Cloning and nucleotide sequence of a gene for Actinomyces naeslundii WVU45 type 2 fimbriae.

A genomic library of Actinomyces naeslundii WVU45 DNA in Escherichia coli was screened for antigen expression with rabbit antibody against A. naeslundii fimbriae. Western blotting (immunoblotting) of one recombinant clone carrying a 13.8-kilobase-pair insert revealed a 59-kilodalton (kDa) immunoreactive protein. A protein of similar electrophoretic mobility was detected from the isolated fimbrial antigen. Expression of the 59-kDa cloned protein in E. coli was directed by a promoter from the insert. The DNA sequence of the subunit gene was determined, and an open reading frame of 1,605 nucleotides was identified which was preceded by a putative ribosome-binding site and followed by two inverted repeats of 14 and 17 nucleotides, respectively. The reading frame encoded a protein of 534 amino acids (calculated molecular weight, 57,074), and the N-terminal sequence resembled that of a signal peptide. The presence of a 32-amino-acid signal peptide was indicated by amino-terminal sequencing of the fimbriae from A. naeslundii. The sequence, as determined by Edman degradation, was identical to that deduced from the DNA sequence beginning at predicted residue 33 of the latter sequence. Moreover, the amino acid composition of the predicted mature protein was similar to that of the isolated fimbriae from A. naeslundii. Thus, the cloned gene encodes a subunit of A. naeslundii fimbriae.     

Lectin recognition of host-like saccharide motifs in streptococcal cell wall polysaccharides

Viridans streptococci that participate in the microbial colonizationof teeth have cell wall polysaccharides composed of linear phosphodiester-linkedhexa- or heptasaccharide repeating units, each containing ahost-like disaccharide motif, either Galß1     

Immunochemical and functional studies of Actinomyces viscosus T14V type 1 fimbriae with monoclonal and polyclonal antibodies directed against the fimbrial subunit.

Each of five monoclonal antibodies (mAbs) prepared against the type 1 fimbriae of Actinomyces viscosus T14V reacted with a 54 kDa cloned protein previously identified as a fimbrial subunit. This purified protein completely inhibited the reaction of a specific anti-type-1-fimbria rabbit antibody with A. viscosus whole cells. Maximum values for the number of antibody molecules bound per bacterial cell ranged from 7 x 10(3) to 1.2 x 10(4) for the different 125I-labelled mAbs and was approximately 7 x 10(4) for 125I-labelled rabbit IgG or Fab against either type 1 fimbriae or the 54 kDa cloned protein. Although the different mAbs, either individually or as a mixture, failed to inhibit the type-1-fimbria-mediated adherence of A. viscosus T14V to saliva-treated hydroxyapatite, each rabbit antibody gave 50% inhibition of adherence when approximately 5 x 10(4) molecules of IgG were bound per cell. However, binding of each corresponding rabbit Fab had no significant effect on bacterial attachment unless much higher concentrations were used. These findings suggest that antibodies directed solely against the 54 kDa fimbrial subunit do not react with the putative receptor binding sites of A. viscosus T14V type 1 fimbriae. Instead, inhibition of attachment by the polyclonal antibodies may depend on an indirect effect of antibody binding that prevents the fimbria-receptor interaction.     

Detection and localization of a lectin on Actinomyces viscosus T14V by monoclonal antibodies

A cell-associated lectin activity that mediates lactose-inhibitable adherence of Actinomyces viscosus T14V has been localized to a specific population of fimbriae by the use of monoclonal antibodies. Nine monoclonal antibodies were produced that reacted with only 1 of 2 immunoelectrophoretically distinct fimbrial components on T14V. The fibrillar morphology of this component was revealed by the immunoelectronmicroscopic examination of bacteria incubated with the monoclonal antibodies. The lectin activity associated with these structures was detected when isolated fimbriae were cross-linked with monoclonal antibodies to form immune complexes with agglutination activity for neuraminidase-treated human erythrocytes, a reaction that was inhibited by lactose. Although the 9 monoclonal antibodies differed in their fine specificities, they reacted only with strains of A. viscosus and A. naeslundii that exhibited lactose-inhibitable adherence. These findings indicate that the lectin activity common to these bacteria resides on fimbriae that are antigenically related to those of T14V.     

