Evidence for the Presence of an Alternative Glucose Transport System in Clostridium beijerinckii NCIMB 8052 and the Solvent-Hyperproducing Mutant BA101

The effects of substrate analogs and energy inhibitors on glucose uptake and phosphorylation by Clostridium beijerinckii provide evidence for the operation of two uptake systems: a previously characterized phosphoenolpyruvate-dependent phosphotransferase system (PTS) and a non-PTS system probably energized by the transmembrane proton gradient. In both wild-type C. beijerinckii NCIMB 8052 and the butanol-hyperproducing mutant BA101, PTS activity declined at the end of exponential growth, while glucokinase activity increased in the later stages of fermentation. The non-PTS uptake system, together with enhanced glucokinase activity, may provide an explanation for the ability of the mutant to utilize glucose more effectively during fermentation despite the fact that it is partially defective in PTS activity.     

Book Reviews

Book reviewed in this article:
AFRICA: Le Antiche Rovine e Miniere della Rhodesia . L idio C ipriani .
AFRICA: Osservazioni sui Pigmei centro Africani . L idio C ipriani .     

Climate variability and campylobacter infection: an international study

Campylobacter is among the most important agents of enteritis in developed countries. We have described the potential environmental determinants of the seasonal pattern of infection with campylobacter in Europe, Canada, Australia and New Zealand. Specifically, we investigated the role of climate variability on laboratory-confirmed cases of campylobacter infection from 15 populations. Regression analysis was used to quantify the associations between timing of seasonal peaks in infection in space and time. The short-term association between weekly weather and cases was also investigated using Poisson regression adapted for time series data. All countries in our study showed a distinct seasonality in campylobacter transmission, with many, but not all, populations showing a peak in spring. Countries with milder winters have peaks of infection earlier in the year. The timing of the peak of infection is weakly associated with high temperatures 3 months previously. Weekly variation in campylobacter infection in one region of the UK appeared to be little affected by short-term changes in weather patterns. The geographical variation in the timing of the seasonal peak suggests that climate may be a contributing factor to campylobacter transmission. The main driver of seasonality of campylobacter remains elusive and underscores the need to identify the major serotypes and routes of transmission for this disease.     

Distributions of Potential in Cylindrical Coordinates and Time Constants for a Membrane Cylinder

A mathematical problem relating to membrane cylinders is stated and solved; its implications are illustrated and discussed. The problem concerns the volume distribution, in cylindrical coordinates, of the electric potential inside and outside a membrane cylinder of finite length (with sealed ends), during passive decay of an initially nonuniform membrane potential. The time constants for equalization with respect to the angle, theta, are shown to be typically about ten thousand times smaller than the time constant, tau(m) = R(m)C(m), for uniform passive membrane potential decay. The time constants for equalization with respect to length are shown to agree with those from one-dimensional cable theory; typically, they are smaller than tau(m) by a factor between 2 and 10. The relation of the membrane current density, I(m)(theta, x, t), to the values (at the outer membrane surface) of the extracellular potential phi(e)(r, theta, x, t) and of partial differential(2)phi(e)/ partial differentialx(2), is examined and it is shown that these quantities are not proportional to each other, in general; however, under certain specified conditions, all three of these quantities are proportional with each other and with phi(i)(r, theta, x, t) and partial differential(2)phi(i)/ partial differentialx(2) (at the inner membrane surface). The relation of these results to those of one-dimensional cable theory is discussed.     

Effect of 2,4-dichlorophenoxyacetic acid on nuclear division in stem segments ofPisum sativum L. cultivatedin vitro

We have investigated the influence of 2,4-dichlorophenoxyacetic acid (2,4-D) on the appearance of nuclear fragments, caused by direct nuclear division, as well as on mitotic activity in cultivated internodial stem segments ofPisum sativum L., cv. Bördi, during 180 d of cultivation. Direct nuclear fragmentation (dNF) was indicated by the shape and structure of the nucleus as well as by the occurrence of 1C- and 3C-values of DNA, investigated cytophotometrically. The dNF occurred during the whole cultivation period in segments treated by 2,4-D in concentrations from 4 to 32 mg 1^?1. In the presence of 2 mg 1^?1 of 2,4-D the dNF existed in the explants only up to 90 d. Mitotic activity was not observed in the 2,4-D-free control but occurred during the whole cultivation period when 2,4-D was added in concentrations from 2 to 16 mg l^?1. In the presence of 32 mg l^?1 of 2,4-D the level of mitotic activity was very low at the beginning and ceased after 60 d in culture.