Abstract: AIMS: To investigate the ability of bacilli of various species (Bacillus clausii, Bacillus subtilis, Bacillus lentus, Bacillus pumilus. Bacillus megaterium, Bacillus firmus, Bacillus sp.) and origins (probiotic and collection strains) to counteract the activity of some representative DNA-reactive agents. METHODS AND RESULTS: The inhibitory effect of 21 bacilli strains, previously characterized by tDNA-PCR, on four genotoxins, was examined in vitro using the short-term assay SOS-Chromotest. All strains had a high inhibitory activity against 4-nitroquinoline-1-oxide and N-methyl-N'-nitro-nitrosoguanidine (direct agents), whereas the inhibitory activity was high or moderate against 2-amino-3,4-dimethylimidazo[4,5-f]quinoline and aflatoxin B1 (indirect agents). Antigenotoxicity was observed in vegetative cells, but not heat-treated cells or spore suspensions. The spectroscopic properties of compounds were modified after cell co-incubation and all the strains maintained high viability after exposure to the genotoxins. CONCLUSIONS: No relevant differences in antigenotoxicity were evidenced among strains of the examined species or between probiotic and collection strains. SIGNIFICANCE AND IMPACT OF THE STUDY: Although derived from an in vitro model, the results suggest that Bacillus-based probiotics could be useful for reducing the gastrointestinal risk originating from genotoxic agents.
Abstract: The inhibition of direct acting DNA reactive agents by 63 non-starter lactobacilli isolated from raw ewes milk cheeses was examined by short-term assay (SOS-Chromotest) and compared with already characterized starter lactobacilli. The screening revealed strains active against the nitroarene 4-nitroquinoline-1-oxide (NQO) and the alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in different species of the genus Lactobacillus (L. rhamnosus, L. casei, L. plantarum, L. brevis, Lactobacillus spp.). It was proved that the anti-genotoxicity was strain-dependent, and always associated with spectroscopic modification of genotoxins. The frequency of strains inhibiting nitroarene genotoxicity was comparable for non-starter and starter lactobacilli, whereas inhibition of the alkylating agent was largely predominant in non-starter isolates. Seventeen strains presented inhibitory activity against both genotoxins. DNA RAPD-PCR performed with M13, Pro-Up and RPO2 primers on the lactobacilli under examination showed genetic diversity in these strains. The non-starter isolates clustered in seven groups and the strains presenting a high degree of activity against 4-nitroquinoline-1-oxide clustered in a single group with a similarity around 75%. Interestingly, the strains with anti-genotoxic properties also showed acid-bile tolerance, indicating that the autochthonous lactobacilli which survive cheese ripening may also reach the gut as viable cells and could prevent genotoxin DNA damage to enterocytes, as is desirable for probiotic bacteria.
Abstract: The present study was designed to investigate the putative antigenotoxic effects of supplementing the diet of rats treated with the colon carcinogen 1,2-dimethylhydrazine hydrochloride (DMH) with a Lactobacillus casei strain using an in vivo approach. The antigenotoxic response was evaluated in colon and liver cells using the alkaline comet assay. Since the balance between the bioactivation and detoxification metabolic pathways is crucial for the formation of toxic and genotoxic metabolites, alterations in the level of some xenobiotic metabolizing enzymes (XME) were studied in liver preparations. In the challenge group (L. casei + DMH), lactobacilli-supplemented diet, there was a decrease in the extent of DMH-induced DNA damage, especially in colon cells. Compared with control rats, there was less basal DNA damage in colon cells of rats fed on a lactobacilli-supplemented diet. These findings are the first to give clear evidence of DNA-protective effects of lactobacilli against basal DNA damage. Moreover, the chemopreventive effects were accompanied by changes in the activities of several XME. The observed decrease in the concentration of nonenzymatic antioxidants (i.e. GSH) and the reduced activity of enzymatic antioxidants (i.e., GST, GPx, and SOD) in liver could reflect an overall reduction in the level of oxidative stress in rats on a diet supplemented with the L. casei suspension compared with control rats (basal state). Thus, the concentrations of GSH and the activities of GST, GPx, and SOD could be downregulated by supplementing the diet with L. casei as a response to an improved antioxidant status.
