Presentation Information
[P02-226]Analysis and potential applications of silicon-utilizing bacteria in paddy fields
○Megumi Fukushima1, Akio Kuroda1, Takeshi Ikeda1,2 (1. Hiroshima Univ. (Japan), 2. JST PRESTO (Japan))
Keywords:
silicon,rice cultivation,silica-accumulating bacteria,silica-dissolving bacteria,steel slag
Silicon (Si), the second-most-abundant element in the earth’s crust, is an important mineral for some living organisms. For example, diatoms, which have shells made of solid silica (SiO2), require large amounts of soluble silicic acid (Si[OH]4) for growth. In the terrestrial ecosystems, many crops absorb significant amounts of Si(OH)4 and deposit it as silica within their tissues. Rice, in particular, absorbs significant amounts of Si(OH)4; this high uptake may deplete the available Si(OH)4 in paddy soils. Such deficiencies can lead to adverse effects, including increased susceptibility to diseases and reduced crop yields.
On the other hand, Si-utilizing bacteria exist in nature, including both silica-accumulating and silica-dissolving types. Although previously overlooked, they are supposed to play a role in the dynamics of Si in nature. In this study, focusing specifically on paddy soil environments, we investigate the interaction between Si-utilizing bacteria and the dynamics of Si. Furthermore, we aim to develop technologies that address Si(OH)4 deficiency by utilizing silica-dissolving bacteria.
<Experiment1> To assess the dynamics of Si in the paddy field, the concentration of Si(OH)4 in the irrigation water was measured. Immediately after the initial irrigation (the period when rice plants take up little Si(OH)4), the concentration in the outflow water was approximately 20 µg/mL lower than that in the inflow water. This result suggests that the soil and/or the microorganisms therein absorbed the Si(OH)4. To investigate the microbial involvement in this decrease, we incubated sterilized and unsterilized soil in a Si(OH)4 solution and monitored the change in Si(OH)4 concentration. As a result, the unsterilized soil showed a greater decrease in Si(OH)4 concentration than the sterilized soil. These findings suggest that soil microorganisms absorbed Si(OH)4 in paddy fields.
In addition, we analyzed the microbial communities in paddy soil using 16S rRNA gene sequencing and found that the abundance of the family Bacillaceae, which includes known silica-accumulating bacteria, increased immediately after the initial irrigation. These results suggest that the decrease in Si(OH)4 concentration following the initial irrigation may be due to the biological activity of these bacteria.
<Experiment2> To develop a novel technology for supplying Si(OH)4, we screened for bacteria that could leach Si(OH)4 from steel slag (a Si-rich industrial byproduct). To date, two candidate strains have been isolated. We are currently investigating the dissolution mechanisms of these isolates while conducting further screening to elucidate which phylogenetic groups of bacteria possess the capability to leach Si(OH)4 from slag.
On the other hand, Si-utilizing bacteria exist in nature, including both silica-accumulating and silica-dissolving types. Although previously overlooked, they are supposed to play a role in the dynamics of Si in nature. In this study, focusing specifically on paddy soil environments, we investigate the interaction between Si-utilizing bacteria and the dynamics of Si. Furthermore, we aim to develop technologies that address Si(OH)4 deficiency by utilizing silica-dissolving bacteria.
<Experiment1> To assess the dynamics of Si in the paddy field, the concentration of Si(OH)4 in the irrigation water was measured. Immediately after the initial irrigation (the period when rice plants take up little Si(OH)4), the concentration in the outflow water was approximately 20 µg/mL lower than that in the inflow water. This result suggests that the soil and/or the microorganisms therein absorbed the Si(OH)4. To investigate the microbial involvement in this decrease, we incubated sterilized and unsterilized soil in a Si(OH)4 solution and monitored the change in Si(OH)4 concentration. As a result, the unsterilized soil showed a greater decrease in Si(OH)4 concentration than the sterilized soil. These findings suggest that soil microorganisms absorbed Si(OH)4 in paddy fields.
In addition, we analyzed the microbial communities in paddy soil using 16S rRNA gene sequencing and found that the abundance of the family Bacillaceae, which includes known silica-accumulating bacteria, increased immediately after the initial irrigation. These results suggest that the decrease in Si(OH)4 concentration following the initial irrigation may be due to the biological activity of these bacteria.
<Experiment2> To develop a novel technology for supplying Si(OH)4, we screened for bacteria that could leach Si(OH)4 from steel slag (a Si-rich industrial byproduct). To date, two candidate strains have been isolated. We are currently investigating the dissolution mechanisms of these isolates while conducting further screening to elucidate which phylogenetic groups of bacteria possess the capability to leach Si(OH)4 from slag.
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