Oral ecology and virulence of Lactobacillus casei and Streptococcus mutans in gnotobiotic rats

Lactobacilli comprise a small percentage of the normal oral microbial flora of humans and are isolated commonly from saliva and frequently from an active caries lesion. We have compared the pathogenesis and colonization pattern of Lactobacillus casei with that of Streptococcus mutans strain 6715 in gnotobiotic rats. Of the two L. casei strains tested, L. casei strain ATCC 4646 caused slightly more caries than L. casei strain ATCC 11578. However, the level of caries induced by either L. casei strain was significantly lower (P less than 0.01) than that observed in similar-aged rats monoassociated with S. mutans strain 6715. When groups of rats were infected with mixtures of L. casei strain ATCC 4646 and S. mutans strain 6715, or with L. casei followed by S. mutans, higher numbers of L. casei than S. mutans were found associated with the tongue and in saliva; S. mutans always predominated in plaque. The level of caries observed in these groups of rats was similar to that seen with rats monoassociated with S. mutans except when L. casei comprised greater than 1% of the plaque microflora. In this latter situation, the level of caries was significantly lower (P less than or equal to 0.05) than that obtained in S. mutans-monoassociated rats. The results of this study suggest that L. casei colonizes sites in the oral cavity (including the tongue and saliva) other than the tooth surface in rats. The effect of L. casei in plaque toward reduction of S. mutans-induced dental caries in rats is discussed.

Cryoprotected Lactobacillus casei: an approach to standardization of microbiological assay of folic acid in serum

Folate-depleted, cryoprotected preparations of Lactobacillus casei are stable for at least eight months at -18 degrees C, capable of reproducible growth and suitable as a ready source of inoculum for measurement of folates in physiological fluids. Cryoprotected microorganisms can be a commercially available laboratory reagent, thus simplifying and further standardizing the microbiological assay of various nutriments. Standard folate growth curves of cryoprotected L. casei, prepared at intervals over eight months, are superimposable, have a low blank, and should eliminate the variations encountered with the continuous passages of microorganisms required for the classic microbiological assays. Serum folate values obtained by use of the cryoprotected L. casei fall into the same diagnostic groups as determined by the classic microbiological assay.

Folate analogues altered in the C9-N10 bridge region. 16. Synthesis and antifolate activity of 11-thiohomoaminopterin

The synthesis of 11-thiohomoaminopterin (1), which is a close analogue of 11-thiohomofolic acid (2), has been carried out by modification of the Boon-Leigh procedure. Treatment of 1-chloro-4-[p-(carbomethoxy)thiopenoxy]-2-butanone (5) with sodium azide gave 1-azido-4-[p-(carbomethoxy)thiophenoxy]-2-butanone (6). After protection of the carbonyl group of 6, the product 7 was catalytically hydrogenated to 1-amino-4-[p-(carbomethoxy)thiophenoxy]-2-butanone ketal (3). Reaction of 32 with 6-chloro-2,4-diaminmo-5-nitropyrimidine gave the desired pyrimidine intermediate, which was elaborated to 4-amino-4-deoxy-11-thiohomopteroic acid (20) by standard procedures. Alternately, 1-azido-4-[p-(carbomethoxy)thiophenoxy]-2-butanone ketal (7) was hydrolyzed to the corresponding acid (8) and coupled with diethyl L-glutamate to obtain diethyl N-[p-(1-azido-2-oxo-4-thiobutanoyl)benzoyl]-L-glutamate ketal (10), which was used for the large-scale preparation of 11-thiohomoaminopterin (1). Although 11-thiohomoaminopterin showed antifolate activity against two folate-requiring microorganisms and inhibited Lactobacillus casei dihydrogolate reductase, it did not exhibit any antitumor activity against L-1210 lymphoid leukemia in mice at a maximum dose of 48 mg/kg.

In vitro studies on distribution of indigenous lactobacilli of the gastrointestinal tract of rats

To learn the biochemical mechanisms controlling the distribution of indigenous lactobacilli in the gastrointestinal tracts of rats, the effect of pH and stomach and cecal contents on lactobacillus distribution was investigated in vitro with a mixed culture of three lactobacillus strains isolated from the rat intestine. The pH of the growth medium affected the growth of lactobacilli strongly, irrespective of the lumenal contents. Lactobacillus fermentum outnumbered L. acidophilus and L. murini at low pH (PH 4.5; average pH of stomach contents of conventional rats) but at near neutral pH (pH 6.5; average pH of cecal contents of conventional rats), the growth of L. murini was predominant with all strains. More lactic acid was formed by lactobacilli in medium consisting of stomach contents than in cecal contents medium. L. murini grew in the nondialyzable fraction of the stomach contents and L. fermentum grew in the dialyzable fraction, but L. acidophilus did not grow in either fraction. L. murini grew in the nondialyzable fraction treated with hyaluronidase. In contrast, the nondialyzable fraction treated with pronase or chondroitinase did not allow L. murini to grow at all.