Abstract: Twenty-five Lactobacillus casei group strains isolated from ewe cheeses from Abruzzo region, central Italy, were identified by 16S rRNA gene sequencing, differentiated by RAPD-PCR analysis and characterized as in vitro for acid-bile tolerance and antigenotoxic properties. All the strains were very susceptible to simulated gastric fluid (pH 2.0) but most of them recovered viability (ca. 2-3 log-units) when transferred and maintained in simulated intestinal fluid (0.5% w/v bovine bile) for 3 h. Some strains showed potential for deactivating representative genotoxins as highlighted by the SOS-Chromotest. Twelve were active and nine moderately active against 4-nitroquinoline-1-oxide, and one active and only one moderately active against N-methyl-N'-nitro-N-nitrosoguanidine. The active strains produced evident spectroscopic modification of genotoxins after co-incubation. Most isolates with antigenotoxic activity resulted as acid-bile tolerant demonstrating that cheese autochthonous lactobacilli may reach the gut as a viable form and prevent genotoxin DNA damage.
Abstract: AIMS: To study Bacillus clausii from a pharmaceutical product (Enterogermina O/C, N/R, SIN, T) and reference strains (B. clausii and Bacillus subtilis) for eco-physiological aspects regarding the gut environment. METHODS AND RESULTS: Spores and vegetative cells were challenged in vitro miming the injury of gastrointestinal transit: pH variations, exposure to conjugated and free bile salts, microaerophilic and anaerobic growth. No relevant differences were found studying the growth at pH 8 and 10, whereas at pH 7 the yields obtained for O/C and SIN were higher than those obtained for N/R and T strains. The spores were able to germinate and grow in the presence of conjugated bile salts (up to 1%, w/v) or free bile salts (0.2%) and also exhibited tolerance for the combined acid-bile challenge. As evidenced by lag-time, growth rate and cell yield the tolerance of Enterogermina isolates for conjugated salts was comparable with that of B. clausii type strain (DSM 8716(T)), and resulted higher than that observed for B. subtilis (ATCC 6051(T)). All the considered B. clausii strains demonstrated microaerophilic growth, but only some grew anaerobically in a nitrate medium. CONCLUSIONS: The ability of B. clausii spores to germinate after an acid challenge and grow as vegetative cells both in the presence of bile and under limited oxygen availability is consistent with the beneficial health effects evidenced for spore-forming probiotics in recent clinical studies. SIGNIFICANCE AND IMPACT OF THE STUDY: The experimental evidence from this study emphasizes some functional properties of B. clausii strains regarding their use as probiotics.
Abstract: Antigenotoxicity is considered an important property for probiotic lactobacilli. The ability of non probiotic lactobacilli from dairy products and starters to inhibit two reference genotoxins: 4-nitroquinoline-1-oxide and N-methyl-N'-nitro-N-nitrosoguanidine was evaluated. The study was carried out using short-term assays with different targets, such as procaryotic cells (SOS-Chromotest for genotoxicity in Escherichia coli and Ames test for mutagenicity in Salmonella typhimurium) and eucaryotic cells (Comet assay for genotoxicity in Caco-2 enterocytes). A high proportion of strains inhibiting 4-nitroquinoline-1-oxide activity was found in Lactobacillus casei, Lactobacillus acidophilus, Lactobacillus rhamnosus, Lactobacillus delbrueckii subsp. bulgaricus and Lactobacillus plantarum. Inhibition of N-methyl-N'-nitro-N-nitrosoguanidine activity occurred in only one L. acidophilus strain. All the strains with antigenotoxic properties also demonstrated antimutagenic activity and produced modifications in genotoxin spectroscopic profiles. Strain viability during and after genotoxin exposure was confirmed. Concordance of the results obtained with microbial and mammalian cell-based tests is underlined.
