Morphological and physiological response of different root orders to biochar addition in continuous cropping cotton in Xinjiang,China北大核心CSCD

为缓解新疆棉花连作障碍,充分挖掘棉花根系生物学潜力,以新疆棉花根系为研究对象,采用模块根分级的方法探究不同根序根系的形态和生理特征以及它们对添加生物炭(BC)的响应.结果表明:根序对两个时期的生理指标、形态指标和根系生物量有显著影响.随着根序级的增加,吐絮期根系的可溶性蛋白含量、可溶性糖含量、全非结构性碳水化合物含量、第二和第三模块根的平均直径和根系生物量不断增加,两个时期比根长、比表面积和吐絮期组织密度不断减小.与对照相比,添加BC增加蕾期第一、第二模块根的可溶性蛋白含量分别为30.7%和21.8%,增加第一模块根的全非结构性碳水化合物含量79.8%、可溶性糖含量151%、比根长182%和比表面积193%,增加第二模块根的组织密度124%、吐絮期第一模块根的比根长6.3%和第一、第二模块根的组织密度分别为51.2%和23.8%.综上所述,棉花不同根序根系在生理和形态上存在异质性;第一模块根对BC添加最敏感,且BC使其在形态上更细更长,生理上活性更强,这有利于棉花对养分的吸收.(图4表3参57)     

Comparisons in subcellular and biochemical behaviors of cadmium between Iow-Cd and high-Cd accumulation cultivars of pakchoi （Brassica chinensis L.）

Subcellular distributions and chemical forms of cadmium （Cd） in the leaves, stems and roots were investigated in low-Cd accumulation cultivars and high-Cd accumulation cultivars ofpakchoi （Brassica chinensis L.）. Root cell wall played a key role in limiting soil Cd from entering the protoplast, especially in the low-Cd cultivars. The high-Cd cultivars had significantly higher leaf and stem Cd concentrations than the low-Cd cultivars in cell wall fraction, chloroplast/trophoplast fraction, organelle fraction and soluble fraction. In low-Cd cultivars, which were more sensitive and thus had greater physiological needs of Cd detoxification than high-Cd cultivars, leaf vacuole sequestrated higher proportions of Cd. Cd in the form of pectate/protein complexes （extracted by 1 tool. L~ NaC1） played a decisive role in Cd translocation from root to shoot, which might be one of the mechanisms that led to the differences in shoot Cd accumulation between the two types of cultivars. Furthermore, the formation of Cd- phosphate complexes （extracted by 2% HAc） was also involved in Cd detoxification within the roots of pakchoi under high Cd stress, suggesting that the mechanisms of Cd detoxification might be different between low- and high-Cd cultivars.     

Response of the grain yield and quality of hybrid rice to weak light stress北大核心CSCD

In this study, three rice varieties, Byou268 (low light-sensitive type), Nei5you768 (intermediate type), and Yixiangyou1108 (low light-tolerant), were used as experimental materials to investigate the yield and quality responses of different rice varieties to low light stress under normal light (CK) and low light (SH). The results showed the following: (1) Compared with normal light, the decrease in Yixiangyou1108’s 1 000-grain weight, grain number per spike, and seed setting rate under low light treatment were much lower than those of Nei5you768 and Byou268. The yield decline of Yixiangyou1108 (46.5%) was significantly lower than that of Nei5you768 (56.5%) and Byou268 (69.8%). Yixiangyou1108 showed strong tolerance to low light stress in terms of 1 000-grain weight, seed setting rate, grain number per panicle, and yield. (2) Compared with normal light, the reduction in grain length and width of Yixiangyou1108 under low-light treatment was significantly greater than that of Byou268; however, the reduction in the length-width ratio did not reach a significant level. The amylose content and gel consistency of the rice were significantly reduced. The reduction in amylose content of Yixiangyou1108 (24.5%) was significantly lower than that of Nei5you768 (28.1%) and Byou268 (30.6%); however, the decrease in gel consistency of Yixiangyou1108 (14.7%) was significantly higher than that of Nei5you768 (9.8%) and Byou268 (8.1%). After low light treatment, the characteristic values of the RVA curve of rice changed. The peak viscosity and breakdown viscosity of Yixiangyou1108, Nei5you768, and Byou268 were significantly decreased, but the cold glue viscosity and setback viscosity were significantly increased, while there was no significant difference in the peak time and peak temperature. The response of 1 000-grain weight, grain number per spike, and seed setting rate under low light stress can be used as a yield index of rice breeding with low light tolerance; rice grain type, amylose, and gel consistency; and peak viscosity and hot paset viscosity in RVA characteristic values can be used as quality indexes of low-light-tolerant rice material breeding. © 2022 Science Press. All rights reserved.     

