https://mmbr.asm.org/content/mmbr/41/2/391.full.pdf

Fatty acids of the genus Bacillus: an example of branched-chain preference.

One of the unique features of p-lactam antibiotics and other cell-wall inhibitors like vancomycin and bacitracin is that they can rapidly kill and in many cases lyse susceptible bacteria. Many other types of antibacterial agents (e.g., trimethoprim or chloramphenicol) are primarily bacteriostatic: they inhibit multiplication but do not cause an irreversible inactivation of the cell. In 1970 the characterization of a novel type of pneumococcal mutant was reported in the literature [1]. This mutant grows in normal generation times and is as sensitive to growth inhibition by penicillin as the wild-type parent strain. However, while cultures of the parent

Antibiotic tolerance among clinical isolates of bacteria.

Can fluorescent probes tell us anything about membranes

https://mmbr.asm.org/content/mmbr/34/2/194.full.pdf

Bacterial growth and the cell envelope.

Very rapidly frozen cells of Escherichia coli and Bacillus subtilis were substituted at low temperature into acetone with 1% OsO4 and embedded in Epon. They showed ribosome-free spaces filled with globular and fibrillar material of up to 15 nm. The sizes of structures seen do not exclude DNA superstructures such as supercoils, aggregates, and nucleosomes. With the Feulgen analog osmium-ammines stain, DNA was localized within the ribosome-free space. The bulk of DNA, the nucleoid, is therefore a major part of, or identical to, the main ribosome-free space. The ribosome-free space would correspond directly to the light microscopy phase-contrast image of nucleoids in living bacteria. The shape of the ribosome-free space does not reflect intracellular salt concentrations, nor do the Feulgen-positive areas. The previously observed dependency on the salt concentration of the growth medium seems to be due to permeabilization induced by the chemical fixative at room temperature. The ribosome-free space is more cleft in appearance than the nucleoid obtained by fixation with OsO4 but more confined than its very dispersed form found after aldehyde fixation.

Shape and fine structure of nucleoids observed on sections of ultrarapidly frozen and cryosubstituted bacteria

Studies on the phospholipids and morphology of protoplasts of Bacillus megaterium

Addition of glucose to the medium in which Bacillus subtilis was grown lowered the p H and increased the amount of lysylphosphatidylglycerol relative to the phosphatidylglycerol content of the membrane fraction. This change in phospholipid composition was accompanied by changes in the shape and behavior of the gymnoplasts obtained by cell wall removal with lysozyme. These gymnoplasts appeared to retain most of their original cell shape and internal organization, often with preservation of the mesosomes. Cells harvested from neutral growth medium gave the usual spherical gymnoplasts. In a hypotonic medium, the spherical gymnoplasts lysed rapidly, whereas the rod-like gymnoplasts lost only part of their cell content while showing a tendency to preserve the original shape. This type of gymnoplast could not be produced from cells grown in neutral medium by simply raising the magnesium concentration. When this was done the gymnoplasts assumed bizarre shapes; they became compact and susceptible to the tonicity of the medium. Gymnoplasts or protoplasts, produced from bacilli exposed to low p H values, were found not to conform to the formulations on “protoplasts” given in 1958 by 13 authors. Cells exposed to a low environmental p H during growth seemed to possess a more rigid membrane structure than cells grown at neutral p H. Images

Bacteria-shaped Gymnoplasts (Protoplasts) of Bacillus subtilis

The morphology of nucleoids and mesosomes of Bacillus subtilis in stationary-and lag-phase cultures was studied by making three-dimensional cell reconstructions in plastic of electron micrographs of serial sections. In cells from stationary cultures, the dormant nucleoids are frequently, but not always, spherical and the mesosomes are small and compact. It is suggested that the spherical nucleoids represent the resting stage in which replication and segregation have been completed. In cells from lag-phase cultures, the compact mesosomes develop into an elaborate system of tubes and wider sacs which become wrapped around the elongating nucleoids and invade the nucleoplasm in preparation for division.

Nuclear and cell division in Bacillus subtilis: dormant nucleoids in stationary-phase cells and their activation.

Colonies of the three species ofMycoplasma of human origin were frequently found to contain coccoid elements. From electron micrographs it is deduced that the principle component of P.P.L.O. colonies are vesicular units of variable sizes. Usually these vesicular elements are largely vacuolar in nature. They then contrast strongly with the compact cocci. This study gives a number of data which seem to suggest that the coccoid elements and the P.P.L.O. forms belong together. Since the cocci are of definite bacterial structure theMycoplasma species of human origin might represent the L phase variant of minute coccoid bacteria.

On the nature of P.P.L.O. II. Electron microscopy.

Pathogenic avian PPLO,Mycoplasma gallisepticum strains were seen to grow on solid media in two types of colonies. The small ones are typical PPLO, the large ones seem to occupy an intermediate position between PPLO and bacteria. The elements constituting the large colonies must be the so-called Nelson bodies.

W. Van Iterson

Papers

Studies on the phospholipids and morphology of protoplasts of Bacillus megaterium

Bacteria-shaped Gymnoplasts (Protoplasts) of Bacillus subtilis

Nuclear and cell division in Bacillus subtilis: dormant nucleoids in stationary-phase cells and their activation.

On the nature of P.P.L.O. II. Electron microscopy.

Some characteristics of pathogenic avian PPLO