Abstract: The effect of 16 Bacillus strains from pharmaceutical probiotic preparations (Bacillus spp.) and collection (B. subtilis, B. firmus, B. megaterium, B. pumilus) on genotoxicity induced by the known mutagen 4-nitroquinoline-1-oxide (4-NQO) was studied using the short-term bacterial assay SOS-chromotest. with Escherichia coli PQ37 as the tester organism. It was found that the activity of 0.1 mM 4-NQO was reduced (P < 0.01) after coincubation with Bacillus suspensions (10(8) CFU/ml for 150 min at 37 degrees C). All isolates showed potential for deactivating 4-NQO, and genotoxicity inhibition ranged from 92.9 to 100%. There were no appreciable differences in behaviour observed among probiotic and collection strains or in relation to species. The observed antigenotoxicity was associated with a clear-cut modification of 4-NQO molecular characteristics.
Abstract: Antigenotoxic activity against 4-nitroquinoline-1-oxide (4-NQO) of lactic acid bacteria isolated from commercial dairy products was studied using SOS-Chromotest. The supernatants from bacteria-genotoxin co-incubations in general exhibited a strong suppression on SOS-induction produced by 4-NQO on the tester organism Escherichia coli PQ37 (sfiA::lacZ). High genotoxicity inhibition (>75%) was found for 31/67 of the examined bacteria and the maximum values of some strains within the species were as follows: Lactobacillus casei, 99.1%; L. plantarum, 93.3%; L. rhamnosus, 93.4%; L. acidophilus, 90.9%; L. delbrueckii subsp. bulgaricus, 85.7% and Bifidobacterium bifidum, 89.6%; Strains with low antigenotoxicity (5-60%) were evidenced in both L. acidophilus and L. delbrueckii subsp. bulgaricus, whereas some inactive strains were found only in L. casei and L. delbrueckii subsp. bulgaricus. Cell exposure to 100 degrees C for 15 min prevented antigenotoxicity and no effect was evidenced for cell-free spent media. The active strains survived at 0.1 mM 4-NQO exposure and generally presented some relevant functional properties, such as tolerance to bile (0.5%) or acid environment (pH 2.0) and adherence to Caco-2 enterocytes. Antigenotoxicity was always associated with modification of the 4-NQO absorbance profile.
Abstract: The possibility of associating starch degradation with bacterial beta-glucuronidase expression was examined. We proved that starving, in starch medium, amylase-negative Escherichia coli (M94) which has constitutive beta-glucuronidase greatly reduces (p < 0.01) its background activity, but the addition of both cell-free supernatants or cells of Bacillus subtilis (B10) producing amylase greatly increases (p < 0.01) the E. coli beta-glucuronidase activity. Increases in activity were maximal when amylase in the medium ranged from 0.3 to 0.8 U ml-1 and pH from 6.8 to 6.3, whereas higher amylase activity interacted with E. coli viability and the effect on beta-glucuronidase was less evident. The impact of B. subtilis amylase on E. coli beta-glucuronidase induction, observed when the organisms were co-cultured, indirectly supports the hypothesis that amylolytic activity of hindgut bacteria may be effective on beta-glucuronidase induction of the climax microflora. This last finding is important in the health field, considering the implication between the deconjugating role of this enzyme and consequent activation of toxic and carcinogenic compounds.
Abstract: Two Escherichia coli strains in which alpha-amylase production differed were used to study in depth some characteristics related to beta-glucuronidase induction by starch. The beta-glucuronidase background activity in Luria broth medium was comparable for the two isolates, but only amylase positive S1 was able to grow on starch molecules supplied as the sole carbon source. In this case growth resulted at higher beta-glucuronidase levels (p < 0.01) with respect to basal activity and the induced expression was maximal (6.1-fold) when cultures reached the stationary phase. Growth in the presence of a protein synthesis inhibitor (chloramphenicol) was associated with a marked reduction of activity. The beta-glucuronidase activity of amylase negative M94 remained unchanged during starvation on starch medium, but an induced response was observed with methylumbelliferyl-glucuronide. These results further support the hypothesis that starch metabolism is involved in the complex beta-glucuronidase regulation of E. coli strains. This is relevant not only for basic research but also to investigating gut microbial enzymology.
Abstract: Studies with pure cultures growing in laboratory media indicated that beta-glucuronidase expression of Escherichia coli S1 was considerably affected by starch added to the medium as the only carbon source. This result, which may be an aspecific modulation of enzyme expression, was independent of the starch molecular structure and effects were analogous for maize, rice, wheat or potato starches. It was observed that enzyme expression was little affected by the growth rate. The beta-glucuronidase activities of starch-grown bacteria found in the present study agree with those observed in animal and human models performed for in vivo evaluation of effects of dietary starch effects on gut microbial ecosystems.
