Identification of a 100-kilodalton putative coaggregation-mediating adhesin of Streptococcus gordonii DL1 (Challis)

Streptococcus gordonii DL1 (Challis) bears coaggregation-relevant surface proteins which mediate lactose-inhibitable coaggregations with other streptococci. Six spontaneously occurring coaggregation-defective (Cog-) mutants of wild-type strain S. gordonii DL1 unable to coaggregate with wild-type streptococcal partners were characterized. Antiserum raised against wild-type cells and absorbed with Cog- cells specifically blocked lactose-inhibitable coaggregations between S. gordonii DL1 and its streptococcal partner strains; it did not block lactose-noninhibitable coaggregations with actinomyces partners. Surface proteins were released from the cells by mild sonication treatment and separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A 100-kDa surface protein from S. gordonii DL1 was identified by immunoblot analysis with the mutant-absorbed antiserum. Each of the six Cog- mutants lacked the 100-kDa protein. Several other oral viridans streptococci that exhibit intrageneric lactose-inhibitable coaggregations expressed an immunoreactive protein with about the same size as the 100-kDa putative adhesin. It is proposed that the 100-kDa protein is the adhesin which mediates coaggregation between S. gordonii DL1 and its streptococcal partners. The role of this putative adhesin in accretion of streptococci in early colonization of the tooth surface is discussed.     

Invasion of dentinal tubules by oral streptococci is associated with collagen recognition mediated by the antigen I/II family of polypeptides

Cell surface proteins SspA and SspB in Streptococcus gordonii and SpaP in Streptococcus mutans are members of the antigen I/II family of polypeptides produced by oral streptococci. These proteins are adhesins and mediate species-specific binding of cells to a variety of host and bacterial receptors. Here we show that antigen I/II polypeptides are involved in the attachment of oral streptococci to collagen and that they also determine the ability of these bacteria to invade human root dentinal tubules. Wild-type S. gordonii DL1 (Challis) cells showed heavy invasion of tubules to a depth of approximately 200 microm, whereas the abilities of cells of isogenic mutant strains OB220 (sspA) and OB219 (sspA sspB) to invade were 50 and >90% reduced, respectively. Likewise, wild-type S. mutans NG8 cells invaded dentinal tubules, whereas cells of isogenic mutant strain 834 (spaP) did not. The invasive abilities of strains OB220 and OB219 were restored by heterologous expression of S. mutans SpaP polypeptide in these strains. The extents of tubule invasion by various wild-type and mutant strains correlated with their levels of adhesion to type I collagen, a major component of dentin. Furthermore, S. gordonii DL1 cells exhibited a growth response to collagen by forming long chains. This was not shown by ssp mutants but was restored by the expression of SpaP in these cells. The production of SspA polypeptide by S. gordonii DL1, but not production of SspB polypeptide by strain OB220 (sspA), was enhanced in the presence of collagen. These results are the first to demonstrate that antigen I/II family polypeptides bind collagen and mediate a morphological growth response of streptococci to collagen. These antigen I/II polypeptide activities are critical for intratubular growth of streptococci and thus for establishment of endodontic infections.     

Inhibition of Salmonella typhimurium attachment to chicken cecal mucus by intestinal isolates of Enterobacteriaceae and lactobacilli

The ability of selected strains of Enterobacteriaceae or lactobacilli isolated from the intestines of adult chickens to inhibit in vitro attachment of Salmonella typhimurium 3333/O to cecal mucus in the presence or absence of D-mannose was determined. Attachment in the absence of mannose was reduced by prior exposure of mucus to cultures of two isolates of Enterobacteriaceae, an Escherichia coli and a Hafnia alvei strain, but not to a third isolate, an Enterobacter agglomerans strain. Attachment of S. typhimurium was not inhibited when mannose was present in the blocking or attachment step. Formation of fimbriae by the two inhibitory Enterobacteriaceae strains and the S. typhimurium strain, as indicated by titers of mannose-sensitive hemagglutination of guinea pig erythrocytes was optimal in Z biphasic medium (consisting of tryptone, yeast extract, dextrose, and NaCl) incubated anaerobically at 42 C. Fimbriae of each of three strains prepared from these cultures also inhibited attachment. These are characteristics consistent with attachment and inhibition of attachment mediated by a mannose-sensitive adhesin associated with type 1 fimbriae on bacterial cells of Enterobacteriaceae strains. Attachment in the presence of mannose was significantly reduced by prior exposure of mucus to cultures of a Lactobacillus salivarius strain and a Lactobacillus delbrueckii delbrueckii strain but not to a strain of Lactobacillus for which the species had not been determined. Washed cells or spent culture supernatant fluid from brain-heart infusion broth, Z broth, or Z biphasic cultures of the inhibitory strains of lactobacilli incubated at 37 or 42 C inhibited this form of attachment. Of 27 intestinal isolates of Enterobacteriaceae and 21 of lactobacilli, the lactobacilli strains were generally more hydrophobic than the Enterobacteriaceae as determined by adherence to hexadecane. The lactobacilli isolates did not agglutinate guinea pig erythrocytes. The data suggest more than one mechanism for mediating attachment of inhibitory bacterial strains and for subsequent attachment of S. typhimurium.     

