Paracoccus marcusii sp. nov., an orange gram-negative coccus

Area of Science:

• Microbiology
• Bacteriology
• Taxonomy

Background:

• The genus Paracoccus comprises diverse Gram-negative bacteria with significant roles in biogeochemical cycles.
• Accurate species delineation is crucial for understanding microbial diversity and function.
• Contaminants on culture plates can represent novel microbial discoveries.

Purpose of the Study:

• To characterize and formally describe a newly isolated orange Gram-negative coccus.
• To determine the taxonomic placement of this novel strain within the genus Paracoccus.
• To identify unique phenotypic and genotypic features that distinguish it as a new species.

Main Methods:

• Phenotypic analysis including morphology, Gram staining, and biochemical tests.
• Chemotaxonomic analysis to determine cellular fatty acid profiles and polar lipid composition.
• 16S ribosomal DNA (rDNA) gene sequencing for phylogenetic analysis.

Main Results:

• The isolated strain presented as an orange Gram-negative coccus.
• Biochemical tests revealed the inability to utilize nitrate as an electron acceptor.
• Carotenoid analysis confirmed the synthesis of large amounts of astaxanthin, responsible for the orange pigmentation.
• 16S rDNA sequence analysis confirmed its placement within the Paracoccus genus but distinct from known species.

Conclusions:

• The distinct phenotypic characteristics, particularly the orange color due to astaxanthin and nitrate non-utilization, support its classification as a new species.
• The proposed name for this novel species is Paracoccus marcusii, with strain DSM 11574T designated as the type strain.
• This discovery expands the known diversity within the Paracoccus genus and highlights the potential for novel findings from environmental isolates.