Yeast life-span extension by calorie restriction is independent of NAD fluctuation

Calorie restriction (CR) slows aging in numerous species. In the yeast Saccharomyces cerevisiae, this effect requires Sir2, a conserved NAD+-dependent deacetylase. We report that CR reduces nuclear NAD+ levels in vivo. Moreover, the activity of Sir2 and its human homologue SIRT1 are not affected by physiological alterations in the NAD+:NADH ratio. These data implicate alternate mechanisms of Sir2 regulation by CR.     

Polar temperature of venus

The presence of substantial polar cooling of Venus, as derived from microwave interferometry at 10.6 cm wavelength, is shown to be open to doubt. Other microwave measurements give little evidence for significant pole-ward variation in temperature on the planet.     

Corrosion of electronic materials and devices

Electronic materials and devices corrode in the same ways as automobiles, bridges, and pipelines, but their typically small dimensions make them orders of magnitude more susceptible to corrosion failure. As elsewhere, the corrosion involves interactions with the environment. Under control, these interactions can be put to use, as in the formation of protective and functional oxide films for superconducting devices. Otherwise, they cause damage, as in the electrolytic dissolution of conductors, even gold, in the presence of humidity and ionic contamination from atmospheric particles and gases. Preventing corrosion entails identifying the damaging interactions and excluding species that allow them to occur.     

HST2 mediates SIR2-independent life-span extension by calorie restriction

Calorie restriction (CR) extends the life span of numerous species, from yeast to rodents. Yeast Sir2 is a nicotinamide adenine dinucleotide (NAD+-dependent histone deacetylase that has been proposed to mediate the effects of CR. However, this hypothesis has been challenged by the observation that CR can extend yeast life span in the absence of Sir2. Here, we show that Sir2-independent life-span extension is mediated by Hst2, a Sir2 homolog that promotes the stability of repetitive ribosomal DNA, the same mechanism by which Sir2 extends life span. These findings demonstrate that the maintenance of DNA stability is critical for yeast life-span extension by CR and suggest that, in higher organisms, multiple members of the Sir2 family may regulate life span in response to diet.     

Cell biology. An age of instability

It is well established that as we age our cancer risk increases dramatically. As Sinclair explains in his Perspective, the link between cancer and aging is now solidified by new work in budding yeast (McMurray and Gottschling). As yeast cells age there is a marked increase in their genetic instability (a hallmark of cancer), which is independent of the mechanism that determines their life-span.     

Intrinsic antibiotic resistance in relation to colony morphology in three populations of West African cowpea rhizobia

Rhizobia isolated from cowpeas (Vigna unguiculata (L.) Walp.) grown in three west African soils were examined for intrinsic resistance to five antibiotics and were scored for one of two colony morphologies. Half of the strains tested had a “wet”, slimy colony morphology and half had small discrete “dry”, non-slimy colonies. The populations as a whole were resistant to gentamicin (87%) but varied in their resistance to streptomycin, rifampicin, kanamycin and penicillin. Thirteen patterns of resistance were found for the 128 strains screened and strains within the same pattern usually had the same colony type. The most common pattern (32%) was resistance to all five antibiotics. Associations between resistances were random within populations and colony type. Each population was diverse, expressing from 6 to 8 patterns of resistance, but one population was relatively homogeneous, with 68% of its members exhibiting the same pattern. Correlations between intrinsic antibiotic resistance and colony type were demonstrated both for the west African cowpea rhizobia and for a broader group of cowpea miscellany rhizobia. The method was practical, rapid and reliable for identification of groups within populations.     

Terrestrial microarthropods of Victoria Land and Queen Maud Mountains, Antarctica: Implications of climate change

We review aspects of climate change likely to impact upon the Collembola and mites (microarthropods) of Victoria Land and the Queen Maud Mountains (VLQMM) in the Ross Sea Region of Antarctica. Five important aspects of biological and biological-environmental interactions are identified as key for understanding the impact of climate change on VLQMM microarthropods: (1) Water availability and utilization; (2) mean temperature (which will affect development and population processes) and extreme temperatures (which affect persistence); (3) ultraviolet radiation, although we note that the periods of peak UV irradiance and microarthropod activity do not coincide; (4) dispersal within and between habitats; and (5) potential establishment of invasive species from within and without Antarctica. The current evidence for effects of climate change on VLQMM microarthropods is equivocal, and we advocate targeted experimental and monitoring studies. Finally, we highlight several areas of high priority for future research, particularly on the mite fauna for which detailed information is currently lacking. These are: (1) functional ecology (including thermal biology, feeding and nutrition and water relations); (2) distribution, dispersal and colonization processes and (3) population and community ecology.