Development and validation of a FACS-based lipoprotein localization screen in the Lyme disease spirochete <Emphasis Type="Italic">Borrelia burgdorferi</Emphasis>

Background  

In our previous studies on lipoprotein secretion in the Lyme disease spirochete Borrelia burgdorferi, we used monomeric red fluorescent protein 1 (mRFP1) fused to specifically mutated outer surface protein A (OspA) N-terminal lipopeptides to gather first insights into lipoprotein sorting determinants. OspA:mRFP1 fusions could be detected by epifluorescence microscopy both in the periplasm and on the bacterial surface. To build on these findings and to complement the prior targeted mutagenesis approach, we set out to develop a screen to probe a random mutagenesis expression library for mutants expressing differentially localized lipoproteins.     

Abscisic add levels of individual leaf cells

Abscisic acid (ABA) concentrations of guard cells, subsidiary cells and epidermis cells of Comrnelina communis L. and Tradescantia virginiana L. were determined in cell sap samples extracted by means of micro glass capillaries. Concentrations up to 6.7 m M were indicated by commercial immunoassay test kits. A gradient of ABA concentration was found between guard cells (2,49 ± 1.81 m M , n = 25), subsidiary cells (1.25 ± 1.46 m M , n = 21) and epidermis cells (0.86 ± 0.76 m M , n = 20; mean values ± SD).     

Predicting physiological concentrations of metabolites from their molecular structure.

Physiological concentrations of metabolites can partly be explained by their molecular structure. We hypothesize that substances containing certain chemical groups show increased or decreased concentration in cells. We consider here, as chemical groups, local atomic configurations, describing an atom, its bonds, and its direct neighbor atoms. To test our hypothesis, we fitted a linear statistical model that relates experimentally determined logarithmic concentrations to feature vectors containing count numbers of the chemical groups. In order to determine chemical groups that have a clear effect on the concentration, we use a regularized (lasso) regression. In a dataset on 41 substances of central metabolism in different organisms, we found that the physical concentrations are increased by the occurrence of amino and hydroxyl groups, while aldehydes, ketones, and phosphates show decreased concentrations. The model explains about 22% of the variance of the logarithmic mean concentrations.     

Pre-imaginal flight motor pattern in Locusta

In a wind stream, larval stages of Locusta usually show a tonic muscle activity but they can also exhibit a rhythmic motor output. With ageing such a pattern can be released sooner, the trains become longer. The basic rhythm of 10 Hz does not change. The initial co-contraction of specific muscles is substituted later in development by an antagonistic recruitment. This activity resembles the flight motor pattern of young locusts which lack phasic sensory feedback from the wing region. Azadirachtin, an insect growth regulator, has been used to produce a permanent 5th larval instar. However, the extension of the last larval stage does not lead to a further development of the motor pattern to a level comparable to mature animals.     

Comparative study of the fatty acid composition of some groups of purple nonsulfur bacteria

The fatty acid composition (FAC) of 43 strains of purple nonsulfur bacteria belonging to six genera--Rubrivivax, Rhodopseudomonas, Rhodoplanes, Blastochloris, Rhodobium, and Rhodomicrobium--was studied by capillary gas chromatography. The cultures were grown on standard medium under standard conditions. Automatic identification of the fatty acid methyl esters and statistical processing of the results were performed by the computerized Microbial Identification System (M.I.S). Significant differences between the FACs of different genera, species, and, sometimes, strains were revealed. 16S rRNA genes of some of the new isolates, primarily those having a specific FAC, were sequenced. The taxonomic status of a number of the strains in question was determined using the FAC characteristics as one of the criteria. It was shown that the FAC characteristics may be used both for affiliating the isolates to known species and for revealing new taxa.     

Abscisic acid relations of plants grown on tungsten enriched substrates

The effect of tungsten as a potential inhibitor of ABA biosynthesis in plants was tested both under controlled conditions in the greenhouse or laboratory and in the field at a site naturally enriched with tungsten. Although as predicted in all cases the activity of aldehyde oxidase was strongly inhibited by tungsten, in well watered, greenhouse-grown maize plants increased concentrations of tungsten did not reduce ABA concentration in tissues. Depending on the time of incubation, mostly an accumulation due to an increased net ABA synthesis could be observed. Under drought stress, however, tungsten may have an inhibitory effect on ABA accumulation. Field experiments with drought-stressed clover and dandelion plants from a habitat close to a former tungsten mine confirm those of the greenhouse and laboratory. The ineffectiveness of tungsten in decreasing ABA levels in well-watered plants and its minimal effects in inhibiting ABA accumulation of droughted plants indicate that it is unsuitable as an inhibitor of ABA biosynthesis.