Zwitterionisella

Zwitterionisella is a genus of bacteria that belongs to the phylum Actinobacteria, specifically within the family *Corynebacteriaceae*. The name "Zwitterionisella" derives from the German word "Zwitterion," referring to the amphoteric nature of certain amino acids, which may reflect the physiological characteristics of the organisms in this genus. The genus was proposed in 2018 to accommodate a group of Gram-positive, non-motile, rod-shaped bacteria that exhibit aerobic respiration.

Members of *Zwitterionisella* are typically isolated from environmental sources, including soil and water, though some strains have been associated with clinical samples. These bacteria are non-spore-forming and generally exhibit a slow growth rate under laboratory conditions. They are catalase-positive and oxidase-negative, which helps distinguish them from related genera. The optimal growth temperature for most species in this genus ranges between 25°C and 37°C, with some tolerance for salt concentrations up to 5%.

The type species of the genus is *Zwitterionisella multivorans*, which was initially described as *Corynebacterium multivorans* before being reclassified. The genus currently includes a few characterized species, though taxonomic revisions may expand its membership as more strains are studied. Phylogenetic analysis based on 16S rRNA gene sequences places *Zwitterionisella* closely related to other coryneform bacteria, such as *Corynebacterium* and *Rothia*.

While *Zwitterionisella* species are not widely recognized as human pathogens, some strains have been implicated in opportunistic infections, particularly in immunocompromised individuals. Further research is needed to fully characterize their metabolic pathways, ecological roles, and potential clinical significance. The genus remains of interest in microbial taxonomy and environmental microbiology due to its distinct physiological traits and phylogenetic placement.