Francesca Trotta

Lactic Acid Bacteria Isolated from Dairy Products Inhibit Genotoxic Effect of 4-Nitroquinoline-1-oxide in SOS-Chromotest

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.

Tolerance to challenges miming gastrointestinal transit by spores and vegetative cells of Bacillus clausii

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.

Inhibition of 4-nitroquinoline-1-oxide genotoxicity by Bacillus strains

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.

Numerical analysis and DNA base compositions of some thermophilic Bacillus species

Morphological, physiological, and biochemical characteristics and the DNA base compositions of 133 thermophilic Bacillus strains were determined. A total of 54 of these strains were received as identified species (mainly Bacillus stearothermophilus, Bacillus coagulans, Bacillus brevis, and Bacillus licheniformis) from international culture collections, and 79 newly isolated strains, which were isolated mainly from sugar diffusion juices of Italian plants, were also examined. Numerical taxonomy techniques (simple matching coefficient and unweight pair grouping using the mathematical average) and DNA G + C values showed that the strains aggregated into nine clusters. Both B. licheniformis and B. brevis were well separated from the other organisms. B. stearothermophilus and B. coagulans were confirmed as separate clusters and exhibited greater heterogeneity than previously shown. The B. stearothermophilus strains clustered into four groups, three of which have been recognized previously by other authors; the members of the fourth group had distinctive characteristics, including considerable biochemical inertness, an inability to grow at temperatures greater than 60 degrees C, and a high G + C content. Within the B. coagulans cluster the strains with characteristics very similar to those of the new species Bacillus smithii clustered together. However, the remaining strains were still clearly separated into two groups; one of these groups was considered B. coagulans sensu stricto, and the other was distinguished by morphological and biochemical criteria, such as spores which do not swell the sporangia, utilization of citrate, a higher proteolytic activity, and acidification of some carbohydrates. Our results were confirmed by comparing them with distinctive characteristics of recently described thermophilic Bacillus species.

In vitro inhibitory activity of probiotic spore-forming bacilli against genotoxins.

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.

Modulatory Activity of a Lactobacillus casei Strain on 1,2-Dimethylhydrazine-Induced Genotoxicity in Rats

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. Environ. Mol. Mutagen., 2008.

Bacterial amylolytic activity enhancesβ-glucuronidase expression of amylase-negativeEscherichia coli strain in starch-medium

The possibility of associating starch degradation with bacterial β‐glucuronidase expression was examined. We proved that starving, in starch medium, amylase‐negative Escherichia coli (M94) which has constitutive β‐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 β‐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 β‐glucuronidase was less evident. The impact of B. subtilis amylase on E. coli β‐glucuronidase induction, observed when the organisms were cocultured, indirectly supports the hypothesis that amylolytic activity of hindgut bacteria may be effective on β‐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.

Contribution to the Characterization of Bacillus megaterium

A study of the cellular and colonial morphologies, the deoxyribonucleic acid (DNA) base composition, the degree of lysis by lysozyme, and some fundamental biochemical reactions was carried out on 23 strains previously identified as members of Bacillus megaterium. Included among these was NCTC 10342, the neotype strain of B. megaterium. The results showed that, primarily on the basis of their biochemical reactions, two of the strains belong to B. cereus, two belong to B. subtilis, and 19 belong to B. megaterium. The first two strains mentioned above clearly differed from B. megaterium strains with respect to their DNA base composition (33.2 and 34.3 mol% guanine plus cytosine [G+C]), their lysis by lysozyme (5.6 and 6.6%), and the morphology of their macro- and microcolonies. These properties were not helpful in differentiating the other two strains from the B. megaterium strains, for the two strains showed high G+C values (45.9 and 47.4 mol%) and high values of lysis by lysozyme, (92.9 and 96.7%). The 19 remaining strains, confirmed as members of B. megaterium, had G+C contents which varied from 37.3 to 43.0 mol% and lysis percentages which varied from 67.0 to 94.9. For these strains, a significant (P < 0.05) correlation was found between the DNA base composition and lysis by lysozyme. Three biogroups were established on the basis of the biochemical reactions of the 19 strains. These biogroups are similar to the “aggregate” and the “intermediate” strains of B. megaterium established by Gordon et al.

In Vitro Inhibition of 4-Nitroquinoline-1-Oxide Genotoxicity by Probiotic Lactobacillus rhamnosus IMC501.

Inhibition of 4-nitroquinoline-1-oxide (4-NQO) genotoxicity by a probiotic strain of Lactobacillus rhamnosus (IMC501) was assessed by the prokaryotic short-term bioassay SOSChromotest, using Escherichia coli PQ37 as the target organism. Results showed the ability of strain IMC501 to rapidly and markedly counteract, in vitro, the DNA damage originated by the considered genotoxin. The inhibition was associated with a spectroscopic hypsochromic shift of the original 4-NQO profile and progressive absorbance increase of a new peak. IR-Raman and GC-MS analyses confirmed the disappearance of 4-NQO after contact with the microorganism, showing also the absence of any genotoxic molecule potentially available for metabolic activation (i.e., 4-hydroxyaminoquinoline-1-oxide and 4-nitrosoquinoline-1-oxide). Furthermore, we have shown the presence of the phenyl-quinoline and its isomers as major non-genotoxic conversion products, which led to the hypothesis of a possible pattern of molecular transformation. These findings increase knowledge on lactobacilli physiology and contribute to the further consideration of antigenotoxicity as a nonconventional functional property of particular probiotic strains.

Chemical characterization and biological properties of airborne particulate matter

SummaryThe presence of heavy metals and Polynuclear Aromatic Hydrocarbons (PAH) has been evidenced in airborne particulate matters samples collected in the atmosphere of a non-industrialized middle size Italian town (150.000 inhabitants). The PAH concentrations, higher in winter than in other seasons, was inversely correlated with some meteorological variables such as temperature (p<0.01) and wind speed (p<0.05). The positive correlation found (p<0.01) between lead and total PAH seems to indicate traffic as the most important source of pollution.All samples were mutagenic in the Ames test and the highest mutagenicity levels were obtained in winter samples. The positive correlation found between Benzo(a)Pyrene {B(a)P} concentration and the number of revertants/m3 air, suggests that B(a)P could be an index of mutagenic potential of the matrix considered.The airborne particulate matter extracts obtained by organic solvents were able to inhibit the phagocytosis of mice alveolar macrophages, giving further proof of the possibility of interaction between air-particulate chemical compounds and important biological functions.