N-Benzoyl derivatives of amino acids and amino acid analogs as growth inhibitors in microbial antitumor screen

Twenty-seven N-benzoyl derivatives of amino acids and amino acid analogs were prepared and tested for growth-inhibitory activity in a microbial antitumor screen. Of these, 19 showed some inhibitory capacity, from a modest 13% to a potent 96% at 1 mg/ml. The activities of the "modest" inhibitors were comparable to those of most inhibitory chloracetyl and trifluoroacetyl derivatives reported earlier. The intermediate inhibitors were as active as N-chloroacetyl-beta-hydroxy-D-norleucine isomer B, the most active acyl derivative noted previously. The most active compounds in this study were N-benzoyl-p-chloro-DL-phenylalanine and N-benzoyl-m-fluoro-DL-phenylalanine, which inhibited the test organism almost completely under the assay conditions.

Folate analogues altered in the C9-N10 bridge region: 11-thiohomofolic acid

The synthesis of 11-thiohomofolic acid (2) has been accomplished by an unambiguous procedure. Reaction of 1-chloro-4-[p-(carbomethoxy)thiophenoxy]-2-butanone (10) with hydroxylamine under carefully controlled conditions gave the corresponding oxime 33. Conversion of this oxime to 1-phthalimido-4-[p-(carbomethoxy)thiophenoxy]-2-butanone oxime (4) was carried out by its reaction with potassium phthalimide using crown 18 ether as a catalyst. Hydrazinolysis of compound 4 gave 1-amino-4-[p-(carbomethoxy)thiophenoxy]-2-butanone oxime (5), which was used for the construction of the title compound 2 by modification of the Boon and Leigh procedure. An alternate synthesis utilizing 1-hydroxy-4-[p-(carbomethoxy)thiophenoxy]-2-butanone (11) and 4-hydroxy-2,5,6-triaminopyrimidine has also been carried out. Compound 2 did not exhibit any antifolate activity against Lactobacillus casei or Streptococcus faecium. The dithionite reduction product, 7,8-dihydro-11-thiohomofolic acid, was able to function as a substrate of L. casei dihydrofolate reductase. The catalytic reduction product of 2, consisting of a mixture of diastereomers, exhibited powerful antifolate activity against both these organisms.

Methotrexate analogues. 12. Synthesis and biological properties of some aza homologues

Methotrexate analogues, in which an additional nitrogen atom is inserted between the phenyl ring and the carbonyl group of the side chain, were prepared by photochemical methods. The compounds were less inhibitory toward dihydrofolate reductase and thymidylate synthetase derived from Lactobacillus casei than was methotrexate. They were also less cytotoxic against human lymphoblastic leukemia cells (CCRF-CEM). In vivo against L-1210 leukemia in mice, the aza homologue of methotrexate showed significant antitumor activity (%ILS = 55%) compared to methotrexate (%ILS = 88%).

Synthesis of aza homologues of folic acid

Folic acid analogues containing an additional nitrogen atom between the phenyl ring and the carbonyl group of the side chain were synthesized. None of the compounds showed significant inhibitory activity against human lymphoblastic leukemia cells (CCRF-CEM) in culture or against Lactobacillus casei (ATCC 7469) growth. Against L1210 leukemia in mice, the aza homologue of folic acid, 4, and the aspartic acid analogue, 14, showed no increase in life span over control animals. These compounds were more toxic in vivo than the corresponding methotrexate analogues. Compound 4 supported the growth of Streptococcus faecium (ATCC 8043), and its tetrahydro derivative supported the growth of Pediococcus cerevisiae (ATCC 8081). These results strongly suggest that 4 can substitute for folate derivatives as cofactors for serine transhydroxymethylase, thymidylate synthetase, and dihydrofolate reductase.

