The phylum planctomycetes

Abstract

The Planctomycetes is a bacterial phylum with multiple distinctive, and often unique, morphological, structural, metabolic, and genomic characteristics. Perhaps, the most important of which are the peptidoglycan-less cell walls and the intracellular compartmentalization. Isolation, as well as 16S rRNA gene-based diversity, surveys established the ubiquitous distribution of Planctomycetes. Currently, the phylum contains two classes, Planctomycetia and Phycisphaerae; three orders, Phycosphaerales, Planctomycetales, and Cand. Brocadiales (comprising all members of the anaerobic ammonia-oxidizing microorganisms); twelve genera; and five candidate genera. Thirteen Planctomycetes genomes covering ten genera have been either partially or completely sequenced. Recently, a significant step towards genetic manipulation has been taken by establishing a genetic system for one of the members of Planctomycetes, Planctomyces limnophilus. In this chapter, we highlight the common structural and morphological features of members of Planctomycetes; shed some light on their genomics, molecular analysis, and phylogeny; and emphasize the metabolic capabilities and physiological properties of pure cultures as well as those inferred from genomes. Characteristics that collectively differentiate Planctomycetes from other bacteria, as well as those that are taxonomically informative and could be used for genera and species differentiation, are discussed. Finally, enrichment and isolation procedures are presented.