A candidate division, candidate phylum or candidate division-level is a lineage of Prokaryotic organisms for which no cultured

Microbiology

Microbiology is the study of microorganisms, which are defined as any microscopic organism that comprises either a single cell , cell clusters or no cell at all . This includes eukaryotes, such as fungi and protists, and prokaryotes...

 representatives have been found, but evidence of the existence of the clade has been obtained by 16S rRNA metagenomic analysis

Metagenomics

Metagenomics is the study of metagenomes, genetic material recovered directly from environmental samples. The broad field may also be referred to as environmental genomics, ecogenomics or community genomics. Traditional microbiology and microbial genome sequencing rely upon cultivated clonal cultures...

 of environmental samples. The term candidatus

Candidatus

Candidatus is in scientific classification a component of the taxonomic name for a bacterium that cannot be maintained in a Bacteriology Culture Collection. It is an interim taxonomic status for noncultivable organisms. An example would be "Candidatus Phytoplasma allocasuarinae"...

 in fact means a species which there is insufficient information to call it a new species according to the International Code of Nomenclature of Bacteria

International Code of Nomenclature of Bacteria

The International Code of Nomenclature of Bacteria or Bacteriological Code governs the scientific names for bacteria, including Archaea. It denotes the rules for naming taxa of bacteria, according to their relative rank...