• Journal of Microbiology and Biotechnology
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• v.21 no.6
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• pp.590-598
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• 2011

Bacterial assimilation of $CO_2$ into stable biomolecules using electrochemical reducing power may be an effective method to reduce atmospheric $CO_2$ without fossil fuel combustion. For the enrichment of the $CO_2$-fixing bacteria using electrochemical reducing power as an energy source, a cylinder-type electrochemical bioreactor with a built-in anode compartment was developed. A graphite felt cathode modified with neutral red (NR-graphite cathode) was used as a solid electron mediator to induce bacterial cells to fix $CO_2$ using electrochemical reducing power. Bacterial $CO_2$ consumption was calculated based on the variation in the ratio of $CO_2$ to $N_2$ in the gas reservoir. $CO_2$ consumed by the bacteria grown in the electrochemical bioreactor (2,000 ml) reached a maximum of approximately 1,500 ml per week. Time-coursed variations in the bacterial community grown with the electrochemical reducing power and $CO_2$ in the mineral-based medium were analyzed via temperature gradient gel electrophoresis (TGGE) of the 16S rDNA variable region. Some of the bacterial community constituents noted at the initial time disappeared completely, but some of them observed as DNA signs at the initial time were clearly enriched in the electrochemical bioreactor during 24 weeks of incubation. Finally, Alcaligenes sp. and Achromobacter sp., which are capable of autotrophically fixing $CO_2$, were enriched to major constituents of the bacterial community in the electrochemical bioreactor.

• Journal of Microbiology and Biotechnology
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• v.32 no.10
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• pp.1292-1298
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• 2022

Soil autotrophic bacterial communities play a significant role in the soil carbon (C) cycle in paddy fields, but little is known about how rhizosphere soil microorganisms respond to different long-term (35 years) fertilization practices under double rice cropping ecosystems in southern China. Here, we investigated the variation characteristics of rhizosphere soil RubisCO gene cbbL in the double rice ecosystems of in southern China where such fertilization practices are used. For this experiment we set up the following fertilizer regime: without any fertilizer input as a control (CK), inorganic fertilizer (MF), straw returning (RF), and organic and inorganic fertilizer (OM). We found that abundances of cbbL, 16S rRNA genes and RubisCO activity in rhizosphere soil with OM, RF and MF treatments were significantly higher than that of CK treatment. The abundances of cbbL and 16S rRNA genes in rhizosphere soil with OM treatment were 5.46 and 3.64 times higher than that of CK treatment, respectively. Rhizosphere soil RubisCO activity with OM and RF treatments increased by 50.56 and 45.22%, compared to CK treatment. Shannon and Chao1 indices for rhizosphere soil cbbL libraries with RF and OM treatments increased by 44.28, 28.56, 29.60, and 23.13% compared to CK treatment. Rhizosphere soil cbbL sequences with MF, RF and OM treatments mainly belonged to Variovorax paradoxus, uncultured proteobacterium, Ralstonia pickettii, Thermononospora curvata, and Azoarcus sp.KH33C. Meanwhile, cbbL-carrying bacterial composition was obviously influenced by soil bulk density, rhizosphere soil dissolved organic C, soil organic C, and microbial biomass C contents. Fertilizer practices were the principal factor influencing rhizosphere soil cbbL-carrying bacterial communities. These results showed that rhizosphere soil autotrophic bacterial communities were significantly changed under conditions of different long-term fertilization practices Therefore, increasing rhizosphere soil autotrophic bacteria community with crop residue and organic manure practices was found to be beneficial for management of double rice ecosystems in southern China.

• Journal of Applied Biological Chemistry
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• v.42 no.1
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• pp.1-6
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• 1999

Poly-${\beta}$-hydroxybutyrate (PHB) and enzymes related PHB metabolism have been measured in nitrogen-fixing symbiosis of chickpea and cowpea plants. Bacteroids from chickpea and cowpea contained PHB to 0.8% and 43% of their dry weight, respectively, whereas the free-living cells CC 1192 and I 16 produced $285{\pm}55mg$ and $157{\pm}18mg$ of PHB g (dry weight)$^{-1}$. To further understand why chickpea bacteroids contained little PHB, the enzyme activities of PHB metabolism (3-ketothiolase, acetoacetyl-CoA reductase, PHB depolymerase, and 3-hydroxybutyrate dehydrogenase), the TCA cycle (malate dehydrogenase, citrate synthase, and isocitrate dehydrogenase), and related reactions (malic enzyme, pyruvate dehydrogenase, and glutamate:2-oxoglutarate transaminase) were compared in extracts from chickpea and cowpea bacteroids and the respective free-living bacteria. Significant differences were observed between chickpea and cowpea bacteroids and between the bacteroid and free-living forms of CC 1192, with respect to the capacity for some of these reactions. It is indicated that a greater potential for oxidizing malate to oxaloacetate in chickpea bacteroids could be a factor that favors the utilization of acetyl-CoA in TCA cycle rather than for PHB synthesis.

• Proceedings of KOSOMES biannual meeting
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• 2006.05a
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• pp.71-77
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• 2006

There is a growing concern about the damage to aquatic ecosystem caused by immigration of non-indigenous species. It is estimated that more than 10,000 million tons of ballast water is transported by shipping activities annually, and ballast water has been recognised as a major vector for the transplant of aquatic species across bio-geographical boundaries. The problem of harmful aquatic organism in ballast water for the control and management of ships' ballast water and sediments was adopted and diplomatic conference of IMO at February 2004. At once ballast water is transported by shipping activities for organic compounds, nitrogen, phosphorus and heavy metal etc. but, It's fixing a focus only for the transported of pathogenic bacteria and non-indigenous species. Hence, this studies on the distribution of organic compounds, nitrogen, phosphorus and heavy metal in ballast water during the shipping activity with the basic data which is necessary to the systemic manage of ballast water.

• Journal of Microbiology and Biotechnology
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• v.30 no.8
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• pp.1169-1179
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• 2020

In this study, two soybean genotypes, i.e., aluminum-tolerant Baxi 10 (BX10) and aluminumsensitive Bendi 2 (BD2), were used as plant materials and acidic red soil was used as growth medium. The soil layers from the inside to the outside of the root are: rhizospheric soil after washing (WRH), rhizospheric soil after brushing (BRH) and rhizospheric soil at two sides (SRH), respectively. The rhizosphere bacterial communities were analyzed by high-throughput sequencing of V4 hypervariable regions of 16S rRNA gene amplicons via Illumina MiSeq. The results of alpha diversity analysis showed that the BRH and SRH of BX10 were significantly lower in community richness than that of BD2, while the WRH exhibited no significant difference between BX10 and BD2. Among the three sampling compartments of the same soybean genotype, WRH had the lowest community richness and diversity while showing the highest coverage. Beta diversity analysis results displayed no significant difference for any compartment between the two genotypes, or among the three different sampling compartments for any same soybean genotype. However, the relative abundance of major bacterial taxa, specifically nitrogen-fixing and/or aluminum-tolerant bacteria, was significantly different in the compartments of the BRH and/or SRH at phylum and genus levels, indicating genotype-dependent variations in rhizosphere bacterial communities. Strikingly, as compared with BRH and SRH, the WRH within the same genotype (BX10 or BD2) always had an enrichment effect on rhizosphere bacteria associated with nitrogen fixation.