Fungal N₂O production in an arable peat soil in Central Kalimantan, Indonesia

Abstract

To clarify the microbiological factors that explain high N 2 O emission in an arable peat soil in Central Kalimantan, Indonesia, a substrate-induced respiration-inhibition experiment was conducted for N 2 O production. The N 2 O emission rate decreased by 31% with the addition of streptomycin, whereas it decreased by 81% with the addition of cycloheximide, compared with a non-antibiotic-added control. This result revealed a greater contribution of the fungal community than bacterial community to the production of N 2 O in the soil. The population density of fungi in the soil, determined using the dilution plate method, was 5.5 log c.f.u. g -1 soil and 4.9 log c.f.u. g -1 soil in the non-selective medium (rose bengal) and the selective medium for Fusarium, respectively. The N 2 O-producing potential was randomly examined in each of these isolates by inoculation onto Czapek agar medium (pH 4.3) and incubation at 28°C for 14 days. Significant N 2 O-producing potential was found in six out of 19 strains and in five out of seven strains isolated from the non-selective and selective media, respectively. Twenty-three out of 26 strains produced more than 20% CO 2 during the 14-day incubation period, suggesting the presence of facultative fungi in the soil. These strains were identified to be Fusarium oxysporum and Neocosmospora vasinfecta based on the sequence of 18S rDNA, irrespective of the N 2 O-producing potential and the growth potential in conditions of low O 2 concentration.

Nitrous oxide emission derived from soil organic matter decomposition from tropical agricultural peat soil in central Kalimantan, Indonesia

“…in the surface soil in CL-A, and suggested the possibility of inactivity of nos of Janthinobacterium spp. Furthermore, Yanai et al (2007) reported N 2 O-producing fungi Fusarium oxysporum and Neocosmospora vasinfecta were isolated in CL-A. Because the inactivity of nos in some fungal species were reported (Shoun et al 2006), nos of the fungi in our study sites was possibly inactive.…”

“…Also, N 2 O-producing bacteria or fungi (e.g. Janthinobacterium spp., Fusarium oxysporum, and Neocosmospora vasinfecta) probably were important decomposers of peat during the rainy season (Yanai et al 2007;Hashidoko et al 2008).…”

Detection and Diversity of Fungal Nitric Oxide Reductase Genes ( p450nor ) in Agricultural Soils

“…These efforts suggested that fungi play a large but unrecognized role in N turnover and N 2 O flux (9,(11)(12)(13). Although the SIRIN methodology has provided valuable insight into the fungal contribution to denitrification, the application of SI-RIN to soils can be problematic as incomplete inhibition can bias the observations (14)(15)(16). Hence, alternative approaches (e.g., PCR) that selectively target fungal genes involved in denitrification are desirable to advance understanding of the fungal diversity contributing to N cycling in environments such as soils, aquifers, and deep-ocean sediments, where denitrifying fungi have been cultivated (7,13,17,18).…”

Novel P450nor Gene Detection Assay Used To Characterize the Prevalence and Diversity of Soil Fungal Denitrifiers

“…The fungal contribution to N 2 O production in soils is often measured using substrate-induced respiration-inhibition (SIRIN) in combination with cycloheximide, a fungal growth inhibitor, to measure the decrease in the flux of N 2 O in soil samples. These types of studies have shown that the addition of cycloheximide decreased N 2 O production by up to 89% in a perennial ryegrass field (6), 63% to 85% in semiarid soils (7,8), 81% in an arable peat soil (9), 40 to 51% in soil farming systems (10), and 18% in a sandy loam ley grass field (11). In some studies, the decrease in N 2 O flux when inhibiting fungi was greater than that when inhibiting bacteria, clearly demonstrating that fungal denitrification was more important than bacterial denitrification in certain ecosystems (6,8,9).…”