Planctomycetales

Planctomycetales is an order of bacteria belonging to the phylum Planctomycetes. These bacteria are notable for their unique cellular characteristics, including the absence of peptidoglycan in their cell walls, which is a common component of most bacterial cell walls. Instead, their cell envelopes are composed of other polymers.

A defining feature of many Planctomycetales is the presence of internal membrane-bound organelles. This is highly unusual in prokaryotes, which typically lack such structures. These organelles can include a nucleus-like body called the nucleoid, and other compartments involved in processes like protein secretion and nutrient storage.

Planctomycetales are found in a variety of aquatic environments, including freshwater, brackish water, and marine waters. They are often isolated from soil and sediment samples as well. Many species are aerobic, meaning they require oxygen for respiration, while some can also survive under anaerobic conditions.

Some members of Planctomycetales, such as members of the genus Planctomyces, exhibit a stalked morphology, attaching themselves to surfaces. This stalk is often composed of proteinaceous material and can bear a holdfast structure for attachment. Other genera, like Gemmata, are coccoid and may be found free-swimming or attached.

Reproduction in Planctomycetales can occur through budding, a process where a smaller cell grows from a parent cell and then detaches. This is another characteristic that sets them apart from many other bacteria that divide by binary fission. The ecological roles of Planctomycetales are diverse, with some species implicated in the nitrogen cycle, such as ammonia oxidation.