# Planctomycetaceae

Planctomycetaceae is the only family in the order Planctomycetales within the Bacteria. Species within this family are mostly spherical, inhabiting a vast array of aquatic environments with the majority being in marine ecosystems. Planctomycetaceae species are generally aerobic, but are uniquely classified by fatty acid synthesis and stalk-like formations.

## Morphology

When compared to other species of the order Planctomycetales, species of the Planctomycetaceae family have very few unique characteristics that can taxonomically distinguish them from other related families. Planctomycetaceae species typically form colonies of a pink or white hue. Their cell structure has been recorded to be spherical, but many species are elliptical or pear-shaped; all species range from 0.4 micrometers to 2.5 micrometers in size.
When reproducing, cell structures of Planctomycetaceae are usually observed to be in either a rosette or aggregate grouping; the species Thalassoglobus neptunius is the only known example in this family capable of growing in chains. Some members of Planctomycetaceae (including other taxonomic groups of Planctomycetota) develop stalk-like projections. The species Planctomyces bekefii is well-known in this family for its stalks, using them to connect newly produced cells.

## Physiology

Families in Planctomycetales that have more research conducted have been noted to undergo anaerobic respiration, with the family Brocadiaceae being well known for its anaerobic ammonium redox (anammox) capabilities. Planctomycetaceae is one of the many families of Planctomycetales that is both aerobic and cannot do anammox reactions.
Similar to other families, members of Planctomycetaceae are capable of motility using flagella with some having cycles of motile and immotile lifestyles. Standing out from other bacteria, this group has been able to utilize its stalk-like structures to aid in biofilm production, providing a second source of adherence than usual extracellular polymeric substances.
Fatty acids and lipids synthesized by Planctomycetaceae are similar in composition to other families of the order Planctomycetales, but are unique enough to be considered taxonomically critical. Phosphocholine, phosphatidylcholine, and phosphatidylglycerol are considered the major lipids of this family, which only some other families are capable of synthesizing. Most notably, fatty acid C$_{18:1}$-ω9C is synthesized only within this family of Planctomycete bacteria.

## Phylogeny

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI). As of 2022, researchers have discovered that there are currently 14 genera and 29 species within Planctomycetaceae.
| 16S rRNA based LTP_10_2024 | 120 marker proteins based GTDB 09-RS220 |
| Schlesneria Kulichevskaya et al. 2007 Planctopirus Scheuner et al. 2015 Polystyrenella Peeters et al. 2021 Symmachiella Salbreiter et al. 2021 Fuerstiella Kohn et al. 2020 Gimesia Scheuner et al. 2015 Thalassoroseus Kumar et al. 2023 Stratiformator Kumar et al. 2024 Calycomorphotria Schubert et al. 2021 Alienimonas Boersma et al. 2021 Rubinisphaera Scheuner et al. 2015 Maioricimonas Rivas-Marin et al. 2021 Caulifigura Kallscheuer et al. 2021 Planctomicrobium Kulichevskaya et al. 2015 Thalassoglobus Kohn et al. 2020 | Symmachiella Schlesneria Planctopirus Polystyrenella Thalassoroseus Fuerstiella Calycomorphotria Alienimonas Gimesia Rubinisphaera Maioricimonas Caulifigura Planctomicrobium Thalassoglobus |
Genera incertae sedis:
* Planctomyces Gimesi 1924
* Planctellipticum corrig. Wurzbacher et al. 2024
* "Rhodopilula" Frank 2011
* "Thermopirellula" Liu et al. 2012