17Ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA) co-exist in soil, 18 but their relative distribution may vary depending on the environmental conditions. Effects of 19 changes in soil organic matter and nutrient content on the AOB and AOA are poorly 20 understood. Our aim was to compare effects of long-term soil organic matter depletion and 21 amendments with labile (straw) and more recalcitrant (peat) organic matter, with and without 22 easily plant-available nitrogen, on the activities, abundances and community structures of 23 AOB and AOA. Soil was sampled from a long-term field site in Sweden that was established 24 in 1956. The potential ammonia oxidation rates, the AOB and AOA amoA gene abundances 25 and the community structures of both groups based on T-RFLP of amoA genes were 26 determined. Straw amendment during 50 years had not altered any of the measured soil 27 parameters, while the addition of peat resulted in a significant increase of soil organic carbon 28 as well as a decrease in pH. Nitrogen fertilization alone resulted in a small decrease in soil 29 pH, organic carbon and total nitrogen, but an increase in primary production. Type and 30 amount of organic matter had an impact on the AOB and AOA community structures and the 31 AOA abundance. Our findings confirmed that AOA are abundant in soil, but showed that 32 under certain conditions the AOB dominate, suggesting niche differentiation between the two 33 groups at the field site. The large differences in potential rates between treatments correlated 34 to the AOA community size, indicating that they were functionally more important in the 35 nitrification process than the AOB. The AOA abundance was positively related to addition of 36 labile organic carbon, which supports the idea that AOA could have alternative growth 37 strategies using organic carbon. The AOB community size varied little in contrast to that of 38 the AOA. This indicates that the bacterial ammonia oxidizers as a group have a greater 39 ecophysiological diversity and potentially cover a broader range of habitats. 40

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Sustainable management of toilet waste must prevent disease transmission but allow reuse of plant nutrients. Inactivation of uterus-derived Ascaris suum eggs was studied in relation to ammonia in source-separated urine without additives and in human feces to which urea had been added, in order to evaluate ammonia-based sanitation for production of safe fertilizers from human excreta. Urine was used concentrated or diluted 1:1 and 1:3 with tap water at 4, 14, 24, and 34°C. Fecal material, with and without ash, was treated with 1% or 2% (wt/wt) urea at 24 and 34°C. At 34°C eggs were inactivated in less than 10 days in urine and in amended feces. At 24°C only feces with 2% (wt/wt) urea or 1% (wt/wt) urea at high pH (10) inactivated all eggs within 1 month, and no inactivation was observed after 75 days in urine diluted 1:3 (18 ؎ 11 mM NH 3 ). At temperatures of >24°C, NH 3 proved to be an efficient sanitizing agent in urine and feces at concentrations of >60 mM. Treating fecal material at 34°C can give a 6-log 10 egg inactivation within 1 month, whereas at 24°C 6 months of treatment is necessary for the same level of egg inactivation. At temperatures of 14°C and below, inactivation rates were low, with viable eggs after 6 months even in concentrated urine.

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Global food security is one of the most pressing issues for humanity, and agricultural production is critical for achieving this. The existing analyses of specific threats to agricultural food production seldom bring out the contrasts associated with different levels of economic development and different climatic zones. We therefore investigated the same biophysical threats in three modelled types of countries with different economic and climatic conditions. The threats analysed were environmental degradation, climate change and diseases and pests of animals and plants. These threats were analysed with a methodology enabling the associated risks to be compared. The timeframe was 2012-2050 and the analysis was based on three underlying assumptions for 2050: the world population will have increased to 9 billion people, there will be a larger middle class in the world and climate change will be causing more extreme weather events, higher temperatures and altered precipitation. It is suggested that the risks, presented by the biophysical threats analysed, differ among the three modelled types of countries and that climate zone, public stewardship and economic strength are major determinants of these differences. These determinants are far from evenly spread among the world's major food producers, which implies that diversification of risk monitoring and international assessment of agricultural production is critical for assuring global food security in 2050.

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The aims of the study were to determine the survival of Escherichia coli O157 on lettuce as a function of temperature and light intensity, and to use that information in a screening-level quantitative microbial risk assessment (QMRA) in order to evaluate risk-reducing strategies including irrigation water quality guidelines, rinsing, and holding time between last irrigation and harvest. Iceberg lettuce was grown in a climate chamber and inoculated with E. coli O157. Bacterial numbers were determined with the standard plate count method after inoculation and 1, 2, 4, and 7 day(s) postinoculation. The experiments were carried out at 11, 18, and 25°C in light intensities of 0, 400, and 600 mmol (m(2))(-1) s(-1). There was a significant effect of temperature and light intensity on survival, with less bacteria isolated from lettuce incubated at 25 and 18°C compared with 11°C (P < 0.0001), and in light intensities of 400 and 600 mmol (m(2))(-1) s(-1) compared with 0 mmol (m(2))(-1) s(-1) (P < 0.001). The average log reductions after 1, 2, 4, and 7 day(s) were 1.14, 1.71, 2.04, and 3.0, respectively. The QMRA compared the relative risk with lettuce consumption from 20 scenarios. A stricter water quality guideline gave a mean fivefold risk reduction. Holding times of 1, 2, 4, and 7 day(s) reduced the risk 3, 8, 8, and 18 times, respectively, compared with harvest the same day as the last irrigation. Finally, rinsing lettuce for 15 s in cold tap water prior to consumption gave a sixfold risk reduction compared with eating unrinsed lettuce. Sensitivity analyses indicated that variation in bacterial inactivation had the most significant effect on the risk outcome. A QMRA determining the relative risks between scenarios reduces uncertainty and can provide risk managers with decision support.

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