Planctomycetes are gram negative bacteria. This phylum contains two orders, Planctomycetales and Brocadiales.  They have stalks, and their cells are arranged in rosettes. Planctomycetes lack peptidoglycan in their cell wall. Since they lack peptidoglycan in their cell wall, they are resistant to antibiotics like penicillin and cephalosporin, antibiotics that interfere with peptidoglycan synthesis.  Planctomycetes also have cellular compartments that resemble organelles in eukaryotes.

Planctomyces, the best-characterized genus in Planctomycetes, is a stalked bacterium. The stalk has no cell wall or cytoplasm and is used for attachment. Planctomyces habitat is primarily aquatic and is facultatively aerobic chemoorganotrophs that grow by fermentation or respiration of sugars.