Studies on Streptococci

The population levels of bacteria in the contents and the walls of the gastrointestinal tract of gnotobiotic rats inoculated with lactic acid bacteria (streptococci, lactobacilli, and bifidobacteria) from humans and rats were determined. Lactobacilli as well as streptococci isolated from rats colonized in the digestive tracts of the gnotobiotic rats at a high population level, characteristically highest in the stomach. On the other hand, in the rats inoculated with human lactic acid bacteria, streptococci were dominant in the lower tract. The human lactobacilli or bifidobacteria did not colonize when the organisms in each genus were inoculated together with streptococci. However, when all three genera were inoculated together, lactobacilli and bifidobacteria colonized. Observations on the species of streptococci showed that the intestinal type of streptococci was found to colonize at a high population level, but the oral type was not. Strains of the same genus of lactic acid bacteria from humans and from rats showed different colonization patterns.     

Studies on Streptococci: I. Distribution of Fecal Streptococci in Man

To understand the significance to the host of streptococci as part of the intestinal microflora, we first tried to investigate the distribution of human fecal streptococci on the species level. Of the selective media compared, KMN agar was more effective than the other media for the isolation of streptococci from human feces. We made an effort to improve streptococcal classification. Especially we used utilization of 1% pyruvate, 1% arginine, and 1% citrate for differentiation between Streptococcus faecalis and S. faecium. In a tellurite tolerance test, S. faecalis was distinguished more clearly from S. faecium in the medium containing 0.16 or 0.32% tellurite. We devised methods of presumptive identification of fecal streptococci from the results of the characteristics of 1,442 isolates. These methods enabled us to identify many strains rapidly. Different results in the distribution of species of streptococci between children and adults were observed. S. faecalis and S. faecium were isolated constantly from both groups. S. bovis and S. avium were isolated frequently from the feces of children. On the other hand, “viridans” streptococci, e.g. S. salivarius, S. mitis and S. MG-intermedius were present at a high frequency in, and no S. avium could be isolated from, the feces of adults.     

Electron Microscopic Studies on Opaque Colony Variants of Group A Streptococci

Opaque colony variants of two strains of group A streptococci have been compared with blue colonies of the same strains by electron microscopy. In opaque colonies, the cocci are joined into elongated chains by exaggerated intercellular septa that often occupy the major portion of each cell's circumference. The thickness and lamination of cell walls in opaque colony variants are identical to those aspects of cell walls in blue colony forms. The similarity in cell wall architecture is found between opaque and blue forms whether or not M protein (and M associated surface fimbriae) is present. Extensive, direct contact between the nucleoid and the cytoplasmic membrane beneath intercellular septa is seen in opaque colony variants. The relationship of this marked nucleoid-cytoplasmic membrane association to the unusual chain forms in the opaque colony variants is unclear.     

On the Mechanism of Respiratory Control

Control of oxidation is the key mechanism in the regulation of energy metabolism. In glycolysis the oxidation of glyceraldehyde-3-phosphate is controlled by DPNH, which inhibits glyceraldehyde-3-phosphate dehydrogenase. In oxidative phosphorylation the inhibition of electron flow from DPNH to oxygen, called "respiratory control," is the subject of this paper. After a discussion of the physiological significance of the "tight coupling" between phosphorylation and oxidation, studies on "loosely coupled" submitochondrial particles are reported. These particles are capable of oxidative phosphorylation in the presence of a suitable phosphate acceptor system, but in contrast to controlled, intact mitochondria they oxidize DPNH in the absence of phosphate and ADP. The addition of o-phenanthroline to submitochondrial particles gives rise to an inhibition of respiration, which is partly reversed by phosphate and ADP or by dinitrophenol. The properties of this model system of respiratory control will be described.     

Intraphagocytic Degradation of Group A Streptococci: Electron Microscopic Studies

The morphological changes that occur during intraphagocytic digestion of group A streptococci were studied by electron microscopy The first evidence of degradation of the ingested organism was the appearance of reticular changes in the bacterial endoplasm. This was followed by gradual swelling and dissolution of the bacterial wall, with final degradation of all the constitutuents to electron-dense debris. Accompanying changes in the phagocytic cell were observed; they consisted of vacuole formation, fusion of lysosomes with the wall of the yacuole, release of the lysosomal contents into the vacuole, and aggregation of the lysosomal contents around the ingested organism. Changes in the morphology of the organism similar to those observed during intraphagocytic digestion were also obtained by subjecting streptococcal cells to the action of the phage-associated lysin.     

Respiratory Studies on the Giant Amoeba Pelomyxa palustris1

ABSTRACT. The large fresh-water microaerobic amoeba Pelomyxa palustris does not contain mitochondria, but three types of bacterial endosymbionts are always present. Thus, it is of interest in the discussion of the possible origin of mitochondria from primitive prokaryotes. Gas exchanges (O2 , CO2 ) and concentration of endosymbionts were determined in individual amoebae, in which the life cycle stage was noted. Grey type (stationary phase) amoebae had a lower O2 uptake and lower endosymbiont concentration than light type (growth phase) amoebae, and highest O2 uptake was found in centrifugal pieces of light type Pelomyxa, centrifuged in vivo, which contained nearly all of the endosymbionts. In light type amoebae, the respiratory activity was independent of O2 concentration between 1 and 21%, and, when compared on the basis of dry weight and protein, of the same order as that of other free-living protozoa. The R.Q. was slightly higher than 1, indicating that glycolysis does not play a significant role in energy metabolism. It is concluded that P. palustris is fully aerobic, and suggestions are presented as to the role of the endosymbionts in its respiratory metabolism.