Cell-wall Constituents of Rickettsiae and Psittacosis-Lymphogranuloma Organisms

Abstract

SUMMARYThe taxonomic position of organisms belonging to the rickettsiae and psittacosis-lymphogranuloma groups is controversial. Although, like viruses, all pathogenic forms of these organisms are obligate intracellular parasites, in other respects they resemble bacteria. Since a cell wall, deriving its rigidity from mucopeptide, which contains the amino sugar muramic acid as a key constituent, has so far only been found in bacteria and the closely related blue-green algae, the presence of muramic acid in an organism may be used as a taxonomic criterion. The mucopeptides of bacterial cell walls are also often sensitive to lysozyme, so that dissolution by this enzyme serves as an indication of the presence of mucopeptide. Organisms of the rickettsiae and psittacosis-lymphogranuloma groups have been examined for the presence of muramic acid. Critical chemical tests have shown that this substance is present in organisms of both groups. Cell walls of Rickettsia burnetii were dissolved by lysozyme. In the light of these and other results the taxonomic position of these groups of organisms is discussed.

Reduction in Chlamydial Infectivity by Lysozyme

“…While the lysozyme failed to inactivate a majority of the infective chlamydial particles, it consistently produced a significant reduction in chlamydial infectivity. This supports other chemical evidence that the cell walls of infective chlamydial particles do contain glycopeptide (3,4,9) and therefore are, in fact, structurally very closely related to the cell walls of bacteria. The limited degree of inactivation, however, suggests that lysozyme alone will not suffice to prevent ocular chlamydial infection, and if lysozyme is implicated at all in a "protective defense mechanism" against chlamydiae, it must operate in conjunction with other tear constituents (10).…”

A Search for the Bacterial Mucopeptide Component, Muramic Acid, in Chlamydia

“…Although Perkins & Allison (1963) detected muramic acid in several strains of Chlamydia, Manire & Tamura ( I 967) found none in meningopneumonitis elementary bodies or walls. There are three possible explanations for this discrepancy:…”

Discovery of chlamydial peptidoglycan reveals bacteria with murein sacculi but without FtsZ

“…This fits to the notion that PG-loss renders FtsZ dispensable, like in mycoplasmas 6 or L-form bacilli 7 . While from genome sequences it is clear that chlamydiae do not possess FtsZ, the presence or absence of chlamydial PG has been highly controversial 8, 9, 10, 11, 12, 13, 14, 15, 16 . One early study reported the colorimetric detection of muramic acid in chlamydiae 14 , but more reliable chromatographic methods subsequently failed to confirm this result 11, 15 .…”

“…While from genome sequences it is clear that chlamydiae do not possess FtsZ, the presence or absence of chlamydial PG has been highly controversial 8, 9, 10, 11, 12, 13, 14, 15, 16 . One early study reported the colorimetric detection of muramic acid in chlamydiae 14 , but more reliable chromatographic methods subsequently failed to confirm this result 11, 15 . All attempts to purify chlamydial sacculi have failed 10, 12 and no periplasmic density layers have been detected between the inner and outer membranes of chlamydiae by electron microscopy (including for instance 17, 18, 19 ).…”