Modified thioglycolate medium: a simple and reliable means for detection of Trichomonas vaginalis

Despite the declining rate of sexually transmitted diseases in developed countries, trichomoniasis is still one of the most common venereal infections. While diagnosis of this condition is commonly based on the microscopic wet-mount method, culture remains the most accurate single procedure for detecting the presence of Trichomonas vaginalis in clinical samples. In the present study, the efficacy of a modified formula of the commonly available thioglycolate medium was compared with that of the standard Diamond's medium for detection of T. vaginalis in samples from 176 women with vaginal symptoms. Thioglycolate medium supplemented with yeast extract, horse serum, and antimicrobial agents was as reliable as Diamond's medium for detection of T. vaginalis in vaginal fluid samples. Modified thioglycolate medium may be used as a readily available, low-cost substitute for the standard medium for culturing T. vaginalis.

[Survival ability of Trichomonas vaginalis in mineral baths]

The role of mineral thermal baths and particularly of bath fittings such as benches and toilet seats in the spreading of Trichomonas vaginalis is controversial. In order to clarify the possibility of transmission by smear infection of this ubiquitous urogenital parasite the ability to survive was investigated in 11 mineral baths in Baden-Württemberg by contamination of water samples of varying mineral content. In addition, Trichomonas-contaminated water samples were placed in Petri-dishes on different benches in the bath area to determine the different milieu-factors influencing survival and thus the possibility of smear infections. The determination of viable cells was carried out by recultivation and semiquantitative extinction measurement. The survival time of Trichomonas vaginalis in the water samples of the 11 mineral baths varied considerably from 30 min up to more than 3 hours. The total mineral content played the most important role. When exposed in Petri dishes in addition the evaporation of the medium (mineral water) is of importance. Generally at high evaporation rates the cells will lose viability faster than in closed tubes. But also in open dishes in 4 mineral baths viable Trichomonads were still detectable after 3 hours. Generally the ability of Trichomonas vaginalis to survive in water of a total mineral content of 0.05-2.2% is increased to such an extent that infection is theoretically possible. Transmission in the mineral pool itself appears nevertheless highly unlikely due to the dilution effect of the enormous water volume. However transmission of infection via wet, contaminated benches and toilet seats cannot be generally ruled out.

[Effect of sodium nitrite on Trichomonas vaginalis]

We have investigated the action of sodium nitrite on the growth and morphologic changes of T. vaginalis and on the treatment of subcutaneous abscess by trichomonad in mice. Sodium nitrite inhibited the growth of metronidazole-sensitive KT9 isolate and metronidazole-resistant CDC85 strain of T. vaginalis as concentration of 6 mM and 10 mM, respectively. Intraperitoneal injection of sodium nitrite (70 micrograms, 100 micrograms, 130 micrograms/g body weight) did not reduce the size of abscess produced by subcutaneous inoculation of T. vaginalis in mice. T. vaginalis, treated with sodium nitrite at concentration giving about 50% inhibition of growth, showed fissures, many vacuoles and electron-translucent zone in the cytoplasm by transmission electron microscopy. In the case of CDC85 treated with 9 mM sodium nitrite, hydrogenosomal matrical change, destruction of hydrogenosomal membrane, autophagic vacuoles, disappearance of Golgi complex and polysome were notably observed. With above results, it is assumed that sodium nitrite inhibits the growth of metronidazole-sensitive and--resistant strains of T. vaginalis and induces the morphological changes of T. vaginalis although it does not affect in reducing of abscess size by T. vaginalis in mice.

Uptake of amino acids by the parasitic, flagellated protist Trichomonas vaginalis

HPLC techniques have been applied to study amino acid uptake and release by Trichomonas vaginalis under a variety of conditions. Studies on the growth of T. vaginalis in complex media and the survival of the parasite in simple media, with and without amino acids and/or maltose, have shown that the growth or survival of T. vaginalis is better in the presence of maltose than when it is absent, and that greater amounts of amino acids are consumed by T. vaginalis in the absence of maltose. The results are consistent with several amino acids, notably arginine, threonine, leucine and methionine, being used by T. vaginalis as energy substrates. T. vaginalis released alanine and glycine into the culture media, the excretion being greater in the presence of maltose. These studies have provided new data on the uptake and release of amino acids by T. vaginalis and pave the way for detailed analysis of key enzymes and the regulation of the pathways involved.

