Pseudoglutamicibacter cumminsii is a Gram-positive, rod-shaped bacterium belonging to the high G+C content Actinobacteria. It is widely distributed in nature, frequently isolated from soil and water environments. The bacterium also colonizes humans and is recovered from clinical samples, including those from hospitalized settings. While its role in human infectious disease is still being clarified, it is recognized as a potential opportunistic pathogen that requires careful identification.
Classification and Naming History
The bacterium is classified within the Phylum Actinomycetota, Class Actinomycetia, Order Micrococcales, and Family Micrococcaceae. This hierarchical structure helps scientists understand its genetic relationship to other known bacteria. The species was originally described in 1997 as Arthrobacter cumminsii, based on morphological and biochemical analyses.
Advanced scientific methods necessitated a major taxonomic revision of the Arthrobacter genus to accurately reflect genetic differences. Using a polyphasic taxonomic approach combining 16S ribosomal RNA gene sequencing and chemotaxonomic data, researchers re-evaluated the species. Molecular and chemical analyses revealed that A. cumminsii was phylogenetically distinct from core Arthrobacter species, justifying its move into the newly proposed genus, Pseudoglutamicibacter, in 2016.
Reclassification was driven by distinct chemotaxonomic markers, such as a complex polar lipid profile and a specific peptidoglycan structure, which differentiate Pseudoglutamicibacter from Arthrobacter. This careful renaming process ensures the species is correctly positioned within the bacterial tree of life.
Defining Biological Characteristics
Pseudoglutamicibacter cumminsii exhibits a classic coryneform morphology, appearing as irregularly shaped rods during the growth phase. It is a Gram-positive organism, non-motile, and does not form spores.
The bacterium is an obligate aerobe, requiring oxygen for survival and metabolic functions. It is mesophilic, thriving best at moderate temperatures, and utilizes oxidative metabolism.
The species has a unique cell wall composition, including the A4\(\alpha\) peptidoglycan structure. The cell membrane contains a distinctive quinone system, with menaquinone MK-8(H2) as the primary component for energy production. These chemical signatures were instrumental in the species’ definitive reclassification.
The cellular fatty acid profile is specific, dominated by anteiso-C15:0, iso-C16:0, and anteiso-C17:0. This profile contributes to the stability and fluidity of the cell membrane. Its complex polar lipid profile includes diphosphatidylglycerol, phosphatidylglycerol, and dimannosylglyceride.
The natural reservoir of P. cumminsii is primarily the environment, particularly soil and water. Its ability to survive and metabolize various organic compounds explains why it is occasionally encountered in clinical settings, often through colonization of the skin and mucous membranes.
Roles in Health and Biotechnology
The most significant role of P. cumminsii is its status as a rare opportunistic pathogen in clinical settings. It can cause infection when the host’s immune system is compromised or when it accesses a sterile body site. Clinical relevance has been observed in infections affecting the urinary tract, wounds, and blood.
Infections are often found in polymicrobial cultures, suggesting it acts as a co-infecting agent. However, pure-culture isolation from sites like synovial fluid and urine confirms its capacity to be the sole cause of infection. This distinction helps clinical microbiologists determine if the organism is the actual source of the disease.
The organism is most frequently isolated from urine samples associated with urogenital infections, and from wound swabs. It has also been implicated in serious conditions, such as bacteremia (blood infection) and polymicrobial osteomyelitis (bone infection). Accurate identification using advanced techniques like mass spectrometry is essential for proper diagnosis.
Analysis of its antibiotic susceptibility profile indicates high susceptibility to certain classes of antibiotics, such as beta-lactams and linezolid. However, some strains show variable susceptibility to other drugs, including fluoroquinolones. This variable resistance highlights the importance of performing antimicrobial susceptibility testing to guide effective patient therapy.
While its primary relevance is clinical, its environmental origin and metabolic capabilities offer research potential. Its ability to thrive in diverse environments and utilize different carbon sources suggests potential for bioremediation applications. The species also serves as a valuable subject for genomic and phylogenetic studies within the Actinobacteria phylum.