Effects of sterilization techniques on chemodenitrification and N<sub>2</sub>O production in tropical peat soil microcosms

Abstract

Abstract. Chemodenitrification – the non-enzymatic process of nitrite reduction – may be an important sink for fixed nitrogen in tropical peatlands. Rates and products of chemodenitrification are dependent on O2, pH, Fe2+ concentration, and organic matter composition, which are variable across peat soils. Assessing abiotic reaction pathways is difficult because sterilization and inhibition agents can alter the availability of reactants by changing iron speciation and organic matter composition. We compared six commonly used soil sterilization techniques – γ irradiation, chloroform, autoclaving, and the use of three different chemical inhibitors (mercury, zinc, and azide) – for their compatibility with chemodenitrification assays for tropical peatland soils (organic-rich, low-pH soil from the eastern Amazon). Out of the six techniques, γ irradiation resulted in soil treatments with the lowest cell viability and denitrification activity and the least effect on pH, iron speciation, and organic matter composition. Nitrite depletion rates in γ-irradiated soils were highly similar to untreated (live) soils, whereas other sterilization techniques showed deviations. Chemodenitrification was a dominant process of nitrite consumption in tropical peatland soils assayed in this study. Nitrous oxide (N2O) is one possible product of chemodenitrification reactions. Abiotic N2O production was low to moderate (3 %–16 % of converted nitrite), and different sterilization techniques lead to significant variations on production rates due to inherent processes or potential artifacts. Our work represents the first methodological basis for testing the abiotic denitrification and N2O production potential in tropical peatland soil.

Decrypting bacterial polyphenol metabolism in an anoxic wetland soil

“…This latter control did not contain amplifiable DNA over the course of the experiment, supporting microbial-inactivation during the time course monitored in this treatment (Supplementary Note 1 ). While we recognize the potential for autoclaving to alter soil chemistry 25 , we show at inoculation there was little difference in the soil chemical landscape between autoclaved and unautoclaved CT-amended soil microcosms (Supplementary Fig. 2 ).…”

Sulphide addition favours respiratory ammonification (DNRA) over complete denitrification and alters the active microbial community in salt marsh sediments

“…However, in the 1000 μM treatment, the sum of the products 15 NH 4 and 29+30 N 2 only accounted for an average of 76% of the 15 NO x − consumed during the incubation. It is possible that the use of zinc chloride to preserve samples for N 2 analysis enhanced nitrous oxide in the sample due to interactions with Fe 2+ resulting in chemodenitrification (Ostrom et al, 2016;Buessecker et al, 2019). However, since zinc chloride was used across all treatments this effect would likely be consistent across treatments and may not be a valid explanation for the 'missing' N in the high P sulphide mass balance.…”

Human-scale tissues with patterned vascular networks by additive manufacturing of sacrificial sugar-protein composites

“…If instantaneous stronger mechanical properties were immediately required beyond that of the hydrogel used, then the PCL could be left as seen in other strategies [21] . Chloroform has been used as a method to sterilize biomass [31] and collagen hydrogels [32] for decades. Therefore this chloroform step could be used in all applications to remove bacterial and viral load of good manufacture practice (GMP) materials to generate GSM for translation.…”