Occurrence and distribution of sucrose-metabolizing enzymes in oral streptococci

Specific growth rates, growth yields, and the level and cellular distribution of three sucrose-metabolizing enzyme activities were determined for seven oral streptococci (Streptococcus mutans strains E49, BHT, 10449, SL-1, and LM-7, S. sanguis 10558, and S. salivarius 25975). Cultures were grown in a fermentor at pH 6 with either 20 mM glucose or 10 mM sucrose. Generation times varied between 21 and 70 min. Whereas some strains grew 10 to 50% more slowly with sucrose than with glucose, others did not. Growth was always logarithmic, and the growth yields were similar. Glcosyl transferase (EC 2.4.1.5) was largely extracellular; in sucrose cultures it was appreciably lower, but no major shift to a cell-associated form was found. In glucose cultures, the activity varied between 4 and 140 IU per 6-liter culture. The glucan formed was mostly or exclusively water insoluble. Glcosyl transferase was stimulated weakly (60% or less) by various dextrans. Fructosyl transferase (EC 2.4.1.10) was primarily extracellular (except in glucose cultures of S. salivarius) and varied between 0 and 337 IU/culture. In S. salivarius, the extracellular fructosyl transferase was induced by sucrose. In all S. Mutans cultures, the total fructosyl transferase activity was lower after growth with sucrose. All strains had extra- and intracellular invertase (EC 3.2.1.26) activity. Total levels varied between 210 and 3,500 IU/culture. Less extracellular activity was present in sucrose cultures. Only S. salivarius had appreciable activity in the cellular particulate fraction. Invertase activity was significantly higher than the combined glucosyl and fructosyl transferase activities in all cultures.     

Refractive hazards of intraoperative retinal photocoagulation

Coaggregations between bacterial species have been widely studied in vitro but not in the mouth. A new in vivo assay was used to measure the rate and composition of indigenous plaque formation onto bovine enamel chips covered with a continuous layer of bacteria. Chips were covered with Streptococcus oralis ATCC 10557, which coaggregated with many oral species, or Streptococcus gordonii S7, which did not coaggregate with these oral species, and placed in the mouth for 4 and 24 h. There were no differences in the number of most indigenous bacterial species isolated from the two streptococcal surfaces. However, the number of Actinomyces viscosus as a proportion of total Actinomyces spp. was significantly different on the two surfaces at 24 h. With the exception of Actinomyces naeslundii and A. viscosus removed from the S7 surface, all indigenous species increased significantly in number from 4 to 24 h, irrespective of the streptococcal surface. This study demonstrated that interbacterial coaggregation had only a limited effect on in vivo plaque development. Thus suggesting that environmental factors, growth or other adherence phenomena are dominant in in vivo plaque formation.     

Methodological issues in mammography double reading studies

Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus cultures were treated with ethanol and tested for viability and beta-galactosidase activity. Exposure of the biomass of test cultures to 30%-55% ethanol (vol/vol) caused a 100% loss of viability and up to 15-fold increase in measurable beta-galactosidase activity in both streptococci and lactobacilli. Ethanol-treated cell suspensions could be stored for up to 6 months without loss of enzyme activity. The nonviable permeabilized biomass of the more active S. thermophilus was used to achieve up to 80% hydrolysis of lactose in aqueous solutions and non-fat milk.     