YI-S, a casein-free medium for axenic cultivation of Entamoeba histolytica, related Entamoeba, Giardia intestinalis and Trichomonas vaginalis

Pancreatic digests of casein are major ingredients of media used in the axenic cultivation of lumen-dwelling parasitic protozoa, especially Entamoeba, Giardia, and trichomonads. The digest used almost exclusively in the development of these media, Medo-Peptone (Trypticase BBL), has not been available since 1981. Moreover, none of dozens of similar type digests tested since then in our laboratory has proved equal to Medo-Peptone, and in the last two years it has become increasingly difficult to obtain new batches which will support even modest growth of Entamoeba histolytica. In response to this problem we have developed a casein-free medium, YI-S, consisting of a nutrient broth, vitamin mixture and serum. We recommend it as a replacement for the casein-dependent medium TYI-S-33, currently the most widely used for axenic culture of Entamoeba histolytica and other lumen-dwellers.

Evaluation of two cultural media (CPLM & TYM) for isolation and maintenance of Trichomonas vaginalis stocks in the laboratory

Five hundreds vaginal discharge specimens were inoculated simultaneously in 2 axenic culture media (CPLM & TYM), in order to compare their ability to isolate and to maintain the growth of T. vaginalis in the laboratory. While both media were found to be equally good in detecting the organisms in vaginal discharges, yet, T. vaginalis stocks were maintained for a longer time in TYM medium (one year), than in the CPLM medium (2 weeks). The yields of the parasites with different inocula subcultured and after different incubation periods were counted in the TYM medium.

Adaptation of the carbon metabolism of Trichomonas vaginalis to the nature and availability of the carbon source

The anaerobic parasitic protist Trichomonas vaginalis was adapted in chemostats to eight different conditions defined by different growth rates and carbon regimens. Glucose or maltose was used as carbon and energy source. Cells cultured under well-defined steady states were tested in short-term experiments. The kinetics of glucose and maltose uptake were determined and their glucokinase and alpha-glucosidase activities were measured. Uptake in 20 min was measured with radiolabelled glucose and maltose, rather than analogues, using the silicone oil centrifugation technique. Hence, the accumulated label represents both transport and metabolic activity. The total uptake of glucose was highest in organisms that had been starved for glucose during growth. The kinetics of glucose uptake can be understood by assuming rate-limitation by transport across the plasma membrane at low external concentrations and by the subsequent metabolism at concentrations exceeding a cross-over value. The specific glucokinase activity correlated in only four out of eight cases with the saturation uptake. The kinetics of maltose uptake indicated rate-limitation at low maltose concentrations by a diffusion-limited step and at higher levels by metabolic steps. The uptake of maltose was primarily affected by the growth rate during culture, the highest growth rates resulting in most uptake. Maltose uptake was determined only partially by the cellular alpha-glucosidase activity. The activities of both transport and metabolic enzymes changed due to the culture conditions suggesting that the control over glucose and maltose metabolism is shared by several steps in the pathway.

Carbohydrate metabolism and physiology of the parasitic protist Trichomonas vaginalis studied in chemostats

The parasitic protist Trichomonas vaginalis was cultured in chemostats with glucose or maltose as carbon and energy source. The maximum growth rate was about six divisions per day independent of the substrate, and the apparent Km for glucose was 0.375 mM. While growing on maltose, the growth rate depended linearly on the maltose concentration, indicating that in contrast to glucose metabolism a diffusion step is rate-limiting to maltose metabolism. Cultures were examined over a wide range of growth rates under four conditions: utilizing glucose or maltose as carbon and energy source, with the carbon source rate-limiting or present in excess. Cell density, cellular protein and carbohydrate content as well as residual substrate concentration in the culture fluid were measured at each steady state. The protein content was constant at 100 pg protein per cell except when T. vaginalis was cultured under glucose limitation; in the latter case, slow-growing cells had less protein than cells grown at high rates. When growing under glucose limitation T. vaginalis metabolism changed to become more energy efficient at growth rates exceeding about half the maximum rate. The maintenance energy at the low growth rates accounted for approximately half of the total carbon consumption, which is high in comparison to other micro-organisms. At low growth rates the yield on maltose exceeded that on glucose, when expressed in terms of carbon equivalents. The yields on maltose and glucose were equal, but much lower, when the carbon source was not rate-limiting.(ABSTRACT TRUNCATED AT 250 WORDS)

Trichomonas vaginalis: dominant G2 period and G2 phase arrest in a representative of an early branching eukaryotic lineage

