Identification of cell wall antigens associated with a large conjugative plasmid encoding phage resistance and lactose fermentation ability in lactic streptococci

In order to begin to analyze the gene products encoded by phage resistance plasmids in lactic streptococci, we identified phage-resistance plasmids by screening resistant strains from commercial starter cultures for the ability to carry out unselected cotransfer, by conjugation, of phage resistance with lactose fermentation ability (lac+). In this fashion, we identified a large (90 kilobases) plasmid, pCLP51R, that encodes the lac+ marker, resistance to a lytic phage called LP10G (1pr+), high-frequency conjugal donor ability (hft+), and clumpy growth of host bacteria in broth culture (clu+). The mechanism of resistance conferred by this plasmid appears to involve interference with a step in the phage replication cycle that occurs after the initial attachment of the phage. Polyacrylamide gel electrophoresis of cell surface extracts of isogenic strains, carrying or lacking pCLP51R, combined with immunoblotting analysis, showed that there were several plasmid-related differences in the banding pattern of low molecular weight proteins and that the plasmid resulted in production of several unique antigenic polypeptides in the size range of 15-30 kd, as well as modification of chromosomally encoded antigens to different molecular weight forms.     

A review of symbiotic fungal endophytes in lycophytes and ferns – a global phylogenetic and ecological perspective

We present a review of the documented fungal colonizations of presumably symbiotic nature in lycophytes and ferns (“pteridophytes”). The sampling covers ca. 11 % (1287 spp.) of the estimated global diversity of these taxa (ca. 12,000 spp.) and shows an average presence of fungal endophytes of 68 %, which is significantly lower than the average presence of mycorrhiza of 80–85 % for the remaining tracheophytes. Above-average colonization rates up to 100 % among ferns are mainly found in phylogenetically old lineages, whereas below-average mycorrhization characterizes the Polypod I clade and the Aspleniaceae of the derived leptosporangiate ferns. Arbuscular Mycorrhizal Fungi (AMF) are found in 54 % of the species, to which 6 % of unspecified records of mycorrhizae should probably be added. Dark Septate Endophytes (DSE) are found in 13 % of the species, in about half the cases (6 %) together with AMF. Ectomycorrhizae have not been confirmed for pteridophytes so far, and basidiomycetes are found very rarely in mycoheterotropic gametophytes. Fungal endophytes are unevenly distributed across the life forms and most frequent with 75 % in the terrestrial species, followed with 69 % in saxicolous and with 58 % in epiphytic species. Although AMF have a low dispersal potential and thus are considered unreliable symbiotic partners for epiphytes, they are still present in 27 % of the investigated epiphytic pteridophytes. The occurrence of mycorrhizae across the taxa of pteridophytes bears a phylogenetic signal, as the derived ferns show a notable trend towards a growing independence from AM, in epiphytes more pronouncedly so than in terrestrial taxa.     

Accessibility percolation on Cartesian power graphs

Journal of Mathematical Biology -     

A TOR (target of rapamycin) and nutritional phosphoproteome of fission yeast reveals novel targets in networks conserved in humans

Fluctuations in TOR, AMPK and MAP-kinase signalling maintain cellular homeostasis and coordinate growth and division with environmental context. We have applied quantitative, SILAC mass spectrometry to map TOR and nutrient-controlled signalling in the fission yeast Schizosaccharomyces pombe. Phosphorylation levels at more than 1000 sites were altered following nitrogen stress or Torin1 inhibition of the TORC1 and TORC2 networks that comprise TOR signalling. One hundred and thirty of these sites were regulated by both perturbations, and the majority of these (119) new targets have not previously been linked to either nutritional or TOR control in either yeasts or humans. Elimination of AMPK inhibition of TORC1, by removal of AMPKα (ssp2::ura4⁺), identified phosphosites where nitrogen stress-induced changes were independent of TOR control. Using a yeast strain with an ATP analogue-sensitized Cdc2 kinase, we excluded sites that were changed as an indirect consequence of mitotic control modulation by nitrogen stress or TOR signalling. Nutritional control of gene expression was reflected in multiple targets in RNA metabolism, while significant modulation of actin cytoskeletal components points to adaptations in morphogenesis and cell integrity networks. Reduced phosphorylation of the MAPKK Byr1, at a site whose human equivalent controls docking between MEK and ERK, prevented sexual differentiation when resources were sparse but not eliminated.     

Toxoplasma gondii: characterization of monoclonal antibodies that recognize rhoptries

We have previously reported on a series of monoclonal antibodies that recognize the rhoptries of Toxoplasma gondii and that interfere with the action of penetration enhancing factor. The antibodies immunoprecipitate several related antigens from [35S]methionine-labeled parasites that range in size from 60 to 43 kDa. By immunoblot, one of the antibodies reacts with the 60 kDa protein in the presence of protease inhibitors. Trypsin digestion of the antigen destroyed antigenic reactivity indicating that the 60 kDa antigen is a protein. The antigen was stable to periodate oxidation and failed to react with Schiff's reagent, indicating that the antigen contains little or no carbohydrate. Two-dimensional gel electrophoresis followed by immunoblot showed that the antigen recognized by Tg 49 was an acidic protein with an approximate pI of 5.8.     

Translational control in influenza virus-infected cells

Influenza virus type A has been shown to establish a translational control system such that during infection there is a dramatic inhibition of host cell protein synthesis and viral mRNAs are selectively and efficiently translated. The following review summarizes the complex strategies employed by influenza to accomplish these goals. These include: (i) preventing newly made cellular mRNAs from entering the cytoplasm of infected cells; (ii) inhibiting the initiation and elongation steps of translation of preexisting cellular mRNAs; (iii) possessing RNAs with structural features which enhance translation; (iv) encoding mechanisms to downregulate the interferon induced protein kinase thus allowing overall protein synthesis levels to remain high.