Activity of the renin-angiotensin-aldosterone system in euglycemic type I diabetic patients on intensive insulin treatment without diabetic neuropathy

The yeast Candida albicans coaggregates with a variety of streptococcal species, an interaction that may promote oral colonization by yeast cells. C. albicans and Candida tropicalis are the yeasts most frequently isolated from the human oral cavity and our data demonstrate that both these species bind to Streptococcus gordonii NCTC 7869 while two other Candida species (Candida krusei and Candida kefyr) do not. Adherence of C. albicans was greatest when the yeast had been grown at 30 degrees C to mid-exponential growth phase. For 21 strains of C. albicans there was a positive correlation between the ability to adhere to S. gordonii and adherence to experimental salivary pellicle. Whole saliva either stimulated or slightly inhibited adherence of C. albicans to S. gordonii depending on the streptococcal growth conditions. The results suggest that the major salivary adhesins and coaggregation adhesins of C. albicans are co-expressed.     

Adherent mechanism of the mutans of Actinomyces viscosus T14V

Three mutans of Actionmyces viscous T14V lacking type1 (5951), type 2 (5519) and both types of fimbriae (147) were selected in this study. We compared the ability of their adsorption to the test-tube wall, the result of the cellular coaggregation between these mutant strains and Streptococcus sanguis 34, Streptococcus sanguis black bova, Streptococcus mutans ingbritte, Streptococcus sobrinus 6715 and analysed the chemical characterization of cell walls of the three mutans. We found that the specific fimbriae and cell hydrophobicities had great effect on the bacteria adsorption or coaggregation.     

Lactobacilli and streptococci induce interleukin-12 (IL-12), IL-18, and gamma interferon production in human peripheral blood mononuclear cells

Human peripheral blood mononuclear cells (PBMC) were stimulated with three nonpathogenic Lactobacillus strains and with one pathogenic Streptococcus pyogenes strain, and cytokine gene expression and protein production were analyzed. All bacteria strongly induced interleukin-1beta (IL-1beta), IL-6, and tumor necrosis factor alpha mRNA expression and protein production. S. pyogenes was the most potent inducer of secretion of IL-12 and gamma interferon (IFN-gamma), and two of three Lactobacillus strains induced IL-12 and IFN-gamma production. All strains induced IL-18 protein production. IL-10 and IL-4 production was induced weakly and not at all, respectively. Our data show that nonpathogenic lactobacilli and pathogenic streptococci can induce Th1 type cytokines IL-12, IL-18, and IFN-gamma in human PBMC.     

Action potential fatigue in nonmyelinated nerve fibers: garfish olfactory and rabbit vagus nerve

With the new method the fecal flora of 13 clinically healthy dogs aged 3 to 42 months was analysed qualitatively and quantitatively. It was characterized by that bacteroidaceae constituted the most prodominant flora, catenabacteria, streptococci, peptostreptococci, lactobacilli and bifidobacteria were the next most numerous, enterobacteria consisted the accompanying flora. The numbers of Clostridium perfringens were remarkably fluctuated and seem to be influenced by the composition of the food ingested by the host. The total cultivable counts averaged log 10.8 +/- 0.2/g. The composition of the Lactobacillus flora and Bifidobacterium flora in the feces of 34 dogs from 3 different age groups was analysed. In the feces of all age groups L. acidophilus, L. salivarius and L. fermenti with 9 different types were found. Within the lactobacilli L. acidophilus type VI c, L. salivarius type VI a and L. fermenti type IV b were most frequently found. L. acidophilus types VI c and XI, L. salivarius types VI a and VI b could not be placed in any established types of each species, and were described as new types. Bifidobacteria were regularly found in large numbers in the feces of dogs aged 2 to 24 months. B. adolescentis and B. pseudolongum consisted the main Bifidobacterium flora.     

Co-adhesion of oral microbial pairs under flow in the presence of saliva and lactose

