Glucose transport into the extremely halophilic archaebacteria

Penetration of glucose into cells of several extremely halophilic archaebacteria of the Halobacterium and Haloferax genera (Halobacterium saccharovorum and Halobacterium salinarium, Haloferax volcanii and Haloferax mediterranei) has been studied. Some characteristics of transport systems of carbohydrate-utilizing halobacteria Halobacterium saccharovorum, Haloferax mediterranei and Haloferax volcanii (pH and temperature optima, stereospecificity, kinetic parameters) have been determined. Inability of H. salinarium cells for active glucose transport has been shown. The dependence of glucose transport on the Na⁺ ions gradient (on the whole cells and membrane vesicles) has been demonstrated. Cells or membrane vesicles of carbohydrate-utilizing halobacteria grown in media containing this sugar indicated the activation of glucose transport, whereas cells grown in media without sugars did not. This fact has allowed us to conclude that corresponding transport systems are inducible.     

Physiological role of tyrosine transport systems in Halobacterium salinarium

The quantitative content of three transport systems for aromatic amino acids in cells of Halobacterium salinarium was measured: the common system (K _m is about 10^-6 M) and two tyrosine-specific systems with high and low affinity (K _m is about 10^-8 and 10^-5 M, respectively). To determine the activity of each of three systems separately, a method was developed based on the selective phenylalanine effect on these activities. When phenylalanine exeeds [¹⁴C]tyrosine by four to sixforld, it inhibits competitively the activity of the common system, and its 50- to 100-fold molar excess is inhibitory in a non-competitive way for the specific high affinity system (HAT system). The specific low affinity system (LAT system) is practically insensitive to phenylalanine. The activities of tyrosine-specific transport systems are slightly dependent on the culture age, and the observed decrease in transport activity during growth is due mainly to the decreased content of the common system. The HAT system formation is regulated by the repression type, and the effectors are aromatic amino acids especially tyrosine itself. The physiological sense of the tyrosine transport system's multiplicity in H. salinarium is discussed.     

Biocorrosion of Synthetic Plastics: Degradation Mechanisms and Methods of Protection

Microbiology - The mechanisms of microbial action on synthetic plastics are analyzed, with the focus on the most widespread polymers produced on an industrial scale. The effect of microbial enzymes...     

Phylogeny of the M superhaplogroup inferred from complete mitochondrial genome sequence of Indian specific lineages

Background  

Phylogenetic analysis of human complete mitochondrial DNA sequences has largely contributed to resolving phylogenies and antiquity of different lineages belonging to the majorhaplogroups L, N and M (East-Asian lineages). In the absence of whole mtDNA sequence information of M lineages reported in India that exhibits highest diversity within the sub-continent, the present study was undertaken to provide a detailed analysis of this haplogroup to precisely characterize the lineages and unravel their intricate phylogeny.     

Influence of the degree of aeration on halotolerance of yeasts of the genera Candida,Rhodotorula, and Malassezia

The biochemical mechanisms were studied that determine different reactions of yeasts of different genera to two simultaneously imposed stressors, hypoxia and osmotic shock. For Candida lipolytica, these two stressors were antagonistic, which resulted in stimulation of yeast growth by NaCl (in a wide range of concentrations) under microaerobic conditions. The reaction of Malassezia sp. was different: the degree of halotolerance of this microorganism was lower under microaerobic conditions. An intervening reaction pattern was characteristic of Rhodotorula aurantiaca. These differences were found to be determined, above all, by the induction of a salt-resistant respiratory system (oxidase) in Candida lipolytica, which could not be induced in Malassezia sp. In addition, the synthesis of catalase was enhanced in Candida lipolytica, which provided for neutralization of the active forms of oxygen accumulating as a result of inhibition of other protective enzymes by salt.     