Eukaryotic mitotic cell cycles have been extensively studied in yeasts and vertebrate cells but little is known about cell cycle mechanisms in early branches of the eukaryotic lineage. Trichomonas vaginalis represents one of the earliest branching eukaryotic lineages available for study. In contrast with most yeasts and vertebrate cells, the T. vaginalis G2 period was prolonged, comprising 50 to 58% of the cell population. Hydroxyurea, aphidicolin, and excess thymidine, all of which arrest yeasts and vertebrate cells at the G1/S phase boundary, had no effect on the T. vaginalis cell cycle, probably due to the known absence of synthetic pathways. The anti-microtubule mitotic inhibitors, colchicine and nocodazole, induced G2 phase synchrony. Metronidazole, a therapeutic reagent, also caused G2 phase arrest. These observations suggest that T. vaginalis is similar to yeasts and vertebrate cells in G2 and M phases, but the parasite's G1/S phase transition is distinctive. The results also suggest potentially therapeutic, anti-trichomonad activity of microtubule inhibitors such as nocodazole. The cultured parasite may prove useful as a model for the mitotic cell cycle in the absence of G1/S phase transitional activities universal in yeasts and vertebrate cells.

The interaction of Lactobacillus acidophilus and Trichomonas vaginalis in vitro

Recent work with a mouse model of Trichomonas vaginalis infection indicated that estrogenized BALB/c mice that were preinfected with Lactobacillus acidophilus showed a greater duration of T. vaginalis infection as compared to a control group of mice that were not treated with L. acidophilus. To examine the interaction between T. vaginalis and L. acidophilus further we performed in vitro competitive growth assays between the 2 species. Although the addition of L. acidophilus to the T. vaginalis cultures slowed the growth of the protozoa, the added bacteria did not increase trichomonad death. However, T. vaginalis had a deleterious effect on L. acidophilus growth in combined cultures when compared to matched controls. Using an initial inoculum of 10(5)/ml, at 40 hr the control L. acidophilus concentrations had grown to 1.3 x 10(7)/ml. However, in combined culture with T. vaginalis, L. acidophilus concentrations at 40 hr had fallen to 7.8 x 10(5)/ml and 6.1 x 10(4)/ml for the 10:1 (T. vaginalis at 10(4)) and 1:1 (T. vaginalis at 10(5) test ratios, respectively (P < 0.01). This demonstrates that T. vaginalis can cause the concentration of L. acidophilus to fall in vitro and may explain why the concentration of L. acidophilus in the vagina falls in trichomoniasis.

Protein kinases in divergent eukaryotes: identification of protein kinase activities regulated during trypanosome development

The role of protein kinases in organisms that diverged early in the eukaryotic lineage is relatively unexplored. In this study, we determined that primitive parasitic protozoa possess multiple protein-serine kinases and inferred the presence of protein-tyrosine kinases through sensitive immunoblotting techniques. To further explore the role of protein kinases in parasite development, we examined the activity of eight renaturable protein kinases during the life cycle of the protozoan parasite Trypanosoma brucei. The activities of six protein-serine/threonine kinases were regulated during development, with several distinct patterns of regulation. In addition, an 89-kDa protein kinase was detected in dividing cells but not in nondividing cells. Our data indicate that even the most primitive eukaryotes possess a large complement of protein kinases, including protein-tyrosine kinases as well as protein-serine/threonine kinases. The data further suggest that protein kinases may play a pivotal role in regulation of proliferation and differentiation in protozoa.

[A rapid staining method for the study of the flagellar and round forms of Trichomonas vaginalis from culture]

This method has been developed for the routine observation of the different forms of Trichomonas vaginalis in axenic culture with a low rate of cell loss. This rapid dyeing process is especially suitable for the examination of the ratio between the flagellated and round forms of the parasite. As a result of this staining one can not see fine cell details but can firmly distinguish between flagellated forms and multi-nucleated, multi-flagellated forms (i.e. dividing cells forms).

