Wolbachia replication and host cell division in Aedes albopictus

Wolbachia pipientis is an obligate intracellular endosymbiont of a range of arthropod species. The microbe is best known for its manipulations of host reproduction that include inducing cytoplasmic incompatibility, parthenogenesis, feminization, and male-killing. Like other vertically transmitted intracellular symbionts, Wolbachiarsquos replication rate must not outpace that of its host cells if it is to remain benign. The mosquito Aedes albopictus is naturally infected both singly and doubly with different strains of Wolbachia pipientis. During diapause in mosquito eggs, no host cell division is believed to occur. Further development is triggered only by subsequent exposure of the egg to water. This study uses diapause in Wolbachia-infected Aedes albopictus eggs to determine whether symbiont replication slows or stops when host cell division ceases or whether it continues at a low but constant rate. We have shown that Wolbachia densities in eggs are greatest during embryonation and then decline throughout diapause, suggesting that Wolbachia replication is dependent on host cell replication.

Wolbachia pipientis: intracellular infection and pathogenesis in Drosophila

Wolbachia pipientis is a vertically transmitted, obligate intracellular symbiont of arthropods. The bacterium is best known for its ability to manipulate host reproductive biology where it can induce cytoplasmic incompatibility, parthenogenesis, feminization and male-killing. In addition to the various reproductive phenotypes it generates through interaction with host reproductive tissue it is also known to infect somatic tissues. However, relatively little is known about the consequences of infection of these tissues with the exception that in some hosts Wolbachia acts as a classical mutualist and in others a pathogen, dramatically shortening adult insect lifespan. Manipulation experiments have demonstrated that the severity of Wolbachia-induced effects on the host is determined by a combination of host genotype, Wolbachia strain, host tissue localization, and interaction with the environment. The recent completion of the whole genome sequence of Wolbachia pipientis wMel strain indicates that it is likely to use a type IV secretion system to establish and maintain infection in its host. Moreover, an unusual abundance of genes encoding proteins with eukaryotic-like ankyrin repeat domains suggest a function in the various described phenotypic effects in hosts.

The future of tobacco control: project summary

The National Health and Medical Research Council has funded Professor Wayne Hall (University of Queensland) and Professor Simon Chapman (University of Sydney) for three years 2006-2008, to research aspects of the future of tobacco control, particularly in nations with advanced tobacco control programs like Australia. Dr Coral Gartner (UQ) and Ms Becky Freeman (USyd) are also working on the project. The University of Queensland's eSpace site provides links to papers and data appendices produced by the University of Queensland team on the project. Materials relevant to this project produced by the University of Sydney group are available at the link provided.

(FAB05_058) The cathedral precinct: ideal and contingency

Henry-Russell Hitchcock, in his review of High Victorian Gothic architecture in Australia, writes that the Anglican Cathedral in Brisbane is perhaps the finest. John Loughborough and Frank Loughborough Pearson's designs for Brisbane embody the full ideal of the nineteenth-century English cathedral. While the ideal represented in the cathedral church itself might be readily appreciated, the more encompassing ideal for housing an entire Anglican cathedral establishment may be less well known and less apparent on the site. Although it is only partly built, St John's is probably the only Anglican cathedral in Australia with a comprehensive nineteenth-century precinct plan.

Development of a physical and genetic map of the virulent Wolbachia strain wMelPop

We report here the construction of a physical and genetic map of the virulent Wolbachia strain, wMelPop. This map was determined by ordering 28 chromosome fragments that resulted from digestion with the restriction endonucleases FseI, ApaI, SmaI, and AscI and were resolved by pulsed-field gel electrophoresis. Southern hybridization was done with 53 Wolbachia-specific genes as probes in order to determine the relative positions of these restriction fragments and use them to serve as markers. Comparison of the resulting map with the whole genome sequence of the closely related benign Wolbachia strain, wMel, shows that the two genomes are largely conserved in gene organization with the exception of a single inversion in the chromosome.

The potential of virulent Wolbachia to modulate disease transmission by insects

A virulent strain of Wolbachia has recently been identified in Drosophila that drastically reduces adult lifespan. It has been proposed that this phenotype might be introduced into insect disease vector populations to reduce pathogen transmission. Here we model the requirements for spread of such an agent and the associated reduction in disease transmission. First, a simulation of mosquito population age structure was used to describe the age distribution of mosquitoes transmitting dengue virus. Second, given varying levels of cytoplasmic incompatibility and fecundity effect, the maximum possible longevity reduction that would allow Wolbachia to invade was obtained. Finally, the two models were combined to estimate the reduction in disease transmission according to different introduction frequencies. With strong CI and limited effect of fecundity, an introduction of Wolbachia with an initial frequency of 0.4 could result in a 60–80% reduction of transmitting mosquitoes. Greater reductions are possible at higher initial release rates.