Processing of viral envelope glycoprotein by the endomannosidase pathway: evaluation of host cell specificity

Endo-alpha-D-mannosidase is an enzyme involved in N-linked oligosaccharide processing which through its capacity to cleave the internal linkage between the glucose-substituted mannose and the remainder of the polymannose carbohydrate unit can provide an alternate pathway for achieving deglucosylation and thereby make possible the continued formation of complex oligosaccharides during a glucosidase blockade. In view of the important role which has been attributed to glucose on nascent glycoproteins as a regulator of a number of biological events, we chose to further define the in vivo action of endomannosidase by focusing on the well characterized VSV envelope glycoprotein (G protein) which can be formed by the large array of cell lines susceptible to infection by this pathogen. Through an assessment of the extent to which the G protein was converted to an endo-beta-N- acetylglucosaminidase (endo H)-resistant form during a castanospermine imposed glucosidase blockade, we found that utilization of the endomannosidase-mediated deglucosylation route was clearly host cell specific, ranging from greater than 90% in HepG2 and PtK1 cells to complete absence in CHO, MDCK, and MDBK cells, with intermediate values in BHK, BW5147.3, LLC-PK1, BRL, and NRK cell lines. In some of the latter group the electrophoretic pattern after endo H treatment suggested that only one of the two N-linked oligosaccharides of the G protein was processed by endomannosidase. In the presence of the specific endomannosidase inhibitor, Glcalpha1-->3(1- deoxy)mannojirimycin, the conversion of the G protein into an endo H- resistant form was completely arrested. While the lack of G protein processing by CHO cells was consistent with the absence of in vitro measured endomannosidase activity in this cell line, the failure of MDBK and MDCK cells to convert the G protein into an endo H-resistant form was surprising since these cell lines have substantial levels of the enzyme. Similarly, we observed that influenza virus hemagglutinin was not processed in castanospermine-treated MDCK cells. Our findings suggest that studies which rely on glucosidase inhibition to explore the function of glucose in controlling such critical biological phenomena as intracellular movement or quality control should be carried out in cell lines in which the glycoprotein under study is not a substrate for endomannosidase action.      

Influence of language and ancestry on genetic structure of contiguous populations: A microsatellite based study on populations of Orissa

Background

Although cystic fibrosis is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, the severity of disease is highly variable indicating the influence of modifier genes. The intestines of Cftr deficient mice (CF mice: Cftr ^tm1Unc ) are prone to obstruction by excessive mucus accumulation and are used as a model of meconium ileus and distal intestinal obstruction syndrome. This phenotype is strongly dependent on the genetic background of the mice. On the C57Bl/6 background, the majority of CF mice cannot survive on solid mouse chow, have inflammation of the small intestine, and are about 30% smaller than wild type littermates. In this work potential modifier loci of the CF intestinal phenotype were identified.

Results

CF mice on a mixed genetic background (95% C57Bl/6 and 5% 129Sv) were compared to CF mice congenic on the C57Bl/6 background for several parameters of the intestinal CF phenotype. CF mice on the mixed background exhibit significantly greater survival when fed dry mouse chow, have reduced intestinal inflammation as measured by quantitative RT-PCR for marker genes, have near normal body weight gain, and have reduced mucus accumulation in the intestinal crypts. There was an indication of a gender effect for body weight gain: males did not show a significant improvement at 4 weeks of age, but were of normal weight at 8 weeks, while females showed improvement at both 4 and 8 weeks. By a preliminary genome-wide PCR allele scanning, three regions were found to be potentially associated with the milder phenotype. One on chr.1, defined by marker D1Mit36, one on chr. 9 defined by marker D9Mit90, and one on chr. 10, defined by marker D10Mit14.

Conclusion

Potential modifier regions were found that have a positive impact on the inflammatory phenotype of the CF mouse small intestine and animal survival. Identification of polymorphisms in specific genes in these regions should provide important new information about genetic modifiers of the CF intestinal phenotype.     

Absorption of 14C-dicarboxylic acids by bacteria of the family Halobacteriaceae

Cultures of the family Halobacteriaceae belonging to the species Halobacterium halobium, H. cutirubrum, H. vallismortis and Halococcus morrhuae were shown to be capable of assimilating 14C-succinate. Halobacterium salinarium lacked this ability. The transport systems of C4-dicarboxylates differed in Halobacterium halobium 996 and H. vallismortis 1398, on the one hand, and Halococcus morrhuae 1235, on the other. The differences involve the kinetic parameters and stereospecificity of transport systems, the ability to take up different labelled C4-dicarboxylates, the pH-dependence of transport, and the action of CCCP, a protonophorous uncoupling agent. Halobacteria are capable of labelled succinate uptake at a lower NaCl content in the incubation medium than it is necessary for their growth. The optimal temperature for 14C-succinate uptake by halobacteria is higher than the optimal temperature of their growth. For all of the studied cultures, the transport system of dicarboxylate was shown to differ from that of E. coli common for C4-dicarboxylates and aspartate.