Characterization of lipid accumulation and lipidome analysis in the oleaginous yeasts Rhodosporidium azoricum and Trichosporon oleaginosus.

The influence of cultural conditions on lipid production was investigated in two species, Trichosporon oleaginosus and Rhodosporidium azoricum. We showed that nitrogen limitation is not the main factor triggering the mechanism of lipid accumulation in T. oleaginosus. Moreover, a scarce availability of oxygen negatively affected lipid synthesis to a lesser extent in T. oleaginosus than in R. azoricum. This highlights how the importance of controlling fermentation parameters is strictly linked to the yeast species employed. We showed that these parameters affect the activity of important enzymes, influencing the metabolic fluxes into different pathways, in particular pentose phosphate pathway and cytoplasmic pyruvate bypass. Furthermore, T. oleaginosus exhibited wider substrate flexibility, faster growth and higher lipid accumulation in fed-batch cultivation. Microbial oils obtained from both yeasts proved a valuable feedstock, alternative to vegetable oils, for advanced diesel biofuel production.

Microbiological and genetic identification of some probiotics proposed for medical use in 2011.

The aim of this work was to evaluate if dietary supplements for medical use available on the Italian and European market in 2011 were correctly labelled in terms of amount of viable bacteria, identity of species or genera and lack of cross contamination by species out of label. Fourteen in twenty-four products (58%) contained all the labelled species in the declared amount and were free of bacterial contamination. Ten in twenty-four products (42%) did not contain the labelled bacterial amount. Moreover, in four of these products (17%), we could not find any viable colony of at least one of the declared species. In two of them the DNA of all missing species could be detected by extracting DNA directly from the product. In conclusion, some products available on the Italian and European market in 2011 were not correctly labelled and did not comply with the specific guidelines.

Cultivable and pyrosequenced fecal microflora in centenarians and young subjects.

GOAL: The aim of this study was to characterize the composition of the intestinal microbiota in healthy centenarians in comparison with younger adults, considering both quantitative and qualitative aspects of gut community structure. BACKGROUND: The gut microbiota plays an essential role in human health. Toward seniority, its balance is affected by deep physiological changes. Long-lived people (age >90 y) have unusual features that differ from the younger elderly, so they should be considered separately when analyzing age-related features. However, they have been included in few studies and they have usually been grouped together with the younger elderly. STUDY: The gut microbiota of 14 centenarians and 10 younger adults was analyzed. Cultivable bacteria belonging to the following groups were enumerated: enterobacteriaceae, Enterococcus, Staphylococcus, Lactobacillus, Bifidobacterium, Clostridium, Bacteroides, and yeast. Lactobacilli and Bifidobacteria were further characterized at the species level by pyrosequencing. RESULTS: : In centenarians, we observed a reduction in the quantity of enterobacteriaceae, bifidobacteria, and bacteroides and an increase in clostridia sensu stricto (P<0.05). The number of Lactobacillus and Bifidobacterium species isolated in centenarians and younger adults was similar. The composition of the Lactobacillus subpopulation was quite different between the groups. The presence of Bifidobacterium longum in the gut seems to be a particular feature in centenarians. It is interesting to note that only 1 strain of B. longum was isolated from each centenarian subject. CONCLUSIONS: The gut microbiota of centenarians has particular features that differ from both younger adults and the younger elderly. Further studies would help to understand whether the intestinal microbiota can influence life expectancy and whether the administration of probiotic bacteria could help to extend the longevity of human life.

Macrolide resistance and in vitro selection of resistance to antibiotics in Lactobacillus isolates.

Spreading of resistance to antibiotics is of great concern due to the increasing rate of isolation of multiresistant pathogens. Since commensal bacteria may transfer determinants of resistance to pathogens, studies on development of resistance should include also lactobacilli. Resistance to macrolides, penicillins and tetracycline was determined in 40 isolates of Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus crispatus, and Lactobacillus casei isolated from faeces of apparently healthy volunteers. Frequency of mutation and changes in susceptibility after serial exposure to these antibiotics at concentrations of 4× and 8× MIC were evaluated in susceptible isolates. Acquired resistance was defined as an increment in MIC values of at least four times in respect to the pre-selection values. Resistance to macrolides and/or tetracycline was identified in 14 and 4 isolates, respectively. ermB gene and A2058G mutation in 23S rRNA were detected in macrolide resistant isolates. Frequencies of mutation of susceptible isolates (n=26) were lower for ampicillin and erythromycin than for tetracycline. Serial exposure to antibiotics led to selection of resistant mutants. However, acquired resistance was rather unstable and was lost after subcultures in antibiotic-free medium in most mutants. Resistance to erythromycin was associated to a A2058G mutation in 23S rRNA. In conclusion, results indicate that resistance to macrolides and tetracycline is present among intestinal lactobacilli. Decrease in susceptibility following serial exposure to antibiotics might occur in lactobacilli, in a strain- and antibiotic-dependent way. Since lactobacilli are often used as probiotics, their ability to acquire resistance should be evaluated for isolates candidate to be included in probiotics based products.