Browsing by Author "Andrew, Peter"
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- Stress response of Listeria monocytogenes isolated from cheese and other foodsPublication . Faleiro, Maria Leonor; Andrew, Peter; Power, DeborahThe responses to pH and sodium chloride of four strains of Listeria monocytogenes isolated from Portuguese cheese, with a sodium chloride concentration of about 2% (w/v) and a pH value from 5.1 to 6.2, were studied. Two isolates from meat and two clinical isolates related to food-borne listeriosis, in which the implicated food product had about 2–3.5% (w/v) sodium chloride, also were studied. The effect of temperature on pH and sodium chloride sensitivity was also determined. The results show that natural isolates vary in response to these stresses and the data were often at variance with previously published data. Strains varied in sensitivity to low pH and to high sodium chloride concentration but the cheese isolates tended to be more resistant. A lower temperature was associated with a decrease in resistance to low pH and to sodium chloride. All strains showed an acid tolerance response induction when grown at pH 5.5 and although the time required for maximum induction of the response varied between strains, 2 h of acid adaptation, at least, was necessary which is longer than previously reported. Some strains showed an osmotolerance response after incubation in 3.5% (w/v) sodium chloride. Osmoadaptation, in addition to inducing an osmotolerance response, also induced cross-protection against acid shock conditions (pH 3.5). The acid tolerance response also induced a cross-protection against osmotic shock conditions (20% (w/v) sodium chloride). In some cases there was a relationship between the degree of resistance and adaptation, but usually the behaviour of a particular strain was independent of the conditions from which it was isolated.
- The intestinal proteome of diabetic and control children is enriched with different microbial and host proteinsPublication . Pinto, Elsa; Anselmo, Marisol; Calha, Maria; Bottrill, Andrew; Duarte, Isabel; Andrew, Peter; Faleiro, LeonorIn this study the intestinal microbial proteome of children with established type 1 diabetes (T1D) was compared with the proteome of healthy children (Control) with the aim to identify differences in the activity of the intestinal microbiota that will not only contribute to a deeper knowledge of the functionality of the gut in these children but may also provide new approaches to improve the Control of the disease. Fecal protein extracts collected from three T1D children (aged of 9.3 - 0.6) and three Control children (aged of 9.3 - 1.5) were analyzed using a combination of two-dimensional gel electrophoresis (2-DE) and spectral counting. The results evidenced markedly differences between the intestinal proteome of T1D children and the Control. The T1D microbial intestinal proteome was enriched with proteins of clostridial cluster XVa and cluster IV and Bacteroides. In contrast, the Control proteome was enriched with bifidobacterial proteins. In both groups proteins with moonlight function were observed. Human proteins also distinguished the two groups with T1D children depleted in exocrine pancreatic enzymes.