Regulation of spvR, the positive regulatory gene of Salmonella plasmid virulence genes

Abstract The regulation of the spvR promoter from the Salmonella dublin virulence plasmid was monitored using proter-reporter gene fusion constructs. Activity was dependent upon the presence of the spv region and was affected by the number of copies of the spv region present with the cell. Activity remained constant throughout exponential growth, and increased rapidly with the onset of stationary phase, under both aerobic and anaerobic conditions. Additionally, the level of spvR expression was controlled by the availability of iron, activity being greatest under low iron conditions in stationary phase. The spvA gene product negatively regulated spvR expression in a dose-dependent manner, indicating that SpvA provides a negative feedback mechanism for this operon.     

Sex determination and population biology in the hymenoptera

The Hymenoptera (ants, bees, wasps and sawflies) display a great variety of social systems and sex ratios and have played a key role in the development and testing of many evolutionary models. Traditionally, considerable emphasis was placed on the fact that hymenopterans have haploid males and diploid females but it is now clear that many species also regularly produce sterile, diploid males. Recent studies explore the diverse ways in which production of these diploid males influences selection on mating systems, sex ratios and social behaviour.     

The relationship between a summer fry (0+) abundance index, derived from semi-quantitative electrofishing, and egg deposition of Atlantic salmon, in the River Bush, Northern Ireland

Atlantic salmon survival in the R. Bush (N. Ireland) from egg to summer 0+ was inversely density-dependent on egg deposition ( P <0.05). A stock-recruitment relationship derived from egg deposition and summer 0+ abundance index data was compared to that derived from adult and smolt counts based on total trapping. Fitted Ricker curves indicated maximum recruitment at around 2.35 million eggs and 2.46 million eggs for 0+ index and smolt count methods, respectively. Salmon 0+ abundance index data from semi-quantitative electrofishing could be obtained with relatively little effort, and used to derive whole-river stock-recruitment relationships on rivers where only adult count or some other estimator of parental stock is available. The derivation and expression of spawning targets from stock/recruitment relationships is discussed with reference to the R. Bush data.     

Application of a fry (0+;) abundance index, based on semi-quantitative electrofishing, to predict Atlantic salmon smolt runs in the River Bush, Northern Ireland

An abundance index for 0+ Atlantic salmon was based on semi-quantitative electrofishing estimates at 137 sites in typical juvenile habitat throughout the River Bush (N. Ireland). 0 + abundance was linearly related to total smolt numbers migrating through a downstream trap in subsequent years ( r ²= 0.716, P <0.001), suggesting a high degree of predictive ability. This predictive ability decreased as smolt age increased, suggesting influence of density-independent mortality. Potential application of the technique to estimate smolt production from rivers having no trapping facilities is discussed, together with sources of variability potentially affecting estimates.     

Analysis of picogram quantities of indole-3-acetic acid by high performance liquid chromatography-fluorescence procedures

The use of spectrofluorimeter coupled to a reverse phase high performance liquid chromatography column permits selective detection of indole-3-acetic acid at the low picogram level. The value of the technique is demonstrated by the analysis of endogenous IAA in elongating shoots, xylem sap and callus of Douglas-fir. The data are also used to illustrate a procedure whereby the accuracy of chromatographic analyses can be verified within definable probability limits.Abbreviations GC-MS combined gas chromatography-mass spectrometry - HPLC high performance liquid chromatography - IAA indole-3-acetic acid - SEC steric exclusion chromatography - SICM selected ion current monitoring Technical Paper No. 5379 from the Oregon State University Agricultural Experiment Station     

Diversity of anaerobic gut fungal populations analysed using ribosomal ITS1 sequences in faeces of wild and domesticated herbivores

Gut fungal-specific PCR primers have been used to selectively amplify the ITS1 region of gut fungal rDNA recovered from faeces of domestic and wild animals to investigate population diversity. Two different gel-based methods are described for separating populations of gut fungal rDNA amplicons, namely (1) denaturing gradient gel electrophoresis (DGGE) and (2) separation according to small size differences using Spreadex, a proprietary matrix for electrophoresis. Gut fungal populations were characterised by analysis of rDNA in faeces of seventeen domesticated and ten wild herbivores. Sequences derived from these gel-based characterisations were analysed and classified using a hidden Markov model-based fingerprint matching algorithm. Faecal samples contained a broad spectrum of fungi and sequences from five of the six recognised genera were identified, including Cyllamyces, the most recently described gut fungal genus, which was found to be widely distributed in the samples. Furthermore, four other novel groupings of gut fungal sequences were identified that did not cluster with sequences from any of the previously described genera. Both gel- and sequence- based profiles for gut fungal populations suggested a lack of geographical restriction on occurrence of any individual fungal type.     

Enrichment and characterization of marine anammox bacteria associated with global nitrogen gas production

Microbiological investigation of anaerobic ammonium oxidizing (anammox) bacteria has until now been restricted to wastewater species. The present study describes the enrichment and characterization of two marine Scalindua species, the anammox genus that dominates almost all natural habitats investigated so far. The species were enriched from a marine sediment in the Gullmar Fjord (Sweden) using a medium based on Red Sea salt. Anammox cells comprised about 90% of the enrichment culture after 10 months. The enriched Scalindua bacteria displayed all typical features known for anammox bacteria, including turnover of hydrazine, the presence of ladderane lipids, and a compartmentalized cellular ultrastructure. The Scalindua species also showed a nitrate-dependent use of formate, acetate and propionate, and performed a formate-dependent reduction of nitrate, Fe(III) and Mn(IV). This versatile metabolism may be the basis for the global distribution and substantial contribution of the marine Scalindua anammox bacteria to the nitrogen loss from oxygen-limited marine ecosystems.