Planctomycetota,
Verrucomicrobiota, and
Chlamydiota in the
traditional molecular phylogeny view are considered as phyla and also cluster together in the PVC superphylum, along with the
candidate phyla Omnitrophica (previously OP3) and the Poribacteria. An important molecular marker in the form of a
conserved signature protein has been found to be consistently shared by PVC members, with the exception of
Poribacteria. The conserved signature protein may be a marker that represents a
synapomorphic quality and a means to distinguish this bacterial group. In 2014, studies have characterized this protein and it has been attributed to play an important housekeeping function in DNA/RNA binding. This observation not only provides a means to demarcate the PVC superphylum, but it supports strongly supports an evolutionary relationship shared by this clade that is distinct from other bacteria.
Conserved signature indels (CSIs) have also been found specific for the
Planctomycetota,
Verrucomicrobiota, and
Chlamydiota that distinguish each respective phylum from one another, and from other bacteria. A three-amino-acid insert in the
RNA polymerase protein
RpoB has been found that is shared by all sequenced Verrucomicrobia, Chlamydiae, and
Lentisphaerae species. The CSI is absent from neighbouring Planctomycetes' and Poribacteria, suggesting common ancestry among the groups for which the CSI is specific. These include the presence of membrane coat-like proteins,
tubulin,
sterol synthesis, and the presence of condensed DNA. ==References==