bakteerille

Bakteerille is a term used in microbiology to denote ultra-small bacteria‑like organisms at the lower size limit of cellular life. The name combines "bakteer"—the word for bacteria in several languages—with the diminutive suffix "-ille." In usage, bakteerille may refer to individual cells, lineages, or communities within the broader group of ultra-small bacteria or the Candidate Phyla Radiation.

Typical characteristics include very small cell size, generally around 0.1 to 0.4 micrometers in diameter, and simple morphological forms that are often coccoid or filamentous. Genomes in many bakteerille are markedly reduced compared with free-living bacteria, and many exhibit limited metabolic capabilities, making them dependent on other microbes or host organisms for essential nutrients or cofactors. This suggests a symbiotic or dependent lifestyle for a substantial portion of bakteerille.

Habitats span diverse environments, including soils, freshwater and marine systems, sediments, and microbiomes associated with eukaryotes or animals. They may contribute to nutrient cycling and form syntrophic interactions within microbial communities, though their exact ecological roles are still being investigated. Their small size and streamlined genomes can influence how they interact with neighbors and compete for resources.

Taxonomy and research status are unsettled; bakteerille are often placed within various bacterial lineages or as members of the CPR (Candidate Phyla Radiation), with ongoing debate about whether they form a cohesive group or represent multiple independent lineages of ultra-small bacteria. Detection relies on advanced methods such as metagenomics, single-cell genomics, fluorescence in situ hybridization, and electron microscopy, while cultivation in isolation remains challenging.