An electron microscopic study of the location of teichoic acid and its contribution to staining reactions in walls of Streptococcus faecalis 8191

Ruthenium red and the bacterial glycocalyx

Ruthenium red, a promising cationic reagent for electron microscopy (EM), has long been an important tool in histology. The reagent was initially used by botanists as a semispecific stain for pectic substances, but it has gradually been embraced by investigators in microbiology and the animal sciences as a stain for anionic glycosylated polymeric substances. Luft developed a reliable method and demonstrated that ruthenium red was a useful reagent for visualizing ultrastructural detail. Many investigators, using modifications of Luft's approach, have identified numerous applications for this important reagent. Ruthenium red has been used to show the ultrastructural detail of bacterial glycocalyces. Strong, sharp and consistent observations of this ultrastructural component of the bacterial cell have given a better understanding its fibrous anionic matrix. Any variations in staining owing to artifactual alteration of the fine delicate ultrastructural features have been overcome by incorporation of diamine lysine into ruthenium red methods, thus providing flexible processing times under less than ideal laboratory sampling conditions. Ruthenium red has broad utility in the biological sciences, and in combination with lysine, it is an excellent EM stain for enhanced visualization of bacterial glycocalyx from culture or from clinical specimens.

Structure of an antigenic teichoic acid shared by clinical isolates of Enterococcus faecalis and vancomycin-resistant Enterococcus faecium

A shared antigenic teichoic acid, previously found to be a surface capsule-like polysaccharide, was isolated from clinical isolates of Enterococcus faecalis and vancomycin-resistant E. faecium. It was composed of glucose, glycerol, and phosphate as determined by chemical and GC-MS analysis. The repeating-unit structure was elucidated by a series of 1H, 13C, and 31P NMR spectroscopy to be the following: [formula: see text]

The structure of the cell wall of Staphylococcus aureus studied with neutron scattering and magnetic birefringence

The cell wall complex was extracted from Staphylococcus aureus and characterized in suspension by means of small-angle neutron scattering and magnetically induced birefringence. The neutron scattering measurements show that the complex has a thickness of approximately 420 A, a mass per unit area of 93 +/- 11 daltons/A2 and is approximately 75% water by volume. The neutron scattering density is higher near the surface than in the interior in accordance with a trilamellar structure. The magnetically induced birefringence measurements demonstrate that a high degree of magnetic orientation is possible due to the anisotropic nature of the wall complex structure.

Major sites of metal binding in Bacillus licheniformis walls

Isolated and purified walls of Bacillus licheniformis NCTC 6346 his contained peptidoglycan, teichoic acid, and teichuronic acid (0.36 mumol of diaminopimelic acid, 0.85 mumol of organic phosphorus, and 0.43 mumol of glucuronic acid per mg [dry weight] of walls, respectively). The walls also contained a total of 0.208 mumol of metal per mg. When these walls were subjected to metal-binding conditions (T. J. Beveridge and R. G. E. Murray, J. Bacteriol. 127:1502-1518, 1976) for nine metals, the amount of bound metal above background ranged from 0.910 mumol of Na to 0.031 mumol of Au per mg of walls. Most were in the 0.500-mumol mg-1 range. Electron-scattering profiles from unstained thin sections indicated that the metal was dispersed throughout the wall fabric. Mild alkali treatment extracted teichoic acid from the walls (97% based on phosphorus) but left the peptidoglycan and teichuronic acid intact. This treatment reduced their capacity for all metals but Au. Thin sections revealed that the wall thickness had been reduced by one-third, but metal was still dispersed throughout the wall fabric. Trichloroacetic acid treatment of the teichoic acid-less walls removed 95% of the teichuronic acid (based on glucuronic acid) but left the peptidoglycan intact (based on sedimentable diaminopimelic acid). The thickness of these walls was not further reduced, but little binding capacity remained (usually less than 10% of the original binding). The staining of these walls with Au produced a 14.4-nm repeat frequency within the peptidoglycan fabric. Sedimentation velocity experiments with the extracted teichuronic acid in the presence of metal confirmed it to be a potent metal-complexing polymer. These results indicated that teichoic and teichuronic acids are the prime sites of metal binding in B. licheniformis walls.

Teichoic and teichuronic acids: biosynthesis, assembly, and location

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Demonstration of an internal fraction plane in cell walls of Streptococcus faecalis and Streptococcus mutans

The proposed lower internal density of the gram-positive wall was confirmed by observed an internal fracture plane in the walls of Streptococcus faecalis and Streptococcus mutans. However, the granular surfaces produced by this cleavage appeared to be more of a reflection of distortion during preparation than of subunit construction.

