We have studied the genotoxicity of TiO2 particles with a Comet assay on a unicellular organism, Tetrahymena thermophila. Exposure to bulkor nanoTiO2 of free cells, cells embedded in gel or nuclei embedded in gel, all resulted in a positive Comet assay result but this outcome could not be confirmed by cytotoxicity measures such as lipid peroxidation, elevated reactive oxygen species or cell membrane composition. Published reports state that in the absence of cytotoxicity, nanoand bulkTiO2 genotoxicity do not occur directly, and a possible explanation of our Comet assay results is that they are false positives resulting from post festum exposure interactions between particles and DNA. We suggest that before Comet assay is used for nanoparticle genotoxicity testing, evidence for the possibility of post festum exposure interactions should be considered. The acellular Comet test described in this report can be used for this purpose.
COBISS.SI-ID: 2573903
Ruminococcus flavefaciens is an important fibre-degrading bacterium found in the mammalian gut. Our study provides new information on the extracellular proteome of R. flavefaciens and its regulation in response to different growth substrates. The major proteins associated with the bacterial cell surface and with the culture supernatant were analyzed for R. flavefaciens cotton non-degrading strain (007S) and cotton-degrading strain (007C) grown with cellobiose, xylan or Avicel cellulose as energy sources. The study revealed that cellulosomal GH48 hydrolase, a rubrerthyrin-like protein and a type IV-pili associated protein were the most strongly up-regulated in 007C cultures grown on Avicel compared with cellobiose. Strain 007S also showed substrate-related changes, but supernatant expression of the Pil protein and rubrerythrin in particular were markedly lower in 007S than in 007C during growth on Avicel. This suggest the potential role of the latter proteins in cotton cellulose degradation.
COBISS.SI-ID: 3233672
The aim of study was to compare recommendations for vitamin E (VE) supplementation and bioactivity of RRR (rT) and all-rac--tocopherol (racT) with respect to oxidative (OX) stress and OX stability of broiler meat. All groups (5) received high fat (7.5%) diets, one with palm and others with linseed oil (LO), which were unsupplemented or supplemented with VE to contain 85 or 200 IU racT and 85 IU rT. OX stress was studied by measuring DNA damage, MDA and ACL. Tocopherols in plasma, liver, and meat were analyzed. OX stability was studied in fresh, stored, and heat-treated meat. LO induced DNA damage and MDA formation. Both forms and levels of VE reduced DNA damage and meat MDA. T levels in tissues and plasma were influenced by supplementation level. For good OX stability of meat, higher VE supplementation is needed. Results confirm that bioactivity ratio rT to racT is 1.39.
COBISS.SI-ID: 2888840
The Shine-Dalgarno sequence is a key element modulating the translation initiation in bacteria. Bioinformatic analysis of forty genomes from the major bacterial phylum Bacteroidetes revealed general absence of SD sequence, drop in GC content and consequently reduced tendency to form secondary structures in 5'UTRs. The experiments using Prevotella bryantii TC1-1, a member of Bacteroidetes, also suggested that a functional SD interaction does not take place during the translation initiation in P. bryantii TC1-1and possibly other members of phylum Bacteroidetes. We thus propose that in the absence of the SD sequence interaction, the selection of start codons in Bacteroidetes is accomplished by binding of ribosomal protein S1 to unstructured 5'UTR as opposed to coding region which is inaccessible due to mRNA secondary structure.
COBISS.SI-ID: 2912136
Nisin is the most studied bacteriocin of lactic acid bacteria, typical for Lactococcus lactis sp. In the presentation the dynamics of 11 gene expression involved in the production of nisin by Lc. lactis M78 in model cheese was described. The presence of nisin in model cheese was confirmed also by biological assay. The work is important because it shows a new approach (RNA isolation, RT realtime PCR) for the study of bacteriocins in a complex environment such as food or digestive tract, which can be used also in studies of other bacteriocins.
COBISS.SI-ID: 2799240