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Electron Microscopic Observations on the Fine Structure of Cell Walls of Chlamydia psittaci
1Department of Bacteriology and Immunology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27514.
Abstract:
L-cell cultures were infected with elementary bodies (EB) of meningopneumonitis organisms. Cell walls were prepared from reticulate bodies (RB), which are the intracellular developmental forms into which EB are converted, and from EB at appropriate times after infection. When fragmented EB cell walls were shadowcast with platinum palladium alloy, about one-half of the fragments were seen to be composed of hexagonally arrayed structures on the inner side of the cell wall. When EB cell walls were negatively stained with phosphotungstic acid, they all showed this fine structural array. These macromolecular units were estimated to be about 18 nm in diameter. RB cell walls, harvested at various times after infection, were similarly stained; about 20% of RB walls at 15 hr after infection showed traces of these regular structures, but only 2% of them had the structures at 24 hr. When RB cell walls prepared from penicillin-containing culture were examined, they were observed to be similar to RB without penicillin. When EB cell walls were treated with formamide at 160 C, and then centrifuged in a 10 to 40% potassium tartrate density gradient, hexagonal particles about 20 nm in diameter were obtained as a middle band in the gradient column. These particles were not obtained from RB cell walls harvested from cultures with or without penicillin. It is concluded that the particles are macromolecular subunits located on the inner side of the EB cell walls, that the subunits probably provide the structural rigidity found in the EB, and that their synthesis is inhibited by penicillin.
Insights
Researchers discovered macromolecular subunits on the inner side of elementary body (EB) cell walls of meningopneumonitis organisms. These structures provide rigidity and their synthesis is inhibited by penicillin.
Area of Science:
- Microbiology
- Cell Biology
- Structural Biology
Background:
- Meningopneumonitis organisms exhibit distinct developmental forms: elementary bodies (EB) and reticulate bodies (RB).
- Understanding the structural components of these forms is crucial for comprehending their life cycle and susceptibility to antimicrobial agents.
Purpose of the Study:
- To investigate the fine structural components of elementary body (EB) and reticulate body (RB) cell walls of meningopneumonitis organisms.
- To characterize macromolecular subunits present on EB cell walls and their potential role in structural integrity.
- To determine the effect of penicillin on the synthesis of these subunits.
Main Methods:
- Preparation and structural analysis of EB and RB cell walls using techniques like platinum palladium shadowcasting and negative staining with phosphotungstic acid.
- Fractionation of EB cell walls using formamide treatment and density gradient centrifugation.
- Microscopic examination of cell wall structures at various time points post-infection and in the presence/absence of penicillin.
Main Results:
- Hexagonally arrayed macromolecular subunits, approximately 18-20 nm in diameter, were identified on the inner surface of EB cell walls.
- These structures were abundant in EB cell walls but present only transiently and in low abundance in RB cell walls (around 20% at 15 hr, 2% at 24 hr).
- Penicillin treatment did not affect the observed structures in RB cell walls, and hexagonal particles were not recovered from RB cell walls, suggesting their specific association with EB.
Conclusions:
- The identified hexagonal particles represent macromolecular subunits located on the inner side of EB cell walls.
- These subunits likely contribute to the structural rigidity of the elementary bodies.
- The synthesis of these subunits appears to be inhibited by penicillin, indicating a potential mechanism of action for the antibiotic.
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