BackgroundSensing and responding to environmental changes is a central aspect of cell division regulation. Mycobacterium tuberculosis contains eleven Ser/Thr kinases, two of which, PknA and PknB, are key signaling molecules that regulate cell division/morphology. One substrate of these kinases is Wag31, and we previously showed that partial depletion of Wag31 caused morphological changes indicative of cell wall defects, and that the phosphorylation state of Wag31 affected cell growth in mycobacteria. In the present study, we further characterized the role of the Wag31 phosphorylation in polar peptidoglycan biosynthesis.ResultsWe demonstrate that the differential growth among cells expressing different wag31 alleles (wild-type, phosphoablative, or phosphomimetic) is caused by, at least in part, dissimilar nascent peptidoglycan biosynthesis. The phosphorylation state of Wag31 is found to be important for protein-protein interactions between the Wag31 molecules, and thus, for its polar localization. Consistent with these results, cells expressing a phosphomimetic wag31 allele have a higher enzymatic activity in the peptidoglycan biosynthetic pathway.ConclusionsThe Wag31Mtb phosphorylation is a novel molecular mechanism by which Wag31Mtb regulates peptidoglycan synthesis and thus, optimal growth in mycobacteria.

Articles you may be interested inCharacterizations of Ga-doped ZnO films on Si (111) prepared by atmospheric pressure metal-organic chemical vapor deposition Identification of important growth parameters for the development of high quality Al x > 0.5 Ga 1 − x N grown by metal organic chemical vapor deposition J. Vac. Sci. Technol. A 25, 441 (2007); 10.1116/1.2713409 Ductile relaxation in cracked metal-organic chemical-vapor-deposition-grown AlGaN films on GaN

Thin films of vanadium dioxide have been deposited on glass by low pressure metal-organic chemical vapour deposition using the b-diketonate complex, vanadyl acetylacetonate, as the precursor. It is found that nearly monophasic, monoclinic VO 2 (M) films are formed in the narrow temperature range 475-520 uC, films formed outside this range comprising significant proportions of other vanadium oxide phases beside VO 2 (M). The microstructure of these well-crystallized films varies significantly with temperature in this range. Films grown at 475 uC are dense and have a very strong (200) orientation. At 520 uC, films are somewhat porous, and display little preferred orientation. Film microstructure influences the semiconductor-metal transition noticeably. Films deposited at 475 uC have a large change in resistance at 66 uC, and display a small temperature hysteresis in the transition. The transition temperature in films grown at 520 uC is higher (72 uC), whereas the change in resistance is smaller and the hysteresis larger. An attempt has been made to understand the unusual microstructure of VO 2 films grown on glass substrates. The variation in the phase transition characteristics is interpreted in terms of the observed film microstructure. The thermal properties of the CVD precursor are also reported.

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We have synthesized a range of transition-metal-doped BiFeO(3) thin films on conducting silicon substrates using a spin-coating technique from metal-organic precursor solutions. Bismuth, iron and transition-metal-organic solutions were mixed in the appropriate ratios to produce 3% transition-metal-doped samples. X-ray diffraction studies show that the samples annealed in a nitrogen atmosphere crystallize in a rhombohedrally distorted BiFeO(3) structure with no evidence for any ferromagnetic secondary phase formation. We find evidence for the disappearance of the 404 cm(-1) Raman mode for certain dopants indicative of structural distortions. The saturation magnetization of these BiFeO(3) films has been found to increase on doping with transition metal ions, reaching a maximum value of 8.5 emu cm(-3) for the Cr-doped samples. However, leakage current measurements find that the resistivity of the films typically decreases with transition metal doping. We find no evidence for any systematic variation of the electric or magnetic properties of BiFeO(3) depending on the transition metal dopant, suggesting that these properties are determined mainly by extrinsic effects arising from defects or grain boundaries.

We report the structural and optical properties of xSnO2–yFe2O3 nanocrystalline composite thin films. SnO2 and Fe2O3 exhibit strong phase separation instability and their particle size and crystallinity are tunable by changing their composition and annealing temperature. The bandgap for these composites continuously increases from 2.3 to 3.89 eV. We discuss the increasing bandgap values in terms of the quantum confinement effect manifested by the decreasing size of Fe2O3 crystallites. The method provides a generic approach for the tuning of the bandgap in nanocomposite systems.

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