Morphological development and cytochrome c oxidase activity in Streptomyces lividans are dependent on the action of a copper bound Sco protein

Copper has an important role in the life cycle of many streptomycetes, stimulating the developmental switch between vegetative mycelium and aerial hyphae concomitant with the production of antibiotics. In streptomycetes, a gene encoding for a putative Sco-like protein has been identified and is part of an operon that contains two other genes predicted to handle cellular copper. We report on the Sco-like protein from Streptomyces lividans (Sco Sl ) and present a series of experiments that firmly establish a role for Sco Sl as a copper metallochaperone as opposed to a role as a thiol-disulphide reductase that has been assigned to other bacterial Sco proteins. Under low copper concentrations, a Δ sco mutant in S. lividans displays two phenotypes; the development switch between vegetative mycelium and aerial hyphae stalls and cytochrome c oxidase (CcO) activity is significantly decreased. At elevated copper levels, the development and CcO activity in the Δ sco mutant are restored to wild-type levels and are thus independent of Sco Sl . A CcO knockout reveals that morphological development is independent of CcO activity leading us to suggest that Sco Sl has at least two targets in S. lividans . We establish that one Sco Sl target is the dinuclear Cu A domain of CcO and it is the cupric form of Sco Sl that is functionally active. The mechanism of cupric ion capture by Sco Sl has been investigated, and an important role for a conserved His residue is identified. </jats:p

Quantification of long-term precipitation use efficiencies of different maize production practices on a semi-arid ecotope in the Free State Province

Precipitation use efficiency (PUE) was estimated for four production practices, i.e. conventional tillage with November planting (CTN), conventional tillage with January planting (CTJ), in-field rainwater harvesting with November planting (WHBN), and in-field rainwater harvesting with January planting (WHBJ), over 80 maize seasons for a semi-arid ecotope in the central Free State Province of South Africa. An empirical yield prediction model was used to obtain maize grain yields. PUE was expressed as the ratio of transpiration: rainfall for each growing season (PUET), while transpiration was calculated from total biomass yield, vapour pressure deficit and a transpiration efficiency coefficient for maize. The following equation, based on 10 years of measured data, was developed to estimate daily vapour deficit pressure for the 80 seasons from daily maximum temperature: Vd = 0.163 x Tmax – 2.88 (R2 = 0. 73). Mean PUET values over the 80 seasons were: 0.260 for CTN, 0.320 for WHBN, 0.334 for CTJ, and 0.400 for WHBJ. These results confirmed and quantified the advantage of in-field rainwater harvesting over conventional tillage, and the advantage of January planting over November planting. PUET results were also expressed as cumulative probability functions. Significance tests showed that PUET for in-field rainwater harvesting was significantly better than PUET for conventional tillage, and that January planting was significantly better than November planting. It was concluded that the advantage of in-field rainwater harvesting over conventional tillage was mainly due to the absence of runoff and reduced evaporation in the former practice. The use of a short-growing cultivar, which flowers during the month with the most favourable climate, i.e. March, probably resulted in the advantage of January planting over November planting

On variational principles for coherent vortex structures

Different approaches are discussed of variational principles characterizing coherent vortex structures in two-dimensional flows. Turbulent flows seem to form ordered structures in the large scales of the motion and the self-organization principle predicts asymptotic states realizing an extremal value of the energy or a minimum of enstrophy. On the other hand the small scales take care of the increase of entropy, and asymptotic results can be obtained by applying the theory of equilibrium statistical mechanics

Influence of bioreaction on a long-term operation of a submerged membrane adsorption hybrid system

This study investigates the long-term performance of a submerged membrane adsorption hybrid system (SMAHS) for organic matter removal from synthetic wastewater representing biologically treated wastewater by using a low dose of powdered activated carbon (PAC). A simple periodic backwash system is used to de-clog the hollow fiber membrane. In this reactor, bioreaction takes place due to the growth of the biomass in the system. This hybrid system was able to remove effectively the small- and large-molecular weight organic matters from 270 to 36,270 Da. The effect of PAC replacement in the reactor was also studied and it was shown that PAC replacement could enhance both biological activity and adsorption. With PAC replacement of 2.5%(total amount) per day, the total organic carbon (TOC) removal efficiency was 10% higher than without PAC replacement. In another long-term experiment, the TOC removal efficiency was maintained over 85% even after 55-day operation (with PAC replacement rate of 2.5%(total amount) every two days). © 2006

A web-accessible computer program for calculating electrical potentials and ion activities at cell-membrane surfaces

Increasing evidence indicates that plant responses to ions (uptake/transport, inhibition, and alleviation of inhibition) are dependent upon ion activities at the outer surface of root-cell plasma membranes (PMs) rather than activities in the bulk-phase rooting medium

Severe axial vertebral rotation treated with a modified Boston brace: a case report

We report the case of a 13-year-old Caucasian girl suffering from severe axial rotation of the T5 to L4 vertebrae. The patient (initially examined during a school screening study) was at first considered to be suspicious of suffering from scoliosis due to a highly positive Adam's forward bending test. However, her radiographic evaluation revealed the existence of axial rotation in 12 of her vertebrae, without inclination in the sagittal and coronal planes. After an observation period of 12 months and due to the fact that both her physical appearance and the measured vertebral rotation deteriorated, the patient was given a modified thoracolumbar Boston brace that had an immediate positive derotational effect on all but two vertebrae. Twenty four months later, the progress of the vertebral rotation(s) seems to have been halted and most affected vertebrae appear to be stabilized in their new, 'post-brace', reduced position, with better results shown when the Boston brace is worn. The patient remains under constant medical observation. The application of a modified Boston brace seems to have served well (so far) a useful purpose for reducing and stabilizing this case of severe axial vertebral rotation, providing less deformity and (possibly) offering a better final cosmetic result