Abstract: The expression of some faecal hydrolytic enzymes in rats fed for 4 months on sucrose or starch enriched diets was compared with a standard diet. The assay reliability was confirmed for animal and experimental variability. The beta-D-glucuronidase and beta-D-glucosidase activities were always higher in rats fed on starch than on other diets. N-acetyl-beta-D-glucosaminidase and N-acetyl-beta-D-galactosaminidase showed decreased activity when passing from a standard to a sucrose, and from a sucrose to a starch diet. There was little modification in the levels of faecal alpha-D-glucosidase, sulphatase and protease with the various experimental diets.
Abstract: 4-Methylumbelliferyl-beta-D-galactoside and 4-methylumbelliferyl-beta-D-glucuronide were added to MacConkey broth and their diagnostic powers for total coliforms (TC) and Escherichia coli, respectively, were tested by membrane filtration at primary isolation. Examining water samples from different sources proved the usefulness of fluorogenic rather than reference media both as regards recovery efficiency and rapidity (possible within 12 h) of analyses. The recoveries obtained by fluorogenic and conventional tests for both TC and E. coli were correlated. Values were comparable in surface water samples, while a higher sensitivity of fluorogenic media was observed in samples of shallow contaminated ground water. Results seem to indicate that the use of fluorogenic membrane filtration analysis for colimetric indicators could be favourably considered especially for sanitary surveying of drinking water.
Abstract: Two forms of beta-N-acetylhexosaminidase from Serratia marcescens with an optimum pH of 5.0 and 6.5, respectively, to 4-methylumbelliferyl-2-acetamido-2-deoxy-beta-D-glucopyranoside were separated by DEAE-cellulose chromatography and Sephacryl S-200 chromatography. On the basis of their molecular weights, thermal stability, substrate specificity and isoelectric points, the form with an acidic pH optimum resembled hexosaminidase B, whereas the form with a neutral pH optimum resembled hexosaminidase C. Lectin binding studies showed that the acidic form does not bind to concanavalin-A-Sepharose, Tetragonolobus purpurea-agarose, wheat germ-agglutinin-Sepharose or Ricinus communis-agglutinin-agarose, whereas the neutral form binds to the last two lectin columns.
Abstract: We examined the effectiveness of fluorogen in detecting bacterial enzymes in atypical or injured coliform strains in environmental water samples. 4-methylumbelliferyl-beta-D-galactoside and 4-methylumbelliferyl-beta-D-glucuronide, substrates for beta-galactosidase and beta-glucuronidase respectively, were used as markers for total and faecal coliform bacteria and it was confirmed that fluorogenic assays have a greater sensitivity than reference methods. It was also observed that adding MU-conjugates (50 micrograms/ml) to low selective media for membrane filtration, besides shortening test times, reduces false negative results when detecting sanitary microbial indicators of water pollution.
Abstract: Antibiotic-resistance is widely spread phenomenon in the environment because of uncontrolled discharge of urban and animal wastewaters. Sewage treatment can significantly reduce the number of both sensitive and resistant bacteria. A reduction of about 1.5 logarithmic units in faecal coliforms was observed during biological treatment (3, 7), but a simultaneous increase in the percentage of resistant strains occurred because of not well understood selection phenomena. The above reported bacterial reduction is not always sufficient to meet the quality standards of Italian legislation required to discharge the treated effluents into surface waters, and so, chlorination become a compulsory additional treatment whose impact on both sensitive and resistant microflora must be evaluated. The results obtained in the present research have demonstrated that chlorine concentrations in the range of 0.5-2 ppm are able to reduce significantly the faecal coliforms concentrations and, in particular, treatment with 1 ppm of chlorine for 1 hour reduces the concentration of the above reported bacteria to the extent of 2 logarithmic units, so that their final concentration are of the about 10(2)/100 ml. The surviving chlorine tolerant bacteria seem to be antibiotic resistant in higher percentage than the chlorine sensitive ones and so, as a consequence, a significant increase in the antibiotic resistance and multiresistance was observed in the chlorinated effluents. In this context it is interesting to underline the larger variety of resistance patterns observed in the chlorine-resistant bacteria in comparison with the uniformity in the resistance patterns observed in isolated from unchlorinated effluents. The selected chlorine-tolerant strains seem to be less able to transfer their resistances under laboratory conditions, not because of curing effect of chlorine on the plasmids but, probably, because of the damage to cellular cell envelopes.
