large invaginations of their cytoplasmic membrane, pulling away from the peptidoglycan cell wall and leaving room for the periplasm. Traditionally, the cytoplasmic membrane has been thought to be responsible for controlling the osmotic pressure of bacterial cells. Yet due to the folds in the cytoplasmic membrane, and the existence of large spaces of periplasm within Planctomycetota, their peptidoglycan acts as an osmotic barrier with the periplasm being isotonic to the cytosol. Anaerobic ammonium oxidation (anammox) Anammox is the process of oxidizing ammonium where nitrite acts as the electron acceptor. This process creates energy for the organism performing the reaction in the same way humans gain energy from oxidizing glucose. In a marine environment, this ultimately removes nitrogen from the water, as N2 gas cannot be used by phytoplankton and is released into the atmosphere. Up to 67% of dinitrogen gas production in the ocean can be attributed to anammox and about 50% of the nitrogen gas in the atmosphere is thought to be produced from anammox. Planctomycetota are the most dominant phylum of bacteria capable of performing anammox, thus the Planctomycetota capable of performing anammox play an important role in the global cycling of nitrogen. Sterol synthesis The synthesis of sterols, often observed in eukaryotes and uncommon among bacteria, has been observed very rarely in Planctomycetota. The synthesis of sterols such as lanosterol has been observed in G. obscuriglobus. Lanosterol is common in eukaryotes and two other groups of bacteria, both methylotrophic Pseudomonadota and myxobacteria. The synthesis of sterols observed in G. obscuriglobus is unique within Planctomycetota. Sterol synthesis is suggested to be associated with regulation of membrane fluidity in Planctomycetota, and has been described as essential to the proper growth and reproduction of G. obscuriglobus. Biotechnology and human applications Recently, interest has arisen in examining the Planctomycetota regarding their potential roles in biotechnology, mainly as a source of bioactive molecules, of interest mainly to the pharmaceutical industry. Bioactive compounds are mainly present as secondary metabolites, although little is known about Planctomycetota secondary metabolites. This is unexpected, as the Planctomycetota have several key features as other known producers of bioactive molecules, such as the Myxobacteria. However, a number of ongoing studies serve as various first steps in including Planctomycetota in small-molecule drug development for humans. Planctomycetota species are worthwhile considerations in challenging the current models for the origin of the nucleus, along with other aspects of origin and evolution of