Maltose excretion by the symbiotic Chlorella of the heliozoan Acanthocystis turfacea

Chlorella sp. strain 3.83, a symbiotic Chlorella isolated from the heliozoan Acanthocystis turfacea, excreted between 8% and 16% of assimilated ¹⁴CO₂ as maltose in the light (15000 lx), with a pH optimum around 4.8. This percentage increased when the illuminance was lowered (36% at 1700 lx). Release of [¹⁴C]maltose continued in darkness and could be inhibited by the uncoupler carbonyl cyanide p-trifluoro-methoxyphenylhydrazone and by diethylstilbestrol. Net efflux of maltose was observed even at a concentration ratio of extracellular/intracellular maltose of 7.8. Exogenous [¹⁴C]maltose (5 mM) was taken up by the cells with a rate <2% of that of simultaneous maltose release, indicating a practically unidirectional transport. It is concluded that maltose excretion is an active-transport process.Abbreviations DES diethylstilbestrol - FCCP carbonyl cyanide p-trifluoromethoxyphenyl hydrazone - p.c. packed cells This work was supported by the Deutsche Forschungsgemeinschaft. Thanks are due to Doris Meindl for skillful experimental help.     

Comparison of OspA Serotypes for Borrelia burgdorferi Sensu Lato from Japan,Europe and North America

Sixty-one Borrelia burgdorferi sensu lato strains from various sources (ticks, human, and wild animals) in Japan and two strains from ticks in Far Eastern Russia were classified on the basis of reactivity with 16 monoclonal antibodies (mAb) to outer surface protein A (OspA) and by DNA-DNA hybridization assay. Eleven OspA serotypes (J1 to J11) were recognized among the Japanese and the Far East Russian isolates (serotypes J1 to J9 were identified as B. garinii, serotype J10 was identified as B. afzelii, and serotype J11 corresponded to B. japonica), whereas 7 OspA serotypes for North American and European isolates previously reported (Bettina Wilske et al, J. Clin. Microbiol. 31:340-350, 1993) were not observed except for OspA serotype 2 which showed identical reactivity with OspA serotype J10. This finding provides helpful information for understanding the geographical distribution of Lyme disease borrelia and the development of vaccine and diagnostic tests. In conclusion: 1. B. burgdorferi sensu stricto has not been observed in Japan, 2. Japanese B. afzelii isolates are closely related to those from Europe, 3. B. garinii isolates from Japan are highly heterogeneous and apparently different from European B. garinii isolates.     

Replicate plating: does it increase reliability?

K.K. WILLE, B.R. VOWELS, A.N. FOGLIA, C.A. BERGE, B.M. SCHNELL AND F.W. BRIESE. 1996. As a part of a clinical study to evaluate the antibacterial effect of a topically applied erythromycin gel, microbiological specimens were taken from two groups of patients : one group using 2% erythromycin gel and the other group using a placebo gel. These specimens were plated in triplicate using a common source on bacteriological media using standard procedures. After the appropriate incubation times, the numbers of aerobic and anaerobic organisms were counted separately from each of three plates. A comparison of the bacterial colony counts from the replicate plates showed a high degree of similarity for each type of organism. Tests for treatment differences in organism counts were performed based on single, double and triplicate plating. The results obtained were almost identical, suggesting that replicate plating from a common source is no more accurate than single plating. The only apparent advantage of this type of replicate plating is heightened confidence in the reliability of bacterial counts from single plates.     

Theobroma cacao L.: a genetic linkage map and quantitative trait loci analysis

A genetic linkage map of Theobroma cacao (cocoa) has been constructed from 131 backcross trees derived from a cross between a single tree of the variety Catongo and an F1 tree from the cross of Catongo by Pound 12. The map comprises 138 markers: 104 RAPD loci, 32 RFLP loci and two morphologic loci. Ten linkage groups were found which cover 1068 centimorgans (cM). Only six (4%) molecular-marker loci show a significant deviation from the expected 11 segregation ratio.The average distance between two adjacent markers is 8.3 cM. The final genome-size estimates based on two-point linkage data ranged from 1078 to 1112 cM for the cocoa genome. This backcross progeny segregates for two apparently single gene loci controlling (1) anthocyanidin synthesis (Anth) in seeds, leaves and flowers and (2) self-compatibility (Autoc). The Anth locus was found to be 25 cM from Autoc and two molecular markers co-segregate with Anth. The genetic linkage map was used to localize QTLs for early flowering, trunk diameter, jorquette height and ovule number in the BC₁ generation using both single-point ANOVA and interval mapping. A minimum number of 2–4 QTLs (P<0.01) involved in the genetic expression of the traits studied was detected. Coincident map locations of a QTL for jorquette height and trunk diameter suggests the possibility of pleiotropic effects in cocoa for these traits. The combined estimated effects of the different mapped QTLs explained between 11.2% and 25.8% of the phenotypic variance observed in the BC₁ population.     

The osmoprotectant proline betaine is a major substrate for the binding-protein-dependent transport system ProU of Escherichia coli K-12

The ProP and ProU transport systems of Escherichia coli mediate the uptake of several osmoprotectants including glycine betaine. Here we report that both ProP and ProU are involved in the transport of the potent osmoprotectant proline betaine. A set of isogenic E. coli strains carrying deletions in either the proP or proU loci was constructed. The growth properties of these mutants in high osmolarity minimal media containing 1 mM proline betaine demonstrated that the osmoprotective effect of this compound was dependent on either an intact ProP or ProU uptake system. Proline betaine competes with glycine betaine for binding to the proU-encoded periplasmic substrate binding protein (ProX) and we estimate a K_D of 5.2 μM for proline betaine binding. This value is similar to the binding constant of the ProX protein determined previously for the binding of glycine betaine (K_D of 1.4 μM). Our results thus demonstrate that the binding-protein-dependent ProU transport system of E. coli mediates the efficient uptake of the osmoprotectants glycine betaine and proline betaine.