Proton pumps of the plasmalemma of the yeast Rhodotorula gracilis Their coupling to fluxes of potassium and other ions

(1) Intact cells of the obligatory aerobic yeast Rhodotorula gracilis (glutinis) generate a difference of the electrochemical proton potential (Δμ_H⁺) across the plasmalemma. In the range from pH 4.0 to 7.0 its value remains close to 12 kJ/mol. At pH 4.0 it is composed of the pH difference (inside alkaline) alone, at pH 7.0 of the membrane potential alone. (2) Both components of Δμ_H⁺ are generated by an active process, as shown by their rapid dissipation under anaerobic conditions. (3) In order to find out by which type of mechanism Δμ_H⁺ is generated the effect of a number of inhibitors of transport-ATPases (among them ouabain, triphenyltin chloride, quercetin, oligomycin, venturicidin, dicyclohexylcarbodiimide, Dio-9) were tested both on the generation of the membrane potential and on the extrusion of protons either in the absence or the presence of potassium ions. We found that all three processes were inhibited by Dio-9 and dicyclohexylcarbodiimide, which are specific for H⁺-ATPases. Triphenyltin chloride inhibited the K⁺/H⁺-exchange without having any effect either on the extrusion of H⁺ alone or on the membrane potential. (4) Dicyclohexylcarbodiimide and Dio-9, but not triphenyltin chloride inhibited at pH 4.0 the active transport of sugars. This class of substrates has been shown earlier to be transported by an electrogenic H⁺ symport driven by Δμ_H⁺ across the cell membrane. (5) Neither the rate of respiration nor the intracellular level of ATP were significantly decreased by any of these inhibitors (except for venturicidin). (6) We conclude that in Rhodotorula gracilis the difference of the electrochemical potential of H⁺ is created by an electrogenic proton pump, presumably in ATPase. The extrusion of protons in exchange against potassium is catalyzed by a different energy-dependent but electroneutral system. This conclusion is based on the observation that the H⁺/K⁺ exchange does not work under conditions where the membrane potential is large, and vice versa.     

Molecular diagnosis of the Prader-Willi and Angelman syndromes by detection of parent-of-origin specific DNA methylation in 15q11-13

The Prader-Willi syndrome (PWS) and the Angelman syndrome (AS) are distinct genetic disorders that are caused by a deletion of chromosome region 15q11-13 or by uniparental disomy for chromosome 15. Whereas PWS results from the absence of a paternal copy of 15q11-13, the absence of a maternal copy of 15q11-13 leads to AS. We have found that an MspI/HpaII restriction site at the D15S63 locus in 15q11-13 is methylated on the maternally derived chromosome, but unmethylated on the paternally derived chromosome. Based on this difference, we have devised a rapid diagnostic test for patients suspected of having PWS and AS.     

Cell types in the adenohypophysis of the hagfish,Myxine glutinosa (Cyclostomata)

Summary The anterior pituitary of the Atlantic hagfish, Myxine glutinosa, was investigated by transmission electron microscopy. The cells of the adenohypophysis are arranged in follicles surrounded by connective tissue. Five cell types containing granules and one agranular cell type were identified. At the present state of the study the function of these cells remains open to discussion.This study was supported by the Austrian Fonds zur Förderung der wissenschaftlichen Forschung (Grant no. 4070) and the Stiftungs- und Förderungsgesellschaft der Paris Lodron-Universität in Salzburg. The authors are grateful to the Director of the Biological Station in Drøbak (Norway), Amanuensis Finn Walvig, for procuring the material     

Nucleic acid hybridization of group N and group D streptococci

Streptococci of serological groups N and D were found to belong to three different 23S ribosomal RNA (rRNA) homology clusters which are not closely related to each other. One cluster includes the group N streptococci:Streptococcus lactis, S. cremoris, S. diacetylactis, and, in addition, two lactobacilli, Lactobacillus hordniae andL. xylosus. The second one is composed ofStreptococcus faecium, S. durans, andS. faecalis with its subspecies. All are members of serological group D. The third group includes the group D streptococciStreptococcus bovis andS. equinus together withS. thermophilus andS. salivarius. DNA-DNA hybridization studies confirm the close genetic relationship within each of the rRNA homology clusters.     

Spermine-binding protein and polyamine metabolism in duodenal mucosa of chick embryo

The spermine-binding activity of a cytosolic protein from chick intestine increases during embryogenesis and in the first week of life. Ornithine and S-adenosylmethionine decarboxylase activities assayed under the same experimental conditions increase showing a maximum at day 18 and 20 respectively. The behaviour of either enzyme activity is reflected in the pattern of duodenal polyamine concentration measured during the same period. The possibility that duodenal spermine-binding protein may be correlated with spermine accumulation in the tissue is discussed.     

Genome-wide association studies reveal the role of polymorphisms affecting factor H binding protein expression in host invasion by Neisseria meningitidis

Many invasive bacterial diseases are caused by organisms that are ordinarily harmless components of the human microbiome. Effective interventions against these microbes require an understanding of the processes whereby symbiotic or commensal relationships transition into pathology. Here, we describe bacterial genome-wide association studies (GWAS) of Neisseria meningitidis, a common commensal of the human respiratory tract that is nevertheless a leading cause of meningitis and sepsis. An initial GWAS discovered bacterial genetic variants, including single nucleotide polymorphisms (SNPs), associated with invasive meningococcal disease (IMD) versus carriage in several loci across the meningococcal genome, encoding antigens and other extracellular components, confirming the polygenic nature of the invasive phenotype. In particular, there was a significant peak of association around the fHbp locus, encoding factor H binding protein (fHbp), which promotes bacterial immune evasion of human complement by recruiting complement factor H (CFH) to the meningococcal surface. The association around fHbp with IMD was confirmed by a validation GWAS, and we found that the SNPs identified in the validation affected the 5’ region of fHbp mRNA, altering secondary RNA structures, thereby increasing fHbp expression and enhancing bacterial escape from complement-mediated killing. This finding is consistent with the known link between complement deficiencies and CFH variation with human susceptibility to IMD. These observations demonstrate the importance of human and bacterial genetic variation across the fHbp:CFH interface in determining IMD susceptibility, the transition from carriage to disease.     

Cost and Advantage of Soil Channel Formation by Contractile Roots in Successful Plant Movement

In most cases, contractile roots not only produce a pullingforce on an underground plant (bulb, corm), but also push awaythe substratum and create a soil channel in which plant movementis made easier. Two specially-constructed experimental set-upsallowed the pulling and pushing activity of contractile rootsin underground plant movement to be measured under identicalstandard conditions. Our results show that root channel formationis always advantageous for the accomplishment of movement. Theextent of channel formation in relation to the size of the bulbor corm being moved was calculated as a percentage channel effect.A value of 100% indicates a channel effect sufficient to allowplant movement with no resistance. For smaller distances moved(20-30 mm) a small channel effect (10-40%) was found to be veryefficient. For more extensive movement (> 50 mm) a 100% channeleffect seems to be the optimum energetically. These systemsof movement commonly exist in nature.Copyright 1995, 1999 AcademicPress Contractile root, root contraction, soil channel, channel effect, plant movement