Abstract: The efficiency of anaerobic treatment of animal wastes and aerobic treatment of urban sewage in removing faecal coliforms and their effect on the antibiotic-resistant coliforms was evaluated in this study. A two reactor anaerobic digester and six activated sludge plants were studied. The concentrations of both faecal coliforms in sampling from influents and treated effluents were calculated to determine efficiency of plants during depuration treatments. Anaerobic and aerobic treatments resulted in 90% and 97% (arithmetic mean values) efficiency in removing faecal coliforms. Although neither anaerobic nor aerobic treatment seems to significantly increase the percentage of antibiotic-resistant bacteria, during the aerobic treatment of urban sewage there was a tendency for the percent of antibiotic-resistant bacteria to increase.
Abstract: The tests commonly used for bacterial identification, especially in the field of microbial environmental analyses frequently do not provide a sufficient strain differentiation. Considering the importance that accurate characterization of bacterial pollution indicators could have as epidemiological tools, this study used a resistogram subtyping method for Escherichia coli as a tentative method of effecting a good monitoring of the environmental spread of this microorganism. The resistance of 313 E. coli strains of different origin (human, animal, sewage), previously identified by standard biochemical reactions, to 8 chemical compounds (inorganic, organic and dyes) and to 7 antibiotics was tested. The results indicated this method has a higher discriminatory power for chemicals than for drugs. Some typical resistotype patterns for E. coli from various sources are described.
Abstract: The validity of the submarine agarose gel electrophoresis as routine method for plasmidic epidemiology was considered. Using standard plasmids, the efficiency of a performed protocol conditions (5 V/cm for 3 hours, 0.8% agarose) in screening plasmids of different size was studied. The results provide sharp profile resolution and an accurate estimate of molecular weights in the range from 1.2 to 112 megadaltons.
Abstract: The antibiotic and metal resistance percentages of 315 E. coli strains, isolated from: a sample population not-exposed to antibiotics, hospitalized inpatients and from bred animals, were compared with the resistance percentages of 217 environmental isolates (sewage and river isolates). The highest levels of resistance and multiresistance were found for clinical and river isolates. A wider number of resistance markers, observed for environment isolates with respect to human and animal isolates, made it possible to hypothesis e that the resistant strains could possess some selective advantage that enhances their survival in the environment. Association of antibiotic resistance and metal-resistance has been demonstrated in all isolates but it is particularly evident in the environment and clinical isolates. Correlation analysis revealed that the patterns of antibiotic and metal resistance of environmental E. coli isolates are in good agreement with those of human origin and that sewage and river E. coli isolates are well correlated too.
Abstract: The present study evaluates the effect of the cadmium (Cd2+) on the growth and protein synthesis of some Gram-positive (Staphylococcus aureus, Bacillus subtilis and Streptococcus faecium) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria and the cadmium uptake by the same micro-organisms. The Gram-negative bacteria tested were less sensitive to metal ions than the Gram-positive, and P. aeruginosa was the most resistant. The Gram-negative bacteria were also able to accumulate higher amounts of cadmium during growth than the Gram-positive bacteria. The maximum values of specific metal uptake (microgram of Cd2+ incorporated per mg of protein) were: 0.52 for S. aureus, 0.65 for S. faecium, 0.79 for B. subtilis, 2.79 for E. coli and 24.15 for P. aeruginosa, respectively. The differences in the ability to accumulate metal found between Gram-negative and Gram-positive bacteria seems to account for different mechanisms of metal resistance.
