Identification of the lipooligosaccharide biosynthetic gene cluster from Mycobacterium marinum

Lipooligosaccharides (LOSs) are antigenic glycolipids that are present in some species of Mycobacterium including the Canetti strain of M. tuberculosis. The core LOS structures from several mycobacterial organisms have been established, but the biosynthetic pathways of LOSs remain unknown. In this study, we describe two transposon insertion mutants of M. marinum that exhibit altered colony morphology. Cell wall analysis reveals that the MRS1271 mutant is defective in the synthesis of LOS-II, whereas the MRS1178 mutant accumulates an intermediate between LOS-I and -II. The genetic lesions were localized to two genes, MM2309 and MM2332. MM2309 encodes a UDP-glucose dehydrogenase that is involved in the synthesis of d-xylose. MM2332 is predicted to encode a decarboxylase. These two genes and a previously identified losA gene are localized in a gene cluster likely to be involved in the biosynthesis of LOSs. Our results also show that LOSs play an important role in sliding motility, biofilm formation, and infection of host macrophages. Taken together, our studies have identified, for the first time, a LOS biosynthetic locus. This is an important step in assessing the differential distribution of LOSs among Mycobacterium species and understanding the role of LOSs in mycobacterial virulence.     

E-LDL upregulates TOSO expression and enhances the survival of human macrophages

Uptake of modified lipoproteins by macrophages causes foam cell formation and promotes atherosclerosis. Atherogenic lipoproteins are cytotoxic and induce cell death under certain conditions but may also enhance macrophage survival. Macrophages treated with enzymatically modified LDL (E-LDL) were subjected to GeneChip analysis and the antiapoptotic gene TOSO was found induced. TOSO mRNA is upregulated and apoptosis is reduced in E-LDL but not in oxidized LDL (Ox-LDL) loaded macrophages. FLIP(L) abundance was suggested to mediate the antiapoptotic properties of TOSO; however, FLIP(L) was not changed. Ox-LDL is internalized predominantly by scavenger receptors such as CD36 while E-LDL particles are preferentially internalized by Fc- and complement-receptor dependent phagocytosis and internalization of phagobeads by macrophages upregulates TOSO. In COS-7 cells however, phagocytotic activity was not affected by TOSO. These data indicate that E-LDL-generated foam cells are protected from cell death most likely through the expression of TOSO by a FLIP(L) independent mechanism.     

The design and evaluation of a virtual distributed computing environment

Current advances in high-speed networks such as ATM and fiber-optics, and software technologies such as the JAVA programming language and WWW tools, have made network-based computing a cost-effective, high-performance distributed computing environment. Metacomputing, a special subset of network-based computing, is a well-integrated execution environment derived by combining diverse and distributed resources such as MPPs, workstations, mass storage, and databases that show a heterogeneous nature in terms of hardware, software, and organization. In this paper we present the Virtual Distributed Computing Environment (VDCE), a metacomputing environment currently being developed at Syracuse University. VDCE provides an efficient web-based approach for developing, evaluating, and visualizing large-scale distributed applications that are based on predefined task libraries on diverse platforms. The VDCE task libraries relieve end-users of tedious task implementations and also support reusability. The VDCE software architecture is described in terms of three modules: (a) the Application Editor, a user-friendly application development environment that generates the Application Flow Graph (AFG) of an application; (b) the Application Scheduler, which provides an efficient task-to-resource mapping of AFG; and (c) the VDCE Runtime System, which is responsible for running and managing application execution and for monitoring the VDCE resources. We present experimental results of an application execution on the VDCE prototype for evaluating the performance of different machine and network configurations. We also show how the VDCE can be used as a problem-solving environment on which large-scale, network-centric applications can be developed by a novice programmer rather than by an expert in low-level details of parallel programming languages. This revised version was published online in July 2006 with corrections to the Cover Date.     

Warm temperature accelerates short photoperiod-induced growth cessation and dormancy induction in hybrid poplar (Populus × spp.)

