Differentiation between Xanthomonas campestris pv. graminis (ISPP List 1980), pv. phleipratensis (ISPP List 1980) emend., pv. poae Egli and Schmidt 1982 and pv. arrhenatheri Egli and Schmidt 1982, by Numerical Analysis of Phenotypic Features and Protein Gel Electrophoregrams

A numerical analysis of 257 phenotypic features of 45 bacterial isolates from grasses, revealed three phenons corresponding to (i) X. campestris pv. graminis (ISPP List 1980), (ii) X. campestris pv. phleipratensis (ISPP List 1980) and (iii) X. campestris pv. poae Egli and Schmidt 1982 and X. campestris pv. arrhenatheri Egli and Schmidt 1982. In each phenon, the strains clustered together regardless of the geographical origin of the isolates orthe year of isolation. Polyacrylamide gel electrophoresis of soluble proteins and host range studies, revealed four groups corresponding to the pathovars mentioned above. The four pathovars constitute definite biological entities that can be differentiated by phenotypic, gel electrophoretic and host range features.     

Reductive dechlorination of 2,4-dichlorobenzoate to 4-chlorobenzoate and hydrolytic dehalogenation of 4-chloro-, 4-bromo-, and 4-iodobenzoate by Alcaligenes denitrificans NTB-1.

Alcaligenes denitrificans NTB-1, previously isolated on 4-chlorobenzoate, also utilized 4-bromo-, 4-iodo-, and 2,4-dichlorobenzoate but not 4-fluorobenzoate as a sole carbon and energy source. During growth, stoichiometric amounts of halide were released. Experiments with whole cells and cell extracts revealed that 4-bromo- and 4-iodobenzoate were metabolized like 4-chlorobenzoate, involving an initial hydrolytic dehalogenation yielding 4-hydroxybenzoate, which in turn was hydroxylated to 3,4-dihydroxybenzoate. The initial step in the metabolism of 2,4-dichlorobenzoate was catalyzed by a novel type of reaction for aerobic organisms, involving inducible reductive dechlorination to 4-chlorobenzoate. Under conditions of low and controlled oxygen concentrations, A. denitrificans NTB-1 converted all 4-halobenzoates and 2,4-dichlorobenzoate almost quantitatively to 4-hydroxybenzoate.     

Effect of pH on the kinetics of Na+-dependent phosphate transport in rat renal brush-border membranes

The kinetics of Na+-dependent phosphate uptake in rat renal brush-border membrane vesicles were studied under zero-trans conditions at 37 degrees C and the effect of pH on the kinetic parameters was determined. When the pH was lowered it turned out to be increasingly difficult to estimate initial rates of phosphate uptake due to an increase in aspecific binding of phosphate to the brush border membrane. When EDTA or beta-glycerophosphate was added to the uptake medium this aspecific binding was markedly reduced. At pH 6.8, initial rates of phosphate uptake were measured between 0.01 and 3.0 mM phosphate in the presence of 100 mM Na+. Kinetic analysis resulted in a non-linear Eadie-Hofstee plot, compatible with two modes of transport: one major low-affinity system (Km approximately equal to 1.3 mM), high-capacity system (Vmax approximately equal to 1.1 nmol/s per mg protein) and one minor high-affinity (Km approximately equal to 0.03 mM), low-capacity system (Vmax approximately equal to 0.04 nmol/s per mg protein). Na+-dependent phosphate uptake studied far from initial rate conditions i.e. at 15 s, frequently observed in the literature, led to a dramatic decrease in the Vmax of the low-affinity system. When both the extra- and intravesicular pH were increased from 6.2 to 8.5, the Km value of the low-affinity system increased, but when divalent phosphate is considered to be the sole substrate for the low-affinity system then the Km value is no longer pH dependent. In contrast, the Km value of the high-affinity system was not influenced by pH but the Vmax decreased dramatically when the pH is lowered from 8.5 to 6.2. These results suggest that the low-affinity, high-capacity system transports divalent divalent phosphate only while the high-affinity, low-capacity system may transport univalent as well as divalent phosphate. Raising medium sodium concentration from 100 to 250 mM increased Na+-dependent phosphate uptake significantly but the pH dependence of the phosphate transport was not influenced. This observation makes it rather unlikely that pH changes only affect the Na+ site of the Na+-dependent phosphate transport system.     

