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Five strains, representative of Streptococcus mutans genetic group III antigenic group d, synthesized and degraded less intracellular polysaccharide (IPS) then 17 strains representative of other S. mutans groups. The strains that synthesize IPS degraded it rapidly. The production of acid in titratable amounts from endogenous IPS was usually complete within 1 h. IPS synthesis in S. mutans increased abruptly at culture glucose concentrations between 0.2 and 0.5% and was quantitated as both iodine-and glucose oxidase-positive material in cell hyrolysates. IPS degradation was measured by acid production in a pH-stat maintained at 7. The existence within group III d of a strain recently shown to be cariogenic in experimental animals suggest that IPS may not be a prerequisite for virulence in these cariogenic bacteria.

An electron microscopic study of S. mutans6715-13 wild type and representatives of three distinct classes of glucan synthesis-defective mutants (which fail to form adherent microbial plaques but agglutinate normally in the presence of exogenous glucans) disclosed the presence of two sucrose-dependent, glucanase-sensitive, extracellular components. In the wild type, these extracellular glucans had predominantly fibrillar (with some globular) morphologies. However, in the mutant strains, there was a consistent reduction in or loss of the fibrillar components and dramatic increases in globular forms. A cell surface-associated fuzzy coat was consistently seen, and it was neither sucrose-dependent nor glucanase-sensitive. The data indicated that in vitro and in vivo adhesion and virulence at smooth tooth surfaces (all these properties dramatically reduced in the mutants) were causally and functionally related to the extracellular, fibrillar, glucan component, whereas in vitro glucan-mediated agglutination may be related to the cell-associated surface fuzzy coat.

Two carbamylating agents, carbamyl phosphate and sodium cyanate, are currently being evaluated as therapeutic drugs for the treatment of sickle cell anemia. Since the clinical usefulness of these drugs might be limited by toxicity, a comparative in vitro study of the relative inhibition of human sickle cell and rabbit reticulocyte protein synthesis was performed. Sodium cyanate was found to inhibit human sickle cell protein synthesis at concentrations one-eighth that of carbamyl phosphate. Carbamyl phosphate lowered reduced glutathione levels to a similar degree as sodium cyanate and was slightly more effective as an in vitro antisickling agent, which is evidence that carbamyl phosphate enters these cells. When rabbit reticulocyte protein synthesis was investigated, carbamyl phosphate was found to be noninhibitory at concentrations as high as 128 mol/mol of hemoglobin in the incubation medium, while cyanate was inhibitory at much lower concentrations. The effect of carbamyl phosphate on glutathione concentrations, however, was virtually identical to that of cyanate. These results show that the effect on protein synthesis does not result from the lowered glutathione levels. It is concluded that both the therapeutic and toxic effects of sodium cre, there might be differences in toxicity between animals and humans.

The virulence of cell surface-associated, glucan synthesis-defective mutants of Streptococcus mutansstrain 6715-13 was studied. Representatives from three groups of such mutants were tested for their pathogenicity in conventionalized, specific pathogen-free rats and gnotobiotic rats. The mutants differ from the wild-type strain in that each failed to form plaque on the smooth surfaces of the teeth and to cause smooth surface caries. Although the ability to form cell surface-associated glucans was not a strict requirement for the expression of virulence in the sulci of the teeth, it augmented virulence at such sites. However, the ability to form cell surface-associated glucans and to adhere to the teeth was clearly not the sole determinant of virulence.

The traits adhesion and cohesion are manifested in Streptococcus mutansby in vitro plaque formation and glucan-mediated agglutination and have been dissociated in mutants of this caries-associated microbe. In these mutants, which differ from each other in colonial morphology, we have observed a consistent loss of ability to form adhesive microbial deposits (plaque) on wires, but only a minimal alteration from the wild type in ability to agglutinate into macroscopic clumps in the presence of exogenous glucans or sucrose. Also, when these mutants were cultured in sucrose-containing medium, there was an increase in the synthesis of water-soluble, extracellular glucans and a decrease in the synthesis of alkali-soluble, cell-associated glucans. Based on these findings, it appears (i) that in vitro plaque formation and agglutination are distinct and dissociable traits, and (ii) that adhesion but not agglutination appears related to the synthesis of alkali-soluble, cell-associated glucans.

