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Background Duckweed (family Lemnaceae) has recently been recognized as an ideal biomass feedstock for biofuel production due to its rapid growth and high starch content, which inspired interest in improving their productivity. Since microbes that co-exist with plants are known to have significant effects on their growth according to the previous studies for terrestrial plants, this study has attempted to understand the plant-microbial interactions of a duckweed, Lemna minor, focusing on the growth promotion/inhibition effects so as to assess the possibility of accelerated duckweed production by modifying co-existing bacterial community. Results Co-cultivation of aseptic L. minor and bacterial communities collected from various aquatic environments resulted in changes in duckweed growth ranging from −24 to +14% compared to aseptic control. A number of bacterial strains were isolated from both growth-promoting and growth-inhibitory communities, and examined for their co-existing effects on duckweed growth. Irrespective of the source, each strain showed promotive, inhibitory, or neutral effects when individually co-cultured with L. minor. To further analyze the interactions among these bacterial strains in a community, binary combinations of promotive and inhibitory strains were co-cultured with aseptic L. minor, resulting in that combinations of promotive-promotive or inhibitory-inhibitory strains generally showed effects similar to those of individual strains. However, combinations of promotive-inhibitory strains tended to show inhibitory effects while only Aquitalea magnusonii H3 exerted its plant growth-promoting effect in all combinations tested. Conclusion Significant change in biomass production was observed when duckweed was co-cultivated with environmental bacterial communities. Promotive, neutral, and inhibitory bacteria in the community would synergistically determine the effects. The results indicate the possibility of improving duckweed biomass production via regulation of co-existing bacterial communities.

ABSTRACT Plant growth-promoting bacteria (PGPB) have recently been demonstrated as a promising agent to improve wastewater treatment and biomass production efficiency of duckweed hydrocultures. With a view to their reliable use in aqueous environments, this study analysed the plant colonization dynamics of PGPB and the ecological consequences for the entire duckweed-associated bacterial community. A PGPB strain, Aquitalea magnusonii H3, was inoculated to duckweed at different cell densities or timings in the presence of three environmental bacterial communities. The results showed that strain H3 improved duckweed growth by 11.7–32.1% in five out of nine experiments. Quantitative-PCR and amplicon sequencing analyses showed that strain H3 successfully colonized duckweed after 1 and 3 d of inoculation in all cultivation tests. However, it significantly decreased in number after 7 d, and similar bacterial communities were observed on duckweed regardless of H3 inoculation. Predicted metagenome analysis suggested that genes related to bacterial chemotactic motility and surface attachment systems are consistently enriched through community assembly on duckweed. Taken together, strain H3 dominantly colonized duckweed for a short period and improved duckweed growth. However, the inoculation of the PGPB did not have a lasting impact due to the strong resilience of the natural duckweed microbiome. Duckweed microbiome can be modified for accelerated biomass production.

Coping with intergenerational conflicts is one of the fundamental keys to building a sustainable society. However, current decision-making systems tend to be inclined towards the preferences of present generations, simply because future generations do not yet exist and therefore cannot participate in present-day negotiating processes. In this paper, with an aim towards reconciling possible intergenerational conflicts, we present the first attempt at creating a participatory intergenerational deliberation practice by creating “imaginary future generation” groups to represent future generations and negotiate with present-generation groups regarding future visions and associated decision making. To accomplish this, a series of workshops were organized in a local municipality in Japan in which participating imaginary future-generation groups and present-generation groups first deliberated separately, and then worked together, to form a consensus over prioritizing policy measures associated with their separate visions of the municipality in 2060. We then analyzed deliberation and consensus-building processes used and observed a stark contrast in deliberation styles and priorities between the groups. For example, imaginary future-generation-group measures were primarily characterized by utilizing existing local resources, while the present-generation groups aimed more at solving current problems. Notably, the consensus-building processes resulted in choosing more than half of the measures originally proposed by the imaginary future-generation groups, thereby indicating that decision-making preferences had shifted to future generations. We contend that our approach, which is based on introducing imaginary future-generation groups as stakeholders, could provide indicators towards coping with intergenerational conflicts via present-day decision-making processes.