Aerobic resistance of Trichomonas vaginalis to metronidazole induced in vitro

Aerobic resistance of Trichomonas vaginalis to metronidazole was induced in vitro by anaerobic cultivation of drug-susceptible trichomonads with low concentrations of the drug (2-3 micrograms/ml) for 50 days. Minimal lethal concentrations (MLC) for metronidazole of the resistant derivatives were high in aerobic susceptibility assays (MLC = 216-261.5 micrograms/ml) but low in anaerobic assays (MLC = 4.2-6.3 micrograms/ml), surpassing MLC values of their parent strain approximately 50-fold and 3-fold under aerobiosis and anaerobiosis, respectively. Sensitivity to metronidazole under anaerobic conditions and activity of the hydrogenosomal enzyme pyruvate: ferredoxin oxidoreductase indicated that the resistance was of the aerobic type. Dependence of the resistance manifestation on O2 was further confirmed by susceptibility assays in vitro performed in defined gas mixtures of different oxygen content (1-20%). Five percent concentration of O2 proved to be the threshold required for resistance demonstration and the MLC values further increased with increasing O2 concentrations. The in vitro-induced resistance was also demonstrated in vivo by subcutaneous mouse assay. The dose of metronidazole needed to cure 50% of infected mice (DC50) was 223 mg/kg x 3 for resistant derivative MR-3a but 6.6 mg/kg x 3 only for its drug-susceptible parent strain. The metronidazole-resistant strains developed in this study correspond by their properties to drug-resistant T. vaginalis strains isolated from patients refractory to treatment, and promise to be a useful tool in the study of 5-nitroimidazole aerobic resistance.

The plastic envelope method, a simplified technique for culture diagnosis of trichomoniasis

Although culture of Trichomonas vaginalis is more sensitive than wet mounts in the diagnosis of trichomoniasis, the lack of convenience of culture prevents it from being widely used. To improve the acceptability of diagnosis by culture, a plastic envelope method (PEM) was devised. PEM permits both immediate examination and culture in one self-contained system. The medium consists of dry ingredients that are reconstituted with water before use. The effectiveness of immediate examinations by PEM was compared with that of wet mounts, and the effectiveness of culture by PEM was compared with that of culture in Trichomonas Medium No. 2 (Oxoid). Of 710 vaginal secretion specimens from symptomatic and asymptomatic women that were tested by the four methods, 62 (9%) were positive for T. vaginalis. The sensitivity was 66% by wet mount, 66% by immediate examination by PEM, 89% by cultures in Oxoid medium, and 97% by culture by PEM. The two culture methods had equivalent sensitivities but were significantly (P less than 0.0001) more sensitive than the two immediate methods. The combined immediate examination by PEM plus culture was more convenient to use than wet mounts plus culture in Oxoid medium. The long shelf-life of PEM's dry medium and its anticipated low cost are additional advantages.

Adhesion of Trichomonas vaginalis to plastic surfaces: requirement for energy and serum constituents

The ability of Trichomonas vaginalis to adhere to plastic surfaces in the presence of various agents and under different growth conditions was examined in wells of microtitre plates containing unsupplemented TYI medium or the same, with various supplements. Following incubation, the wells were thoroughly washed and adhesion was determined by microscopic counting of the adherent organisms. There was no detectable adhesion in the absence of both serum and carbohydrate. Optimal adhesion (about 10-20% of the total number of parasites) was obtained throughout the growth curve in culture media supplemented with either serum or serum Cohn fractions IV-I (rich in alpha-globulin) or IV-4 (rich in alpha + beta-globulin) and 25 mM glucose, maltose or fructose, but not in plates pre-coated with the Cohn fractions. Cohn fraction II + III (rich in beta + gamma-globulin) moderately enhanced adhesion while Cohn fractions II (rich in gamma-globulin) or V (albumin), fibronectin, Tamm-Horsfall glycoproteins and polylysine were without effect. Non-metabolizable sugars (methyl derivatives of glucose, mannose or fucose) did not support growth, but, surprisingly, enhanced adhesion. At 4 degrees C, the trichomonads were not able to adhere and pre-adherent organisms detached from the plastic surface. Optimal adhesion was obtained at a pH range of 6.5-7.5 but was already detectable at pH 5.5. Cytochalasin E markedly suppressed adhesion.(ABSTRACT TRUNCATED AT 250 WORDS)

Iron regulates growth of Trichomonas vaginalis and the expression of immunogenic trichomonad proteins

