Varying the Abundance of O Antigen in \u3cem\u3eRhizobium etli\u3c/em\u3e and Its Effect on Symbiosis with \u3cem\u3ePhaseolus vulgaris\u3c/em\u3e

Judged by migration of its lipopolysaccharide (LPS) in gel electrophoresis, the O antigen of Rhizobium etli mutant strain CE166 was apparently of normal size. However, its LPS sugar composition and staining of the LPS bands after electrophoresis indicated that the proportion of its LPS molecules that possessed O antigen was only 40% of the wild-type value. Its LPS also differed from the wild type by lacking quinovosamine (2-amino-2,6-dideoxyglucose). Both of these defects were due to a single genetic locus carrying a Tn5 insertion. The deficiency in O-antigen amount, but not the absence of quinovosamine, was suppressed by transferring into this strain recombinant plasmids that shared a 7.8-kb stretch of the R. etli CE3 lps genetic region α, even though this suppressing DNA did not carry the genetic region mutated in strain CE166. Strain CE166 gave rise to pseudonodules on legume host Phaseolus vulgaris, whereas the mutant suppressed by DNA from lps region α elicited nitrogen-fixing nodules. However, the nodules in the latter case developed slowly and were widely dispersed. Two other R. etli mutants that had one-half or less of the normal amount of O antigen also gave rise to pseudonodules on P. vulgaris. The latter strains were mutated in lps region α and could be restored to normal LPS content and normal symbiosis by complementation with wild-type DNA from this region. Hence, the symbiotic role of LPS requires near-normal abundance of O antigen and may require a structural feature conferred by quinovosamin

The 10 micron spectral structure in comets

The 10 micron spectra of comets Halley (1982i), Wilson (1986l), Kohoutek (1973f) and Bradfield (1987s) are presented and compared. The silicate emission profiles of Halley and Bradfield are seen to be remarkably similar in that both contain a sharp break in the spectrum at 11.3 microns. Comet Bradfield does not show the same double peak structure seen in olivine and reported in Comet Halley be Campins and Ryan (1988) and Bregman, et al. (1987). The authors interpret the 11.3 micron signature as being due to olivine-type dust grains with at least some degree of crystallinity. Olivine alone is not enough to reproduce the shape of the 10 micron structure. However, in view of the authors' past success in fitting interstellar dust features with the emissivity profile obtained from amorphous grains produced by laser-vaporizing olivine, this is a very appealing identification. They note that there are significant variations in olivine spectra due to compositional differences, grain size distribution and related grain temperature variations to make the olivine identification tentative. They further tentatively identify the 9.8 micron feature in Halley as being due to either amorphorous olivine or a phyllosilicate (layer lattice). Neither the spectra of Halley, Kohoutek, nor Bradfield exhibited the 12.2 micron feature seen in Comet Wilson, which may prove diagnostic of the composition or thermal history differences between these comets. IR spectra of various mineral samples are discussed in terms of their match to cometary spectra

Expression of \u3cem\u3eRhizobium leguminosarum\u3c/em\u3e CFN42 Genes for Lipopolysaccharide in Strains Derived from Different \u3cem\u3eR. leguminosarum\u3c/em\u3e Soil Isolates

Two mutant derivatives of Rhizobium leguminosarum ANU843 defective in lipopolysaccharide (LPS) were isolated. The LPS of both mutants lacked O antigen and some sugar residues of the LPS core oligosaccharides. Genetic regions previously cloned from another Rhizobium leguminosarum wild-type isolate, strain CFN42, were used to complement these mutants. One mutant was complemented to give LPS that was apparently identical to the LPS of strain ANU843 in antigenicity, electrophoretic mobility, and sugar composition. The other mutant was complemented by a second CFN42 lps genetic region. In this case the resulting LPS contained O-antigen sugars characteristic of donor strain CFN42 and reacted weakly with antiserum against CFN42 cells, but did not react detectably with antiserum against ANU843 cells. Therefore, one of the CFN42 lps genetic regions specifies a function that is conserved between the two R. leguminosarum wild-type isolates, whereas the other region, at least in part, specifies a strain-specific LPS structure. Transfer of these two genetic regions into wild-type strains derived from R. leguminosarum ANU843 and 128C53 gave results consistent with this conclusion. The mutants derived from strain ANU843 elicited incompletely developed clover nodules that exhibited low bacterial populations and very low nitrogenase activity. Both mutants elicited normally developed, nitrogen-fixing clover nodules when they carried CFN42 lps DNA that permitted synthesis of O-antigen-containing LPS, regardless of whether the O antigen was the one originally made by strain ANU843

