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Mismanagement of the composting process can result in emissions of CH 4 , N 2 O, and NH 3 , which have caused severe environmental problems. This study was aimed at determining whether CH 4 , N 2 O, and NH 3 emissions from composting are affected by bulking agents during rapid composting of pig manure from the Chinese Ganqinfen system. Three bulking agents, corn stalks, spent mushroom compost, and sawdust, were used in composting with pig manure in 60 L reactors with forced aeration for more than a month. Gas emissions were measured continuously, and detailed gas emission patterns were obtained. Concentrations of NH 3 and N 2 O from the composting pig manure mixed with corn stalks or sawdust were higher than those from the spent mushroom compost treatment, especially the sawdust treatment, which had the highest total nitrogen loss among the three runs. Most of the nitrogen was lost in the form of NH 3 , which accounts for 11.16% to 35.69% of the initial nitrogen. One-way analysis of variance for NH 3 emission showed no significant differences between the corn stalk and sawdust treatments, but a significant difference was noted between the spent mushroom compost and sawdust treatments. The introduction of sawdust reduced CH 4 emission more than the corn stalks and spent mushroom compost. However, there were no significant differences among the three runs for total carbon loss. All treatments were matured after 30 d.

BackgroundHoming endonuclease genes (HEGs) are widely distributed genetic elements in the mitochondrial genomes of a diversity of eukaryotes. Due to their ability to self-propagate within and between genomes, these elements can spread rapidly in populations. Whether and how such elements are controlled in genomes remains largely unknown.ResultsHere we report that the HEG-containing introns in the mitochondrial COX1 gene in Cryptococcus neoformans are mobile and that their spread in sexual crosses is influenced by mating type (MAT) α-specific homeodomain gene SXI1α. C. neoformans has two mating types, MATa and MATα. In typical crosses between strains of the two mating types, only a small portion (< 7%) of diploid fusants inherited the HEGs from the MATα parent. However, disruption of the SXI1α gene resulted in the majority (> 95%) of the diploid fusants inheriting the HEG-containing introns from the MATα parent, a frequency significantly higher than those of intronless mitochondrial genes.ConclusionsOur results suggest that SXI1α not only determines uniparental mitochondrial inheritance but also inhibits the spread of HEG-containing introns in the mitochondrial genome in C. neoformans.