Iron is an essential nutrient for Trichomonas vaginalis and is acquired via highly specific receptor-mediated mechanisms from the host. Responses of T. vaginalis to conditions of iron limitation or iron excess were analysed in order to determine whether iron levels in the growth medium regulate certain properties of the parasite. When compared with organisms grown in excess iron, iron limitation resulted in greater than or equal to 80% lower rates of protein synthesis and greater than or equal to 3-fold decreases in cell densities. These parasites also exhibited generation times of approximately 10 hours, 2.5-fold longer than organisms grown in the usual complex medium. Iron-restricted growth also resulted in increased binding of lactoferrin by trichomonads, which paralleled elevated expression of the lactoferrin-binding receptor protein having a relative molecular mass of 136,000 daltons (136 kDa). A Mr 126 kDa protein was concomitantly repressed in low-iron-grown parasites. The greater amounts of lactoferrin bound by iron-depleted T. vaginalis organisms corresponded with both the expression of additional receptors onto trichomonal surfaces and increased affinity of the receptor for the lactoferrin molecule. Finally, immunoblot analysis of parasites grown under high- and low-iron conditions using sera from patients with trichomoniasis further revealed the synthesis by T. vaginalis of at least 19 iron-regulated immunogens, and patients' sera also detected the lactoferrin receptor. These data not only show the overall importance of iron to the biology of this protozoan, but illustrate the in vivo iron modulation of gene expression of the biofunctional lactoferrin receptor and other immunogens.

Effect of beta-estradiol on production of the cell-detaching factor of Trichomonas vaginalis

Despite over 40 years of study, the pathogenetic mechanisms of Trichomonas vaginalis are just starting to be elucidated. We have recently reported that T. vaginalis produces a virulence factor, cell-detaching factor (CDF), that likely causes the cell sloughing seen in clinical disease. This 200-kDa glycoprotein is acid and heat labile and correlates with clinical symptoms. We applied a McCoy cell culture system to study the effects of various concentrations of beta-estradiol (10(-6) to 10(-10) M) on T. vaginalis growth and CDF production. T. vaginalis growth was unaffected by the different concentrations of beta-estradiol studied, in comparison with the growth of control cultures without beta-estradiol. However, beta-estradiol significantly diminished the activity of CDF at all concentrations and did so most profoundly at 10(-7) and 10(-8) M (P less than 0.0001). This suggests that the symptoms of T. vaginalis infection may be influenced by the vaginal concentration of estrogens, and further studies of the interactions between T. vaginalis and estrogens are warranted.

The role of immunoglobulin and complement in enhancing the respiratory burst of neutrophils against Trichomonas vaginalis

Human neutrophils, alone, did not kill Trichomonas vaginalis. More than 90% of T. vaginalis (10(5)/ml) survived in the presence of 10% normal human serum (NHS) while 90% of these organisms were killed in the presence of a combination of neutrophils (10(6)/ml) and 10% NHS. Mechanisms responsible for this serum-mediated neutrophil killing of T. vaginalis were demonstrated through a process of lucigenin-amplified neutrophil chemiluminescence. As evidenced by indirect immunofluorescence, NHS showed specific immunoglobulin G (IgG) titre of 1:8 for T. vaginalis. Purified IgG, at 1.6 mg/ml, showed no direct opsonizing or lytic effect on this organism. Formalin-fixed trichomonads opsonized by C2 deficient human serum promote 4 times more neutrophil chemiluminescence than those opsonized by Factor B deficient human serum. With the addition of purified IgG (5 mg/ml) neutrophil chemiluminescence was increased by 4 times and further improved trichomonal killing by neutrophils (from 5 +/- 4% to 78 +/- 16%) via activation of the classical complement pathway, but did not alter that due to activation of the alternative complement pathway. These studies indicate that both an IgG-enhanced classical complement pathway activation and an antibody-independent alternative complement pathway activation provide opsonin (C3) for T. vaginalis to facilitate the neutrophil killing mechanism.

An evaluation of an InPouch TV culture method for diagnosing Trichomonas vaginalis infection

A new culture method for Trichomonas vaginalis, the InPouch TV test, was evaluated for its sensitivity and specificity in supporting growth of trichomonads. Five clinical isolates remained viable for periods from 41 to 131 days. A strain from the ATTC 30001 remained viable for 91 days. As few as four trichomonads/ml of culture medium could be viewed microscopically within 24 h. Doubling time for growth of trichomonad varied between 5 to 8 h. In a clinical study of 102 wet-mount negative specimens, 15 culture positive patients were observed with the InPouch TV test compared with 12 of the same patients with Hollander's fluid medium.