This study verifies the effectiveness of Imaginary Future Generation (IFG) in promoting the Sustainable Development Goals (SDGs). Using data from an online survey, we calculated sustainable development component measurements to assess the understanding of SDGs and demonstrated whether IFG can influence futurability components. Statistical analysis shows that knowledge significantly impacts people’s attitudes towards SDGs, with informed individuals more likely to cooperate in addressing these issues. Comparing the treatment and control groups revealed that participants asked to envision themselves as residents of 2050 (IFG) better grasped the essence of Agenda 2030 and exhibited more cooperative attitudes toward sustainability. Regression analysis confirmed these effects after controlling for individual attributes and SDG knowledge. The study finds that while raising awareness is crucial, IFG makes people perceive sustainability problems as personal concerns. IFG enhances respondents’ futurability, encouraging positive attitudes and long-term thinking. Additionally, IFG promotes participation, inclusive ideas, and increased SDG knowledge.

Environmental sustainability is crucial to the Sustainable Development Goals (SDGs). We can gain an overview of a region’s or country’s dynamics by quantifying and analyzing its patterns over time and space. It can then be used to develop more sustainable policies. This study created a database of indices covering China’s environment, economy, and resource domains. Using an improved Environmental Sustainability Index (ESI) approach, we assessed sustainability and its spatiotemporal dynamics in 31 Chinese provinces between 2000 and 2017. Our findings suggest that provinces with high levels of socioeconomic development tend to have higher environmental scores, especially after experiencing severe environmental issues. Some underdeveloped provinces achieved high scores due to their relatively low environmental pressure and high resource efficiency. However, most underdeveloped provinces had high environmental pressure and low resource efficiency, leading to low environmental sustainability. We also discovered that sustainability scores improved between 2000 and 2017, mainly due to socioeconomic advancements. Yet, some environmental issues, such as air pollution, worsened during the latter part. Therefore, we confirmed an inverted U-curve relationship between environmental, resource, and socioeconomic components. Clustering analysis based on provincial economic and demographic characteristics also revealed different chronological patterns of environmental scores across the clusters. Additionally, we detected the transfer of pollution from developed to less-developed regions during the early 2000s.

We conducted a Future Design deliberation workshop on the theme of the “3rd Environmental Master Plan” of Suita City, Osaka Prefecture over four sessions in 2019, with the participation of both city residents and officials of the city government. To condition the deliberations of participants, we adopted the method of Imaginary Future Generations (IFGs) and analyzed its impact on their future vision of the city in 2050, policy options needed to shape that future, and changes in their perceptions. We also investigated how the adoption of IFGs affects the relationships between personal attributes and the changes in their perception. The results of variance analysis and multiple linear regression analysis based on data from the deliberations and questionnaire surveys of participants revealed the following: (1) the content and quality of the 2050 vision of society and policy options conceived from the perspective of the IFGs significantly differed from those conceived from the perspective of the current generations; (2) IFGs heightened certain perceptions, such as “a sense of crisis about the future” and “a shared recognition of goals that are desirable for society as a whole”; and (3) although the degree of “critical thinking”, as a disposition of individuals, influences the heightening of perceptions in decision-making from the perspective of the current generations, when IFGs is adopted, the degree of “critical thinking” seems to be no longer a factor in heightening these perceptions. These findings could be useful for designing mechanisms to facilitate sustainable decision-making that considers the interests of future generations.

Bacterial communities associated with aquatic macrophytes largely influence host primary production and nutrient cycling in freshwater environments; however, little is known about how specific bacteria migrate to and proliferate at this unique habitat. Here, we separately identified bacterial genes involved in the initial colonization and overall fitness on plant surface, using the genome-wide transposon sequencing (Tn-seq) of Aquitalea magnusonii H3, a plant growth-promoting bacterium of the floating macrophyte, duckweed. Functional annotation of identified genes indicated that initial colonization efficiency might be simply explained by motility and cell surface structure, while overall fitness was associated with diverse metabolic and regulatory functions. Genes involved in lipopolysaccharides and type-IV pili biosynthesis showed different contributions to colonization and fitness, reflecting their metabolic cost and profound roles in host association. These results provide a comprehensive genetic perspective on aquatic-plant-bacterial interactions, and highlight the potential trade-off between bacterial colonization and proliferation abilities on plant surface. Genome-wide transposon sequencing reveals the genes driving bacterial colonization of duckweed. These genes indicate a trade-off between the colonization and proliferation abilities on the host plant.

