Stimulation of laccases from Trametes pubescens: Use in dye decolorization and cotton bleaching

The production of laccases from Trametes pubescens was investigated along with the role of nutrients and elicitors. Copper proved to be a fundamental inducer, although productivity yields were consistently enhanced only in the presence of additional compounds (textile dyes). Using a central composite design, the optimal culture condition was examined, by taking into consideration the three distinct variables and their combinatorial effect. The 290?U?ml^?1 of laccases were produced after setting nitrogen, copper, and reactive blue 19 concentration; in a bioreactor, activity recovery was lower (90?U?ml^?1) and pellet morphology was different. The activity of the laccase crude extract was maximal at 60°C and stable for 14?h at 50°C and for 2 months at pH 6 and room temperature. The biotechnological potential was assessed, confirming the capacity to decolorize single or mixed solutions of textile dyes and to enhance the whitening yield of raw cotton fibers, working in synergism with the conventional H₂O₂-based method.     

Occurrence, diversity, and pathogenicity of halophilic Vibrio spp. and non-O1 Vibrio cholerae from estuarine waters along the Italian Adriatic coast.

The occurrence, diversity, and pathogenicity of Vibrio spp. were investigated in two estuaries along the Italian Adriatic coast. Vibrio alginolyticus was the predominant species, followed by Vibrio parahaemolyticus, non-O1 Vibrio cholerae, and Vibrio vulnificus. By using a biochemical fingerprinting method, all isolates were grouped into nine phenotypes with similarity levels of 75 to 97.5%. The production of toxins capable of causing cytoskeleton-dependent changes was detected in a large number of Vibrio strains. These findings indicate a significant presence of potentially pathogenic Vibrio strains along the Adriatic coast.     

Enzymatic surface modification and functionalization of PET: A water contact angle,FTIR, and fluorescence spectroscopy study

The purpose of this study was to investigate the changes induced by a lypolytic enzyme on the surface properties of polyethylene terephthalate (PET). Changes in surface hydrophilicity were monitored by means of water contact angle (WCA) measurements. Fourier Transform Infrared spectroscopy (FTIR) in the Attenuated Total Reflectance mode (ATR) was used to investigate the structural and conformational changes of the ethylene glycol and benzene moieties of PET. Amorphous and crystalline PET membranes were used as substrate. The lipolytic enzyme displayed higher hydrolytic activity towards the amorphous PET substrate, as demonstrated by the decrease of the WCA values. Minor changes were observed on the crystalline PET membrane. The effect of enzyme adhesion was addressed by applying a protease after‐treatment which was able to remove the residual enzyme protein adhering to the surface of PET, as demonstrated by the behavior of WCA values. Significant spectral changes were observed by FTIR–ATR analysis in the spectral regions characteristic of the crystalline and amorphous PET domains. The intensity of the crystalline marker bands increased while that of the amorphous ones decreased. Accordingly, the crystallinity indexes calculated as band intensity ratios (1,341/1,410 cm^?1 and 1,120/1,100 cm^?1) increased. Finally, the free carboxyl groups formed at the surface of PET by enzyme hydrolysis were esterified with a fluorescent alkyl bromide, 2‐(bromomethyl)naphthalene (BrNP). WCA measurements confirmed that the reaction proceeded effectively. The fluorescence results indicate that the enzymatically treated PET films are more reactive towards BrNP. FTIR analysis showed that the surface of BrNP‐modified PET acquired a more crystalline character. Biotechnol. Bioeng. 2009;103: 845–856. © 2009 Wiley Periodicals, Inc.     

Influence of cetylpyridinium chloride on the ultrastructural appearance of sulphated glycosaminoglycans in human colonic mucosa

Summary The effect of adding cetylpyridinium chloride to the fixative on the preservation of sulphated glycosaminoglycans (SGs) was studied in human normal colonic mucosa. SGs were visualized at the ultrastructural level through the application of Spicer's High Iron Diamine (HID) technique followed by a post-fixation with potassium ferrocyanide-reduced osmium tetroxide. SGs were mainly localized in basement membranes of epithelium and capillary wall and along collagen fibers. The morphology of the reactive sites depended on the presence of cetylpyridinium chloride, SGs being granular in absence of the salt and more or less elongated when cetylpyridinium chloride was added to the fixative.We suggest that the use of cetylpyridinium chloride during fixation may help to preserve SG molecule at the ultrastructural level.     

On the mode of action ofClostridiumdifficile toxin A: aninvitro study

C. difficile toxin A causes the rounding up and the formation of surface blebs in normal rat intestinal crypt cells (IEC-6). These phenomena, together with the inhibition of DNA synthesis and the cell lysis, could be the mechanisms leading the toxin-treated cells to death.     

Suicide behavior of target cells after binding with natural killer cells

Human natural killer (NK) cell activity seems to be related to the integrity and function of the cytoskeletal apparatus. It has been hypothesized that microfilaments and microtubules play a pivotal role. In particular, the binding of the NK cell to the target cell requires microfilament integrity, and the lysis of bound targets seems to depend on microtubule assembly. We focused on the changes occurring in cytoskeletal elements and surface structures of NK cells and of target cells highly sensitive to NK activity (K562). Our observations, performed by fluorescence and scanning electron microscopy, besides confirming a rearrangement of the cytoskeletal apparatus in the effector cell, provide evidence that target cell cytoskeletal elements are involved in NK cell function. In K562 cells, after binding with NK cells, there is marginal rearrangement of actin and polarization of tubulin and vimentin in the contact regions, accompanied by modification of surface structures. These findings suggest that the target cell plays an active role in its own death by participating in the formation of an extended area of intimate contact with the killer cell. In addition, they lend credence to the surprising proposal that NK cells may induce a suicide mechanism in target cells.     

Biofilm-growing intestinal anaerobic bacteria

Sessile growth of anaerobic bacteria from the human intestinal tract has been poorly investigated, so far. We recently reported data on the close association existing between biliary stent clogging and polymicrobial biofilm development in its lumen. By exploiting the explanted stents as a rich source of anaerobic bacterial strains belonging to the genera Bacteroides, Clostridium, Fusobacterium, Finegoldia, Prevotella, and Veillonella, the present study focused on their ability to adhere, to grow in sessile mode and to form in vitro mono- or dual-species biofilms. Experiments on dual-species biofilm formation were planned on the basis of the anaerobic strains isolated from each clogged biliary stent, by selecting those in which a couple of anaerobic strains belonging to different species contributed to the polymicrobial biofilm development. Then, strains were investigated by field emission scanning electron microscopy and confocal laser scanning microscopy to reveal if they are able to grow as mono- and/or dual-species biofilms. As far as we know, this is the first report on the ability to adhere and form mono/dual-species biofilms exhibited by strains belonging to the species Bacteroides oralis, Clostridium difficile, Clostridium baratii, Clostridium fallax, Clostridium bifermentans, Finegoldia magna, and Fusobacterium necrophorum.     

Interaction of<Emphasis Type="Italic">Escherichia coli</Emphasis> cytotoxic necrotizing factor type 1 (CNF1) with cultured cells

The cytotoxic necrotizing factor type 1 (CNF1) fromE. coli causes necrosis in rabbit skin and multinucleation in cultured cells. Cells exposed to CNF1 were characterized by changes in actin organization, mainly consisting in the presence of well-developed stress fibers and membrane ruffles. The interaction of CNF1 with the cell cytoskeleton probably promotes the cell spreading and interferes with the cytokinesis, leading to the formation of giant multinucleated cells.