Navegando por Autor "Tarrah, Armin"
Agora exibindo 1 - 6 de 6
- Resultados por Página
- Opções de Ordenação
Item Comparative transcriptomic analysis of Streptococcus thermophilus TH1436 and TH1477 showing different capability in the use of galactose(Frontiers in Microbiology, 2018-08) Duarte, Vinícius da Silva; Giaretta, Sabrina; Treu, Laura; Vendramin, Veronica; Tarrah, Armin; Campanaro, Stefano; Corich, Viviana; Giacomini, AlessioStreptococcus thermophilus is a species widely used in the dairy industry for its capability to rapidly ferment lactose and lower the pH. The capability to use galactose produced from lactose hydrolysis is strain dependent and most of commercial S. thermophilus strains are galactose-negative (Gal − ), although galactose-positive (Gal + ) would be more technologically advantageous because this feature could provide additional metabolic products and prevent galactose accumulation in foods. In this study, a next generation sequencing transcriptome approach was used to compare for the first time a Gal + and a Gal − strain to characterize their whole metabolism and shed light on their different properties, metabolic performance and gene regulation. Transcriptome analysis revealed that all genes of the gal operon were expressed very differently in Gal + and in the Gal − strains. The expression of several genes involved in mixed acid fermentation, PTS sugars transporter and stress response were found enhanced in Gal + . Conversely, genes related to amino acids, proteins metabolism and CRISPR associated proteins were under-expressed. In addition, the strains showed a diverse series of predicted genes controlled by the transcriptional factor catabolite control protein A (CcpA). Overall, transcriptomic analysis suggests that the Gal + strain underwent a metabolic remodeling to cope with the changed environmental conditions.Item A cryptic non-inducible prophage confers phage-immunity on the Streptococcus thermophilus M17PTZA496(Viruses, 2019-01) Duarte, Vinícius da Silva; Giaretta, Sabrina; Campanaro, Stefano; Treu, Laura; Armani, Andrea; Tarrah, Armin; Paula, Sérgio Oliveira de; Giacomini, Alessio; Corich, VivianaStreptococcus thermophilus is considered one of the most important species for the dairy industry. Due to their diffusion in dairy environments, bacteriophages can represent a threat to this widely used bacterial species. Despite the presence of a CRISPR-Cas system in the S. thermophilus genome, some lysogenic strains harbor cryptic prophages that can increase the phage-host resistance defense. This characteristic was identified in the dairy strain S. thermophilus M17PTZA496, which contains two integrated prophages 51.8 and 28.3 Kb long, respectively. In the present study, defense mechanisms, such as a lipoprotein-encoding gene and Siphovirus Gp157, the last associated to the presence of a noncoding viral DNA element, were identified in the prophage M17PTZA496 genome. The ability to overexpress genes involved in these defense mechanisms under specific stressful conditions, such as phage attack, has been demonstrated. Despite the addition of increasing amounts of Mitomycin C, M17PTZA496 was found to be non-inducible. However, the transcriptional activity of the phage terminase large subunit was detected in the presence of the antagonist phage vB_SthS-VA460 and of Mitomycin C. The discovery of an additional immune mechanism, associated with bacteriophage-insensitive strains, is of utmost importance, for technological applications and industrial processes. To our knowledge, this is the first study reporting the capability of a prophage integrated into the S. thermophilus genome expressing different phage defense mechanisms. Bacteriophages are widespread entities that constantly threaten starter cultures in the dairy industry. In cheese and yogurt manufacturing, the lysis of Streptococcus thermophilus cultures by viral attacks can lead to huge economic losses. Nowadays S. thermophilus is considered a well-stablished model organism for the study of natural adaptive immunity (CRISPR-Cas) against phage and plasmids, however, the identification of novel bacteriophage-resistance mechanisms, in this species, is strongly desirable. Here, we demonstrated that the presence of a non-inducible prophage confers phage-immunity to an S. thermophilus strain, by the presence of ltp and a viral noncoding region. S. thermophilus M17PTZA496 arises as an unconventional model to study phage resistance and potentially represents an alternative starter strain for dairy productions.Item Differences in carbohydrates utilization and antibiotic resistance between Streptococcus macedonicus and Streptococcus thermophilus strains isolated from dairy products in Italy(Current Microbiology, 2018-06-18) Duarte, Vinicius; Tarrah, Armin; Treu, Laura; Giaretta, Sabrina; Corich, Viviana; Giacomini, AlessioStreptococcus thermophilus and S. macedonicus are the only two species of the genus related to food productions so far known. In the present study, eight S. thermophilus and seven S. macedonicus strains isolated from dairy environments in Italy were compared in order to evidence possible species-specific technological characteristics. Their capability to use lactose, galactose, fructose, and glucose, sugars commonly present in foods and two carbohydrates considered as prebiotics, xylose and inulin, along with the respective growth kinetics were studied. Results showed a luxuriant growth on lactose and different behaviors on galactose, glucose, and fructose. No