Biofilm formation and partial biodegradation of polystyrene by the actinomycete <Emphasis Type="Italic">Rhodococcus ruber</Emphasis>

Polystyrene, which is one of the most utilized thermoplastics, is highly durable and is considered to be non-biodegradable. Hence, polystyrene waste accumulates in the environment posing an increasing ecological threat. In a previous study we have isolated a biofilm-producing strain (C208) of the actinomycete Rhodococcus ruber that degraded polyethylene films. Formation of biofilm, by C208, improved the biodegradation of polyethylene. Consequently, the present study aimed at monitoring the kinetics of biofilm formation by C208 on polystyrene, determining the physiological activity of the biofilm and analyzing its capacity to degrade polystyrene. Quantification of the biofilm biomass was performed using a modified crystal violet (CV) staining or by monitoring the protein content in the biofilm. When cultured on polystyrene flakes, most of the bacterial cells adhered to the polystyrene surface within few hours, forming a biofilm. The growth of the on polystyrene showed a pattern similar to that of a planktonic culture. Furthermore, the respiration rate, of the biofilm, exhibited a pattern similar to that of the biofilm growth. In contrast, the respiration activity of the planktonic population showed a constant decline with time. Addition of mineral oil (0.005% w/v), but not non-ionic surfactants, increased the biofilm biomass. Extended incubation of the biofilm for up to 8 weeks resulted in a small reduction in the polystyrene weight (0.8% of gravimetric weight loss). This study demonstrates the high affinity of C208 to polystyrene which lead to biofilm formation and, presumably, induced partial biodegradation.     

Improvement of natural isolates of <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> strains for synthesis of a chiral building block using classic genetics

The asymmetric bio-reduction of 4-chloro-acetoacetic-acid-ethyl-ester to the pharmaceutical building block (S)-4-chloro-3-hydroxybutanoate-ethyl-ester requires the utilization of an enantioselective robust biocatalyst. Some of the natural Saccharomyces cerevisiae strains, isolated from Mount Carmel National Park in Israel, were characterized as resistant to environmental stress. Nevertheless, these strains showed relatively low enantiomeric-excess (ee), while a laboratory strain, Y103, exhibited a selectivity of 98% ee. The enantioselective lab strain was crossed with the multi-stress resistant environmental isolate (93% ee) followed by backcross with Y103, to subsequently obtain a haploid offspring of backcross-1, exhibiting both high multi-stress resistance and high enantioselectivity (98% ee). Introducing osmotic (1 M NaCl), oxidative (0.6 mM H₂O₂) and thermal stress (44°C) to growing cultures of the enantioselective parent, resulted in a decrease of 24–32% in specific activity, while the enantioselectivity of the stress-resistant parent decreased by 4–12% ee. Unlike its original parental strains, the new strain maintained constant specific activity and enantioselectivity when introduced to the various stress factors. This work shows that the classic introgression method, can serve as a viable approach for creating a robust enantioselective biocatalyst, designed for industrial production of chiral compounds.     

Klatskin tumor--results of surgical therapy

Between January 1st 1990 and December 31st 1999, 24 patients affected by Klatskin tumor underwent operation in our department of surgery. According to Bismuth's classification, there were 0 (0%) type I, 5 (21%) type II, 6 (25%) type IIIa, 4 (17%) type IIIb and 9 (37%) type IV tumors. Five patients (21%) were treated by curative resection (group I) while in 14 patients (58%) palliative surgical procedure was performed (group II). In 5 cases (21%) the extension of malignancy did not allowed any procedure (group III). Curative resection for malignant tumors of the hepatic duct bifurcation included wide tumor excision and bile duct resection at the liver hilum (with wedge hepatic resection in one patient) and creation of biliary-enteric anastomosis. Palliative surgical procedure included stent insertion. Jaundice was completely relieved in all patients undergoing resection, since 3 patients (21%) after stenting hadn't satisfactory biliary drainage. There was 1 (20%) perioperative death in the group 1, while in group 2, 5 patients (36%) died postoperatively. In this series, the mean postoperative survival of all patients was 16 months. The mean postoperative survival of patients undergoing localized tumor resection with curative intent was 38 months, in contrast to 10 months for those undergoing operative stent insertion. in addition, only 1 patient from group III, in whom only exploratory surgery were performed survived 7 months, while other 4 patients died in the hospital. This retrospective review suggests that aggressive surgical treatment could improve survival and quality of life in patients suffering from Klatskin tumor.     

Enhanced recognition of human NK receptors after influenza virus infection

The NK cell cytotoxic activity is regulated by both inhibitory and activating NK receptors. Thus, changes in the expression levels and in the affinity or avidity of those receptors will have a major effect on the killing of target cells. In this study, we demonstrate that the binding of NK-inhibitory receptors is enhanced after influenza virus infection. Surprisingly, however, no change in the level of class I MHC protein expression was observed on the surface of the infected cells. The increased binding was general, because it was observed in both the killer cell Ig-like receptor 2 domain long tail 1 and leukocyte Ig-like receptor-1. The increased binding was functional, was not dependent on the interaction with viral hemagglutinin-neuraminidase, was not dependent on the glycosylation site, and was not abolished after mutating the transmembrane or cytosolic portions of the class I MHC proteins. Confocal microscopy experiments showed increased binding of NK receptor-coated beads to infected cells expressing the appropriate class I MHC proteins. In addition, specific cell-free bead aggregates covered with class I MHC proteins were observed only in infected cells. We therefore suggest that the influenza virus use a novel mechanism for the inhibition of NK cell activity. This mechanism probably involves the generation of class I MHC complexes in infected cells that cause increased recognition of NK receptors.     