The key role of peptidoglycan in the opsonization of Staphylococcus aureus

In an effort to determine the staphylococcal cell surface component(s) of importance in opsonization, cell walls (peptidoglycan and teichoic acid) and peptidoglycan were isolated from Staphylococcus aureus strain H grown in [3H]glycine-containing broth. After incubation of the cell walls and peptidoglycan with various opsonic sources, uptake by human polymorphonuclear leukocytes was measured. The opsonic requirements for phagocytosis of cell walls and peptidoglycan were found to be similar to those of intact bacteria. Removal of teichoic acid from the cell wall did not affect opsonization. Likewise, a teichoic acid-deficient mutant strain of S. aureus H was opsonized in a manner similar to that of the parent strain. Immunoglobulin G functioned as the major heat-stable opsonic factor and both the classical and alternative pathways participated in opsonization. Kinetic studies revealed that opsonization of peptidoglycan, as well as C3-C9 consumption by peptidoglycan, proceeded at a slower rate via the alternative pathway (C2-deficient serum) than when the classical pathway was present (normal serum). The ability of peptidoglycan to activate C3-C9 was significantly reduced when normal and C2-deficient sera were preabsorbed with peptidoglycan at 2 degrees C suggesting that antibodies to peptidoglycan may be involved in activation of both the classical and alternative complement pathways. Thus, peptidoglycan appears to be the key cell wall component involved in staphylococcal opsonization, and it is suggested that host response to peptidoglycan, a major cell wall component of most gram-positive bacteria, may be related to the development of "natural immunity" to this group of microorganisms.

Structural arrangement of polymers within the wall of Streptococcus faecalis

The structure of the cell wall of Streptococcus faecalis was studied in thin sections and freeze fractures of whole cells and partially purified wall fractions. Also, the structures of wall preparations treated with hot trichloroacetic acid to remove non-peptidoglycan wall polymers were compared with wall preparations that possess a full complement of accessory polymers. The appearance of the wall varied with the degree of hydration of preparations and physical removal of the cell membrane from the wall before study. Seen in freeze fractures of whole cells, the fully hydrated wall seemed to be a thick, largely amorphic layer. Breaking cells with beads caused the cell membrane to separate from the wall and transformed the wall from a predominantly amorphic layer to a structure seemingly made up of two rows of "cobblestones" enclosing a central channel of lower density. Dehydration of walls seemingly caused the cobblestones to be transformed into two bands which continued to be separated by a channel. This channel was also observed in isolated wall preparations treated with hot trichloroacetic acid to remove non-peptidoglycan polymers. These observations are consistent with the interpretation that both peptidogylcan and non-peptidoglycan polymers are concentrated at the outer and inner surfaces of cell walls. These observations are discussed in relation to possible models of wall structure and assembly.

Uptake and retention of metals by cell walls of Bacillus subtilis

Isolated walls of Bacillus subtilis Marburg, prepared in a manner which avoided metal contamination other than by the growth medium, were incubated in dilute metal solutions, separated by membrane filtration (0.22 mum), and monitored by atomic absorption to give uptake data for 18 metals. Substantial amounts of Mg2+, Fe3+, Cu2+, Na+, and K+ (amounts which were often visible as Au3+, and Ni2+ (the higher atomic-numbered elements also visible as electron scattering), and small amounts of Hg2+, Sr2+, Pb2+, and Ag+ were taken into the wall. Some (Li+, Ba2+, Co2+, and Al3+) were not absorbed. Most metals which had atomic numbers greater than 11 and which could be detected by electron microscopy appeared to diffusely stain thin sections of the wall. Magnesium, on the other hand, partitioned into the central region, and these sections of walls resisted ruthenium red staining, which was not true for the other metals. Areas of the walls also acted as nucleation sites for the growth of microscopic elemental gold crystals when incubated in solutions of auric chloride. Retention or displacement of the metals was estimated by a "chromatographic" method using the walls cross-linked by the carbodiimide reaction to adipic hydrazide agarose beads (which did not take up metal but reduced the metal binding capacity of the walls by ca. 1%) packed in a column. When a series of 12 metal solutions was passed through the column, it became evident that Mg2+, Ca2+, Fe3+, and Ni2+ were strongly bound to the walls and could be detected by both atomic absorption and by their electron-scattering power in thin sections, qhereas the other metals were fisplaced or replaced. Partial lysozyme digestion of the walls (causing a 28% loss of a [3H]diaminopimelic acid label) greatly diminished the Mg2+ retention but not that of Ca2+, Fe3+, or Ni2+, indicating that there are select sites for various cations.

Cell wall assembly in Bacillus subtilis: development of bacteriophage-binding properties as a result of the pulsed incorporation of teichoic acid

Addition of a pulse of excess phosphate to a phosphate-limited culture of Bacillus subtilis W23 resulted in the synthesis and incorporation of wall material that contained teichoic acid. Consequently, the bacteria regained the ability to bind phage SP50 although maximum phage-binding properties did not develop until approximately half a generation time after incorporation of teichoic acid had ceased. The present findings strongly support our earlier suggestion that newly synthesized receptor material is incorporated at the inner surface of the wall and becomes exposed at the outer surface only during subsequent growth.