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Lipid-protein particles originating from the plasma membrane were immunopurified from the cytosol of carnation petal cells (Dianthus caryophyllus L. cv. Improved White Sim) using antibodies raised against the central hydrophilic domain of the H + -ATPase. The immunopurified particles are enriched in lipid metabolites, in particular free fatty acids and steryl/wax esters, by comparison with corresponding microsomal membranes, and the lipids of the particles are more saturated than those of microsomal membranes. Proteolytic catabolites of the H + -ATPase, a protein associated with the plasma membrane, but not the native H + -ATPase protein, are also present in the immunopurified cytosolic particles. Osmiophilic particles were discernible in the cytosol of carnation petal cells by transmission electron microscopy, and the association of H + -ATPase catabolites with a subpopulation of these particles was confirmed by immunogold labelling with H + -ATPase antiserum. Cross-reaction of the H + -ATPase antiserum with elements of the cytosol was also evident by immunofluorescent light microscopy. These observations collectively indicate that lipid-protein particles of plasma membrane origin are present in the cytosol of carnation petal cells and that their formation may serve as a means of removing lipid and protein metabolites from the plasma membrane which would otherwise destabilize its structure.

When the broad host range plasmid vector pGSS15 was used to genetically transform the plant growth promoting rhizobacterium Pseudomonas putida GR12-2, the transformants were physiologically debilitated. It was postulated that the expression of the β-lactamase gene of pGSS15 caused a metabolic load resulting in the impaired functioning of the bacterium. To test this hypothesis, derivatives of pGSS15 that either lack the β-lactamase gene (pYH122) or in which a β-glucosidase gene was substituted for the β-lactamase gene (pYH124) were constructed and examined to see whether their presence also impaired the functioning of P. putida GR12-2. On the basis of growth rates, siderophore production, and the ability to stimulate canola root elongation in sterile growth pouches, neither of the newly constructed plasmids debilitated P. putida GR12-2. In addition, P. putida GR12-2 transformed with pYH124 facilitated the proliferation of the bacterium in minimal medium containing cellobiose at low temperature. This latter trait may enable P. putida GR12-2 to persist in the soil in competition with other microorganisms.Key words: plant growth promoting rhizobacteria, PGPR, bacterial fertilizer, soil bacteria, metabolic load, β-glucosidase

Pseudomonas putida GR12-2, a plant growth promoting rhizobacterium, was transformed with the broad host range plasmid pGSS15. The presence of the plasmid caused (i) a decrease in cell generation times, (ii) an altered pattern of cell proteins, (iii) an inhibition of the enhancement of canola root elongation, (iv) impairment of nitrogen fixation, and (v) a decrease in siderophore production. Strains that were cured of pGSS15, on the other hand, re-established growth rates, levels of siderophore production, and canola root elongation capabilities equivalent to nontransformed P. putida GR12-2. Thus, the transforming plasmid imposes a metabolic load on the recipient bacteria that impacts on a number of different energy-dependent processes. Key words: plant growth promoting rhizobacteria, nitrogen fixation, Pseudomonas, transformation, metabolic load.

Summary: A complete isoleucyl-tRNA synthetase gene (ileS) of Campylobacter jejuni was isolated from a C. jejuni TGH9011 genomic DNA library constructed in pBluescript. The complete coding sequence, flanking regions and transcription start point were determined. The deduced isoleucyl-tRNA synthetase (lleRS) had 917 amino acids with a molecular mass of 105399 Da, which was consistent with the observed size of 105 kDa in Escherichia coli maxicells. The ileS gene was mapped onto the physical map of the C. jejuni genome. Alignment of the C. jejuni lleRS sequence with six other bacterial lleRS sequences and two lower eukaryotic lleRS sequences identified seven conserved motifs, including the two signature sequences, HIGH and KMSKS, of class I aminoacyl-tRNA synthetases.