Co-aggregation (interactions between two suspended micro-organisms) between oral microbial pairs has been studied extensively and is believed to be an important factor in dental plaque formation. However, co-adhesion (interactions between suspended and already-adhering micro-organisms) may well be equally important. The aim of this paper was to determine the influence of saliva and lactose on the co-adhesion of streptococci (S. oralis 34 and S. sanguis PK1889) to actinomyces (A. naeslundii T14V-J1 or 5951) adhering on glass under flow from buffer and saliva in the absence and presence of lactose. The kinetics of co-adhesion as well as co-adhesion in a stationary end-point of co-aggregating and non-co-aggregating pairs was studied in a parallel plate flow chamber by analysis of the spatial arrangement of co-adhering micro-organisms as a function of time. For co-aggregating pairs, initial deposition rates of streptococci in the immediate vicinity of adhering actinomyces (local initial deposition rates) were up to 5 to 10 times higher than the non-local initial deposition rates in buffer and in saliva, respectively. In a stationary end-point of co-adhesion, 5 to 6 times more streptococci co-adhered with the adhering actinomyces than averaged over the entire substratum surface. A non-co-aggregating pair showed only minor preferential (co-)adhesion near the adhering actinomyces. Co-adhesion in buffer was fully lost when lactose was added. However, addition of lactose to saliva did not inhibit co-adhesion, but co-adhesion became more reversible. Detachment of micro-organisms from the substratum due to the passage of an air-liquid interface, as occurs in the oral cavity during eating, drinking, and speaking, was minimal when deposition was carried out from buffer to bare glass. Major detachment of streptococci adhering to the substratum occurred when adhesion was mediated through a salivary conditioning film on the glass, while detachment of adhering actinomyces and streptococci co-adhering with them remained low. It is suggested that, in the development of dental plaque, adhering actinomyces may act as strongholds for other micro-organisms, like streptococci, to adhere.     

Characterization and frequency distribution of species of lactic acid bacteria involved in the processing of mawè, a fermented maize dough from Benin

Lactic acid bacteria involved in the natural fermentation of both home-produced and commercial mawè were investigated during a 72 h fermentation period. Lactobacillus spp. constitute the majority (94%) of the strains of the lactic acid bacteria isolated, among which 89% represent the Betabacterium group. They include L. fermentum (biotype cellobiosus) (41%), L. fermentum or L. reuteri (19%), L. brevis (26%), L. confusus (less than 2%), L. curvatus (less than 1%) and L. buchneri (less than 1%). Other isolated lactic acid bacteria were L. salivarius, Lactococcus lactis, Pediococcus pentosaceus, Pediococcus acidilactici and Leuconostoc mesenteroides. Several species were detected at the early stage of fermentation, but the final stage was dominated by L. fermentum (biotype cellobiosus) and L. fermentum or L. reuteri totalling 90% of the isolated strains. The trend was the same for both home-produced and commercial mawè. No strains of L. plantarum, generally reported as dominating lactic acid bacteria at the final stage of fermentation of most plant foods, were isolated.     

Expression of functional Porphyromonas gingivalis fimbrillin polypeptide domains on the surface of Streptococcus gordonii

Genetically engineering bacteria to express surface proteins which can antagonize the colonization of other microorganisms is a promising strategy for altering bacterial environments. The fimbriae of Porphyromonas gingivalis play an important role in the pathogenesis of periodontal diseases. A structural subunit of the P. gingivalis fimbriae, fimbrillin, has been shown to be an important virulence factor, which likely promotes adherence of the bacterium to saliva-coated oral surfaces and induces host responses. Immunization of gnotobiotic rats with synthetic peptides based on the predicted amino acid sequence of fimbrillin has also been shown to elicit a specific immune response and protection against P. gingivalis-associated periodontal destruction. In this study we engineered the human oral commensal organism Streptococcus gordonii to surface express subdomains of the fimbrillin polypeptide fused to the anchor region of streptococcal M6 protein. The resulting recombinant S. gordonii strains expressing P. gingivalis fimbrillin bound saliva-coated hydroxyapatite in a concentration-dependent manner and inhibited binding of P. gingivalis to saliva-coated hydroxyapatite. Moreover, the recombinant S. gordonii strains were capable of eliciting a P. gingivalis fimbrillin-specific immune response in rabbits. These results show that functional and immunologically reactive P. gingivalis fimbrillin polypeptides can be expressed on the surface of S. gordonii. The recombinant fimbrillin-expressing S. gordonii strains may provide an effective vaccine or a vehicle for replacement therapy against P. gingivalis. These experiments demonstrated the feasibility of expressing biologically active agents (antigens or adhesin molecules) by genetically engineered streptococci. Such genetically engineered organisms can be utilized to modulate the microenvironment of the oral cavity.     

