Isolation and characterization of maltose non utilizing (mnu) mutants mapping outside the MAL1 locus in Saccharomyces cerevisiae

The MAL1 locus of Saccharomyces cerevisiae comprises three genes necessary for maltose utilization. They include regulatory, maltose transport and maltase genes designated MAL1R, MAL1T and MAL1S respectively. Using a MAL1 strain transformed with an episomal, multicopy plasmid carrying the MAL2 locus, five recessive and one dominant mutant unable to grow on maltose, but still retaining a functional MAL1 locus were isolated. All the mutants could use glycerol, ethanol, raffinose and sucrose as a sole carbon source; expression of the maltase and maltose permease genes was severely and coordinately reduced. Only the dominant mutant failed to accumulate the MAL1R mRNA.     

Field test of an automated radio‐telemetry system: tracking local space use of aerial insectivores

Documenting local space use of birds that move rapidly, but are too small to carry GPS tags, such as swallows and swifts, can be challenging. For these species, tracking methods such as manual radio‐telemetry and visual observation are either inadequate or labor‐ and time‐intensive. Another option is use of an automated telemetry system, but equipment for such systems can be costly when many receivers are used. Our objective, therefore, was to determine if an automated radio‐telemetry system, consisting of just two receivers, could provide an alternative to manual tracking for gathering data on local space use of six individuals of three species of aerial insectivores, including one Cliff Swallow (Petrochelidon pyrrhonota), one Eastern Phoebe (Sayornis phoebe), and four Barn Swallows (Hirundo rustica). We established automated radio‐telemetry systems at three sites near the city of Peterborough in eastern Ontario, Canada, from May to August 2015. We evaluated the location error of our two‐receiver system using data from moving and stationary test transmitters at known locations, and used telemetry data from the aerial insectivores as a test of the system's ability to track rapidly moving birds under field conditions. Median location error was ~250 m for automated telemetry test locations after filtering. More than 90% of estimated locations had large location errors and were removed from analysis, including all locations > 1 km from receiver stations. Our automated telemetry receivers recorded 17,634 detections of the six radio‐tagged birds. However, filtering removed an average of 89% of bird location estimates, leaving only the Cliff Swallow with enough locations for analysis of space use. Our results demonstrate that a minimal automated radio‐telemetry system can be used to assess local space use by small, highly mobile birds, but the resolution of the data collected using only two receiver stations was coarse and had a limited range. To improve both location accuracy and increase the percentage of usable location estimates collected, we suggest that, in future studies, investigators use receivers that simultaneously record signals detected by all antennas, and use of a minimum of three receiver stations with more antennas at each station.     

Superconductivity in Bismuth. A New Look at an Old Problem

To investigate the relationship between atomic topology, vibrational and electronic properties and superconductivity of bismuth, a 216-atom amorphous structure (a-Bi216) was computer-generated using our undermelt-quench approach. Its pair distribution function compares well with experiment. The calculated electronic and vibrational densities of states (eDOS and vDOS, respectively) show that the amorphous eDOS is about 4 times the crystalline at the Fermi energy, whereas for the vDOS the energy range of the amorphous is roughly the same as the crystalline but the shapes are quite different. A simple BCS estimate of the possible crystalline superconducting transition temperature gives an upper limit of 1.3 mK. The e-ph coupling is more preponderant in a-Bi than in crystalline bismuth (x-Bi) as indicated by the λ obtained via McMillan’s formula, λ^c = 0.24 and experiment λ^a = 2.46. Therefore with respect to x-Bi, superconductivity in a-Bi is enhanced by the higher values of λ and of eDOS at the Fermi energy.     

Protein Folding: Is Hierarchical versus Nonhierarchical a Productive Issue?

Abstract

A coarse-grained simulation accessing relevant folding timescales for β-lactoglobulin was corroborated experimentally and reveals a dynamic role for nonnative structures dictated by local propensity vis-à-vis the large-scale context. This picture prompts us to shift focus, leaving aside the hierarchical vs. nonhierarchical controversy.     

Antibacterial Activity of Pseudoalteromonas in the Coral Holobiont

Corals harbor diverse and abundant prokaryotic populations. Bacterial communities residing in the coral mucus layer may be either pathogenic or symbiotic. Some species may produce antibiotics as a method of controlling populations of competing microbial species. The present study characterizes cultivable Pseudoalteromonas sp. isolated from the mucus layer of different coral species from the northern Gulf of Eilat, Red Sea, Israel. Six mucus-associated Pseudoalteromonas spp. obtained from different coral species were screened for antibacterial activity against 23 tester strains. Five of the six Pseudoalteromonas strains demonstrated extracellular antibacterial activity against Gram-positive—but not Gram-negative—tester strains. Active substances secreted into the cell-free supernatant are heat-tolerant and inhibit growth of Bacillus cereus, Staphylococcus aureus, and of ten endogenous Gram-positive marine bacteria isolated from corals. The Pseudoalteromonas spp. isolated from Red sea corals aligned in a phylogenetic tree with previously isolated Pseudoalteromonas spp. of marine origin that demonstrated antimicrobial activity. These results suggest that coral mucus-associated Pseudoalteromonas may play a protective role in the coral holobiont's defense against potential Gram-positive coral pathogens.     

Fluorescence recovery after photobleaching: direct measurement of diffusion anisotropy

Biomechanics and Modeling in Mechanobiology - Fluorescence recovery after photobleaching (FRAP) is a widely used technique for studying diffusion in biological tissues. Most of the existing...     

Molecular dynamics of water in the neighborhood of aquaporins

Present knowledge obtained by molecular dynamics (MD) simulation studies regarding the dynamics of water, both in the vicinity of biological membranes and within the proteinaceous water channels, also known as aquaporins (AQPs), is reviewed. A brief general summary of the water models most extensively employed in MD simulations (SPC, SPC/E, TIP3P, TIP4P), indicating their most relevant pros and cons, is likewise provided. Structural considerations of water are also discussed, based on different order parameters, which can be extracted from MD simulations as well as from experiments. Secondly, the behaviour of water in the neighbourhood of membranes by means of molecular dynamics simulations is addressed. Consequently, the comparison with previous experimental evidence is pointed out. In living cells, water is transported across the plasma membrane through the lipid bilayer and the aforementioned AQPs, which motivates this review to focus mostly on MD simulation studies of water within AQPs. Relevant contributions explaining peculiar properties of these channels are discussed, such as selectivity and gating. Water models used in these studies are also summarised. Finally, based on the information presented here, further MD studies are encouraged.