The Relative Abundance of Mountain Pine Beetle Fungal Associates Through the Beetle Life Cycle in Pine Trees

The mountain pine beetle (MPB) is a native bark beetle of western North America that attacks pine tree species, particularly lodgepole pine. It is closely associated with the ophiostomatoid ascomycetes Grosmannia clavigera, Leptographium longiclavatum, Ophiostoma montium, and Ceratocystiopsis sp.1, with which it is symbiotically associated. To develop a better understanding of interactions between beetles, fungi, and host trees, we used target-specific DNA primers with qPCR to assess the changes in fungal associate abundance over the stages of the MPB life cycle that occur in galleries under the bark of pine trees. Multivariate analysis of covariance identified statistically significant changes in the relative abundance of the fungi over the life cycle of the MPB. Univariate analysis of covariance identified a statistically significant increase in the abundance of Ceratocystiopsis sp.1 through the beetle life cycle, and pair-wise analysis showed that this increase occurs after the larval stage. In contrast, the abundance of O. montium and Leptographium species (G. clavigera, L. longiclavatum) did not change significantly through the MPB life cycle. From these results, the only fungus showing a significant increase in relative abundance has not been formally described and has been largely ignored by other MPB studies. Although our results were from only one site, in previous studies we have shown that the fungi described were all present in at least ten sites in British Columbia. We suggest that the role of Ceratocystiopsis sp.1 in the MPB system should be explored, particularly its potential as a source of nutrients for teneral adults.     

Sequence Analysis of Spiroplasma phoeniceum and Spiroplasma kunkelii Spiralin Genes and Comparison with Other Spiralin Genes

The spiralin genes from two phytopathogenic spiroplasmas, Spiroplasma phoeniceum and Spiroplasma kunkelii, were amplified by PCR, cloned, and sequenced. Comparison of the amino acid sequences of the five spiralins analyzed to date confirm that the spiralins have a general amphiphilic character and possess a conserved lipoprotein signal peptide. It also shows that a conserved central region and an amino acid repetition, including a VTKXE consensus sequence, are present in all spiralins analyzed. Received: 11 March 1997 / Accepted: 14 April 1997     

A comparison of conventional culture and three rapid methods for the detection of Salmonella in poultry feeds and environmental samples

Three rapid methods, an impedance method (Malthus 2000 Analyzer), a colorimetric DNA hybridization method (Gene-Trak) and a post-enrichment enzyme-linked immunosorbent assay (Salmonella-Tek) were compared with conventional culture for the detection of Salmonella in poultry feeds, and in fluff and dust samples from poultry housing. The percentage positive samples for Salmonella by each of the methods were 25.5% for conventional culture, 38.4% for the Malthus, 28.9% for the Gene-Trak and 28.5% for the Salmonella-Tek. By any method 60/153 (39.2%) of the samples tested were positive on confirmed culture.     

Early glycogenesis in the uterine glandular cells of the rabbit induced by progestins: a quantitative investigation

A single administration of progesterone (P) to primed immature rabbits induces the appearance of glycogen in uterine glandular cells. This phenomenon, which is rapid and transitory, precedes a mitotic surge in the glandular epithelium. Ultrastructural studies allowed us to observe the beginning of glycogenesis as early as 1 h after the injection of P. Quantitative image analysis in the course of a kinetic study showed that glycogen levels reached a maximum at the sixth h and after 24 h had fallen dramatically. Promegestone, a potent progestomimetic compound, gave similar results, but estradiol, testosterone and dexamethasone failed to induce the appearance of glycogen in the uterine glands. Mifepristone (RU 486) had an antagonistic effect on the action of P. These results suggest that early P-dependent glycogenesis in the endometrial glandular cells of the rabbit may play an important role in the increased rate of mitosis and cellular proliferation that are necessary events in preparing the endometrium for implantation.     