Development of a probiotic cheddar cheese containing human-derived Lactobacillus paracasei strains

Cheddar cheese was manufactured with either Lactobacillus salivarius NFBC 310, NFBC 321, or NFBC 348 or L. paracasei NFBC 338 or NFBC 364 as the dairy starter adjunct. These five strains had previously been isolated from the human small intestine and have been characterized extensively with respect to their probiotic potential. Enumeration of these strains in mature Cheddar cheese, however, was complicated by the presence of high numbers (>10(7) CFU/g of cheese) of nonstarter lactic acid bacteria, principally composed of lactobacilli which proliferate as the cheese ripens. Attempts to differentiate the adjunct lactobacilli from the nonstarter lactobacilli based on bile tolerance and growth temperature were unsuccessful. In contrast, the randomly amplified polymorphic DNA method allowed the generation of discrete DNA fingerprints for each strain which were clearly distinguishable from those generated from the natural flora of the cheeses. Using this approach, it was found that both L. paracasei strains grew and sustained high viability in cheese during ripening, while each of the L. salivarius species declined over the ripening period. These data demonstrate that Cheddar cheese can be an effective vehicle for delivery of some probiotic organisms to the consumer.     

Acid tolerance response and survival by oral bacteria

Using 21 species of oral bacteria, representing six acidogenic genera, we undertook to determine whether the pH-limiting exponential growth is related to the ability of the organisms to generate an acid-tolerance response that results in enhanced survival at low pH. The lower pH limit of exponential growth varied by more than two units with that of Neisseria A182 at pH 6.34; growth of Lactobacillus casei RB1014 stopped at pH 3.81, with species of Actinomyces, Enterococcus, Prevotella and Streptococcus falling between these limits. The working hypothesis was that the organisms with the higher pH limits for growth are unable to respond to acidic environments in order to survive, whereas the more aciduric organisms would possess or acquire acid tolerance. Adaptation to acid tolerance was tested by determining whether the prior exposure of exponential-phase cells to a low, sub-lethal pH would trigger the induction of a mechanism that would enhance survival at a pH killing pH 7.5 control cells. The killing pH varied from pH 4.5 for Prevotella intermedia ATCC 25611 to pH 2.3 for the three Lactobacillus casei strains in the study, with the three Streptococcus mutans strains killed at pH 3.0 for 3 h. The adaptation experiments revealed three groups of organisms: non-acid-responders, generally representing strains with the highest terminal pH values; weak acid-responders in the middle of the pH list, generating low numbers of survivors at one or two pH values, and the aciduric, strong responders generating a high number of survivors at pH values in the range 6.0 to 3.5, but not at pH 7.5. Predominant among the latter group were the S. mutans and Lactobacilli casei strains, with the most significant adaptive response exhibited by S. mutans LT11 and S. mutans Ingbritt, involving a process that required protein synthesis. Time course experiments with the latter organisms indicated that 90-120 min was required after exposure to the triggering pH before the acid response was fully functional. These results indicate that the sudden exposure of strains of oral streptococci and lactobacilli, as well as Enterococcus faecalis, to pH values between 6.0 and 3.5 results in the induction of an acid tolerance response that enhances the survival of these strains at or below pH 3.5.     

Lactic acid-mediated suppression of Helicobacter pylori by the oral administration of Lactobacillus salivarius as a probiotic in a gnotobiotic murine model

OBJECTIVES: We examined whether or not the lactobacilli administered to treat Helicobacter pylori (H. pylori) infection can suppress the colonization of H. pylori, and we also sought to elucidate the mechanism of such suppression. METHODS: We used an in vitro culture system and an H. pylori-infected gnotobiotic murine model. RESULTS: Among the lactobacillus species examined in vitro, Lactobacillus salivarius (L. salivarius) but not L. casei or L. acidophilus proved to be capable of producing a high amount of lactic acid and thus completely inhibiting the growth of H. pylori in a mixed culture. The validity of L. salivarius as a probiotic to suppress H. pylori and thus reduce the inflammatory response was again confirmed in vivo by using an H. pylori-infected gnotobiotic murine model. CONCLUSION: Based on our findings, L. salivarius was found to be a potentially effective probiotic against H. pylori.     

Adherence of human vaginal lactobacilli to vaginal epithelial cells and interaction with uropathogens

Three strains of Lactobacillus, identified as Lactobacillus acidophilus, Lactobacillus gasseri, and Lactobacillus jensenii, were selected from among 70 isolates from the vaginas of healthy premenopausal women for properties relevant to mucosal colonization or antagonism. All three self-aggregated and adhered to epithelial vaginal cells, displacing well-known vaginal pathogens, such as G. vaginalis, and inhibiting the growth in vitro of Escherichia coli and Streptococcus agalactiae. The surface components involved in self-aggregation appeared to be proteins for L. gasseri and lipoproteins for L. acidophilus and L. jensenii, as judged by susceptibility to treatment with appropriate degrading enzymes. The factors responsible for adherence to epithelial vaginal cells seemed to be glycoproteins (L. acidophilus and L. gasseri) and carbohydrate (L. jensenii). The receptors of the vaginal cells were glycolipids, which presumably were the targets of the competition observed between the lactobacilli and the pathogenic microbes.     

