Escherichia coli produces phosphoantigens activating human gamma delta T cells.

Human Vgamma9delta2 T lymphocytes are suggested to play an important role in the immune response to various microbial pathogens. In contrast to alphabeta T cells, gammadelta T lymphocytes recognize small, non-protein, phosphate-bearing antigens (phosphoantigens) in a major histocompatibility complex-independent manner. Four different phosphoantigens termed TUBag1 to TUBag4 with a common 3-formyl-1-butyl-pyrophosphate moiety and isopentenyl-pyrophosphate have been isolated and identified from mycobacteria. However, natural occurring gammadelta T cell ligands from other bacterial species were not characterized so far. Here, we describe the structural identification of the two compounds responsible for the gammadelta T cell-stimulating capacity of Escherichia coli as similar to the mycobacterial phosphoantigens 3-formyl-1-butyl-pyrophosphate and its M(r) 275 homologue TUBag2. In addition, E. coli phosphoantigens exert bioactivities on gammadelta T cells with similar potencies to the mycobacterial phosphoantigens at 5-15 nm concentration. Furthermore, our results clearly prove that the deoxyxylulose 5-phophate pathway (also referred to as Rohmer metabolic route of isoprenoid biosynthesis) is essential for the biosynthesis of the phosphoantigens in E. coli. Because this pathway is absent from human cells, it proves an ideal target for focusing efficiently the antimicrobial selectivity of human gammadelta T lymphocytes.     

Conjugative Plasmid Transfer in Gram-Positive Bacteria

Conjugative transfer of bacterial plasmids is the most efficient way of horizontal gene spread, and it is therefore considered one of the major reasons for the increase in the number of bacteria exhibiting multiple-antibiotic resistance. Thus, conjugation and spread of antibiotic resistance represents a severe problem in antibiotic treatment, especially of immunosuppressed patients and in intensive care units. While conjugation in gram-negative bacteria has been studied in great detail over the last decades, the transfer mechanisms of antibiotic resistance plasmids in gram-positive bacteria remained obscure. In the last few years, the entire nucleotide sequences of several large conjugative plasmids from gram-positive bacteria have been determined. Sequence analyses and data bank comparisons of their putative transfer (tra) regions have revealed significant similarities to tra regions of plasmids from gram-negative bacteria with regard to the respective DNA relaxases and their targets, the origins of transfer (oriT), and putative nucleoside triphosphatases NTP-ases with homologies to type IV secretion systems. In contrast, a single gene encoding a septal DNA translocator protein is involved in plasmid transfer between micelle-forming streptomycetes. Based on these clues, we propose the existence of two fundamentally different plasmid-mediated conjugative mechanisms in gram-positive microorganisms, namely, the mechanism taking place in unicellular gram-positive bacteria, which is functionally similar to that in gram-negative bacteria, and a second type that occurs in multicellular gram-positive bacteria, which seems to be characterized by double-stranded DNA transfer.     

Staining of Merkel cells of pig snout epidermis using the uranaffin reaction

The uranaffin reaction (UR) specifically stains neurosecretory (NS) granules of the neuroendocrine system when performed at pH 3.9 and at a 4% concentration of uranyl acetate. Merkel-cell NS granules stained using the UR were found to have a different appearance than granules observed after routine processing. We therefore compared the average values obtained with both methods, examining the maximum diameter, area, form factor, and numerical density of such NS granules. The maximum diameter and area of NS granules were significantly greater (P less than 0.001) in samples stained using a conventional technique (CT) (93.30 nm, 6,411 nm2) that in those stained with the UR (63.95 nm, 2,148 nm2). The form factor of conventionally stained NS granules (0.9) was significantly greater (P less than 0.001) than that of granules stained with the UR (0.7). No significant difference in numerical density was found for the two techniques (CT: 8.11 +/- 2.51; UR: 6.14 +/- 2.38). It was found that the UR is a useful cytochemical marker for NS granules of Merkel cells, and that the ultrastructural morphology and intracellular arrangement of NS granules stained with the UR are different from those revealed using CT.     

Localization of the gene encoding insulin-degrading enzyme to human chromosome 10, bands q23----q25.

Insulin-degrading enzyme (IDE) is a cytosolic proteinase involved in the cellular processing of insulin. Using somatic cell hybrid analysis and in situ chromosomal hybridization, we have localized the gene encoding IDE to human chromosome 10, bands q23----q25. The murine Ide gene was previously mapped to Chromosome 19; together, these results suggest that the IDE gene is a member of a conserved syntenic group on human chromosome 10, bands q23----q25 and mouse Chromosome 19.     

Incidence of Fungal Necrotrophic and Biotrophic Pathogens in Pioneer and Shade‐tolerant Tropical Rain Forest Trees

This study assessed the hypothesis that plant life history traits determine the incidence of fungal biotrophic and necrotrophic pathogens in pioneer vs. shade‐tolerant tropical plant species. Considering that pioneer species mainly invest in induced defenses, we expected a negative relationship between the incidence of biotrophic and necrotrophic pathogens; in contrast, as shade‐tolerant species invest heavily in constitutive defenses, we expected to find no correlation between the incidence of biotrophic and necrotrophic pathogens. These ideas were evaluated by assessing standing levels of fungal damage in a set of pioneer and shade‐tolerant species from the Lacandona tropical rain forest (Mexico). The results showed that among pioneer plant species, leaves with biotrophic lesions were between 34 and 44 percent more abundant than those with necrotic lesions. In contrast, among shade‐tolerant species, the proportions of leaves with necrotic lesions were 17–23 percent higher than those of leaves with injuries caused by biotrophic pathogens. Our study suggests that tropical tree species might present different defense strategies depending on the life‐style of the pathogens that attack them, and the life history strategy of the attacked host plant species. Thus, the host constitutive and induced defenses, as well as the mechanisms used by different types of pathogens to circumvent those defenses maybe responsible for the patterns of attack observed in perennial tropical plants. Abstract in Spanish is available at http://www.blackwell‐synergy.com/loi/btp .     

ATM regulates cell fate choice upon p53 activation by modulating mitochondrial turnover and ROS levels

Despite extensive study, the mechanisms of cell fate choice upon p53 activation remain poorly understood. Using genome-wide shRNA screening, we recently identified the ATM kinase as synthetic lethal with Nutlin-3, an MDM2 inhibitor that leads to non-genotoxic p53 activation. Here, we demonstrate that while this synthetic lethal interaction relies upon components of both the intrinsic and extrinsic apoptotic pathways (e.g., BAX and BID), it is not due to significant ATM effects on the expression of p53 target genes. Instead, loss of ATM activity results in increased mitochondria and reactive oxygen species that drive apoptosis. Finally, we provide evidence that pharmacologic inhibition of ATM blocks autophagy in direct opposition to p53, which activates this process, and that inhibition of autophagy is sufficient to elicit an apoptotic response when combined with Nutlin-3.