Comparison of the morphology of PPLO and L-forms of bacteria with light and electron microscopy

Studies on the minimum reproducible unit of staphylococcal L-forms

The minimum size of a reproducible unit of staphylococcal L-forms was determined by filtration and electron microscopic methods. Ultrathin sections of an induced strain of Staphylococcal L-forms (STA-EMT-1) in liquid medium revealed several types of structures, all of which were bound by a single membrane and most of which possessed ribosome-like granules. Many of the small granules were less than 0.3 micron and were attached to the membrane of the large bodies. Using a serial filtration method, it was observed that viable L-forms were still detected in 0.22 micron filtrate, but the viable cell count of L-forms decreased in number with the decrease in pore size of membrane filters. A fractionation technique, using L-forms filtered through a membrane filter with a 0.45 micron pore size, revealed that there were three classes of small bodies but only the first class with ribosome-like granules over approximately 0.2 micron in diameter seems to be able to reproduce.

Characterization of a stable spheroplast type L-form of Proteus mirabilis D 52 as cell envelope mutant. II. Electronmicroscopic investigations

The ultrastructural analysis of a stable spheroplast type L-form of Proteus mirabilis D 52 revealed characteristic alterations in the organization of the cell envelope including defective changes in the cell envelope structure as for instance the loss of a coherent murein layer, the loss of some components in the outer cell wall layer, the formation of small membraneous vesicles at the tips of loose extensions of the cell wall, a decrease in associations and bindings between wall and membrane, an extension of the periplasmic space, an increase in membrane defects, as well as a disturbed cell division causing unusual modes of multiplication and the formation of various intracellular structures like membrane complexes, characteristic sheet-like membraneous bodies, typical inclusion bodies, and defective phage structures, which all could not be observed in normal rod-shaped cells. The results of these investigations and of those given in a previous paper (Gumpert and Taubeneck 1975) show, that the stable spheroplast type L-form LD 52 B must be considered as a true cell envelope mutant in which the biosynthesis and structure of the cell envelope is altered genetically by one or several mutations whereas the main biochemical activities are the same like those of the parent bacterium. The profound alterations in the cell envelope system, however, lead to some changes in the whole cell organization, which apparently in turn cause disorders even in metabolic and biosynthetic processes not directly involved in the biosynthesis of the cell envelope.

Characterization of a stable spheroplast type L-form of Proteus mirabilis D 52 as cell envelope mutant. I. Isolation, growth characteristics, biochemical activities, and sensitivity to bacteriophages

A stable spheroplast type L-form could be isolated by transferring 627 single colonies and 195 agar blocks with several colonies of unstable L-forms of Proteus mirabilis D 52 on agar media without supplements of penicillin. The L-form grows well on complex and synthetic agar media, however, it failed to grow in any of the liquid media which have been proved. With one exception (formation of acid from maltose) the L-form shows the same bioche mical activities like the parent rod-shaped bacterium. However, the insensitivity for various phages and the failure of DAP in the envelopes demonstrate that there are profound alterations in the biosynthesis and structure of the murein and of the outer wall layers. The results of these investigations and an ultrastructural analysis (Gumpert and Taubeneck 1975) show that the stable spheroplast type L-form LD 52 B of Proteus mirabilis must be considered as a true cell envelope mutant.

Morphology and ultrastructure of staphylococcal L colonies: light, scanning, and transmission electron microscopy

Scanning electron microscopy utilizing critical point drying was used in parallel with light and transmission electron microscopy to study L colonies produced by a stable L-phase variant of Staphylococcus aureus (AH24H).

Ultrastructure of a mycoplasma recovered from the bone marrow in systemic lupus erythematosus

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Three-dimensional morphology, ultrastructure, and replication of Mycoplasma felis

The morphology and replication of Mycoplasma felis in relation to growth phase in culture were studied by electron microscopy. The organisms showed 1.0 to 1.45-hr doubling times with typical bacterial-type growth curves when grown in dialysate broth supplemented with horse serum. Organisms were fixed for electron microscopy by using Veronal acetate-buffered 0.8% OsO(4) (pH 6.1) in 20% sucrose. The morphology of exponential-phase organisms differed markedly from that of stationary or death-phase organisms, which were essentially large round forms with either dispersed or abnormally aggregated cytoplasm. Plasticine models prepared from serial sections of organisms in exponential phase showed the organisms to be either disc-shaped, triangular, horseshoe-shaped, or multilobular. A central "hole" was frequently present in these structures and could be visualized in the lobular forms as an interconnecting circular membrane. The inner surface of this membrane often showed contact with a small membranous body about 0.12 mum in diameter. The significance of this body is unknown. The morphology of the various shapes was confirmed by using the phosphotungstic acid and critical point methods. When the ratios of the various forms in exponential-phase cultures were determined, it was found that a replication sequence could be proposed which accounted for not only the volume increase required to accommodate deoxyribonucleic acid (DNA) replication but also the distribution of that DNA. Although it is likely that DNA replication in M. felis is a binary process, it appears that the mechanism for production of new cells need not be a binary process.

Selection of media for the isolation of common bacterial L-phase organisms from a clinical specimen

The L-phase of 13 bacteria commonly associated with disease were induced by penicillin and inoculated into various solid and broth media; their growth was recorded for a period of 14 days. Plates containing highly purified agar and sucrose as the stabilizing agent and those incubated under aerobic conditions gave the best results. Magnesium seems to be necessary for growth in broth media on primary isolation, although it may not be necessary on multiple transfers after a more stable state has been reached. Growth in broth media is much more difficult to achieve. Reversion is aided by using a higher concentration of agar in plates, by decreasing the sucrose concentration, and by omitting the antibiotics and horse serum. A procedure has been outlined for the routine culture and identification of L-phase organisms from a clinical specimen.

Bacterial L-forms in the blood and joint fluids of arthritic subjects

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