Recent attempts to build machines that, by means of optical pattern recognition techniques, can automatically identify visual patterns and extract information from them have met with some success. Automated inspection and photogrammetric equipment, for example, have been in production for several years and robots have been constructed that successfully negotiate simple obstacle courses. But the most progress is evident in commercial machines that have the limited capability of “reading” printed matter and converting it into machine-usable form. Such devices are called optical character readers and the task they perform is referred to as optical character recognition (OCR).

Escherichia coliB/r and Bs-1ceased division and increased in mean cell volume soon after infection with T-even phage. The effect was obtained with wild-type or rapid lysis mutants, as well as with ultraviolet light-killed phage and with bacteriophage ghosts which lack deoxyribonucleic acid. The cell response did not require the presence of phage genetic material or the production of progeny phage. A Poisson distribution of the fraction of adsorbed phage at different multiplicites of infection indicates that one phage per bacterium will produce maximum increase in cell volume. T-even phage-resistant E. colimutants showed no enlargement response, and phage T1, T3, and T7 elicited neither abrupt termination of cell division nor host cell enlargement. Infection with baseplate-defective T4D 12-amber mutants, which bind reversibly to but do not penetrate the bacterium, also had no effect. In vitro restoration of normal baseplate function in these defective viruses allowed phage adsorption and penetration and caused host cell division arrest and enlargement. These findings indicate that arrest of division and increase in mean cell volume occur together when a sensitive strain of E. coliis infected with T-even phage that adsorb and penetrate normally.

Division of Escherichia coliwas stopped and mean cellular volume was increased after infection with T-even phage. This host cell enlargement was temperature-dependent, cyanide-sensitive, and stable in the presence of hypertonic medium. Enlargement ceased at about the same time that energy metabolism ceased. Initially, enlargement was accompanied by a decrease in mean cell density. Tritiated 2, 6-diaminopimelic acid was accumulated and incorporated into cold acid-insoluble material at the preinfection rate. These findings suggest that the effect on host cell size is only in part an osmotic phenomenon and that it also reflects continued growth of the surface of the infected cell in the absence of cell division.

Zu protein, a γ3-heavy chain disease protein isolated from the urine of a patient with γ-heavy chain disease and amyloidosis, was digested with pepsin in pH 3.5 buffer at 37d`C. The precipitate which formed was Congo red positive and exhibited green birefringence in polarized light. Electron microscopy, by negative staining, revealed fibrils with dimensions 70-80 Å x 850 - 1950 Å. These findings were consistent with those obtained from amyloid fibrils derived from pepsin digestion of certain Bence Jones proteins. The X-ray diffraction pattern of the dried precipitate yielded two rings. The outer ring corresponded to a spacing of approximately 4.7 Å, and the inner ring corresponded to a spacing of approximately 10.6 Å. These dimensions are consistent with β-pleated sheet structure. The mildly reduced and alkylated Zu precipitate demonstrated an approximate molecular weight of 8000 daltons on SDS polyacrylamide gel electrophoresis. Automatic amino-terminal sequence analyses of the mildly reduced and alkylated Zu precipitate suggested that the polypeptide chain was blocked. It seems reasonable to assume that Zu γ3-heavy chain disease protein was related to the widespread amyloidosis found in this patient.

The changes in the macromolecular composition of Micrococcus radiodurans with increasing medium-determined growth-rate are similar to such alterations in more radiosensitive bacterial strains. As the growth-rate and quantity of cellular macromolecules increase, the x-radiation sensitivity tends to increase when measured by the D0 or the LD90 exposure. The amounts of endogenous, possibly radioprotective sulphydryls do not account for the increased radiosensitivity. It is also found that the assay of cells on minimal agar generally improves the survival after irradiation. These findings in M. radiodurans suggest that damage to DNA and to the division mechanisms of the cells may account for the heightened radiosensitivity found in conditions of rapid growth.

The average amount of deoxyribonucleic acid (DNA) per cell was measured in steady-state cultures of Escherichia coliB/r grown at 37 C in glucose-limited chemostats or in batch cultures in the exponential growth phase as maintained with one of several carbon sources. Within experimental errors, DNA content was dependent only on growth rate and independent of the type of culture, the carbon source, or the addition of growth factors. The amount of DNA per cell increased continuously with growth rate over the range of 0.02 to 3 divisions per hour. The data over the entire range of growth rates are in agreement with a constant time for a single replication point to traverse the entire genome, 47 min, and with cell division following 25 min after termination of replication. The measured amount of DNA per genome was 4.2 × 10−15g (or 2.5 × 109daltons).