Despite the considerable role of aquatic plant-associated bacteria in host plant growth and nutrient cycling in aquatic environments, the mode of their plant colonization has hardly been understood. This study examined the colonization and competition dynamics of a plant growth-promoting bacterium (PGPB) and two plant growth-inhibiting bacteria (PGIB) in the aquatic plant Lemna minor (common duckweed). When inoculated separately to L. minor, each bacterial strain quickly colonized at approximately 10⁶ cells per milligram (plant fresh weight) and kept similar populations throughout the 7-day cultivation time. The results of two-membered co-inoculation assays revealed that the PGPB strain Aquitalea magnusonii H3 consistently competitively excluded the PGIB strain Acinetobacter ursingii M3, and strain H3 co-existed at almost 1:1 proportion with another PGIB strain, Asticcacaulis excentricus M6, regardless of the inoculation ratios (99:1–1:99) and inoculation order. We also found that A. magnusonii H3 exerted its growth-promoting effect over the negative effects of the two PGIB strains even when only a small amount was inoculated, probably due to its excellent competitive colonization ability. These experimental results demonstrate that there is a constant ecological equilibrium state involved in the bacterial colonization of aquatic plants.

1,4-Dioxane (DX) is a recalcitrant cyclic ether that has gained attention as an emerging pollutant in the aquatic environment. Enrichment of indigenous DX-degrading bacteria, which are considered to be minor populations even in DX-impacted environments, is the key for efficient biological DX removal. Therefore, this study aimed to explore carbon sources applicable for the enrichment of DX-degrading bacteria present in landfill leachate, which is a potential source of DX pollution. Microorganisms collected from landfill leachate were cultivated on six different carbon sources (DX, tetrahydrofuran (THF), 1,3,5-trioxane (TX), ethylene glycol (EG), diethylene glycol (DEG), and 1,4-butanediol (BD)) in a sequential batch mode. Consequently, enrichment cultures cultivated on THF in addition to DX improved the DX degradation ability compared to that of the original leachate sample, while those on the other test carbon sources did not. The results indicated that THF can be an alternative carbon source to enrich DX-degrading bacteria, and that TX, EG, DEG and BD are not applicable to concentrate DX-degrading bacteria in complex microbial consortia. In addition, sequencing analyses of 16S rRNA and soluble di-iron monooxygenase (SDIMO) genes revealed notable dominance of thm/dxm genes involved in group 5 SDIMO both in DX- and THF-enrichment cultures. The analysis also showed a predominance of Pseudonocardia in THF-enrichment culture, suggesting that Pseudonocardia harboring thm/dxm genes contributes to enhanced DX degradation in THF-enrichment culture.

Endotherms increase the rate of metabolism in metabolic organs as one strategy to cope with a decline in the temperature of the external environment. However, an additional major contributor to maintenance of body temperature in a cold environment is contraction-based thermogenesis in skeletal muscle. Here, we show that impairment of hind limb muscle contraction by cast immobilization induced a loss of function of skeletal muscle and activated brown adipose tissue (BAT) thermogenesis as a compensatory mechanism. BAT utilizes free branched-chain amino acids (BCAAs) derived from skeletal muscle as an energy substrate for thermogenesis, and interleukin-6 released by skeletal muscle stimulates BCAAs production in muscle for support of BAT thermogenesis. Additionally, this thermoregulatory system between BAT and skeletal muscle may also play an important role in response to cold temperatures or acute stress. Our findings suggest that BAT and skeletal muscle cooperate to maintain body temperature in endotherms.