Expression of the plasmid pKM101-determined DNA repair system in recA? and lex? strains of Escherichia coli

Summary pKM101, a plasmid R factor of the N compatibility group increases methylmethane sulfonate mutagenesis and diminishes UV-killing in recA ⁺ lex ⁺ and recA ⁺ lex ^– strains, but not in recA ^– lex ⁺ strains. The induction of a reclex dependent colicin is not present in lex ^– strains carrying the pKM101 factor. These facts indicate that pKM101 acts through an error-prone DNA repair system, which is recA ⁺ dependent, but not lex ⁺ dependent.This paper is published on the occasion of Dr. C. Callerio's seventy-fifth birthday     

Simulation of biological growth

Researchers concerned with the growth of biological tissue often use models that predict the growth as a function of a mechanical stimulus such as stress, strain or elastic energy. However, a general theory for bulk growth should consider that the mechanical stimulus may only be one of many factors contributing to growth. Another important factor could be time, as living tissues can be assumed to have a pre-programmed directional biological growth that is independent of mechanical stimuli. This paper has two objectives: the first is to introduce the concept of directional biological growth within a well developed growth theory, the second is to present the computational methods by which three-dimensional growth that encompasses time and stress effects can be simulated using commercially available finite element analysis software.     

Spatio-Temporal Distribution of Injured Elephants in Masai Mara and the Putative Negative and Positive Roles of the Local Community

Background

Very few studies have ever focused on the elephants that are wounded or killed as local communities attempt to scare these animals away from their settlements and farms, or on the cases in which local people take revenge after elephants have killed or injured humans. On the other hand, local communities live in close proximity to elephants and hence can play a positive role in elephant conservation by informing the authorities of the presence of injured elephants.

Methodology/Principal Findings

Between 2007 and 2011, 129 elephants were monitored in Masai Mara (Kenya), of which 54 had various types of active (intentionally caused) or passive (non-intentionally caused) injuries. Also studied were 75 random control samples of apparently unaffected animals. The observed active injuries were as expected biased by age, with adults suffering more harm; on the other hand, no such bias was observed in the case of passive injuries. Bias was also observed in elephant sex since more males than females were passively and actively injured. Cases of passive and active injuries in elephants were negatively related to the proximity to roads and farms; the distribution of injured elephants was not affected by the presence of either human settlements or water sources. Overall more elephants were actively injured during the dry season than the wet season as expected. Local communities play a positive role by informing KWS authorities of the presence of injured elephants and reported 43% of all cases of injured elephants.

Conclusions

Our results suggest that the negative effect of local communities on elephants could be predicted by elephant proximity to farms and roads. In addition, local communities may be able to play a more positive role in elephant conservation given that they are key informants in the early detection of injured elephants.     

Polymerase manager protein UmuD directly regulates Escherichia coli DNA polymerase III α binding to ssDNA

Replication by Escherichia coli DNA polymerase III is disrupted on encountering DNA damage. Consequently, specialized Y-family DNA polymerases are used to bypass DNA damage. The protein UmuD is extensively involved in modulating cellular responses to DNA damage and may play a role in DNA polymerase exchange for damage tolerance. In the absence of DNA, UmuD interacts with the α subunit of DNA polymerase III at two distinct binding sites, one of which is adjacent to the single-stranded DNA-binding site of α. Here, we use single molecule DNA stretching experiments to demonstrate that UmuD specifically inhibits binding of α to ssDNA. We predict using molecular modeling that UmuD residues D91 and G92 are involved in this interaction and demonstrate that mutation of these residues disrupts the interaction. Our results suggest that competition between UmuD and ssDNA for α binding is a new mechanism for polymerase exchange.     

The Synechocystis PCC6803 MerA-Like Enzyme Operates in the Reduction of Both Mercury and Uranium under the Control of the Glutaredoxin 1 Enzyme

In a continuing effort to analyze the selectivity/redundancy of the three glutaredoxin (Grx) enzymes of the model cyanobacterium Synechocystis PCC6803, we have characterized an enzyme system that plays a crucial role in protection against two toxic metal pollutants, mercury and uranium. The present data show that Grx1 (Slr1562 in CyanoBase) selectively interacts with the presumptive mercuric reductase protein (Slr1849). This MerA enzyme plays a crucial role in cell defense against both mercuric and uranyl ions, in catalyzing their NADPH-driven reduction. Like MerA, Grx1 operates in cell protection against both mercury and uranium. The Grx1-MerA interaction requires cysteine 86 (C86) of Grx1 and C78 of MerA, which is critical for its reductase activity. MerA can be inhibited by glutathionylation and subsequently reactivated by Grx1, likely through deglutathionylation. The two Grx1 residues C31, which belongs to the redox active site (CX₂C), and C86, which operates in MerA interactions, are both required for reactivation of MerA. These novel findings emphasize the role of glutaredoxins in tolerance to metal stress as well as the evolutionary conservation of the glutathionylation process, so far described mostly for eukaryotes.     

Biostimulation of anaerobic digestion using nanomaterials for increasing biogas production

Reviews in Environmental Science and Bio/Technology - Biomass energy, especially biogas production, is a renewable and sustainable form of energy. Biogas is becoming more important due to its...     

Unanswered ethical and scientific questions for trials of invasive interventions for coronary disease: The case of single vessel disease

Trials in the 1990s demonstrated that medical therapy is as effective as invasive therapies for treating single-vessel coronary disease. Yet more recent studies enrolling patients with this condition have focused on evaluating only invasive approaches, namely, stenting versus coronary artery bypass surgery. Several ethical and scientific questions remain unanswered regarding the conduct of these later trials. Were they justified? Why wasn't a medical therapy arm included? Were subjects informed about the availability of medical therapy as an equivalent option? Was optimized medical therapy given prior to randomization? The absence of clear answers to these questions raises the possibility of serious bias in favor of invasive interventions. Considering that medical therapy is underutilized in patients with coronary disease, efforts should focus more on increasing utilization of medical therapy and proper selection of noninvasive interventions.     

Modelling the behaviour of ligaments: a technical note

Experimental observations suggest that during a ligament tensile strain test, water and glycosaminoglycans are exuded. Many attempts have been tried to model this behaviour using continuum mechanics. We have investigated this unique behaviour and have established three mechanisms which may contribute to the experimental observations: the slackness of the fibres before stretching can lead to a decrease in volume upon straightening; a Poisson's ratio higher than 0.5 from the axial to the lateral direction (as recorded in the literature [Hewitt, J., Guilak, F., Glisson, R. and Parker Vail, T. (2001) "Regional material properties of the human hip joint capsule ligaments", Journal of Orthopaedic Research 19(3), 359-364]) due to the very high level of anisotropy of the tissue; and an osmotic pressure, with a certain level of anisotropy, that causes the swelling of the tissue before loading [Thornton, G.M., Shrive, N.G. and Frank, C.B. (2001) "Altering ligament water content affects ligament pre-stress and creep behaviour", Journal of Orthopaedic Research 19(5), 845-851]. There may be other mechanisms that also contribute in the observed fluid exudation on tensile loading.