Effect of N-trifluoroacetyl derivatives of amino acids and amino acid analogs on microbial antitumor screen

Eighteen trifluoroacetyl derivatives of amino acids and of amino acid analogs were prepared and tested for growth-inhibitory activity using a Lactobacillus casei system as a prescreen for antitumor activity. Of the compounds tested, the trifluoroacetyl derivatives of o-, m-, and p-fluorophenylalanine and of beta-3-thienylalanine showed modest activity; trifluoroacetyl derivatives of phenylalanine and of beta-2-thienylalanine showed marginal activity. The activity exhibited by the active trifluoroacetyl compounds was equal to that noted for most active chloroacetyl derivatives reported previously, as judged by comparison of their activity with that of chloroacetyl-m-fluorophenylalanine. No reversal of inhibition was noted when a representative of these inhibitors was challenged with a corresponding natural metabolite, both as a free amino acid and as a noninhibitory acylated compound.

Adenosine triphosphate content in Lactobacillus casei and the blender-resistant phage-cell complex-forming ability of cells on infection with PL-1 phage

The intracellular ATP content of Lactobacillus casei ATCC 27092 grown in a glucose-containing medium was almost constant (2 to 3 microgram/mg dry wt. cells) through the early to middle stage of logarithmic phase, but it was lowered to less than 0.1 microgram/mg after cessation of growth owing to the exhaustion of available glucose. All the cells in the early stage of stationary phase were still viable and thus considered to be in a starved state. When such starved cells were infected with PL-1 phages in a tris-maleate buffer of pH 6.0, the process of forming blender-resistant phage-cell complexes signifying the complete injection of phage genomes into the cells was much inhibited. There was a good correlation between the ATP content of cells and the extent of the formation of blender-resistant phage-cell complexes and the correlation coefficient between them was 0.89 + 0.09 at the 95% confidence limit. On the other hand, the process of forming both the phage-adsorbed cells and the anti-phage serum-resistant phage-cell complexes were not affected by the ATP content of cells. Feeding of glucose to such starved cell cultures caused the cells to restore both the ATP content and the ability to form blender-resistant phage-cell complexes. Such restoration was also observed when the starved cells collected by centrifugation were incubated in a glucose-containing medium. The significance of the intracellular level of high energy compounds such as ATP for the mechanism of the injection of phage genomes into the cells is discussed.

[Use of labeling with 3H6-thymidine in the study of the multiplication of lactobacillus casei immobilized in a polyacrylamide gel]

When 3H6-thymidine labelled bacteria (1.2 desintegration per cell/day) are immobilized in a polyacrylamide gel lattice, the decimal reduction time for their malic acid decarboxylase activity is extended to 38 days. Thus, the growth of bacteria in the gel lattice is very poor. The author has evaluated both the DNA turnover rate during the exponential growth phase for the free cells and the DNA specific activity of the population of immobilized cells. The viability of bacteria isolated from the gel lattice decreases with time, as does their thermal stability for malic acid decarboxylase activity. This activity is partially restored after 65 days. With respect to the protein, deoxyribose and ribose cell constituents, the protein/deoxyribose, protein/ribose and deoxyribose/ribose ratios fluctuats considerably with time. These fluctuations are more marked than those observed for the free cells during their different growth phases.

[Study on L-malic acid catabolism by "Lactobacillus casei" cells immobilized into polyacrylamide gel lattice (author's transl)]

Study on L-malic acid catabolism by Lactobacillus casei cells immobilized into polyacrylamide gel lattice has shown that the pH profil of malic acid decarboxylase activity does not differ significantly from that of free cells. The apparent enzymatic constant value as determined by the Warburg manometric method is 5 X 10(-3) M for free cells and 1.25 X 10(-2) M for immobilized cells. Malic acid decarboxylase activity can be preserved in immobilized cells over a 12 month period when the reaction vessel is fed continuously with the growth medium. It is noteworthy that the reaction vessel is similar to a constant activity reactor whose apparent enzymatic constant value, of 6,25 X 10(-3) M, does not differ significantly from that of free cells. Labelling of the cells with 14C-glycin has shown that the immobilized cells released 14 per cent of the radioactivity over a 65 hour period, indicating that the cells are possibly in a non proliferating state. After 9 months of working, a large fraction of viable bacterial cells can be isolated again. The use of such a reactor for producing metabolites is proposed.

[Elimination from the digestive tract of a "gnotoxenic" child of a "Lactobacillus casei" strain, isolated from a commercial preparation: antagonistic effect of an "Escherichia coli" strain of human origin, demonstrated in "gnotoxenic" mice (author's transl)]

A strain of Lactobacillus casei from a pharmaceutical preparation became established in the digestive tract of an axenic child. It was eliminated by the first bacteria occurring after inoculation of the child's digestive tract with a human flora, before the child was taken out of the isolator. Using "gnotoxenic" mice, we found that the elimination of L. casei was due to a bactericidal effect of the Escherichia coli of human origin, within the digestive tract.