Effects of lactobacilli on yeast-catalyzed ethanol fermentations

Normal-gravity (22 to 24 degrees Plato) wheat mashes were inoculated with five industrially important strains of lactobacilli at approximately 10(5), approximately 10(6), approximately 10(7), approximately 10(8), and approximately 10(9) CFU/ml in order to study the effects of the lactobacilli on yeast growth and ethanol productivity. Lactobacillus plantarum, Lactobacillus paracasei, Lactobacillus #3, Lactobacillus rhamnosus, and Lactobacillus fermentum were used. Controls with yeast cells but no bacterial inoculation and additional treatments with bacteria alone inoculated at approximately 10(7) CFU/ml of mash were included. Decreased ethanol yields were due to the diversion of carbohydrates for bacterial growth and the production of lactic acid. As higher numbers of the bacteria were produced (depending on the strain), 1 to 1.5% (wt/vol) lactic acid resulted in the case of homofermentative organisms. L. fermentum, a heterofermentative organism, produced only 0.5% (wt/vol) lactic acid. When L. plantarum, L. rhamnosus, and L. fermentum were inoculated at approximately 10(6) CFU/ml, an approximately 2% decrease in the final ethanol concentration was observed. Smaller initial numbers (only 10(5) CFU/ml) of L. paracasei or Lactobacillus #3 were sufficient to cause more than 2% decreases in the final ethanol concentrations measured compared to the control. Such effects after an inoculation of only 10(5) CFU/ml may have been due to the higher tolerance to ethanol of the latter two bacteria, to the more rapid adaptation (shorter lag phase) of these two industrial organisms to fermentation conditions, and/or to their more rapid growth and metabolism. When up to 10(9) CFU of bacteria/ml was present in mash, approximately 3.8 to 7.6% reductions in ethanol concentration occurred depending on the strain. Production of lactic acid and a suspected competition with yeast cells for essential growth factors in the fermenting medium were the major reasons for reductions in yeast growth and final ethanol yield when lactic acid bacteria were present.     

Haemagglutination of twitching Streptococcus sanguis

Among 86, mostly twitching, polarly fimbriated strains of Streptococcus sanguis, 55 agglutinated guinea pig erythrocytes (GPE) after cultivation in Todd-Hewitt broth (TH), and 21 strains agglutinated GPE only after growth in TH with 10% horse serum (THS). Two of the positive strains were non-twitching and unfimbriated. Ten strains failed to haemagglutinate. Among 5 twitching strains belonging to the 10043 group, 3 agglutinated GPE after growth in TH and 2 only after growth in THS. Among 35 non-twitching strains of alpha-haemolytic streptococci, only 6 agglutinated GPE after growth in TH, and among 8 negative strains which were tested after growth in THS, only 1 agglutinated GPE. Tests using 6 different kinds of erythrocytes (guinea pig, rabbit, sheep, horse, chicken, human) revealed that differences between these were slight only. The results do not indicate that there is an absolute association between twitching and haemagglutination in S. sanguis. The haemagglutination of S. sanguis was not mannose-sensitive.     

Origin of esterases in human whole saliva

Whole saliva of 59 healthy persons was used for determination of esterase activity. The pattern of esterase was studied by means of isoelectrofocusing on thin-layer acrylamide gels. The esterases found in whole saliva are suggested to be derived from the cells of the tissue in the oral cavity. This origin is indicated (e.g.) by comparison between isolectrophoretic esterase patterns of whole saliva, submandibular saliva, gingival biopsy and fibroblast culture. Antisera against partially purified saliva esterases were produced in rabbits. These sera, used in immunoelectro-osmophoresis, gave esterase-active immunoprecipitate against whole saliva, the water-soluble materials of disrupted gingival biopsy and fibroblast culture, but not against the material of the bacteria, Streptococcus sanguis, Strptococcus mutans, Streptococcus mitis, Actinomyces viscosus and Lactobacillus fermentum.