Abstract: The effect of mercury, cadmium, copper, zinc, chromium and lead on an environmental strain of Escherichia coli was studied. The tolerance growth limits, growth kinetics and viability were determined. It was found that metal-ion concentrations greater than the threshold values (0.005 microM Hg2+, 0.5 microM Cd2+, 5 microM Cu2+, 23 microM Cr3+, 30 microM Zn2+, 45 microM Pb2+) increase the lag-phases but do not modify the growth kinetics (Pb2+ is an exception). During the lag-phase a reduction in cell viability, varying from a maximum of 89% for lead, to a minimum of 13% for cadmium, was observed. The reduction of viability accounts for a cells physiological adaptation to the metals rather than selection of resistant mutants. Loss of the acquired metal resistance following exposure of the bacterial cells to the metals supported this last point.
Abstract: The incidence and the patterns of the antibiotic and metal resistance in 106 strains of Escherichia coli isolated from ground waters, used also as drinking water supply (sample A), was studied in comparison with the resistance behaviour in the 104 strains of the same microorganism isolated from non hospitalized patients (sample P). Significant differences between the percentage of resistant strains in the two examined samples were found for some of the antibiotics and the metals tested (ampicillin, streptomycin, kanamycin, mercury and zinc) while non statistically significant differences were found for gentamicin, tetracyclin, nalidixic acid and cadmium. From the high percentages of the resistant strains in the environmental sample (up to 44.3% for tetracyclin) we may deduce that also the ground waters, especially if used as drinking water, contribute to the spread of the resistant bacteria. The patterns of the antibiotic multiresistances in the strains isolated from patients and from ground waters do not differ greatly and this strengthens the hypothesis that resistance to antibiotics has been acquired by Escherichia coli strains before reaching the ground waters.
Abstract: Dehydrogenase activity of activated sludges coming from a laboratory plant, has been evaluated by the TTC-test in the presence of some chemical toxics. The results obtained have shown that, for all inhibitors tested, there exists a range of concentrations in which the dose-response relationship is linear. As far as the comparison of the inhibition data from the TTC-test and from the Oxygen-respiration rate is concerned, the results obtained show that the inhibitors tested may be divided into three groups: (i) inhibitors which inhibit the Oxygen-respiration rate more than th Dehydrogenase activity (Zn2+, Cd2+, Ni2+, Hg2+, Zn(CN)4(2-), Cd(CN)4(2-)); (II) inhibitors for which there are no significant differences in the inhibition value obtained by the two methods (CN-, C6H5O-, C6Cl5O-, C6H3ClO-, Hg(CN)4(2-)); (iii) inhibitors which inhibit the dehydrogenase activity more than theoxygen-respiration rate (Cu2+, CrO4(2-), Ni(CN)4(2-)). The inhibition data obtained by other authors evaluating by direct methods (COD reduction, turbidity of the final effluent etc.) the performance of pilot or laboratory plants in the presence of some of the toxics used in the present research, are in sufficient agreement with the dehydrogenase inhibition data obtained in this work.
Abstract: During the year 1977, 1491 urine samples were taken from patients living in the "Alta Valle del Tevere" (Umbria, Italy). The isolated microorganisms were examined and tested against 15 antibiotics. 535 samples (35.88%) were free from bacteria. Among the 1095 isolates, 52.42% were Gram-negative, 46.85% Gram-positive, and only 0.73% Fungi. The genera Citrobacter, Escherichia, Proteus, Pseudomonas, Enterobacter, Klebsiella, Staphylococcus and Enterococcus were identified. A high proportion of strains belonging to the genera Proteus and Pseudomonas were resistant to all the 15 antibiotics tested. However, although in a lower proportion, the multiple drug-resistance was present also in the strains of the genera Escherichia and Staphylococcus.
