Bacterie-fylum Planctomycetes

Planctomycetes are classified into two orders — Planctomycetales and Brocadiales.

These Gram-negative bacteria exhibit unique features. They divide by budding. Some have stalks or appendages, while others form rosette-like cell arrangements. Certain species possess an S-layer in their cell envelope.

All Planctomycetes show intracellular compartments resembling eukaryotic organelles.

They produce specialized structures known as pirellulosomes, which are non-unit membrane-enclosed compartments containing the nucleoid, ribosomes, and other cytoplasmic components.

In the genus Gemmata, the nucleoid is further enclosed by invaginations of the cell membrane, forming a structure surrounded by a true unit membrane.

The genus Isosphaera is a filamentous, gliding bacterium found in hot springs.

An additional noteworthy compartment, the anammoxosome, is found in members of the order Brocadiales, such as Brocadia anammoxidans.

The anammoxosome facilitates the anaerobic oxidation of ammonia — a form of chemolithoautotrophy. The toxic hydrazine intermediate of this reaction is contained within its unique lipid membrane, protecting cytoplasmic components.