There is increasing evidence that temperature, in addition to photoperiod, may be an important factor regulating bud dormancy. The impact of temperature during growth cessation, dormancy development, and subsequent cold acclimation was examined in four hybrid poplar clones with contrasting acclimation patterns: ‘Okanese’—EARLY, ‘Walker’—INT1, ‘Katepwa’—INT2, and ‘Prairie Sky’—LATE. Four day–night temperature treatments (13.5/8.5, 18.5/13.5, 23.5/8.5, and 18.5/3.5°C) were applied during a 60-day induction period to reflect current and predicted future annual variation in autumn temperature for Saskatoon, SK. Warm night temperature (18.5/13.5°C) strongly accelerated growth cessation, dormancy development, and cold acclimation in all four clones. Day temperature had the opposite effect of night temperature. Day and night temperatures appeared to act antagonistically against each other during growth cessation and subsequent dormancy development and cold acclimation. Growth cessation, dormancy development, and cold acclimation in EARLY and LATE were less affected by induction temperature than INT1 and INT2 suggesting that genotypic variations exist in response to temperature. Separating specific phenological stages and the impact by temperature on each clone revealed the complexity of fall phenological changes and their interaction with temperature. Most importantly, future changes in temperature may affect time to growth cessation, subsequently altering the depth of dormancy and cold hardiness in hybrid poplar.     

Pyrite Suspended in Artificial Sea Water Catalyzes Hydrolysis of Adsorbed ATP: Enhancing Effect of Acetate

Minerals have been implicated in different catalytic processes during chemical evolution. It has been proposed that exergonic synthesis of pyrite (FeS₂) could have served to promote the endergonic synthesis of biomonomers in early stages of life formation on Earth. The present study was aimed to investigate whether pyrite can adsorb nucleotides and oxo acids in the potentially mild prebiotic conditions found away from the hot hydrothermal vents. It is shown that pyrite strongly adsorbs adenosine 5-triphosphate in an artificial medium that simulates primordial aqueous environments, and that adsorption is enhanced in the presence of acetate and in an oxygen-free atmosphere. Moreover, the mineral catalyzes the sequential hydrolysis of the and phosphoanhydride bonds of the nucleotide.     

IL-2-activated CD8+CD44high cells express both adaptive and innate immune system receptors and demonstrate specificity for syngeneic tumor cells

CD8(+) T cells depend on the alphabeta TCR for Ag recognition and function. However, Ag-activated CD8(+) T cells can also express receptors of the innate immune system. In this study, we examined the expression of NK receptors on a population of CD8(+) T cells expressing high levels of CD44 (CD8(+)CD44(high) cells) from normal mice. These cells are distinct from conventional memory CD8(+) T cells and they proliferate and become activated in response to IL 2 via a CD48/CD2-dependent mechanism. Before activation, they express low or undetectable levels of NK receptors but upon activation with IL-2 they expressed significant levels of activating NK receptors including 2B4 and NKG2D. Interestingly, the IL-2-activated cells demonstrate a preference in the killing of syngeneic tumor cells. This killing of syngeneic tumor cells was greatly enhanced by the expression of the NKG2D ligand Rae-1 on the target cell. In contrast to conventional CD8(+) T cells, IL-2-activated CD8(+)CD44(high) cells express DAP12, an adaptor molecule that is normally expressed in activated NK cells. These observations indicate that activated CD8(+)CD44(high) cells express receptors of both the adaptive and innate immune system and may play a unique role in the surveillance of host cells that have been altered by infection or transformation.     

Unexpected inhibition of S-adenosyl-L-homocysteine hydrolase by a guanosine nucleoside

A series of shape-modified flexible nucleosides ('fleximers', 1, 2, and 3) was modeled, synthesized and subsequently assayed against S-adenosyl-L-homocysteine hydrolase (SAHase). No inhibitory activity was observed for the adenosine fleximer, which served as a substrate, but moderate inhibitory activity was exhibited by the guanosine fleximers. This is the first known report of a guanosine nucleoside analogue possessing activity against SAHase.