- Source: 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 C18:1-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.
Genera incertae sedis:
Planctomyces Gimesi 1924
"Rhodopilula" Frank 2011
"Stratiformator" Kumar et al. 2023
"Thermopirellula" Liu et al. 2012