Jan Carlsson

Lactobacilli and streptococci in the mouth of children.

The oral establishment of various species of streptococci and lactobacilli has been studied on 25 infants during a period of 5 years. When the children were 3, 4 and 5 years old, their caries and gingival status were recorded. Streptococcus salivarius becomes established within a day of birth, and Streptococcus sanguis after the eruption of the teeth during the first year. Streptococcus mutans was recovered from the infants significantly later and had only become established in half the number of the infants when they had reached 5 years. Lactobacilli were only recovered in low numbers and below 2 years of age they seemed to be mostly transients in the mouth of the infants. The lactobacillus flora which was then isolated, was dominated by Lactobacillus casei and the composition of the flora was significantly different from that which has previously been described for adults.

Fermentation products and bacterial yields in glucose-limited and nitrogen-limited cultures of streptococci

Abstract Streptococcus sanguis, Strep. mutans, Strep. salivarius and Strep. bovis were grown anaerobically in continuous culture at pH 7.0 under conditions of glucose-limitation and nitrogen-limitation in complex and in chemically defined media. Fermentation products in the cultures were analysed and the yield of bacterial mass determined. All streptococci formed lactate as the main fermentation product when grown in a medium containing a surplus of glucose with the nitrogen source limiting growth. When grown in a glucose limiting medium, the main fermentation products formed by Strep. sanguis and Strep. mutans were ethanol, acetate and formate. Whereas Strep. salivarius and Strep. bovis formed some ethanol, acetate and formate, but mainly lactate. There was a significantly higher yield of bacterial mass under conditions of glucose-limitation than under conditions of nitrogen-limitation.

Oxygen tolerance of anaerobic bacteria isolated from necrotic dental pulps.

The oxygen tolerance of 43 anaerobic reference strains and 36 anaerobic strains from necrotic dental pulps was studied. All strains survived for two hours or more as colonies on the surface of a medium supplemented with blood, and as many as 26 of the 79 strains survived for more than seven days. The hemolysed blood in the medium significantly increased the survival time for many of the strains. Factors influencing the death rate were studied in one of the strains and it was found that the lysed red cells of the blood and not the serum had a protective effect and that catalase had the same protective effect as the hemolysed blood. The finding that hemolysed blood significantly increased the oxygen tolerance of many anaerobes may explain some of the divergent results regarding the efficiency of various methods for the recovery of anaerobic bacteria from clinical specimens. The use of media supplemented with blood during various phases of processing a specimen might be more important for a high recovery of anaerobic bacteria from clinical sources than the measures taken to minimize exposure of the specimen to air.

Nutritional requirements of Streptococcus sanguis

Abstract The nutritional requirements of Streptococcus sanguis ATCC strains 10556, 10557 and 10558, Strep. mitis ATCC 9811, Strep. bovis ATCC 9809 and 37 strains isolated from the oral cavity in man and considered to be Strep. sanguis were studied under anaerobic conditions. Streptococcus sanguis ATCC 10558 and 23 of the oral strains required cysteine, glucose, pyridoxine, nicotinic acid, biotin, thiamin, riboflavin, pantothenic acid, ammonia and salts. One oral strain required in addition glutamic acid and Strep. sanguis ATCC 10556 isoleucine and valine. Strep. sanguis ATCC 10557 and 14 of the oral strains required arginine, cysteine, glutamic acid, histidine, glucose, nicotinic acid, biotin, thiamin, riboflavin, pantothenic acid, ammonia and salts. Strep. mitis ATCC 9811 had the same nutritional requirements. One oral strain required adenine in addition. Strep. bovis ATCC 9809 required cysteine, glucose, biotin, thiamin, ammonia and salts.

Oxygen and the Metabolism of Peptostreptococcus anaerobius VPI4330-1

Peptostreptococcus anaerobius VPI4330-1 is an anaerobic organism which has no superoxide dismutase, catalase or peroxidase. It can be protected from the toxic effects of oxygen by catalase in the culture medium. In order to elucidate its mechanisms of oxygen tolerance, the effect of oxygen on the metabolic activity of the organism was studied. In salt solution supplemented with glucose or pyruvate the organism had a more rapid metabolic rate under aerobic conditions than under anaerobic conditions. There were also significant differences in metabolic end-products obtained under aerobic and anaerobic conditions. The crude cell-free extract had NADH oxidase activity, which reduced oxygen to water, and NADPH oxidase activity, which reduced oxygen to superoxide radicals and hydrogen peroxide. The former specific activity was much higher than the latter. The results indicate that the main product of intracellular oxygen reactions was water. Deleterious products such as superoxide radicals and hydrogen peroxide were only formed to a limited extent. NADH oxidase may fulfil an important protective role in this organism.

