The SEG1 element: a new DNA region promoting stable mitotic segregation of plasmids in the zygomycete Absidia glauca.

Summary A series of new vectors for the model zygomycete Absidia glauca was constructed on the basis of the structural neomycin resistance (Neo^r) gene controlled by the promoter of the gene for elongation factor 1 (TEF). In order to select for transformed colonies with a stable Neo^r phenotype, spores from primary transformants were pooled and grown for two sporulation cycles under non-selective conditions. Southern blot analysis of DNA from single spore isolates originating from independent transformant pools allowed the identification of two autonomously replicating plasmids. Retransformation of Escherichia coli and restriction analysis of the two plasmids provided evidence for spontaneous in vivo insertion of a new DNA element (SEG1) from the A. glauca genome. The inserted regions in both plasmids are essentially identical and do not represent repetitive DNA. Compared with other autonomously replicating vectors, these SEG1-containing plasmids are mitotically extremely stable and are passed on to the vegetative spore progeny of a retransformed A. glauca strain. We assume that SEG1 contains structural elements involved in partitioning and stable segregation of plasmids. For the construction of stable transformants of A. glauca, the SEG1 element may be regarded as a major breakthrough, because stabilization of transformed genetic traits by integration is difficult to achieve in all mucoraceous fungi and all known replicating plasmids are mitotically unstable.     

Characterisation of the laccase-encoding gene abr2 of the dihydroxynaphthalene-like melanin gene cluster of Aspergillus fumigatus

Aspergillus fumigatus is an important pathogen of the immunocompromised host. Previously, it was shown that the polyketide synthase encoded by the pksP (alb1) gene represents a virulence determinant. pksP is part of a gene cluster involved in dihydroxynaphthalene (DHN)-like melanin biosynthesis. Because a putative laccase-encoding gene (abr2) is also part of the cluster and a laccase was found to represent a virulence factor in Cryptococcus neoformans, here, the Abr2 laccase was characterised. Deletion of the abr2 gene changed the gray-green conidial pigment to a brown color and the ornamentation of conidia was reduced compared with wild-type conidia. In contrast to the white pksP mutant, the susceptibility of the Δabr2 mutant against reactive oxygen species (ROS) was not increased, suggesting that the intermediate of DHN-like melanin produced up to the step catalysed by Abr2 already possesses ROS scavenging activity. In an intranasal mouse infection model, the Δabr2 mutant strain showed no reduction in virulence compared with the wild type. In the Δabr2 mutant, overall laccase activity was reduced only during sporulation, but not during vegetative growth. An abr2p-lacZ gene fusion was expressed during sporulation, but not during vegetative growth confirming the pattern of laccase activity due to Abr2.     

Esr,a second locus in the house mouse controlling esterase-5

Electrophoretic variation characterized by the presence (ES-5B⁺) or absence (ES-5B^–) of esterase-5B in the plasma of the house mouse has been observed. It is suggested that the expression of esterase-5B is controlled by an autosomal locus, Esr, linked to Ldr-1 on chromosome 6, in addition to the presumptive structural locus Es-5, which is located on chromosome 8. A gene order of Lyt-3-Esr-Ldr-1 was determined by two crosses.Supported by the Deutsche Forschungsgemeinschaft (SFB 46).This is communication No. 33 of a research program devoted to the investigation of cellular distribution and genetics of nonspecific esterases.     

Ectothiorhodospira vacuolata sp. nov., a new phototrophic bacterium from soda lakes

A new phototrophic bacterium was isolated from Jordanian and Kenyan alkaline salt lakes. Cells are rod shaped, 1.5 m wide and 2–4 m long, and motile by polar flagella. They divide by binary fission, and possess photosynthetic membranes as lamellar stacks similar to those in the other species of the genus Ectothiorhodospira and the brown colored Rhodospirillum species. The presence of bacteriochlorophyll a and carotenoids of the normal spirilloxanthin series is indicated by the absorption spectra of living cells. Under certain growth conditions the cells form gas vacuoles, may become immotile and float to the top of the culture medium. Sulfide and thiosulfate are used as photosynthetic electron donors. During the oxidation of sulfide to sulfate, elemental sulfur is formed, which is accumulated outside the cells. The organisms are strictly anaerobic, do not require vitamins, are moderately halophilic and need alkaline pH-values for growth. The new species Ectothiorhodospira vacuolata is proposed.     