Resource density regulates the foraging investment in higher termite species

1. Resource density can regulate the area that animals use. At low resource density, there is a conflict in terms of balance between costs of foraging and benefits acquired. The foraging of the higher termite Nasutitermes aff. coxipoensis consists of searching throughout trails and a building galleries phase. 2. In this study, a manipulative field experiment was used to test the hypothesis that colonies of N. aff. coxipoensis forage towards a more profitable balance between the establishment of trails and gallery construction at low resource density. 3. The experiment was conducted in north‐eastern Brazil. Seven experimental plots were established with a continuous increase in resource density (sugarcane baits). Entire colonies of N. aff. coxipoensis were transplanted from their original sites to the experimental plot, totalling 35 nests. The number, branches and total length of trails and galleries were quantified. 4. The results show that N. aff. coxipoensis optimises its foraging output, intensifying the establishment of trails at the cost of gallery construction when resource density is low. The number of trails, the number of trail branches and the total length of trails decreased with increasing resource density. Interestingly, at low resource density, the search effort was concentrated on forming longer and a greater number of trails, a small proportion of which were converted into galleries. The opposite relationship was observed at high resource density. 5. These results suggest an optimisation of search efforts during foraging depending on resource density, a mechanism that may help researchers to understand the use of space by higher termite species.     

Biotic versus abiotic pollination in Oeceoclades maculata (Lindl.) Lindl. (Orchidaceae)

Geographical variation in the reproductive biology of widespread species often occurs at their distributional boundaries. We sought to determine whether such variation has occurred in an invasive orchid, Oeceoclades maculata, across its naturalized range. We compared its reproductive biology in a Brazilian population with that published for a population on the Caribbean island of Puerto Rico. In the state of São Paulo, O. maculata flowers between December and February, at the height of the rainy season. Similar fruit sets were observed in manual self (76%) and cross (70.4%) pollination treatments. The fruit set of plants protected from both pollinators and rainfall was 6.1%, whereas plants exposed only to rainfall had a fruit set of 41.4%, slightly less than the controls (48.3%). Like the Puerto Rico population, reproduction is primarily through rain‐assisted autogamy, but unlike observations made on the island, outcrossing can eventually occur. We observed two butterfly species (Heliconius ethilla narcaea and Heliconius erato phyllis) pollinating O. maculata. Secretory epidermal cells and trichomes of the spur lumen produced 0.7 µL of 25% (sucrose equivalents) nectar per flower each morning, which was stored in a dilated basal portion of the spur and reabsorbed by the afternoon. Thus, geographical variation in reproductive biology exists across the broad invasive range of O. maculata.     

Effects of cage beddings on microsomal oxidative enzymes in rat liver

The purpose of the present studies was to evaluate the effects of some commercially available cage beddings on rat liver microsomal cytochrome P-450-dependent drug-metabolizing enzyme, ethylmorphine N-demethylase, and the carcinogen-metabolizing enzyme, benzo(a)pyrene hydroxylase. Sprague-Dawley rats were housed in cages containing cedar chip, corncob or heat-treated pinewood bedding for 3 weeks. Control rats were housed in cages on wire bottom floors containing no bedding material. Rats housed in cages containing cedar chip showed 18, 46 and 49% increases in liver cytochrome P-450 content, ethylmorphine N-demethylase and benzo(a)pyrene hydroxylase activities, respectively. The liver enzyme activities of rats housed in cages containing corncob bedding were similar to those obtained with control rats. In contrast, the pinewood-bedded rats showed a 21% decrease in ethylmorphine N-demethylase activity without affecting cytochrome P-450 content and benzo(a)pyrene hydroxylase activity. Hexobarbital-induced sleep times of the variously bedded rats were similar to those of control animals. These data suggest that the commercial bedding materials differ in their abilities to affect liver microsomal enzymes. Thus, interlaboratory variability in basal enzyme activities reported in the literature may be partly due to bedding materials used in the animal's cages.     

A role for oxalic acid generation in ozone‐induced signallization in Arabidopis cells

Ozone (O₃) is an air pollutant with an impact increasingly important in our industrialized world. It affects human health and productivity in various crops. We provide the evidences that treatment of Arabidopsis thaliana with O₃ results in ascorbate‐derived oxalic acid production. Using cultured cells of A. thaliana as a model, here we further showed that oxalic acid induces activation of anion channels that trigger depolarization of the cell, increase in cytosolic Ca²⁺ concentration, generation of reactive oxygen species and cell death. We confirmed that O₃ reacts with ascorbate in the culture, thus resulting in production of oxalic acid and this could be part of the O₃‐induced signalling pathways that trigger programmed cell death.