Decision Support Systems in Australian Agriculture: State of the Art and Future Development

This paper reports and discusses the results of a survey conducted with experts working in the field of decision support systems (DSS) in Australian agriculture. It also reviews the literature on DSS in the light of these experts' responses. The findings from this survey have consolidated our understanding of the current state of DSS in Australian agriculture. The uptake of DSS by farmers has been slow and various issues said to be contributing to this include fear of using computers, time constraints, poor marketing, complexity, lack of local relevance, lack of end-user involvement, and mismatched objectives between developers and users. The future prospect for the development of DSS was generally regarded to be poor. Never-the-less, the authors believe that new DSS which embrace the suggested criteria could be widely accepted by farmers. These criteria mean that to be widely used by farmers, any successful DSS needs to address widespread problems: they need to be location specific, and gain strong support from initial users. They also need to be simple to use, relevant, effective, low cost, and user friendly and it is most likely that farmers would have been involved in their development. We believe that farmers' personalities, and their attitudes towards risk management and decision making, will influence the pattern of adoption of DSS in Australian agriculture while the intergenerational change that is occurring in the management of Australian farms is a positive factor that may encourage more widespread use of these tools.DSS, farmers' decision-making, expert opinion, management decisions, Farm Management, D7, D8, Q12, Q13, Q16,

Genetic Locus and Structural Characterization of the Biochemical Defect in the O-Antigenic Polysaccharide of the Symbiotically Deficient \u3cem\u3eRhizobium etli\u3c/em\u3e Mutant, CE166

The O-antigen polysaccharide (OPS) of Rhizobium etli CE3 lipopolysaccharide (LPS) is linked to the core oligosaccharide via an N-acetylquinovosaminosyl (QuiNAc) residue. A mutant of CE3, CE166, produces LPS with reduced amounts of OPS, and a suppressed mutant, CE166α, produces LPS with nearly normal OPS levels. Both mutants are deficient in QuiNAc production. Characterization of OPS from CE166 and CE166α showed that QuiNAc was replaced by its 4-keto derivative, 2-acetamido-2,6-dideoxyhexosyl-4-ulose. The identity of this residue was determined by NMR and mass spectrometry, and by gas chromatography-mass spectrometry analysis of its 2-acetamido-4-deutero-2,6-dideoxyhexosyl derivatives produced by reduction of the 4-keto group using borodeuteride. Mass spectrometric and methylation analyses showed that the 2-acetamido-2,6-dideoxyhexosyl-4-ulosyl residue was 3-linked and attached to the core-region external Kdo III residue of the LPS, the same position as that of QuiNAc in the CE3 LPS. DNA sequencing revealed that the transposon insertion in strain CE166 was located in an open reading frame whose predicted translation product, LpsQ, falls within a large family of predicted open reading frames, which includes biochemically characterized members that are sugar epimerases and/or reductases. A hypothesis to be tested in future work is that lpsQ encodes UDP-2-acetamido-2,6-dideoxyhexosyl-4-ulose reductase, the second step in the synthesis of UDP-QuiNAc from UDP-GlcNAc

