Bibliography on inactivation of viruses and rickettsiae by heat

Inactivation of viruses and rickettsiae by heat - bibliograph

Tuning excitability by alloying: the Rh(111)/Ni/H2 + O2 system

The dynamic behavior of the O2 + H2 reaction on a Rh(111) surface alloyed with Ni has been studied in the 10(-5) mbar range using photoemission electron microscopy (PEEM) as a spatial resolving method. For T = 773 K and p(O2) = 5 x 10(-5) mbar the bifurcation diagram has been mapped out as a function of the Ni coverage in a range of 0 ML /= 1.3 ML. A critical Ni coverage of Theta(Ni,crit) = 0.13 monolayers (ML) is required for excitability. In the excitable parameter range pulse trains and irregular chemical wave patterns are found. Whereas the propagation speed of the pulses exhibits no clear-cut dependence on the Ni coverage, the frequency of the local PEEM intensity oscillations increases linearly with Ni coverage in the range from Theta(Ni) = 0.13 ML to Theta(Ni) = 1.3 ML.DF

Morphological adaptations of 3.22 Ga-old tufted microbial mats to Archean coastal habitats (Moodies Group, Barberton Greenstone Belt, South Africa)

Microbial life was well established and widespread by the Paleoarchean; however, the degree of evolutionary advancement such as microbial motility, intra- and inter-species interactions, phototropism, or oxygenic photosynthesis by that time remains highly debated. The 3.22 Ga Moodies Group in the Barberton Greenstone Belt (BGB, South Africa) are Earth's oldest well-preserved siliciclastic tidal deposits. They exhibit a unique assemblage of microbial mats, providing an excellent opportunity to decipher the morphological adaptations of microbial communities to different paleoenvironmental settings. The fossil mats are preserved as kerogenous laminations (0.5–1 mm thick) that can be traced laterally for ∼15 km in a ∼1000 m-thick succession of fine- to coarse-grained tidal sandstones and conglomerates. We here present a detailed stratigraphic and depositional facies analysis, documenting the association of the three principal mat morphotypes with specific environmental settings: (1) planar-type in coastal floodplain, (2) wavy-type in intertidal, and (3) tufted-type in upper inter- to supratidal facies. All mat types indicate a flourishing phototrophic biota; moreover, the tufted morphology suggests an intricate level of coordinated growth commonly known from cyanobacterial mats in modern environments

Earth's first snowball event: Evidence from the early Paleoproterozoic Huronian Supergroup

Ever since it was first proposed that the Earth completely froze during glaciations ∼ 640 million years ago evidence supporting this hypothesis has been increasing, primarily from samples of carbonates directly overlying glacial diamictites, termed cap carbonates. However, this was not the first extensive glacial period that affected planet Earth: ∼1750 million years prior to Neoproterozoic glaciations the Earth went through its first major glacial episode, the early Paleoproterozoic Huronian glaciations. The second Huronian ice advance deposited the Bruce Formation, with its overlying cap carbonate, the Espanola Formation. This up to ∼ 300 m thick succession of limestone, siltstone, dolostone and sandstone overlies diamictite containing a dropstone-bearing layer with δ13Ccarb of −10‰. The 12C-enriched interval also has rare earth element (REE) patterns with negative Eu anomalies, radiogenic Sr isotopes, and negative εNd(0) in the carbonate. The first of these observations is probably due to highly reducing conditions in the sediment, and the possible thawing of methane-rich areas, releasing fluids that mixed with the overlying bottom waters; the last two reflect the diagenetic incorporation into the carbonate of radiogenic Sr, and derivation of REEs, including Nd, from abundant silty loess. This infers a stratified water mass with a relatively stagnant bottom layer during disintegration of an ice shelf. Above this REE patterns through the basal Espanola become increasingly more light depleted upwards, C becomes heavier, Sr is less radiogenic, εNd(0) is near 0 and one area has up to ∼ 1300 ppm Ba incorporated into the carbonate, indicating breakdown of water-mass stratification. Vertically over ∼ 200 m δ13Ccarb increases from −4.5 to −2.5‰ as the environment shallowed incorporating gradually increasing amounts of seawater into the freshwater plume, which initially extended to depths below wave base. Strata deposited in the upper Espanola near the strandline contain layers of Fe-Mn-rich dolomite with positive Eu anomalies reflecting Paleoproterozioc seawater composition dominating even the nearshore by this time. These observations are similar to those from Neoproterozoic cap carbonates, and provide new evidence for the possibly snowball Earth-like nature of the ∼ 2.4 Ga Bruce glaciation

Harnessing Natural Diversity to Probe Metabolic Pathways

Analyses of cellular processes in the yeast Saccharomyces cerevisiae rely primarily upon a small number of highly domesticated laboratory strains, leaving the extensive natural genetic diversity of the model organism largely unexplored and unexploited. We asked if this diversity could be used to enrich our understanding of basic biological processes. As a test case, we examined a simple trait: the utilization of di/tripeptides as nitrogen sources. The capacity to import small peptides is likely to be under opposing selective pressures (nutrient utilization versus toxin vulnerability) and may therefore be sculpted by diverse pathways and strategies. Hitherto, dipeptide utilization in S. cerevisiae was solely ascribed to the activity of a single protein, the Ptr2p transporter. Using high-throughput phenotyping and several genetically diverse strains, we identified previously unknown cellular activities that contribute to this trait. We find that the Dal5p allantoate/ureidosuccinate permease is also capable of facilitating di/tripeptide transport. Moreover, even in the absence of Dal5p and Ptr2p, an additional activity—almost certainly the periplasmic asparaginase II Asp3p—facilitates the utilization of dipeptides with C-terminal asparagine residues by a different strategy. Another, as-yet-unidentified activity enables the utilization of dipeptides with C-terminal arginine residues. The relative contributions of these activities to the utilization of di/tripeptides vary among the strains analyzed, as does the vulnerability of these strains to a toxic dipeptide. Only by sampling the genetic diversity of multiple strains were we able to uncover several previously unrecognized layers of complexity in this metabolic pathway. High-throughput phenotyping facilitates the rapid exploration of the molecular basis of biological complexity, allowing for future detailed investigation of the selective pressures that drive microbial evolution.</p