Catalase inhibitiob by sulfide and hydrogen peroxide-induced mutagenicity in Salmonella typhimurium strain TA102

The lethal and mutagenic effects of hydrogen peroxide were studied in exponentially growing cultures of Salmonella typhimurium strain TA102. Exposure of the cultures to non-lethal levels of sodium sulfide significantly increased the lethality and mutagenicity of hydrogen peroxide. The catalase activity was decreased in cells exposed to sodium sulfide, but there were no changes in the cellular levels of superoxide dismutase, glutathione reductase, or NADPH-dependent alkyl hydroperoxide reductase. Hydrogen peroxide-induced mutagenesis and killing of S. typhimurium strain TA102 in the presence of sulfide may in part be explained by an inactivation of catalase by sulfide.

Phosphoenolpyruvate carboxylase and ammonium metabolism in oral streptococci.

Abstract Oral streptococci were grown in media which provide various nitrogen sources. Ammonium fixation was studied in cell-free extracts of the cells. Carbon dioxide fixation was studied in washed intact cells and in crude and partially purified extracts of the cells. High activity of NADP-linked glutamate dehydrogenase was found in Streptococcus sanguis and Strep. mutans. Low activity of a NAD-linked alanine dehydrogenase was found in Strep. sanguis. A phosphoenolpyruvate carboxylase was present in these streptococci. One strain did not have this carboxylase and could not grow, unless glutamate was supplemented, in a medium with glucose as the sole carbon source and with ammonium as the major nitrogen source. The streptococcal phosphoenolpyruvate carboxylase was inhibited by l -aspartate and citrate, was not affected by acetyl-CoA and was stimulated by fumarate. In the presence of 3.3 mM fumarate, enzyme activity was increased about eight times.

Relative role of chloramines, hypochlorous acid, and proteases in the activation of human polymorphonuclear leukocyte collagenase.

The activation of collagenase released by polymorphonuclear leukocytes (PMNs) has been extensively studied in vitro, but the activation of the enzyme in vivo is not fully understood. For further evaluation of the relative role of oxidative and proteolytic mechanisms in the activation of collagenase, PMNs were stimulated by serum‐opsonized zymosan under both aerobic and anaerobic conditions. The results showed that similar amounts of collagenase were released by the PMNs under aerobic and anaerobic conditions, but the activity of the released collagenase was twice as high under aerobic conditions as under anaerobic conditions. Under aerobic conditions the enzyme was rapidly activated by hypochlorous acid and chloramines, which are products of the myeloperoxidase‐H2O2‐chloride system of the PMNs. There was also a slow proteolytic activation of the enzyme, which could be ascribed to cathepsin G and possibly to some other serine proteases of PMNs. When extrapolating these findings to in vivo conditions, it seems probable that the oxidative activation of collagenase will proceed mainly by chloramines, which are more long‐lived in the tissue than hypochlorous acid. In poorly oxygenated tissues, collagenase may be mainly activated by proteolytic mechanisms. J. Leukoc. Biol. 60: 598–602; 1996.

Effect of hydrogen sulfide on the mutagenicity of hydrogen peroxide in Salmonella typhimurium strain TA102

Effect of hydrogen sulfide on the mutagenicity of hydrogen peroxide in Salmonella typhimurium strain TA102

Growth of Streptococcus mutans and Streptococcus sanguis in mixed culture

In an anaerobic atmosphere, Streptococcus mutans strain JC 2 and Streptococcus sanguis strain 804 required ammonia, cysteine, B-vitamins, glucose and salts for growth. The only difference in nutritional requirements between the two strains was a requirement for p-aminobenzoic acid by Strep. mutans, but not by Strep. sanguis. In a mixed culture of Strep. sanguis and Strep. mutans in a p-aminobenzoic acid-free medium, Strep. sanguis supported the growth of Strep. mutans to such an extent that the interaction of the organism would be characterized as a parasitism of Strep. mutans on Strep. sanguis. p-Aminobenzoic acid may be one of the substances determining the establishment and population density of Strep. mutans in the microbial aggregations on the tooth surface.