Individual‐ versus group‐optimality in the production of secreted bacterial compounds

How unicellular organisms optimize the production of compounds is a fundamental biological question. While it is typically thought that production is optimized at the individual‐cell level, secreted compounds could also allow for optimization at the group level, leading to a division of labor where a subset of cells produces and shares the compound with everyone. Using mathematical modeling, we show that the evolution of such division of labor depends on the cost function of compound production. Specifically, for any trait with saturating benefits, linear costs promote the evolution of uniform production levels across cells. Conversely, production costs that diminish with higher output levels favor the evolution of specialization–especially when compound shareability is high. When experimentally testing these predictions with pyoverdine, a secreted iron‐scavenging compound produced by Pseudomonas aeruginosa, we found linear costs and, consistent with our model, detected uniform pyoverdine production levels across cells. We conclude that for shared compounds with saturating benefits, the evolution of division of labor is facilitated by a diminishing cost function. More generally, we note that shifts in the level of selection from individuals to groups do not solely require cooperation, but critically depend on mechanistic factors, including the distribution of compound synthesis costs.     

Prevalence and Correlates of HIV Infection among Street Boys in Kisumu,Kenya

Introduction

Despite their perceived vulnerability to HIV, East African street youth have been neglected in HIV prevention research. We examined HIV seroprevalence and correlates of HIV infection in a sample of male street youth in Kisumu, Kenya.

Methods

We enrolled a street-recruited sample of 13–21 year old street youth. Participants completed a survey followed by voluntary HIV counseling and testing. Survey items included demographics, homelessness history, survival activities, sexual behavior and substance use. We examined the relationship between predictor variables, markers of coercion and marginalization and HIV.

Results

The sample included 296 males. Survival activities included garbage picking (55%), helping market vendors (55%), begging (17%), and working as porters (46%) or domestic workers (4%). Forty-nine percent of participants reported at least weekly use of alcohol and 32% marijuana. Forty-six percent of participants reported lifetime inhalation of glue and 8% fuel. Seventy-nine percent of participants reported lifetime vaginal sex, 6% reported lifetime insertive anal sex and 8% reported lifetime receptive anal sex. Twelve (4.1%; 95% CI: 2.3–7.0) participants tested positive for HIV. Of those, all had been on the street for at least one year and all had engaged in vaginal sex. Occupations placing youth at particular risk of coercion by adults, including helping market vendors (prevalence ratio (PR) = 8.8; 95% CI: 1.2–67.5) and working as domestic workers (PR = 4.6; 95% CI: 1.1–19.0), were associated with HIV infection. Both insertive anal sex (PR = 10.2; 95% CI: 3.6–29.4) and receptive anal sex (PR = 3.9; 95% CI: 1.1–13.4) were associated with HIV infection. Drug use, begging, and garbage picking were not associated with HIV infection.

Conclusions

Although HIV prevalence in our sample of street youth is comparable to that of similarly-aged male youth in Nyanza Province, our findings highlight behavioral factors associated with HIV infection that offer opportunities for targeted prevention among street youth in East Africa.     

Correlates of Recent Declines of Rodents in Northern and Southern Australia: Habitat Structure Is Critical

Australia has experienced dramatic declines and extinctions of its native rodent species over the last 200 years, particularly in southern Australia. In the tropical savanna of northern Australia significant declines have occurred only in recent decades. The later onset of these declines suggests that the causes may differ from earlier declines in the south. We examine potential regional effects (northern versus southern Australia) on biological and ecological correlates of range decline in Australian rodents. We demonstrate that rodent declines have been greater in the south than in the tropical north, are strongly influenced by phylogeny, and are consistently greater for species inhabiting relatively open or sparsely vegetated habitat. Unlike in marsupials, where some species have much larger body size than rodents, body mass was not an important predictor of decline in rodents. All Australian rodent species are within the prey-size range of cats (throughout the continent) and red foxes (in the south). Contrary to the hypothesis that mammal declines are related directly to ecosystem productivity (annual rainfall), our results are consistent with the hypothesis that disturbances such as fire and grazing, which occur in non-rainforest habitats and remove cover used by rodents for shelter, nesting and foraging, increase predation risk. We agree with calls to introduce conservation management that limits the size and intensity of fires, increases fire patchiness and reduces grazing impacts at ecological scales appropriate for rodents. Controlling feral predators, even creating predator-free reserves in relatively sparsely-vegetated habitats, is urgently required to ensure the survival of rodent species, particularly in northern Australia where declines are not yet as severe as those in the south.