Intercellular transfer of carcinoembryonic antigen from tumor cells to NK cells

The inhibition of NK cell killing is mainly mediated via the interaction of NK inhibitory receptors with MHC class I proteins. In addition, we have previously demonstrated that NK cells are inhibited in a class I MHC-independent manner via homophilic carcinoembryonic Ag (CEA) cell adhesion molecules (CEACAM1)-CEACAM1 and heterophilic CEACAM1-CEA interactions. However, the cross-talk between immune effector cells and their target cells is not limited to cell interactions per se, but also involves a specific exchange of proteins. The reasons for these molecular exchanges and the functional outcome of this phenomenon are still mostly unknown. In this study, we show that NK cells rapidly and specifically acquire CEA molecules from target cells. We evaluated the role of cytotoxicity in the acquisition of CEA and demonstrated it to be mostly killing independent. We further demonstrate that CEA transfer requires a specific interaction with an unknown putative NK cell receptor and that carbohydrates are probably involved in CEA recognition and acquisition by NK cells. Functionally, the killing of bulk NK cultures was inhibited by CEA-expressing cells, suggesting that this putative receptor is an inhibitory receptor.     

Toxicological Approach for Assessing the Heavy Metal Binding Capacity of Soils

A toxicological approach was taken to determine the heavy metal binding capacity of soils. A soil heavy metal binding capacity (SHMBC) methodology was developed and was based on the use of the MetPLATE ^TM toxicity test kit, a bioassay that is specific for heavy metal toxicity. SHMBC test is based on the heavy metal binding capacity (HMBC) concept that has been considered in the assessment of the metal binding capacity of surface waters (Huang et al., 1999 Huang, F., Bitton, G. and Kong, I.-C. 1999. Determination of the heavy metal binding capacity of aquatic samples using MetPLATE?: a preliminary study. Sci. Total Environ, 234: 139–145.  [Google Scholar]) and solid wastes landfill leachates (Ward et al., 2005 Ward, M., Bitton, G. and Townsend, T. 2005. Heavy metal binding capacity (HMBC) of municipal solid waste landfill leachates. Chemosphere, 60: 206–215. [Crossref], [PubMed], [Web of Science ®] [Google Scholar]). SHMBC is the ratio of the EC ₅₀ of an added metal in a soil sample divided by the EC ₅₀ of a metal in a reference soil (clean Ottawa sand). A higher SHMBC value indicates higher metal binding to soil and lower bioavailability and potential toxicity to the test bacteria.

Five soils (two sandy soils, two organic soils and a clay soil) were used to determine their binding capacity towards Cu, Zn, and Hg, using the developed SHMBC test. The test measured the ability of the solids to reduce metal bioavailability and toxicity. SHMBC was highest for the clay soil and lowest for the sandy soils. The potential application of this relatively rapid (a few hours) test to predict metal toxicity to terrestrial plants is discussed.     

Virtual dyscalculia induced by parietal-lobe TMS impairs automatic magnitude processing

People suffering from developmental dyscalculia encounter difficulties in automatically accessing numerical magnitudes [1-3]. For example, when instructed to attend to the physical size of a number while ignoring its numerical value, dyscalculic subjects, unlike healthy participants, fail to process the irrelevant dimension automatically and subsequently show a smaller size-congruity effect (difference in reaction time between incongruent [e.g., a physically large 2 and a physically small 4] and congruent [e.g., a physically small 2 and a physically large 4] conditions), and no facilitation (neutral [e.g., a physically small 2 and a physically large 2] versus congruent) [3]. Previous imaging studies determined the intraparietal sulcus (IPS) as a central area for numerical processing [4-11]. A few studies tried to identify the brain dysfunction underlying developmental dyscalculia but yielded mixed results regarding the involvement of the left [12] or the right [13] IPS. Here we applied fMRI-guided TMS neuronavigation to disrupt left- or right-IPS activation clusters in order to induce dyscalculic-like behavioral deficits in healthy volunteers. Automatic magnitude processing was impaired only during disruption of right-IPS activity. When using the identical paradigm with dyscalculic participants, we reproduced a result pattern similar to that obtained with nondyscalculic volunteers during right-IPS disruption. These findings provide direct evidence for the functional role of right IPS in automatic magnitude processing.     

Human sperm chemotaxis: is progesterone a chemoattractant?

Follicular fluid (FF) induces sperm chemotaxis in human spermatozoa. Progesterone also causes sperm accumulation. However, sperm accumulation can be caused by chemotaxis, chemokinesis, and trapping of various kinds. It has been suggested that progesterone also induces chemotaxis in human spermatozoa. In view of the physiological significance of sperm chemotaxis in human fertilization and its potential clinical implications, it is important to determine unequivocally whether chemotaxis is induced by progesterone and, if so, whether progesterone in FF is the chemoattractant. To resolve these questions we looked for characteristic changes in the direction of sperm swimming toward pure progesterone as well as toward FF before and after progesterone removal. Progesterone caused sperm accumulation and hyperactivation-like motility, but it caused very few changes in the direction of sperm swimming that are characteristic of chemotaxis. Removal of progesterone (and other steroids) from FF by charcoal treatment abolished the sperm hyperactivation-like motility but not sperm chemotaxis. These results suggest that while progesterone might be a weak chemoattractant, it is not the major chemoattractant in FF. Progesterone probably causes human sperm accumulation mainly by inducing hyperactivation-like motility and, as a consequence, sperm trapping.