Chloroflexus-like organisms from marine and hypersaline environments: Distribution and diversity

We report the presence of a diverse number ofChloroflexus-like organisms in intertidal marine and submerged hypersaline microbial mats using light, infrared fluorescence, and electron microscopy. The intertidal organisms appear morphologically very similar to thermophilicC. aurantiacus while the 2 hypersaline strains are larger and have a more complex ultrastructure composed of chlorosome-bearing internal membranes that appear to arise as invaginations of the cell membrane. By comparing spectroradiometry of microbial mat layers with microscopic observations, we have confirmed that theChloroflexus-like organisms are major constituents of the hypersaline microbial mat communities. In situ studies on mat layers dominated byChloroflexus-like organisms showed that sulfide-dependent photoautotrophic activity sustained by near infrared radiation prevailed. Autoradiographic analyses revealed that autotrophy was sustained in the filaments by 750 nm radiation. Three morphologically distinct strains are now maintained in mixed culture. One of these appears to be growing photoautotrophically.     

Herbivory on calcicolous lichens: different food preferences and growth rates in two co-existing land snails

A total of 32 calcicolous lichen species, one alga and one bryophyte were recorded on a limestone wall in the grassland Great Alvar on the Baltic island of Öland, Sweden. Fourteen (41%) of these 34 species and free-living cyanobacteria showed herbivore damage, most probably due to grazing by the land snails Chondrina clienta and Balea perversa which inhabited the limestone wall. Three laboratory experiments were conducted to examine the food preferences of individuals of C. clienta and B. perversa collected at this site and to evaluate any association between their preference and the net food quality of the lichens to the snails. Chondrina clienta and B. perversa exhibited food preferences, which differed significantly between species. Within species, variation in food choice was similar among individuals. This indicates that snail populations may be composed of polyphagous individuals with similar food preferences. Different lichen species were of different net food quality to the snails as indicated by growth rate differences. In both snail species the most preferred lichen species of the choice experiment caused the largest weight increase in juveniles, viz. Caloplaca flavovirescens for C. clienta and Aspicilia calcarea for B. perversa. This suggest that the snail species studied differ in their abilities to deal with secondary compounds and physical characteristics of certain lichens or that they can utilize the energy and nutrients of these lichens to a different extent. It is suggested that differential food preferences might reduce the intensity of interspecific competition for resources (lichens) between C. clienta and B. perversa.     

Simultaneous detection of neuropeptides and messenger RNA in the magnocellular hypothalamo-neurohypophysial system by a combination of non-radioactive in situ hybridization histochemistry and immunohistochemistry

A protocol was developed combining non-radioactive in situ hybridization histochemistry with enzyme based immunohistochemistry, detect the expression of mRNA in phenotypically defined neurons. Freefloating brain sections were hybridized with the oligonucleotide probes which have been 3-end labelled with biotin-11-dUTP. The hybridized probe was visualized by a combined avidin-biotin bridge method, anti-avidin immunohistochemistry, and horseradish peroxidase detection using diaminobenzidine as a substrate. The in situ hybridization step yielded a very stable reaction product enabling subsequent immunohistochemical reactions using horseradish peroxidase and benzidine dihydrochloride as a chromogen. Magnocellular neurons of the hypothalamo-neurophypophysial system synthesize either vasopressin or oxytocin; water deprivation and chronic saline ingestion are potent stimuli for the expression of both of the genes encoding these neuropeptides. A number of other neuropeptides with putative transmitter action are synthesized in magnocellular neurons during such stimulation. Experiments were performed to explore whether neuropeptide Y immunoreactivity is present within magnocellular vasopressin mRNA-expressing neurons of the hypothalamo-neurophypophysial system. The results clearly demonstrated that neuropeptide Y-immunoreactive elements were present within a number of magnocellular vasopressin mRNA-containing cells. In addition, immunohistochemical detection of the neuropeptides ocytocin and cholecystokinin was carried out on sections hybridized non-radioactively for vasopressin; as expected vasopressin mRNA did not co-exist with cholecystokinin, whereas a few oxytocin immunoreactive neurons in osmotically stimulated animals also contained vasopressin mRNA. The developed method makes possible the immunohistochemical detection of intracellular antigens with concomitant detection of intracellular mRNA.     

Note on the nomenclature of Cassieae (Leguminosae-Caesalpinioideae) in Malaysia

As a precursor for the treatment of Caesalpiniaceae in Flora Malesiana the following new combinations are proposed: Cassia javanica ssp. pubiflora stat. nov., C. javanica ssp. agnes stat. nov., C. javanica ssp. microcalyx stat. nov. C. javanica ssp. renigera stat. nov., C. javanica ssp. bartonii stat. nov., Senna divaricata comb. nov., Chamae-christa pumila comb. nov. and Chamaechrista mindanaensis comb. nov.     