The effect of ionizing radiation on the viability of Trichomonas vaginalis

1. The effects of continuous gamma radiation on the viability of Trichomonas vaginalis (ATCC 30001) were assessed by a colony count technique. 2. A triphasic survival curve showed an initial shoulder (Dq) of 3 Gy followed by three linear curves with D0 values of 34, 300, and 90 Gy. 3. Sterilization of 10(6) cells/ml occurred from 1600 to 1800 Gy of radiation. 4. Population growth, subsequent to radiation exposure of 17-100 Gy, showed an increased lag time followed by a faster rate of growth, compared with unirradiated cells. 5. Trichomonas vaginalis is more sensitive to ionizing radiation than free-living protozoa and appears as radiosensitive as those parasitic protozoa examined in radioattenuation experiments.

Growth of Trichomonas vaginalis in a serum-free McCoy cell culture system

Axenic cultures of Trichomonas vaginalis normally require serum for proliferation, yet serum-containing medium may interfere with the detection of T. vaginalis-secreted virulence factors. Trichomonas vaginalis can, however, grow in coculture with a McCoy cell monolayer in both the presence and absence of serum. For 6 T. vaginalis isolates examined, growth in this serum-free system shows lower peak concentrations of T. vaginalis and longer doubling times than those apparent in a serum-containing McCoy cell system. McCoy cells employed in the system did not appear to secrete soluble growth factors for T. vaginalis. The presence of McCoy cells was required for serum-free proliferation of T. vaginalis possibly indicating that eukaryotic cell membrane components may be important in supporting serum-free growth in this system.

[Antiprotozoal effects of benzodiazepine derivatives]

It is known that some derivatives of the benzodiazepine group act not only as antipsychotic drugs but also have inhibitory effects on the growth of protozoa. The influence of imipramine and its derivatives clomipramine and desipramine on the multiplication of Crithidia luciliae, Leishmania mexicana amazonensis, Trypanosoma cruzi and Trichomonas vaginalis was investigated using in vitro cultivation of the parasites and compared with the effects of chlorpromazine and metronidazole. All trypanosomatides used were inhibited by imipramine and its derivatives with clomipramine having the strongest influence on the growth of parasites (ID50 12.5-35 micrograms/ml). The Trichomonas vaginalis strain used was susceptible to metronidazole but it was nearly resistant to the tricyclic compounds tested (ID50 greater than 100 micrograms/ml).

Effects of berberine, a plant alkaloid, on the growth of anaerobic protozoa in axenic culture

Extracts obtained by organic solvents from the root of Coptis teeta in Myanmar (Burma), were tested for growth inhibitory activity against Giardia lamblia, Trichomonas vaginalis and Entamoeba histolytica in axenic culture. All extracts had anti-protozoal activity with the methanol extract, in particular, being effective against all 3 parasites. By chromatographic analysis, the extracts were shown to contain berberine compounds and other alkaloids. Comparing the inhibitory effects of the methanol extract with berberine sulfate, a berberine salt previously shown to possess inhibitory activity, it was observed that the crude extract was more effective than the salt. This suggests that the greater inhibitory activity of the crude extract may be due to the cumulative contributions of its contained berberines and alkaloids. Based on these findings, it appears that the berberine compounds may be useful as chemotherapeutic agents against the 3 parasites tested.

Trichomonas vaginalis requires traces of oxygen and high concentrations of carbon dioxide for optimal growth

The effects of O2 and CO2 on the growth in culture of Trichomonas vaginalis strain C1-NIH were investigated. Growth under pre-purified N2 in the absence of CO2 supplementation gave a doubling time of 4.4 h; when traces of O2 (less than 0.25 microM) were present, the doubling time was 3.5 h. Organisms grew most rapidly (doubling time 2.3 h) with traces of O2 (less than 0.25 microM) and with the CO2 level controlled at 5 mM. The balance of fermentation products from maltose was greatly influenced by supplied gases. Under strictly anaerobic conditions at 5 mM CO2, equimolar glycerol and lactate accounted for more than 95% of the measured products, whereas lower CO2 increased acetate production. Under microaerobic conditions (O2 less than 0.25 microM) acetate was the major product when CO2 was limited to that evolved endogenously; again 5 mM CO2 favoured glycerol and lactate production. Activities of key enzymes measured in cell-free extracts (pyruvate:ferredoxin oxidoreductase, hydrogenase, glycerol kinase, malate dehydrogenase (decarboxylating) and lactate dehydrogenase) altered with growth conditions commensurately with observed changes in metabolic flux patterns. These results suggest that T. vaginalis is optimally adapted to conditions it experiences in situ in the vagina (traces of O2, high CO2).