The bacterium Kocuria palustris is frequently encountered in environmental samples across the globe. This microbe is generally considered a non-pathogenic member of the microbial community, yet it possesses characteristics that give it resilience and utility. K. palustris serves significant roles in natural ecological processes while also exhibiting involvement in human health and industrial applications. Understanding this bacterium requires examining its taxonomy, morphology, and ecological functions.
Classification and Naming
Kocuria palustris belongs to the domain Bacteria and the Phylum Actinomycetota, which contains many environmentally important species. Its taxonomic home is the Family Micrococcaceae, placing it among relatives like Micrococcus and certain Staphylococcus species. The species was first formally described in 1999 after isolation from the rhizoplane of the narrow-leaved cattail (Typha angustifolia).
The name palustris is Latin for “marshy” or “swampy,” reflecting its origin. The type strain was collected from a floating mat in the Soroksár tributary of the Danube river in Hungary. Placement into the genus Kocuria is supported by chemotaxonomic markers, including the presence of lysine in its cell-wall peptidoglycan and the specific menaquinone, MK-7(H2).
Physical Appearance and Structure
Kocuria palustris is a Gram-positive bacterium, characterized by a thick peptidoglycan layer in its cell wall that retains the crystal violet stain. The organism is a coccus, meaning it has a spherical shape, typically measuring between 1.0 and 1.5 micrometers in diameter. These cells are non-motile, lacking flagella.
Under a microscope, the cells often arrange themselves in characteristic formations, appearing as pairs, tetrads (groups of four), or small, irregular clusters. The bacterium is an obligate aerobe, requiring oxygen to grow and generate energy. It is also mesophilic, thriving in moderate temperatures. Growth ceases above approximately 30 degrees Celsius, and it prefers a neutral to slightly acidic pH range of 5.7 to 7.7.
Environmental Habitats and Roles
Kocuria palustris has an extensive natural distribution, adapting to various ecological niches, including soil, water, and the rhizoplane of aquatic plants. Its isolation from root environments suggests an active role in nutrient cycling. The bacterium can survive in environments with elevated salt concentrations, showing growth at up to 7% sodium chloride, indicating tolerance for saline habitats.
This resilience allows it to persist in fluctuating conditions. K. palustris participates in the breakdown of complex organic compounds, a fundamental process in decomposition and carbon cycling. Certain strains can degrade crude oil, breaking down hydrocarbons in contaminated sites. This degradation often involves producing biosurfactants, compounds that emulsify oils for consumption.
Relevance to Health and Industry
Health Relevance
In human health, Kocuria palustris is generally regarded as low-virulence, often existing as a harmless member of the skin microbiota. It is recognized as an opportunistic pathogen, capable of causing infection under specific circumstances, particularly in individuals with compromised immune systems. Cases of infection are rare but have included bacteremia (bacteria in the bloodstream), often linked to medical devices such as catheters. It has also been isolated from sites of infection like the eye, specifically in cases of keratitis. The bacterium is also studied for its presence in the microbiomes of patients with conditions like psoriasis and celiac disease, suggesting a potential role in microbial dysbiosis.
Industrial Applications
The hardiness of K. palustris is advantageous in industrial and biotechnological applications, especially for environmental cleanup. Its capacity for hydrocarbon breakdown makes it a candidate for bioremediation efforts aimed at cleaning up contaminated soil and water. Furthermore, the bacterium produces bioactive compounds. For example, marine-derived strains produce a benzimidazole compound that demonstrates antifungal activity against agricultural plant pathogens. These applications suggest a future role for K. palustris in developing new solutions for pollution control and crop protection.