Biology subjects

Minamisawa, K.

Publications and source records attributed to Minamisawa, K..

3 recordsLinked to original sources

bioRxiv2025

Single-cell genomics of single soil aggregates: methodological assessment and potential implications with a focus on nitrogen metabolism

Soil particles in plant rooting zone are largely clustered to form complex porous structural unit called aggregates where highly diverse microbes coexist and drive biogeochemical cycling. The complete extraction of microbial cells and DNA from soil is a substantial task as certain microbes exhibit strong adhesion to soil surfaces and/or inhabit deep within aggregates. Yet, the degree of aggregate dispersion and the efficacy of extraction have rarely been examined, and thus adequate cell extraction method from soil remain unclear. We aimed to develop an optimal method of cell extraction for single-cell genomics (SCG) analysis of single soil aggregates by focusing on water-stable macroaggregates (diameter: 5.6-8.2 mm) isolated from a topsoil of cultivated Acrisol. Using the same six individual aggregates, we performed both SCG sequencing and amplicon analysis. While both bead-vortexing and sonication dispersion methods improved the extractability of bacterial cells compared to previous studies, the latter yielded higher number and more diverse microbes compared to the former. The analyses of nitrogen-cycling and exopolysaccharides-related genes suggested that the sonication-assisted extraction led to greater recovery of microbes strongly attached to soil particles and/or inhabited the aggregate subunits that were more physically stable (e.g., aggregate core). Further SCG analysis revealed that all six aggregates held intact microbes having the genes (i.e., potentials) to convert nitrate into all possible nitrogen forms while some low-abundance genes showed inter-aggregate heterogeneity. In addition, all six aggregates studied showed overall similarity in pore characteristics, phylum-level composition, and the microbial functional redundancy. Together, these results suggest that water-stable macroaggregates may act as a functional unit in soil and show potential as a useful experimental unit in soil microbial ecology. Our study also suggest that conventional methods employed for the extraction of cell and DNA may not be optimal. The current findings underscore the necessity to advance extraction methodologies, thereby facilitating a more comprehensive understanding of the microbial diversity and functioning within soil environments.

microbiology↗

bioRxiv2024

Mitigating nitrous oxide emission by an ultra-fast bioprocess enabling the removal of high concentration N2O

Nitrous oxide (N2O) is known as a greenhouse gas as well as an ozone-depleting substance. Wastewater treatment process is one of the sources of N2O emission, and the high concentrations of N2O in off-gas were reported from an anaerobic ammonium oxidation process. This study developed a novel N2O removal process using a down-flow hanging sponge reactor to remove high concentrations of N2O. More than 96% removal efficiencies were achieved for up to 300 ppm N2O with 3 min gas retention time (GRT), and more than 99% removal efficiency was obtained for 2,000 ppm N2O with 18 min GRT. A maximum removal rate of 161 {+/-} 26 mg-N/L-reactor/day was achieved, that was over 10 times faster than the pioneering process. Kinetic analysis indicated that the N2O dissolution rate is a crucial factor in determining the N2O removal rate in the reactor. Various N2O reducers belonging to both clade I and II were detected in reactors, and Azonexus was thought to play a key role.

microbiology↗

bioRxiv2024

Soil nutrition-dependent dynamics of the root-associated microbiome in paddy rice

O_LIPlants accommodate diverse microbial communities (microbiomes), which can change dynamically during plant adaptation to varying environmental conditions. However, the direction of these changes and the underlying mechanisms driving them, particularly in crops adapting to the field conditions, remain poorly understood. C_LIO_LIWe investigate the root-associated microbiome of rice (Oryza sativa L.) using 16S rRNA gene amplicon and metagenome sequencing, across four consecutive cultivation seasons in a high-yield, non-fertilized, and pesticide-free paddy field, compared to a neighboring fertilized and pesticide-treated field. C_LIO_LIOur findings reveal that root microbial community shifts and diverges based on soil fertilization status and plant developmental stages. Notably, nitrogen-fixing bacteria such as Telmatospirillum, Bradyrhizobium and Rhizomicrobium were over-represented in rice grown in the non-fertilized field, implying that the assembly of these microbes supports rice adaptation to nutrient-deficient environments. C_LIO_LIA machine learning model trained on the microbiome data successfully predicted soil fertilization status, highlighting the potential of root microbiome analysis in forecasting soil nutrition levels. Additionally, we observed significant changes in the root microbiome of ccamk mutants, which lack a master regulator of mycorrhizal symbiosis, under laboratory conditions but not in the field, suggesting a condition-dependent role for CCaMK in establishing microbiomes in paddy rice. C_LI

plant biology↗