Molecular and ultrastructural confirmation of classification of ATCC 35122 as a strain of Pirellula staleyi

A freshwater isolate from Campus Lake, Baton Rouge, LA, USA, strain ATCC 35122 (=ICPB 4362=Schmidt CLPM White=Tekniepe BT2 white), which had been proposed as a putative reference strain for 'Planctomyces staleyi' (later reclassified as Pirellula staleyi), has been re-examined to establish its relationship to the type strain of Pirellula staleyi, ATCC 27377(T). 16S rRNA sequencing confirms its very close relationship to ATCC 27377(T) and its membership of the order Planctomycetales. Ultrastructural characteristics are also consistent with its membership of the planctomycetes and of the genus Pirellula. These characteristics include polar crateriform structures and the occurrence of the unique internal, single-membrane-bounded compartment enclosing the nucleoid and ribosome-like particles, the pirellullosome, and a polar cap region. Cells of strain ATCC 35122 often displayed pointed, hump-like protrusions opposite each other on the cell, constituting prosthecae, and these were also found to be present on cells of strain ATCC 27377(T). The original identification of ATCC 35122 as a strain of Pirellula staleyi is confirmed on both molecular and phenotypic grounds.