Strain Level Identification of Pseudomonads Using Denaturing Gradient Gel Electrophoresis of 16S-23S Spacer Region rDNA

Specific Pseudomonas strains were detected by PCR amplification of the 16S-23S rDNA spacer region followed by denaturing gradient gel electrophoresis (DGGE) to generate DNA banding profiles. In initial studies, two diverse sequence areas within the 16S-23S rDNA spacer region were located in five closely related Pseudomonas fluorescens and P. putida strains. DNA banding profiles of 16 different pseudomonads were generated using PCR primers flanking this region, followed by DGGE of the PCR products. Distinct banding profiles were observed for each strain, and specificity could be increased by designing additional primers within the spacer region. A specific primer (513-1) was used to selectively amplify and detect a plant-disease suppressive bacterium, P. fluorescens strain 513, in soil. Six field soils from different locations were used with the 513-1 primer to test the specificity of this technique. Five soils did not yield any gel bands, but one soil led to a faint 250-bp band, similar in size to that of P. fluorescens 513. Resolution of strain 513 from the indigenous strain in this soil was achieved by DGGE of the amplified DNA fragments. The results therefore demonstrate the utility of PCR-DGGE analysis for strain-specific identification of pseudomonads in environmental samples. Received 17 January 2000/ Accepted in revised form 10 May 2000     

The active site of the plant alternative oxidase: structural and mechanistic considerations

In the present review we seek to provide an up‐to‐date view on the molecular nature of the active site of the plant alternative oxidase which has been postulated to comprise of a binuclear iron centre. A three‐dimensional model of the catalytic centre of the oxidase is presented which is based on the active site structure of the free radical component of ribonucleotide reductase and methane monooxygenase. The model indicates that a highly conserved carboxylate (Glu‐270) occupies a central position within the proposed di‐iron centre as it co‐ordinates both iron atoms. The expression of an alternative oxidase protein in Schizosaccharomyces pombe in which Glu‐270 was mutated to asparagine yields an inactive protein. The implications of this in relation to the structural model of the active site of the oxidase suggests that Glu‐270 is essential for catalytic alternative oxidase activity. A kinetic mechanism is suggested which accounts for the full reduction of dioxygen to water catalysed by a single di‐iron centre. © 2000 Society of Chemical Industry     

Diagnosis and characterization of insecticide-insensitive acetylcholinesterase in three populations of the sweetpotato whitefly Bemisia tabaci

A biochemical approach was used to characterize acetylcholinesterase (AChE) insecticide insensitivity in several sweetpotato whitefly (Bemisia tabaci; SPW) populations. Discriminating doses of insecticide were established to differentiate between sensitive and insensitive SPW strains and to genotype individual whitefly. This technique was then used to examine the frequency of insensitive AChE alleles in several SPW populations and to isolate a line homozygous for insensitive AChE from a heterogenous B-type population. Inheritance of putative altered AChE genotypes was consistent with the proposed haplo-diploid status of B. tabaci. This biochemical diagnostic was also employed to determine the role of insensitive AChE in the observed resistance profiles of several laboratory populations subjected to different selection regimes. In keeping with previous studies on insecticide resistance in SPW, resistance does not appear to be uniquely associated with the B-type but rather with SPW populations found in crop systems. © 1998 SCI.     

Key principles of ecosystem‐based management: the fishermen's perspective

Despite the growing popularity of ecosystem‐based management (EBM) in national legislation and in research and institutional literature, there is often an implementation gap ‘on the ground’, impeding widespread adoption in fisheries. This gap reflects in part the differing understandings of EBM held by fishermen and by management institutions. To explore and seek to close this gap, the underlying principles of EBM considered priorities by fishermen were systematically compared with the priorities identified in the published literature. The fishermen's priorities were determined by asking Atlantic Canadian fishermen to identify the EBM principles they consider most important. Four priority principles were identified: Sustainability, Stakeholder Involvement, Develop Long‐Term Objectives and Use of All Forms of Knowledge. The latter two were not frequently noted as priorities in the literature, while some literature priorities were less commonly chosen by fishermen, indicating a significant difference in perspectives on EBM. The rationale for fishermen's choice of priorities was explored by analysing the fishery management issues they raised – many directly connected to the above four priorities. In addition, another principle, Commit to Principles of Equity, often arose as an implicit priority among fishermen. We suggest that success in implementation of EBM may depend on reconciling differing priorities among its underlying principles, and combining knowledge and expertise from fishermen with research and institutional sources. The comparative methodology used here, which could be replicated elsewhere, should lead to better recognition of local challenges in EBM implementation and encourage support for EBM, to further its contribution to sustainable fisheries.     

Generic solutions for data‐limited fishery assessments are not so simple

The majority of the world's fisheries, by number, are data‐poor/limited, and there is a growing body of literature pertaining to approaches to estimate data‐limited stock status. There are at least two drivers for assessing the status of data‐limited fisheries. The first is to try to understand and report on the global or regional status of fisheries across many stocks. The second is to attempt to assess individual data‐limited stocks, for status reporting and/or guiding management decisions. These drivers have led to attempts to find simple, generic, low‐cost solutions, including the broad application of generically parameterised models, and the blanket application of a single, or limited number of possible, analytical approach(es). It is unclear that generic methods function as intended, especially when taken out of their original design context or used without care. If the intention is to resolve individual stock status for the purposes of management, there is concern with the indiscriminate application of a single method to a suite of stocks irrespective of the particular circumstances of each. We examine why caution needs to be exercised, and provide guidance on the appropriate application of data‐limited assessment methods (DLMs). We recommend: (a) obtaining better data, (b) using care in acknowledging and interpreting uncertainties in the results of DLMs, (c) embedding DLMs in harvest strategies that are robust to the higher levels of uncertainty in the output of DLMs by including precautionary management measures or buffers and (d) selecting and applying DLMs appropriate to specific species’ and fisheries’ data and context.     

Quantifying linkages between watershed factors and coastal wetland plant invasion in the US Great Lakes

Landscape Ecology - Freshwater coastal wetlands provide numerous ecosystem services, including habitat, nutrient uptake, coastal stabilization, and aesthetic value, but the integrity of these...