Novel anaerobic gas-lift reactor (AGLR) with retention of biomass: Start-up routine and establishment of hold up

A start-up routine for a novel type of anaerobic gas-lift reactor using sand as support particles for Bacterial adhesion and involving a dilution rate shift-up is shown to result in rapid formation of mixed-culture aggregates from freely suspended cells. Formation of aggregates changed the general metabolism from acetate-butyrate production to acetate-propionate production. This change is attributed to a selection by washout, favoring propionate-producing bacteria with superior adhesive properties. Sand is shown to be essential in establishing, but not in sustaining, elevated holdup ratios. The importance of maintenance processes and cellular lysis in deeper parts of aggregates are manifest from a reduced effluent biomass concentration and a pronounced production of valeric acid.     

Linkage relationship between the genes for adenosine deaminase and S-adenosyl-homocysteine hydrolase on human chromosome 20

Summary The genes for adenosine deaminase (ADA) and Sadenosyl homocysteine hydrolase (AHCY or SAHH) are known to be syntenic and within measurable distance from each other, on chromosome 20 in man. In the present study an informative family is described in which the recombination fraction (θ) between the respective genes is estimated to be about 0.18. Together with the published finding of θ=0.15 (Eiberg and Mohr 1985) in informative Danish families, the recombination fraction for the pooled data is calculated to be θ=0.14 (in men), (in women) and (both sexes taken together).     

On the stabilization of animal numbers. Problems of testing

Summary When testing for regulation of population numbers, rather than using Bulmer's second test in cases where population numbers are estimated instead of measured, we prefer to correct Bulmer's first test for estimation error. A correction method is expounded, discussed, and applied to two series of census data: the pine looper of Klomp and the garden chafer of Milne. In neither case the tentative conclusion from using the uncorrected test was changed after correction. Therefore, in practice Bulmer's first test without correction can be used well as a first orientation. Twelve long series (more than 10 years) of census data of both univoltine and semelparous (a necessary condition) insects were tested for significant density dependence in the fluctuations of numbers with the randomization test of Pollard et al. None of the series, all we could find to meet the necessary condition as well as being longer than 10 years, showed significant density dependence at the 0.05 level, though the pine looper of Klomp did so at the 0.1 level. Next, the same series were tested for regulation in the sense of keeping density within limits with both the first test of Bulmer and the permutation test of Reddingius and Den Boer. Onky Klomp's pine looper population at Hoge Veluwe scored significantly. In a following paper this population will be considered more closely, in order to enable understanding of this test result.Communication No. 362 of the Biological Station, Wijster     

Structure of the gene of tum- transplantation antigen P91A: the mutated exon encodes a peptide recognized with Ld by cytolytic T cells

Mutagen treatment of mouse P815 tumor cells produces immunogenic mutants that express new transplantation antigens (tum- antigens) recognized by cytolytic T cells. We found that the gene conferring expression of tum- antigen P91A contains 12 exons, encoding a 60 kd protein lacking a typical N-terminal signal sequence. The sequence shows no significant similarity with sequences in current data bases. A mutation that causes expression of the antigen is located in exon 4; it is the only apparent difference between the normal and the antigenic alleles. A short synthetic peptide corresponding to a region of exon 4 located around this mutation makes P815 cells sensitive to lysis by anti-P91A cytolytic T cells. The mutation creates a strong aggretope enabling the peptide to bind the H-2 Ld molecule. Several secondary tumor cell variants that no longer express tum- antigen P91A were found to carry deletions in the gene.