Chemical composition of the peptidoglycan-free cell envelopes of budding bacteria of the Pirella/Planctomyces group

Cell envelopes were prepared from freeze-dried cells of 8 strains of budding bacteria belonging to the Pirella/Planctomyces group. Treatment with 10% sodium dodecylsulfate (SDS) (30 min, 100°C) allowed the isolation of stable cell sacculi which still maintained the original cell shape. The chemical analysis showed, as the main component, protein which was unusually rich in proline and cystine. Except for Planctomyces maris IFAM 1317 (where this protein comprised 62.6% of the total envelope dry weight) the corresponding values for the other strains varied from 75 to 82%. Amino sugars and neutral sugars were present only in small amounts and uronic acids were not found. The ash content varied from 5 to 10% of the dry weight, except for IFAM 1317 which had 19% ash. The high content of cystine indicated a high degree of crosslinking of the cell envelopes through disulfide bonds. Our data show that bacteria of the Pirella/Planctomyces group possess a similar cell wall composition.