming an independent subline among catalase-negative taxa.
• The isolates exhibited unusual growth characteristics, failing to grow in conventional liquid media commonly used for related bacteria despite growing on solid media under elevated CO2.