ABSTRACT
Key biological functions involved in cell survival have been studied to understand the difference between the impact of exposure to TiO2 nanoparticles (TiO2-NPs) and their bulk counterparts (bulk-TiO2). By selecting a unicellular eukaryotic model organism and applying proteomic analysis an overview of the possible impact of exposure could be obtained. In this study, we investigated the early response of unicellular eukaryotic protozoan Tetrahymena thermophila exposed to TiO2-NPs or bulk-TiO2 particles at subtoxic concentrations for this organism. The proteomic analysis based on 2DE + nLC-ESI-MS/MS revealed 930 distinct protein spots, among which 77 were differentially expressed and 18 were unambiguously identified. We identified alterations in metabolic pathways, including lipid and fatty acid metabolism, purine metabolism and energetic metabolism, as well as salt stress and protein degradation. This proteomic study is consistent with our previous findings, where the early response of T. thermophila to subtoxic concentrations of TiO2 particles included alterations in lipid and fatty acid metabolism and ion regulation. The response to the lowest TiO2-NPs concentration differed significantly from the response to higher TiO2-NPs concentration and both bulk-TiO2 concentrations. Alterations on the physiological landscape were significant after exposure to both nano- and bulk-TiO2; however, no toxic effects were evidenced even at very high exposure concentrations. This study confirms the relevance of the alteration of the lipid profile and lipid metabolism in understanding the early impact of TiO2-NPs in eukaryotic cells, for example, phagocytosing cells like macrophages and ciliated cells in the respiratory epithelium.
Subject(s)
Nanoparticles/toxicity , Proteomics , Protozoan Proteins/metabolism , Tetrahymena thermophila/drug effects , Titanium/toxicity , Dose-Response Relationship, Drug , Lipid Peroxidation/drug effects , Metabolic Networks and Pathways/drug effects , Nanoparticles/chemistry , Particle Size , Protozoan Proteins/genetics , Tandem Mass Spectrometry , Tetrahymena thermophila/genetics , Tetrahymena thermophila/metabolism , Time Factors , Titanium/chemistryABSTRACT
A rise in bifidobacterial numbers resembling the Escherichia coli overgrowth phenomenon was observed in the rat small intestine in a feeding experiment with kidney beans. Bifidobacterial colony counts increased from 7.6 x 10(6) to 1.7 x 10(8) cfu.g-1 of intestinal tissue in the anterior part and from less than 1 x 10(5) to 2.65 x 10(8) cfu.g-1 in posterior part of the intestine. Fifteen bifidobacterial strains were purified and further analysed. Random amplified polymorphic DNA (RAPD) assays were used to genetically differentiate bifidobacterial isolates from rat gut and compare them with type strains of 20 different species from the genus Bifidobacterium. A total of 80 arbitrary decamere primers were screened with 6 isolates, and 7 primers were chosen for the final analysis. The amplified DNA bands were scored and analysed by the unweighted pair-group method using arithmetic averages clustering. The isolates were not identical to each other nor to the screened type strains. Whereas it was possible to group 12 of the isolates into 2 separate clusters, 3 strains showed no significant relatedness to any strain. The results of the RAPD analysis indicated that there was a large degree variability among the bifidobacteria in the rat gut and demonstrated the potential applicability of such an approach in the investigation of microbial diversity in complex ecosystems.