Molecular phylogeny of Wolbachia endosymbionts in southeast asian mosquitoes (Diptera: Culicidae) based on wsp gene sequences

Wolbachia are maternally inherited intracellular bacteria that infect a wide range of arthropods and nematodes and are associated with various reproductive abnormalities in their hosts. Insect-associated Wolbachia form a monophyletic clade in the α-Proteobacteria and recently have been separated into two supergroups (A and B) and 19 groups. Our recent polymerase chain reaction (PCR) survey using wsp specific primers indicated that various strains of Wolbachia were present in mosquitoes collected from Southeast Asia. Here, we report the phylogenetic relationship of the Wolbachia strains found in these mosquitoes using wsp gene sequences. Our phylogenetic analysis revealed eight new Wolbachia strains, five in the A supergroup and three in the B supergroup. Most of the Wolbachia strains present in Southeast Asian mosquitoes belong to the established Mors, Con, and Pip groups.

Wolbachia infections of tephritid fruit flies: molecular evidence for five distinct strains in a single host species

Endosymbiotic bacteria of the genus Wolbachia are widespread among arthropods and can induce cytoplasmic incompatibility, thelytokous parthenogenesis, male-killing or feminization in their hosts. Here, we report phylogenetic relationships of Wolbachia in tephritid fruit flies based on wsp gene sequences. We also report, for the first time, five distinct strains of Wolbachia in Bactrocera ascita sp. B. Four of the five Wolbachia strains found in this species were in the same groups as those found in other tephritid fruit flies, suggesting possible horizontal transmission of Wolbachia from other fruit flies into B. ascita sp. B. The unreliability of wsp-specific group primers demonstrated in this study suggests that these primers might be useful only for preliminary identification of Wolbachia. Final determination of group affiliation needs to be verified with wsp sequence data.

Host age effect and expression of cytoplasmic incompatibility in field populations of Wolbachia-superinfected Aedes albopictus

The Asian tiger mosquito, Aedes albopictus (Skuse), is a known vector of dengue in South America and Southeast Asia. It is naturally superinfected with two strains of Wolbachia endosymbiont that are able to induce cytoplasmic incompatibility (CI). In this paper, we report the strength of CI expression in crosses involving field-caught males. CI expression was found to be very strong in all crosses between field males and laboratory-reared uninfected or wAlbA infected young females. In addition, crossing experiments with laboratory colonies showed that aged super- infected males could express strong CI when mated with young uninfected or wAlbA infected females. These results provide additional evidence that the CI properties of Wolbachia infecting Aedes albopictus are well suited for applied strategies that seek to utilise Wolbachia for host population modification.

Wolbachia infection in the Coffee Berry Borer (Coleoptera: Scolytidae)

A nested polymerase chain reaction protocol yielded positive detection of the maternally inherited cytoplasmic proteobacterium Wolbachia in total genomic DNA from coffee berry borers collected in Benin, Brazil, Colombia, Ecuador, El Salvador, Honduras, India, Kenya, Mexico, Nicaragua, and Uganda. Wolbachia was not detected in specimens from Cameroon, the Dominican Republic, Indonesia, Jamaica, and Peru. Amplified bands from India and Brazil were cloned and sequenced. The 438-bp sequence clearly conformed to Wolbachia group B and was nearly identical to that of Ephestia kuehniella. The possible implications of Wolbachia infection in the coffee berry borer are discussed.

Timber cross-bracing, Mooloomba House, Point Lookout, North Stradbroke Island

Detail view of timber cross-bracing with polycarbonate sheeting behind as seen from upper level dining studio.

Mooloomba House, Point Lookout, North Stradbroke Island

North elevation, deck below and belvedere above, as seen from path to beach.

South elevation edge, Mooloomba House, Point Lookout, North Stradbroke Island

View along south elevation, stair to belvedere beyond and bedboxes above.

Entrance deck, Mooloomba House, Point Lookout, North Stradbroke Island

View past kitchen windows and roof overhang to entrance deck to the south-west.

View from Mooloomba House, Point Lookout, North Stradbroke Island

View of ocean and coastal vegetation