Abstract: The authors studied the possible relationship between a genetic characteristic, like DNA base composition, and certain phenotypic characteristics, i.e., sensitivity to lytic agents, morphology of colonies, and biochemical reactions in 34 strains of spore-bearing bacilli. From the results obtained two groups of bacilli have been identified. The first group includes the species B. subtilis, B. pumilus, B. licheniformis, and B. firmus and one strain of B. megaterium. The mean value of the GC% of the DNA is 44.22 +/- 1.76. All the strains examined are highly sensitive to lysozyme and resistant to sodium lauryl sulphate (S.L.S.); the surface colonies have a "rhizoid" appearance and the microcolonies on slide microculture are star-shaped. The second group includes the species B. cereus, B. cereus var. mycoides, B. anthracis, and B. thuringiensis. The mean value of the GC% of the DNA is 33.65 +/- 0.59. All the strains belonging to this group are resistant to both lysozyme and S.L.S., and the surface macro-colonies and the microcolonies have a "medusae head" appearance. The two groups also have certain different biochemical reactions; e.g., anaerobic growth and the egg yolk reaction, with few exception, are negative for the first group and positive for the second; furthermore, the strains in the first group (with rare exceptions) cause fermentation in the three carbohydrates, glucose, arabinose, and xylose, while glucose only is fermented by all strains with one exception in the second group. The position of B. megaterium is not yet clear, although one strain may certainly be included in the first group. Lysis by lipase is extremely variable and does not correlate with any of the other characteristics studied. The other species studied in relation to the characteristics, considered in our research (B. coagulans, B. macerans, B. polymyxa, B. laterosporus, B. alvei, B. circulans, B. stearothermophilus, and B. brevis), are not susceptible to grouping, either in the first, or in the second or even in a separate group.
Abstract: The toxic effect of the metal ions of cadmium, zinc, nickel and mercury and their tetracyanide salt complexes, on the activated sludge not previously acclimated, has been studied. The evaluation of the effect was carried out using both the Warburg and TTC-method. The results obtained have shown that the toxicity of the cadmium and zinc complexes is higher than that of the corresponding metals, while the toxicity of Ni(CN)4(2-) is lower than that of the corresponding metals. No differences have been found between the effect of mercury and the corresponding tetracyanide complex. From the data obtained it appears that it is not possible to generalize about the biological effect of complexation with the CN- group, but it should be stated that, generally, there are substantial differences between metals and their cyanide complexes as far as toxicity for activated sludge is concerned.
Abstract: The effect has been studied of Cd2+ and Cd(CN)2-4 ions on the growth and enzymatic activity of mixed microflora from activated sludges. Both ions tested significantly inhibited the growth of microorganisms, estimated by means of the optical density, and the inhibitory effect of Cd2+ was significantly greater than that of Cd(CN)2-4 at the same mass and molar concentrations. There was also inhibition of the maximum uptake rate of glucose, but in this case there were no statistically significant differences between the inhibitory effect of the corresponding mass and molar concentrations of Cd2+ and Cd(CN)2-4.
Abstract: The previously postulated hypothesis, according to which different species of the genus Bacillus show strictly similar morphological and biological properties when the same variants are considered, has been confirmed by the present research. The "S" (smooth) variants of the five studied species (B. anthracis, B. subtilis, B. cereus, B. megaterium, B. mesentericus) are all lethal, at the experimented dose, for mice, whereas the "R" (rough, "star-shaped" colonies) variant of the same strains of the same species are all not pathogenic for the same animals. Likewise the "S" variants of three species tested in guinea pigs showed to be pathogenic; particularly B. anthracis and B. subtilis were lethal, whereas B. cereus caused a black eschar like that one described in the cutaneous anthrax. The "RS" variant ("medusae head" surface colonies) is not pathogenic for mice and guinea pigs (even B. anthracis) if the tested strains are cultivated for years in ordinary solid nutrient media; the same morphological variants are strongly pathogenic (also B. subtilis), when the strains are recently isolated from infected animals. The similarity between the same "S" variants of different species is proved also by the protection given by anti-anthrax serum to animals infected by B. subtilis.
Abstract: The sensitivity of the dissociative variants "R", "RS" and "S" of the spore-forming bacilli to some lytic agents (lysozyme, sodium lauryl sulphate, lipase, trypsin and some of their associations) has been studied. The research has been carried out on 32 strains: 14 "R", 14 "RS" and 4 "S" of different species of the genus Bacillus. The results have shown that the sensitivity to the studied lytic agents is strictly correlated, not to the species, but to the dissociative phases: these results are in accordance with those obtained in previous researches, carried out by the same Authors, on other characters, both morphological and biological, of the same variants. Thus, also through this way, it is possible to reach the conclusion that within this genus, there is more similarity among the different species of the same dissociative phase than among different dissociative variants of the same species. The results obtained in the present study allow to advance hypothesis, based also on the data of the literature, about the composition of the cell walls of the three above mentioned dissociative variants of the strains belonging to the genus Bacillus.
