To estimate the bacterial communities in rice straw left on the soil surface of paddy fields, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis was conducted. Rice straw samples were placed on the soil surface in a Japanese paddy field under drained conditions after harvest and under flooded conditions after the transplanting of rice. The residual samples on the soil surface under upland conditions were collected just before spring plowing and were replaced again on the soil surface after transplanting, under flooded conditions. The DGGE patterns of the bacterial communities in rice straw on the surface of paddy field soil were divided into three groups, namely rice straw samples before placement, under drained conditions and under flooded conditions. Sequence analysis of DGGE bands indicated that most of the bacterial members in rice straw during decomposition on the soil surface in the paddy field belonged to Gram-negative bacteria. The bands that commonly existed throughout the periods under flooded and upland conditions were closely related to α-Proteobacteria. The groups of Spirochaetes and δ-Proteobacteria were often observed during flooded periods, although the members of Bacteroidetes, α-Proteobacteria, Gemmatimonadetes and Actinobacteria were also detected under flooded conditions. In contrast, the bands characteristic to the rice straw left on the soil surface of the paddy field under drained conditions belonged to Bacteroidetes and γ-Proteobacteria. This finding clearly indicates that the bacterial communities responsible for rice straw decomposition were determined by the water regime in the paddy field, and various members of Gram-negative bacteria have contributed to the decomposition of rice straw left on the soil surface in a paddy field.
Methane-oxidizing bacteria (MOB) are crucial to the reduction of CH 4 emitted to the atmosphere. However, it is unclear how MOB in rice straw are affected by straw decomposition processes. In a Japanese rice field, a year-round experiment was set up to study the effects of agricultural practice (rice cultivation/winter fallow), straw parts (leaf sheath/blade) and the site of straw placement (plow layer/soil surface) on MOB communities in rice straw using denaturing gradient gel electrophoresis (DGGE) and DNA sequencing analyses of key MOB functional genes (pmoA and amoA). Thirty-eight different DGGE bands were observed over the entire investigation period. Principal component analysis of DGGE pattern suggested that agricultural practice is the key factor regulating the MOB communities. Sequencing of dominant DGGE bands showed that: (1) during the rice cultivation period, methanotrophs (particularly type I methanotrophs) dominated the MOB community, (2) during the winter fallow season both type I and type II methanotrophs were dominant in sheath segments placed both on the soil surface and in the plow layer, whereas ammonia oxidizers seemed to dominate blade segments placed in the plow layer. Alignment of diagnostic amino acid sequences of MOB suggested the presence of novel ammonia oxidizers in rice straw in rice fields.
Insect cell transformants, stably expressing human β1, 3-N-acetylglucosaminyltransferase 2 (β3GnT2) as the green fluorescent protein (GFP uv)-fused protein, were efficiently isolated on Western blot by the quantification of the densitometric intensity of the fusion protein. From almost 150 transformants containing the fusion gene linked to three different types of signal sequence, two transformants, Tn-pXme4a and-pX28a, were successfully selected, showing 8.3 and 8.6 mU/ml β3GnT activity, respectively. This is the highest, ever reported enzyme activity for β3GnT2 using a stable cell line. This method requires a screening time almost one-half that required in the isolation of stably transformed cells with high expression levels, and at the same time allows the handling a large number of transformants.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.