Determination of erythrocyte vitamin B12 activity

Data presented in this paper show that there is no significant difference between plasma and serum vitam B12 activity when EDTA is used as the anticoagulant. By drawing 5 ml of blood into a tube containing EDTA, the whole blood and plasma B12 activity can be measured using Lactobacillus leichmannii for the assay as the test organism. Erythrocyte B12 levels can be obtained by difference after correcting for hematocrit. Sodium heparin appears to inhibit the growth of L. leichmannii.

The effect of medium redox potential on the folate-limited growth of Lactobacillus casei var. rhamnosus

The medium redox potential (Eh) influenced the folate-limited growth of Lactobacillus casei; the growth response was maximal at an Eh of +120 mV (pH 6-35). At raised Eh serum folate would support less growth than pteroylglutamic acid, and the response to N5-methyl tetrahydrofolic acid was intermediate between them. Pteroylglutamic acid was not destroyed during 24 h incubation at 37 degrees C in medium with Eh values between +40 and +440 mV. Destruction of N5-methyl tetrahydrofolic acid occurred within 24 h when the medium Eh was greater than +125 mV. Folate was taken up rapidly by L. casei with an Eh optimum at +270 mV.

Experimental production of elevated serum folate in dogs with intestinal blind loops. II. Nature of bacterially produced folate coenzymes in blind loop fluid

Jejunal and ileal blind loops were constructed in separate groups of dogs and the folate coenzymes present in these loops were investigated. Although only those dogs with high blind loops had appreciably elevated folate levels active for Lactobacillus casei but not Streptococcus faecalis, every blind loop appeared to contain four folate compounds--5-formyltetrahydrofolic acid, 5-methyltetrahydrofolic acid, tetrahydrofolic acid and a compound tentatively identified as 5-formyltetrahydrofolic triglutamate. Why increased levels of 5-methyltetrahydrofolate alone are present in the serum of dogs with a high blind loop is discussed.

In vitro determination of the antimicrobial properties of two cyanoacrylate preparations

Isobutyl and trifluoro cyanoacrylates showed varying degrees of inhibition for Lactobacillus casei and Staphylococcus aureus when tested by the spread plate technique. Candida albicans and Pseudomonas aeruginosa were resistant. The results tend to support the view that inhibition of growth was due to the vapor effect and not the diffusibility of the cyanoacrylates.

Genetic basis of nutritional requirements in Lactobacillus casei

In a study of the genetic basis of multiple nutritional requirements in Lactobacillus casei, systematic attempts were made to isolate mutants that can grow in the absence of a specific nutrient required by the parental organism. Such mutants have successfully been isolated with respect to seven of twelve amino acids (aspartic acid, leucine, isoleucine, lysine, methionine, serine, and threonine) and three of four vitamins (pantothenic acid, nicotinic acid, and pyridoxal) tested, after extensive screenings employing various mutagens. Mutants that can grow without tryptophan were not isolated, but those that can grow on anthranilate or indole as well as on tryptophan were obtained at a frequency expected for single-step mutations. Activity of tryptophan synthetase was demonstrated in extracts of these anthranilate-utilizing mutants, but not in the parental strain. These results suggest that the multiple nutritional requirements of L. casei are often, if not always, due to one or a few small lesions such as base substitution mutations rather than large deletions affecting the genes involved in each biosynthetic pathway. The data would also imply that many of the biosynthetic pathways that are not fully functional in L. casei were active at one time and became nonfunctional during evolution of the present species.

Stimulation of lactic acid bacteria by a micrococcus isolate: evidence for multiple effects

Growth of, and rate of acid production by, six cultures of lactic acid bacteria were increased in the presence of Micrococcus isolate F4 or a preparation of its capsular material. Concentrations of hydrogen peroxide found in pure cultures of the lactic acid bacteria were not detectable, or were greatly reduced, in mixed culture with Micrococcus isolate F4. The capsular material was not as effective as whole cells in preventing accumulation of H(2)O(2). Catalase stimulated growth of, and the rate of acid production by, the lactic acid bacteria, but not to the same extent as Micrococcus isolate F4 in some cultures. The existence of two mechanisms for micrococcal stimulation of the lactic acid bacteria is postulated. One mechanism involves removal of H(2)O(2); the other has not been characterized.