A family of lysozyme-like virulence factors in bacterial pathogens of plants and animals.

We describe a conserved family of bacterial gene products that includes the VirB1 virulence factor encoded by tumor-inducing plasmids of Agrobacterium spp., proteins involved in conjugative DNA transfer of broad-host-range bacterial plasmids, and gene products that may be involved in invasion by Shigella spp. and Salmonella enterica. Sequence analysis and structural modeling show that the proteins in this group are related to chicken egg white lysozyme and are likely to adopt a lysozyme-like structural fold. Based on their similarity to lysozyme, we predict that these proteins have glycosidase activity. Iterative data base searches with three conserved sequence motifs from this protein family detect a more distant relationship to bacterial and bacteriophage lytic transglycosylases, and goose egg white lysozyme. Two acidic residues in the VirB1 protein of Agrobacterium tumefaciens form a putative catalytic dyad, Each of these residues was changed into the corresponding amide by site-directed mutagenesis. Strains of A. tumefaciens that express mutated VirB1 proteins have a significantly reduced virulence. We hypothesize that many bacterial proteins involved in export of macromolecules belong to a widespread class of hydrolases and cleave beta-1,4-glycosidic bonds as part of their function.

Identification and characterization of putative transposable DNA elements in solanaceous plants and Caenorhabditis elegans.

Several families of putative transposable elements (TrEs) in both solanaceous plants and Caenorhabditis elegans have been identified by screening the DNA data base for inverted repeated domains present in multiple copies in the genome. The elements are localized within intron and flanking regions of many genes. These elements consist of two inverted repeats flanking sequences ranging from 5 bp to > 500 bp. Identification of multiple elements in which sequence conservation includes both the flanking and internal regions implies that these TrEs are capable of duplicative transposition. Two of the elements were identified in promoter regions of the tomato (Lycoperiscon esculentum) polygalacturonase and potato (Solanum tuberosum) Win1 genes. The element in the polygalacturonase promoter spans a known regulatory region. In both cases, ancestral DNA sequences, which represent potential recombination target sequences prior to insertion of the elements, have been cloned from related species. The sequences of the inverted repeated domains in plants and C. elegans show a high degree of phylogenetic conservation. While frequency of the different elements is variable, some are present in very high copy number. A member of a single C. elegans TrE family is observed approximately once every 20 kb in the genome. The abundance of the described TrEs suggests utility in the genomic analysis of these and related organisms.

Carnivorous plants and "the man eating tree" / by Sophia Prior.

no.23(1939)

(Table A1) Annual biomass of plants and animals recorded on Bylot Island between 1993-2009

Determining the manner in which food webs will respond to environmental changes is difficult because the relative importance of top-down vs. bottom-up forces in controlling ecosystems is still debated. This is especially true in the Arctic tundra where, despite relatively simple food webs, it is still unclear which forces dominate in this ecosystem. Our primary goal was to assess the extent to which a tundra food web was dominated by plant-herbivore or predator--rey interactions. Based on a 17-year (1993-2009) study of terrestrial wildlife on Bylot Island, Nunavut, Canada, we developed trophic mass balance models to address this question. Snow Geese were the dominant herbivores in this ecosystem, followed by two sympatric lemming species (brown and collared lemmings). Arctic foxes, weasels, and several species of birds of prey were the dominant predators. Results of our trophic models encompassing 19 functional groups showed that <10% of the annual primary production was consumed by herbivores in most years despite the presence of a large Snow Goose colony, but that 20-100% of the annual herbivore production was consumed by predators. The impact of herbivores on vegetation has also weakened over time, probably due to an increase in primary production. The impact of predators was highest on lemmings, intermediate on passerines, and lowest on geese and shorebirds, but it varied with lemming abundance. Predation of collared lemmings exceeded production in most years and may explain why this species remained at low density. In contrast, the predation rate on brown lemmings varied with prey density and may have contributed to the high-amplitude, periodic fluctuations in the abundance of this species. Our analysis provided little evidence that herbivores are limited by primary production on Bylot Island. In contrast, we measured strong predator-prey interactions, which supports the hypothesis that this food web is primarily controlled by top-down forces. The presence of allochthonous resources subsidizing top predators and the absence of large herbivores may partly explain the predominant role of predation in this low-productivity ecosystem.

Handbook of the British flora: a description of the flowering plants and ferns indigenous to, or naturalized in, the British Isles /

Mode of access: Internet.

Catalogue of medicinal plants and extracts : to which are affixed their most prominent medical properties : also essential oils, and double distilled fragrant waters /

Advertisements for "Compound fluid extract of Sarsaparilla" on p. [4] of wrapper.

Sandusky flora. A catalogue of the flowering plants and ferns growing without cultivation, in Erie county, Ohio, and the peninsula and islands of Ottawa county,

"Published by the Academy of science, May, 1899."

Mexico, Aztec, Spanish and republican : a historical, geographical, political, statistical and social account of that country from the period of the invasion by the Spaniards to the present time : with a view of the ancient Aztec empire and civilization, a historical sketch of the late war, and notices of New Mexico and California /

Mode of access: Internet.