Little evidence for negative effects of an invasive alien plant on pollinator services

Many invasive alien plants occur in large populations with abundant flowers which are highly attractive to pollinators, and thus might affect pollination of co-occurring native species. This study focuses on the invasive Heracleum mantegazzianum and distance-dependent effects on pollination of Mimulus guttatus in abandoned grassland over 2 years. First, we examined pollinator abundance in yellow traps at 0, 10, 30 and 60–200 m from H. mantegazzianum. We then placed M. guttatus plants at the same distances to monitor effects of the invasive species on pollinator visitation and seed set of neighbouring plants. Finally, we conducted a garden experiment to test if deposition of H. mantegazzianum pollen reduces seed set in M. guttatus. No distance effect was found for the number of bumblebees in traps, although the invasive species attracted a diverse assemblage of insects, and visitation of M. guttatus was enhanced close to H. mantegazzianum. This positive effect was not reflected by seed set of M. guttatus, and heterospecific pollen decreased seed set in these plants. Overall there is little evidence for negative effects of the invasive species on pollination of neighbouring plants, and flower visitation even increases close to the invaded patches. The functional role of the invader and suitable control strategies need further clarification, since removal of H. mantegazzianum may actually damage local pollinator populations. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Phylogeny of Snub-Nosed Monkeys Inferred from Mitochondrial DNA,Cytochrome B,and 12S rRNA Sequences

Snub-nosed monkeys (Rhinopithecus spp.) are confined to isolated mountainous regions in China and North Vietnam. Their systematic classification and phylogenetic relationship has been controversial. The structures of mitochondrial DNA cytochrome b and 12S rRNA show that the 4 species of Rhinopithecus are quite different from other colobines. It is reasonable to regard them as an independent genus, as determined by external features, morphometric characters and behavior. However, whether or not there should be a subdivision between the Vietnamese and Chinese species at the subgeneric level remains to be clarified; more evidence from a large range of Asian colobine species is needed. The Guizhou species, Rhinopithecus brelichi, is a valid species, which is more closely related to Pygathrix than the other species ( R. roxellana, R. bieti and R. avunculus) are. Results also indicate that 3 species—Rhinopithecus roxellana, R. bieti and R. avunculus—might have diverged from R. brelichi, but the phylogenetic relationship of R. avunculus is not clear.     

Sulfate assimilation in Rhodopseudomonas globiformis

Rhodopseudomonas globiformis is able to grow on sulfate as sole source of sulfur, but only at concentrations below 1 mM. Good growth was observed with thiosulfate, cysteine or methionine as sulfur sources. Tetrathionate supported slow growth. Sulfide and sulfite were growth inhibitory. Growth inhibition by higher sulfate concentrations was overcome by the addition of O-acetylserine, which is known as derepressor of sulfate-assimilating enzymes, and by reduced glutathione. All enzymes of the sulfate assimilation pathway. ATP-sulfurylase, adenylylphosphate-sulfotransferase, thiosulfonate reductase and O-acetylserine sulfhydrylase are present in R. globiformis. Sulfate was taken up by the cells and the sulfur incorporated into the amino acids cysteine, methionine and homocysteine. It is concluded, that the failure of R. globiformis to grow on higher concentrations of sulfate is caused by disregulation of the sulfate assimilation pathway. Some preliminary evidence for this view is given in comparing the activities of some of the involved enzymes after growth on different sulfur sources and by examining the effect of O-acetylserine on these activities.Abbreviations DTE dl-dithioerythritol - APS adenosine 5-phosphosulfate, adenylyl sulfate - PAPS 3-phosphoadenosine 5-phosphosulfate, 3-phosphoadenylylsulfate