Host specificity ofAcanthoscelides quadridentatus andA. Puniceus [Col.: Bruchidae] for biological control ofMimosa pigra (with preliminary data on their biology)

The biology and host specificity of the seed-feeding bruchids,Acanthoscelides quadridentatus (Schaeffer) andA. puniceus Johnson, from Mexico were studied in quarantine facilities in Australia. Distinguishing characters in the genitalia of each species are illustrated. Oviposition was recorded on 16 of 73 species of plants tested but larvae died without entering pods or seeds, except onMimosa invisa K. F. P. von Martius andM. pigra L. Larvae entering seeds ofM. invisa died in the first instar. The bruchids were clearly specific toM. pigra and were subsequently released as part of a program for biological control of this weed in the Northern Territory, Australia in April 1983 and thailand in July 1984.      

Estimating selection by comparing synonymous and substitutional changes

A higher ratio of substitutional to synonymous changes in between-species than in within-species comparisons has been taken as evidence for positive selection changing amino acids. A model is presented in which a difference of this kind arises as a result of purely neutral mutations, provided that the species compared are sufficiently different to approach a steady state between forward and backward mutation. In Neissseria, substitutions are twice as frequent, relative to synonymous changes, in between-species comparisons: it is shown that the data are consistent with the neutral model. The argument does not invalidate evidence for positive selection, for example in Drosophila, when the species compared are fairly similar.     

Sulfur cycling in grassland and parkland soils

A conceptual diagram of the S cycle in grassland soils is presented as a framework for discussing S cycling process studies. Changes in the mineralization of S and in the redistribution of³⁵S-labeled sulfate among soil organic matter fractions were investigated during incubation of cropped and uncropped soils.Little mineralization or net immobilization of sulfur occurred in closed system incubations where the soils were left undisturbed throughout the incubations. Significantly more S was mineralized in open system incubations where the soils were leached periodically. Net mineralization was significantly greater in cropped soils compared with uncropped soils. The distribution of³⁵S was significantly affected by the addition of various substrates (sulfate, cellulose or a combination of both) and by the presence of plants. Under conditions of high solution sulfate, the majority of³⁵S incorporated was observed in the HI-reducible S fraction. When the solution sulfate concentrations were lower, there was a reduction in the proportion of³⁵S incorporated into the HI-reducible S fraction. The results of these experiment will be discussed in relation to the hypotheses presented by McGill and Cole (1981) and the conceptual diagram of the S cycle in grassland soils.Contribution from a symposium on the role of sulfur in ecosystem processes held August 10, 1983, at the annual meeting of the A.I.B.S., Grand Forks, ND; Myron Mitchell, convenor.Publication No. R 353 of the Saskatchewan Institute of Pedology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N OWO     

Radioimmunoassay for the detection of hepatitis e antigen (HBeAG) and antibody (anti-HBe).

A solid phase micro-immunoradiometric assay (micro-SPIRA) for the detection of hepatitis e antigen (HBeAg) and antibody has been developed. Chimpanzee anti-HBe/2 was developed by repeated immunizations with purified antigen containing HBeAg/1 and HBeAg/2. An anti-HBe/2 titer of 1:4 was determined by immunodiffusion (ID) analysis. Anti-HBe/1 was not detected. The anti-HBe IgG used in the assay was purified from plasma by a combination of DEAE-cellulose and affinity chromatography. The sensitivity of the micro-SPIRA for antigen and antibody was 193 ng/ml and 65 ng/ml, respectively. By comparing relative endpoint titers obtained by ID to micro-SPIRA, it was determined that micro-SPIRA for antigen and antibody is 320 and greater than 1300 times more sensitive, respectively, than ID. The specificity of the assay was ascertained by the examination of various non-B specimens. The application of the assay to a panel of 50 hepatitis B surface antigen (HBsAg)-positive specimens resulted in an increase in positivity of 18% for antigen and 22% for antibody.     

Stability of a reference panel of lyophilized hepatitis B antigens and antibodies

A lyophilized hepatitis B working/reference panel has been prepared for use in standardization tests. This panel includes HBsAg, anti-HBs, HBeAg/anti-HBe and subtype reagents. Quantitative analysis of the HBsAg reagents indicates that at a storage temperature of -20 degrees C, only 1 log at maximum of RIA counts per minute would be lost in 95 years. After storage at -20 degrees C for 1 year, there has been no loss of reactivity in any of the tests used to detect HBsAg, anti-HBs, HBeAg/anti-HBe or subtypes.     

Hepatitis A

Hepatitis A is a disease of worldwide distribution which occurs in endemic and epidemic form and is transmitted primarily by person-to-person contact through the fecal-oral route. Common source epidemics due to contamination of food are relatively common, and water-borne epidemics have been described less frequently. The presumed etiologic agent of hepatitis A has now been visualized by immune electron microscopic (IEM) techniques in early acute-illness-phase stools of humans with hepatitis A as well as in chimpanzees experimentally infected with material known to contain hepatitis A virus. In addition, several new serologic tests for the detection of antibody against hepatitis A virus have been described. These include complement fixation and immune adherence techniques. Current data suggest that hepatitis A is caused by a single viral agent lacking the morphologic heterogeneity of hepatitis B viral components and that there may be relative antigenic homogeneity between strains of virus recovered from various parts of the world. Serologic studies to date also indicate that hepatitis A virus is not a major contributing cause in post-transfusion hepatitis.     

Reconciling empirical interactions and species coexistence

Coexistence in ecological communities is governed largely by the nature and intensity of species interactions. Countless studies have proposed methods to infer these interactions from empirical data, yet models parameterised using such data often fail to recover observed coexistence patterns. Here, we propose a method to reconcile empirical parameterisations of community dynamics with species‐abundance data, ensuring that the predicted equilibrium is consistent with the observed abundance distribution. To illustrate the approach, we explore two case studies: an experimental freshwater algal community and a long‐term time series of displacement in an intertidal community. We demonstrate how our method helps recover observed coexistence patterns, capture the core dynamics of the system, and, in the latter case, predict the impacts of experimental extinctions. Collectively, these results demonstrate an intuitive approach for reconciling observed and empirical data, improving our ability to explore the links between species interactions and coexistence in natural systems.     

Waterborne pathogen detection by use of oligonucleotide-based microarrays

A small-oligonucleotide microarray prototype was designed with probes specific for the universal 16S rRNA and cpn60 genes of several pathogens that are usually encountered in wastewaters. In addition to these two targets, wecE-specific oligonucleotide probes were included in the microarray to enhance its discriminating power within the Enterobacteriaceae family. Universal PCR primers were used to amplify variable regions of 16S rRNA, cpn60, and wecE genes directly in Escherichia coli and Salmonella enterica serovar Typhimurium genomic DNA mixtures (binary); E. coli, S. enterica serovar Typhimurium, and Yersinia enterocolitica genomic DNA mixtures (ternary); or wastewater total DNA. Amplified products were fluorescently labeled and hybridized on the prototype chip. The detection sensitivity for S. enterica serovar Typhimurium was estimated to be on the order of 0.1% (10(4) S. enterica genomes) of the total DNA for the combination of PCR followed by microarray hybridization. The sensitivity of the prototype could be increased by hybridizing amplicons generated by PCR targeting genes specific for a bacterial subgroup, such as wecE genes, instead of universal taxonomic amplicons. However, there was evidence of PCR bias affecting the detection limits of a given pathogen as increasing amounts of a different pathogen were spiked into the test samples. These results demonstrate the feasibility of using DNA microarrays in the detection of waterborne pathogens within mixed populations but also raise the problem of PCR bias in such experiments.