growth on inulin and xylose was recorded, which is a positive feature for strains intended to be used as starter cultures. Growth parameters, namely, λ, µmax, and Nmax, were estimated by using the Gompertz model. Antibiotic resistance to 14 drugs revealed an overall similar behavior between the two species with only a marked difference regarding gentamycin. Antimicrobial activity was also tested against six deleterious bacterial strains, but none of the strains evidenced inhibitory capabilities. The results presented here could be helpful to compare technological potentialities of the two species and to choose strains of the most suitable species for selected microbiological food transformations.Item Effect of different initial pH on the growth of Streptococcus macedonicus and Streptococcus thermophilus strains(International Dairy Journal, 2018-11) Duarte, Vinícius da Silva; Tarrah, Armin; Noal, Valentina; Giaretta, Sabrina; Treu, Laura; Corich, Viviana; Giacomini, AlessioStreptococcus thermophilus and Streptococcus macedonicus are two known species of the genus related to foods, but little information is available for the latter species, introduced quite recently. Streptococci are widely used as starter cultures to rapidly lower food pH, thus inhibiting the development of deleterious and pathogenic microbes. We compared the growth kinetics over 24 h of nine S. thermophilus and eight S. macedonicus strains, isolated from various dairy environments, at three different pH values, namely 7.0, 6.0 and 5.5. The Gompertz model was used to estimate the three main growth parameters, namely lag phase duration (λ), maximum growth rate (μmax) and maximum cell number at the stationary phase (Nmax). Our results report significantly shorter lag phases and faster growth rates at all the pH conditions tested for S. macedonicus strains, thus indicating this species as a possible interesting substitute for S. thermophilus in selected food productions.Item In vitro probiotic potential and anti-cancer activity of newly isolated folate-producing Streptococcus thermophilus strains(Frontiers in Microbiology, 2018-09) Duarte, Vinicius da Silva; Tarrah, Armin; Castilhos, Juliana de; Rossi, Rochele Cassanta; Ziegler, Denize Righetto; Corich, Viviana; Giacomini, AlessioMost probiotic strains commercially available today are lactic acid bacteria. Withinthis functional group, Streptococcus thermophilus is a thermophilic species widely used as starter culture for a huge number of dairy products. Besides being rapid acidifiers, many S. thermophilus strains are able to produce and release folate during growth but, unfortunately, they are seriously impaired during passage through the human gastrointestinal tract. In this work, we studied eight S. thermophilus strains isolated from dairy environments in Italy, which already had shown good technological properties, to evaluate their possible probiotic potential and cytotoxicity against cancer cells in vitro. All strains were also evaluated for some health-related properties such as susceptibility to most common antibiotics, hemolytic activity, resistance to simulated gastrointestinal conditions, bile salts hydrolytic activity, production of folate, adhesion to HT-29 human colorectal adenocarcinoma cells and cytotoxic activity against cancer cells and production of biogenic amines. Results revealed that two fast acidifying S. thermophilus strains were found to possess in vitro probiotic properties along with anticancer activity and production of folate. These properties resulted similar and, in some cases, superior to those of Lactobacillus rhamnosus GG, a well-known commercial probiotic strain. These findings encourage further in vivo studies to evaluate the actual health benefits of these strains on the human host.Item Short communication: comparison of growth kinetics at different temperatures of Streptococcus macedonicus and Streptococcus thermophilus strains of dairy origin(Journal of Dairy Science, 2018-09) Duarte, Vinícius da Silva; Tarrah, Armin; Noal, Valentina; Treu, Laura; Giaretta, Sabrina; Corich, Viviana; Giacomini, AlessioWithin the genus Streptococcus, S. thermophilus and S. macedonicus are the 2 known species related to foods. Streptococci are widely used as starter cultures to rapidly lower milk pH. As S. macedonicus has been introduced quite recently, much less information is available on its technological potential. Because temperature is an important factor in fermented food production, we compared the growth kinetics over 24 h of 8 S. thermophilus and 7 S. macedonicus strains isolated from various dairy environments in Italy, at 4 temperatures, 30°C, 34°C, 37°C and 42°C. We used the Gompertz model to estimate the 3 main growth parameters; namely, lag phase duration (λ), maximum growth rate (µmax), and maximum cell number at the stationary phase (Nmax). Our results showed significant differences in average growth kinetics between the 2 species. Among the strains tested, 37°C appeared to be the optimal temperature for the growth of both species, particularly for S. macedonicus strains, which showed mean shorter lag phases and higher cell numbers compared with S. thermophilus. Overall, the growth curves of S. macedonicus strains were more similar to each other whereas S. thermophilus strains grew very differently. These results help to better define and compare technological characteristics of the 2 species, in view of the potential use of S. macedonicus in place of S. thermophilus in selected technological applications.