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The traits adhesion and cohesion are manifested in Streptococcus mutans by 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.

The virulence of cell surface-associated, glucan synthesis-defective mutants of Streptococcus mutans strain 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.

An electron microscopic study of S. mutans 6715-13 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.

Escherichia coli B/r and B(s-1) ceased 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. coli mutants 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. coli is infected with T-even phage that adsorb and penetrate normally.

Division of Escherichia coli was 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.

The average amount of deoxyribonucleic acid (DNA) per cell was measured in steady-state cultures of Escherichia coli B/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 x 10(-15) g (or 2.5 x 10(9) daltons).

Cessation of exponential growth of Micrococcus radiodurans heightens X-radioresistance while either increasing or decreasing the deoxyribonucleic acid-protein ratio.

A form of endemic syphilis exists in the Bakwena Reserve of the Bechuanaland Protectorate known by the local name of "dichuchwa". It is similar to bejel, njovera and the endemic syphilis reported elsewhere in the world. The Government of the Protectorate, with the assistance of WHO and UNICEF, began in November 1953 a mass campaign in the Reserve to control this disease and, at the same time, to study its epidemiological, clinical, social and therapeutic aspects. The seropositivity rate in the Reserve was found to be 37%.Dichuchwa is a childhood and family disease, usually spread non-venereally. The early lesions are similar to secondary lesions of sporadic venereal syphilis, and are often followed by tertiary lesions affecting mainly the skin, nasopharynx and long bones. Primary lesions are rare but may occur under certain epidemiological conditions if the inoculum is sufficiently large; thus a mother may develop primary sores on the nipples through suckling an infected infant. Lesions of the cardiovascular and central nervous systems and congenital syphilis are also rare. Superinfection of an already infected and allergic host is probably the chief reason for the frequency of the tertiary lesions.Treatment of the disease with penicillin is very effective, and the authors believe that mass treatment of cases and contacts combined with an improvement in the standards of hygiene could eradicate the disease.

Criteria are presented for distinguishing between synchronous and synchronized cultures (natural vs. forced synchrony) on the basis of characteristics of growth and division during a single generation. These criteria were applied in an examination of the uptake of potassium during the cell growth and division cycle in synchronous cultures and in a synchronized culture of Escherichia coli. In the synchronous cultures the uptake of (42)K doubled synchronously with cell number, corresponding to a constant rate of uptake per cell throughout the cell cycle. In the synchronized culture, uptake rates also remained constant during most of the cycle, but rates doubled abruptly well within the cycle. This constancy of (42)K uptake per cell supports an earlier interpretation for steady-state cultures that uptake is limited in each cell by a constant number of functional sites for binding, transport, or accumulation of compounds from the growth medium, and that the average number of such sites doubles late in each cell cycle. The abrupt doubling of the rate of uptake of potassium per cell in the synchronized culture appears because of partial uncoupling of cell division from activation or synthesis of these uptake sites.

When rabbit reticulocytes are incubated with n-butanol, an agent disruptive to the structure and function of cellular membranes, there is a rapid disaggregation of the polyribosomes. Reaggregation is promoted when the n-butanol is diluted below a critical concentration or when the cells are washed free of the alcohol and the incubation is continued. Neither disaggregation nor regeneration will occur in the absence of protein synthesis. These observations suggest that integrity of the reticulocyte membrane is necessary for the attachment of ribosomes to messenger RNA and for the formation of polyribosomes.

Short-term labeling with radioactive thymidine led to inaccurate estimates of deoxyribonucleic acid synthesis at some growth rates in steady-state cultures of Escherichia coli B/r. Estimates were corrected in chemostat cultures by adding adenosine, a known inhibitor of thymidine phosphorylase.