Modification of substrate specificity in single point mutants of Agrobacterium tumefaciens type II NADH dehydrogenase

Type II NADH dehydrogenases (NDH-2) are monomeric flavoenzymes catalyzing electron transfer from NADH to quinones. While most NDH-2 preferentially oxidize NADH, some of these enzymes have been reported to efficiently oxidize NADPH. With the aim to modify the NADPH vs NADH specificity of the relatively NADH specific Agrobacterium tumefaciens NDH-2, two conserved residues (E and A) of the substrate binding domain were, respectively, mutated to Q and S. We show that when E was replaced by Q at position 203 the enzyme was able to oxidize NADPH as efficiently as NADH. Growth on a minimal medium of an Escherichia coli double mutant lacking both NDH-1 and NDH-2 was restored more efficiently when mutated proteins able to oxidize NADPH were expressed. The biotechnological interest of expressing such modified enzymes in photosynthetic organisms is discussed.     

Linking microarray reporters with protein functions

Background  

The analysis of microarray experiments requires accurate and up-to-date functional annotation of the microarray reporters to optimize the interpretation of the biological processes involved. Pathway visualization tools are used to connect gene expression data with existing biological pathways by using specific database identifiers that link reporters with elements in the pathways.     

Amblyomma sculptum: genetic diversity and rickettsias in the Brazilian Cerrado biome

Amblyomma sculptum (Ixodida: Ixodidae) Berlese, 1888 is the most important tick vector in Brazil, transmitting the bioagent of the most severe form of spotted fever (SF) in part of the Cerrado (in the states of Minas Gerais and São Paulo). In another part of the Cerrado (Central‐West region of Brazil), a milder form of SF has been recorded. However, neither the rickettsia nor the vector involved have been characterized. The aim of the current study was to analyse genetic variation and the presence of rickettsia in A. sculptum in Cerrado, from silent areas and with the milder form of SF. Samples were subjected to DNA extraction, amplification and sequencing of 12S rDNA, cytochrome oxidase subunit II and D‐loop mitochondrial genes (for tick population analyses), and gltA, htrA, ompA and gene D (sca4) genes for rickettsia researches. Exclusive haplotypes with low frequencies, high haplotype diversity and low nucleotide diversity, star‐shaped networks and significant results in neutrality tests indicate A. sculptum population expansions in some areas. Rickettsia amblyommatis, Candidatus Rickettsia andeanae and Rickettsia felis were detected. The A. sculptum diversity is not geographically, or biome delimited, pointing to a different potential in vector capacity, possibly associated with differing tick genetic profiles.     

A root's ability to retain K+ correlates with salt tolerance in wheat

Most work on wheat breeding for salt tolerance has focused mainly on excluding Na(+) from uptake and transport to the shoot. However, some recent findings have reported no apparent correlation between leaf Na(+) content and wheat salt tolerance. Thus, it appears that excluding Na(+) by itself is not always sufficient to increase plant salt tolerance and other physiological traits should also be considered. In this work, it was investigated whether a root's ability to retain K(+) may be such a trait, and whether our previous findings for barley can be extrapolated to species following a 'salt exclusion' strategy. NaCl-induced kinetics of K(+) flux from roots of two bread and two durum wheat genotypes, contrasting in their salt tolerance, were measured under laboratory conditions using non-invasive ion flux measuring (the MIFE) technique. These measurements were compared with whole-plant physiological characteristics and yield responses from plants grown under greenhouse conditions. The results show that K(+) flux from the root surface of 6-d-old wheat seedlings in response to salt treatment was highly correlated with major plant physiological characteristics and yield of greenhouse-grown plants. This emphasizes the critical role of K(+) homeostasis in plant salt tolerance and suggests that using NaCl-induced K(+) flux measurements as a physiological 'marker' for salt tolerance may benefit wheat-breeding programmes.     

Isolation and characterization of microsatellites in Neogobius kessleri (Perciformes,Gobiidae) and cross‐species amplification within the family Gobiidae

Fourteen polymorphic microsatellites were isolated from Neogobius kessleri, a benthic fish of Ponto‐Caspian origin which has been recently introduced into the Middle and Upper Danube River. Number of alleles and heterozygosity per locus in a sample of 32 fish individuals ranged from two to four and from 0.13 to 0.75, respectively. These primers will be useful in determining the population structure of N. kessleri. In addition, successful cross‐amplification was obtained for four related species, N. melanostomus, N. fluviatilis, N. gymnotrachelus and Proterorhinus marmoratus. These microsatellite loci may be useful for the evaluation of the origin of non‐native goby populations.     

Synthesis, X-ray structure and antimycobacterial activity of silver complexes with alpha-hydroxycarboxylic acids

In this paper, synthesis, characterization and antimycobacterial properties of a new water-soluble complex identified as silver-mandelate are described. Elemental and thermal analyses are consistent with the formula [Ag(C(6)H(5)C(OH)COO)](n). The polymeric structure was determined by single X-ray diffraction and the two-dimensional structure is based on the bis(carboxylate-O,O') dimer [Ag-O, 2.237(3), 2.222(3) Angstrom]. The structure is extended along both the b and c axes through two oxygen atoms of a bidentate alpha-hydroxyl-carboxylate residue [Ag-OH(hydroxyl), 2.477(3) Angstrom; Ag-O(carboxylate), 2.502(3) Angstrom; O-Ag-O, 63.94(9) degrees]. A strong d(10)-d(10) interaction was observed between two silver atoms. The Ag - Ag distance is 2.8307(15) Angstrom. The NMR (13)C spectrum in D(2)O shows that coordination of the ligand to Ag(I) occurs through the carboxylate group in solution. Potentiometric titration shows that only species with a molar metal:ligand ratio of 2:2 are formed in aqueous solution. The mandelate complex and the silver-glycolate, silver-malate and silver-hydrogen-tartarate complexes were tested against three types of mycobacteria, Mycobacterium avium, Mycobacterium tuberculosis and Mycobacterium kansasii, and their minimal inhibitory concentration (MIC) values were determined. The results show that the four complexes are potential candidates for antiseptic or disinfectant drugs for discharged secretions of patients affected with tuberculosis.     

电子供体及受体对棕色固氮菌抗氨阻遏能力的影响

电子供体连二亚硫酸钠,甲基紫精及电子受体亚甲蓝均能强烈的抑制棕色固氮菌表达固氮活性,并引起该菌的抗氨阻遏能力减弱,适当提高氧压,能提高菌体的固氮活性近15％,但过高的氧分压反而抑制菌体的固氮活性,此外,提高氢分压能降低棕色固氮菌菌体内的还原电位,从而达到提高菌体抗氨阻遏能力的效果。     

Preliminary evaluation of non-native rainbow trout (Oncorhynchus mykiss) impact on the Cederberg ghost frog (Heleophryne depressa) in South Africa’s Cape Fold Ecoregion

We evaluated the impact of non-native rainbow trout Oncorhynchus mykiss on a population of endemic Cedarberg ghost frog Heleophryne depressa in the upper Krom River (Olifants-Doring River Catchment, Cape Fold Ecoregion). We compared H. depressa abundance (using kick-sampling and underwater video analysis) and environmental conditions between sites above and below a waterfall that marks the upper distribution limit of O. mykiss. Heleophryne depressa abundance was significantly greater above the waterfall than that below it, and, because there was no significant difference in measured environmental variables, O. mykiss presence is identified as the most likely explanation for the observed decrease in H. depressa abundance.