Dynamics of violaxanthin and lutein epoxide xanthophyll cycles in Lauraceae tree species under field conditions.

Two xanthophyll cycles have been described in higher plants: the violaxanthin xanthophyll (V or VAZ) cycle, which is present in all species, and the taxonomically restricted lutein epoxide xanthophyll (Lx) cycle, which involves the light-induced de-epoxidation of Lx to lutein (L) and its epoxidation back to Lx in low light. Laboratory experiments indicate that the first reaction occurs quickly, but the second reaction is much slower. We investigated the Lx cycle under field conditions in several tree species of the Lauraceae family to determine its relationship with the ubiquitous V cycle. The field study was conducted in two natural laurel forests: one in the Canary Islands, where Laurus azorica (Seub.) Franco, Ocotea foetens (Aiton.) Benth, Apollonias barbujana (Cav.) Bornm. and Persea indica (L.) Spreng were studied; and one in the Basque Atlantic coast where Laurus nobilis L. was studied. The results were complemented by a taxonomic study. The presence of Lx was widespread among Lauraceae species, but its concentration varied even among closely related species. The V pool size correlated positively with growth irradiance, whereas the relationship between Lx pool size and growth irradiance varied with species. A functional Lx cycle was confirmed under field conditions only in O. foetens and L. nobilis. Furthermore, in O. foetens, a correlation between Lx de-epoxidation and photoinhibition suggested a protective role for this cycle. We conclude that, unlike the V cycle, which is normally correlated with irradiance, the operation and light dependence of the Lx cycle is species-dependent.

Antitubercular drugs for an old target: GSK693 as a promising InhA direct inhibitor.

Despite being one of the first antitubercular agents identified, isoniazid (INH) is still the most prescribed drug for prophylaxis and tuberculosis (TB) treatment and, together with rifampicin, the pillars of current chemotherapy. A high percentage of isoniazid resistance is linked to mutations in the pro-drug activating enzyme KatG, so the discovery of direct inhibitors (DI) of the enoyl-ACP reductase (InhA) has been pursued by many groups leading to the identification of different enzyme inhibitors, active against Mycobacterium tuberculosis (Mtb), but with poor physicochemical properties to be considered as preclinical candidates. Here, we present a series of InhA DI active against multidrug (MDR) and extensively (XDR) drug-resistant clinical isolates as well as in TB murine models when orally dosed that can be a promising foundation for a future treatment.

Molecular characterization of isoniazid-resistant Mycobacterium tuberculosis clinical strains isolated in the Philippines.

The prevalence of mutations in the katG, inhA and oxyR-ahpC genes of isoniazid (INH)-resistant Mycobacterium tuberculosis isolates in the Philippines were determined. Of 306 M. tuberculosis isolates studied, 81 (26.5%) exhibited INH-resistance. Forty-four strains (54.3%) had mutations in the katG gene, eighteen strains (22.2%) had mutations in the putative inhA locus region, seven had mutations in both regions and five strains had mutations in the oxyR-ahpC operon. Only seven strains had no mutations. A total of 71 of the 81 (87.6%) resistant strains and 65 of the 72 (90.3%) INH sensitive randomly selected strains showed amino acid substitution in codon 463 (Arg to Leu) (88.9%). This fact supports the hypothesis that mutations at codon 463 are independent of INH-resistance and are linked to the geographical origins of the strains.

Radial variation in sap flow in five laurel forest tree species in Tenerife, Canary Islands.

Variations in radial patterns of xylem water content and sap flow rate were measured in five laurel forest tree species (Laurus azorica (Seub.) Franco, Persea indica (L.) Spreng., Myrica faya Ait., Erica arborea L. and Ilex perado Ait. ssp. platyphylla (Webb & Berth.) Tutin) growing in an experimental plot at Agua García, Tenerife, Canary Islands. Measurements were performed around midday during warm and sunny days by the heat field deformation method. In all species, water content was almost constant (around 35% by volume) over the whole xylem cross-sectional area. There were no differences in wood color over the whole cross-sectional area of the stem in most species with the exception of E. arborea, whose wood became darker in the inner layers. Radial patterns of sap flow were highly variable and did not show clear relationships with tree diameter or species. Sap flow occurred over the whole xylem cross-sectional area in some species, whereas it was limited to the outer xylem layers in others. Sap flow rate was either similar along the xylem radius or exhibited a peak in the outer part of the xylem area. Low sap flow rates with little variation in radial pattern were typical for shaded suppressed trees, whereas dominant trees exhibited high sap flow rates with a peak in the radial pattern. Stem damage resulted in a significant decrease in sap flow rate in the outer xylem layers. The outer xylem is more important for whole tree water supply than the inner xylem because of its larger size. We conclude that measurement of radial flow pattern provides a reliable method of integrating sap flow from individual measuring points to the whole tree.

Mycobacterium canariasense sp. nov.

A novel rapidly growing, non-pigmented mycobacterium was isolated from blood samples obtained from 17 patients with febrile syndrome. Bacterial growth occurred at 30 and 37 degrees C on Löwenstein-Jensen medium and also on MacConkey agar without crystal violet. Strains contained alpha- and alpha'-mycolates in their cell wall. Sequence analysis of the hsp65 and 16S rRNA genes identified the isolates as rapidly growing mycobacteria. Sequences of both genes were unique within the mycobacteria. DNA-DNA hybridization showed that the isolates had less than 15 % reassociation with 13 other recognized rapidly growing mycobacteria. The name Mycobacterium canariasense sp. nov. is proposed for this novel opportunistic pathogen, which is most closely related to Mycobacterium diernhoferi. The type strain is 502329T (= CIP 107998T = CCUG 47953T).