Production of nitric oxide by ammonium-oxidizing bacteria colonizing building stones

Abstract Stone samples from corroding historical buildings in Germany released NO in significant amounts during oxidation of ammonium to nitrate. Nitrite intermediately accumulated to low concentrations. Nitrification and NO release were detectable only in stones with neutral pH. Addition of nitrapyrin inhibited both ammonium oxidation and NO production. NO was produced in stone samples containing Nitrosomonas or Nitrosovibrio , but was not produced in samples containing only Nitrobacter . Addition of nitrite stimulated NO production in autoclaved stone samples significantly only if dried to < 2% water content, or in acidic stone samples. In moist neutral stones, NO production was only slightly stimulated by nitrite giving less than about 8% of the NO production observed under nitrifying conditions. Most of the NO production by corroding building stones was apparently due to ammonium-oxidizing nitrifiers.     

Olive phenology as a sensitive indicator of future climatic warming in the Mediterranean

Experimental and modelling work suggests a strong dependence of olive flowering date on spring temperatures. Since airborne pollen concentrations reflect the flowering phenology of olive populations within a radius of 50 km, they may be a sensitive regional indicator of climatic warming. We assessed this potential sensitivity with phenology models fitted to flowering dates inferred from maximum airborne pollen data. Of four models tested, a thermal time model gave the best fit for Montpellier, France, and was the most effective at the regional scale, providing reasonable predictions for 10 sites in the western Mediterranean. This model was forced with replicated future temperature simulations for the western Mediterranean from a coupled ocean‐atmosphere general circulation model (GCM). The GCM temperatures rose by 4·5 °C between 1990 and 2099 with a 1% per year increase in greenhouse gases, and modelled flowering date advanced at a rate of 6·2 d per °C. The results indicated that this long‐term regional trend in phenology might be statistically significant as early as 2030, but with marked spatial variation in magnitude, with the calculated flowering date between the 1990s and 2030s advancing by 3–23 d. Future monitoring of airborne olive pollen may therefore provide an early biological indicator of climatic warming in the Mediterranean.