Valuing remnant vegetation in Central Queensland using choice modelling

In the Desert Uplands region of Central Queensland, many pastoralists are clearing vegetation in order to improve cattle grazing production. A choice modelling study was undertaken to provide estimates of the benefits of retaining remnant vegetation that are appropriate for inclusion in a cost benefit analysis of tighter clearing restrictions. Attributes included in the choice model were reductions in the population size of non‐threatened species, the number of endangered species lost to the region, and changes in regional income and employment. A nested logit model was used to model the data in order to avoid violations of the independence of irrelevant alternatives condition. The estimated benefits are reported for several tree clearing policy regimes that are more stringent than those currently applied.Resource /Energy Economics and Policy,

The extension programme

From the start of the Peel-harvey study in 1976, scientific research and extension have been closely linked. Trials, some involving major drainage works, have been set up on about 30 farms and several field days and seminars have been held. The Peel-Harvey Study Group anticipates that farmer acceptance of the Department of agriculture\u27s recommendations will reduce the phosphorus input to the estuary by 30 to 40 per cent over the next three to five years. At the same time farmers will benefit from modified cultural practices better suited to the sandy soils of the coastal plain

Efficient Dynamic Compressor Optimization in Natural Gas Transmission Systems

The growing reliance of electric power systems on gas-fired generation to balance intermittent sources of renewable energy has increased the variation and volume of flows through natural gas transmission pipelines. Adapting pipeline operations to maintain efficiency and security under these new conditions requires optimization methods that account for transients and that can quickly compute solutions in reaction to generator re-dispatch. This paper presents an efficient scheme to minimize compression costs under dynamic conditions where deliveries to customers are described by time-dependent mass flow. The optimization scheme relies on a compact representation of gas flow physics, a trapezoidal discretization in time and space, and a two-stage approach to minimize energy costs and maximize smoothness. The resulting large-scale nonlinear programs are solved using a modern interior-point method. The proposed optimization scheme is validated against an integration of dynamic equations with adaptive time-stepping, as well as a recently proposed state-of-the-art optimal control method. The comparison shows that the solutions are feasible for the continuous problem and also practical from an operational standpoint. The results also indicate that our scheme provides at least an order of magnitude reduction in computation time relative to the state-of-the-art and scales to large gas transmission networks with more than 6000 kilometers of total pipeline

Characterization of the Lipopolysaccharide from a \u3cem\u3eRhizobium phaseoli\u3c/em\u3e Mutant that is Defective in Infection Thread Development

The lipopolysaccharide (LPS) from a Rhizobium phaseoli mutant, CE109, was isolated and compared with that of its wild-type parent, CE3. A previous report has shown that the mutant is defective in infection thread development, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis shows that it has an altered LPS (K. D. Noel, K. A. VandenBosch, and B. Kulpaca, J. Bacteriol. 168:1392-1462, 1986). Mild acid hydrolysis of the CE3 LPS released a polysaccharide and an oligosaccharide, PS1 and PS2, respectively. Mild acid hydrolysis of CE109 LPS released only an oligosaccharide. Chemical and immunochemical analyses showed that CE3-PS1 is the antigenic O chain of this strain and that CE109 LPS does not contain any of the major sugar components of CE3-PS1. CE109 oligosaccharide was identical in composition to CE3-PS2. The lipid A\u27s from both strains were very similar in composition, with only minor quantitative variations. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of CE3 and CE109 LPSs showed that CE3 LPS separated into two bands, LPS I and LPS II, while CE109 had two bands which migrated to positions similar to that of LPS II. Immunoblotting with anti-CE3 antiserum showed that LPS I contains the antigenic O chain of CE3, PS1. Anti-CE109 antiserum interacted strongly with both CE109 LPS bands and CE3 LPS II and interacted weakly with CE3 LPS I. Mild-acid hydrolysis of CE3 LPS I, extracted from the polyacrylamide gel, showed that it contained both PS1 and PS2. The results in this report showed that CE109 LPS consists of only the lipid A core and is missing the antigenic O chain