Transpiration by an emergent macrophyte: source of water and implications for nutrient supply

The contribution of sediment interstitial water and the water column to the transpiration stream of Myriophyllum aquaticum (Vellozo) Verdcourt was determined to estimate the significance of mass flow in supply of sediment nutrients for plant growth. Sediment interstitial water accounted for about 2% of the water transpired over a 37 day period. Because of the small volume of water that originated in the sediment we concluded that mass flow did not significantly enhance nutrient supply to the roots of M. aquaticum. Relative growth rate (RGR) of adventitious, water roots was greater than whole plant RGR, and RGR of sediment roots was not significantly different from zero, indicating a shift in the biomass allocation after emergence of the apical meristem into the air. Water use, measured by the transpiration coefficient, averaged 260 ml H₂O mg DW^-1, which is similar to C-4 terrestrial plants. M. aquaticum has leaf characteristics commonly associated with xerophytic habitats. These characteristics may be necessary if a high transpiration rate and a mechanical requirement for high cell turgor pressure, required by a reliance upon hydrostatic pressure for support of the aerial stems, are mutually exclusive because of morphological constraints on hydraulic conductivity.     

ANTIVIRAL ACTIVITY OF CULTURED BLUE-GREEN ALGAE (CYANOPHYTA)1

Lipophilic and hydrophilic extracts from approximately 600 strains of cultured cyanophytes, representing some 300 species, were examined for antiviral activity against three pathogenic viruses. Approximately 10% of the cultures produced substances that caused significant reduction in cytopathic effect normally associated with viral infection. The screening program identified the order Chroococcales as commonly producing antiviral agents.     

Linkage analysis of schizophrenia with five dopamine receptor genes in nine pedigrees

Alterations in dopamine neurotransmission have been strongly implicated in the pathogenesis of schizophrenia for nearly 2 decades. Recently, the genes for five dopamine receptors have been cloned and characterized, and genetic and physical map information has become available. Using these five loci as candidate genes, we have tested for genetic linkage to schizophrenia in nine multigenerational families which include multiple affected individuals. In addition to testing conservative disease models, we have used a neurophysiological indicator variable, the P50 auditory evoked response. Deficits in gating of the P50 response have been shown to segregate with schizophrenia in this sample and may identify carriers of gene(s) predisposing for schizophrenia. Linkage results were consistently negative, indicating that a defect at any of the actual receptor sites is unlikely to be a major contributor to schizophrenia in the nine families studied.     

Molecular cut-off values of dialysis membranes for alginate and kappa-carrageenan oligosaccharides

The effective molecular weight cut-off values of dialysis membranes for carrageenan and alginate oligosaccharides were evaluated by gel permeation chromatography and nuclear magnetic resonance spectroscopy. For the different membranes tested, i.e. Medicell, Spectra Por 1000D and 3500D, the porous sizes are analogous to tri- and tetrasaccharides. A simple dialysis can be used to recover the majority of the oligosaccharides produced by a carrageenase or an alginate lyase digestion.     

Mannuronan C-5 epimerase activity in protoplasts of Laminaria digitata

Biosynthesis of alginate in algae may be studied by following the cell wall regeneration of brown seaweed protoplasts in culture. The enzyme mannuronan C-5 epimerase will control the composition of the alginate being synthetized.Freshly isolated protoplasts from the thallus of young Laminaria digitata plants showed only low expression of this enzyme. However, after prolonged periods in culture, this activity increased 15-fold. The synthesis of C-5 epimerase by the protoplasts is probably essential for the formation of a new cell wall.After cellular disruption by osmotic shock and centrifugation, most of the epimerase activity resided in the pellet fraction. This may indicate that the enzyme is membrane associated.     

Improved mating efficiency inAcetabularia acetabulum: recovery of 48–100% of the expected zygotes

Summary We have improved zygote recovery 11–1,000 fold by optimizing the physiology of gamete release and mating inAcetabularia acetabulum. Gamete release was affected by agar purity, concentration, and volume/gametangial pair. Cold pre-treatment of gametangia (14–30 d at 10°C in the dark) synchronized subsequent gamete release at 21°C in the light. Cold pre-treatment was nearly twice as effective in synchronizing subsequent gamete release when intact, gametangia-bearing caps rather than isolated gametangia were pretreated. Synchronizing gamete release doubled mating efficiency. In a wild-type laboratory strain ofA. acetabulum, there were 1,561±207 gametes/gametangium which had half-lives of 14.5 d in 0.1% seawater-agar. We recovered 48–93% of the expected numbers of zygotes from a mass mating of 8 to 1,226 gametangia and 11–128% of the expected numbers of zygotes from mating single gametangial pairs: the large range in the calculated mating efficiency may be attributable to the variation in the numbers of gametes made per gametangium. Zygote recovery from single gametangial pairs was highly dependent on the volume of mating matrix. In addition, most zygotes recovered were unattached to any other zygotes in the subsequent generation (> 95% single cells from matings of 1–500 gametangial pairs). Our improvements in mating conditions and zygote recovery (1) have facilitated cell manipulation and culture ofA. acetabulum in the laboratory; and (2) have made controlled crosses for selection and genetic analysis of mutants feasible. These advances have removed a major barrier to genetic analysis of development inAcetabularia.Abbreviations LB Luria-Bertani bacteriological broth - SE standard error of the mean - T_g agar gelling temperatures - DAPI 4,6-diamidino-2-phenylindole