Effect of iron addition on the performance of anoxic-oxic membrane process and biological phosphorus removal北大核心CSCD

In order to solve the problem of poor treatment of phosphorus in membrane bioreactor (MBR) with long sludge retention time (SRT), a ferric salt was added to enhance phosphorus removal; FeCl36H2O (Fe/P = 2.0) was added to the reactor. The removal efficiency of nitrogen, organic matters, and phosphorus in the MBR was investigated systematically. Moreover, this study focused on the membrane performance, the change of active sludge flora, and the effect of adding a ferric salt on membrane fouling before and after the addition. It was seen that adding the ferric salt could not affect the removal of COD and NH4 +-N and the removal rate of COD and NH4 +-N reached over 90%. However, the average removal rate of phosphorus was 52%, while the removal rate increased by nearly 40% after adding the ferric salt. The effects of adding ferric salts on the dominant bacteria and biological phosphorus removal of activated sludge were further studied. The results showed that the addition of ferric salt (Fe/P = 2.0) decreased the diversity of active sludge flora and relative abundance of some phosphorusaccumulating organisms and had a negative effect on biological phosphorus removal. The analysis of transmembrane pressure difference (TMP) recording revealed that the concentration of iron salts did not exacerbate membrane fouling. The results showed that the concentration of iron salts entering the membrane bioreactor would reduce the relative abundance and phosphorus removal efficiency of the activated sludge in the system to a certain extent, but it had no obvious effect on membrane fouling. It allowed the effluent to attain acceptable standards, especially with respect to phosphorus removal efficiency. © 2018 Science Press. All rights reserved.     

Project Tocoen. the fate of selected pollutants in the environment. Part XIX. the phytotoxicity of organic and inorganic pollutants‐cadmium. The effect of cadmium on the growth of germinating maize plants

The effect of increasing cadmium concentration (10, 100 and 1000 μmol dm^‐3) on the growth, leaf area, content of assimilation pigments, cadmium content and the regulatory ability of the tissue of maize plants was investigated.

The results obtained document, already after 6 days, a significant decrease of dry weight, reduction of leaf area, chlorophyll a and b as well as carotenoids in plants grown in the nutrient solution containing 1000 μmol dm ^‐3 of cadmium. A highly significant inhibition of growth, leaf area and assimilation pigments in plants growing in the nutrient solutions with 100 and 10 μmol dm^‐3 of cadmium was registered after 17 days of cultivation. In plants growing in the nutrient solution containing 100 μmol dm^‐3 of cadmium a demonstrable reduction of the content of assimilation pigments was registered after 11 days of culture.

With increasing cadmium concentration in the nutrient solution as well as in the plant tissue after 6 and 17 days of culture both the range of the regulatory zone and the extent of optimum pH increased into the acid region. The pH values of the isoelectric point decreased with increasing cadmium content in the solution.     

Distribution and diversity of macrobenthic communities in the Jiangsu Reach of the Yangtze River北大核心CSCD

Macrobenthic communities are an important part of aquatic ecological system in the Yangtze River. Studies on macrobenthic community structure and diversity have important significance for development and protection of water resources in the Yangtze River. In this research, macrobenthic communities and their habitat in the Jiangsu Reach of the Yangtze River were investigated at 17 sites in May and September of 2013. Shannon-wiener diversity index was used to assess the diversity of macrobenthic communities. The results showed that there were 36 species at these 17 sites; the abundance and diversity of macrobenthic community were the highest in the Nanjing Reach and the Changzhou Reach, the lowest in the Nantong Reach of the Yangtze River. Nephthys sp., Grandidierella chaohuensis sp., Gammarus sp., Tubifex sp. and Limnodrilus hoffmeisteri were the dominant taxa in the Jiangsu Reach of the Yangtze River. Cluster analysis based on species abundance yielded four groups among the 17 sites. One-way analysis of similarity (ANOSIM) suggested significant differences in macrobenthic community structure among the four groups (P < 0.05). The results indicated that factors including aquatic plants, water flow velocity, sediment types and channels can influence the distribution and diversity of macrobenthic communities in the Jiangsu Reach of the Yangtze River.     

Effects of exotic Spartina alterniflora on rhizosphere and endophytic bacterial community structures and diversity in roots of native mangroves北大核心CSCD

Root-associated microbial communities are very important for biogeochemical cycles of carbon, nitrogen, and sulfur in wetland ecosystems, and help to enhance the mechanisms of plant invasions. In the estuary of Jiulong River (China), Spartina alternifiora has widely invaded Kandelia obovata-dominated habitats, making it necessary to investigate the influence of rootassociated bacteria. The endophytic and rhizosphere bacterial community structures associated with selected plant species were investigated using the barcoded Illumina paired-end sequencing technique. The diversity indices of bacteria associated with the roots of S. alterniflora were higher than those of the transition stands and K. obovata monoculture. Using principal coordinate analysis with UniFrac metrics, the comparison of diversity showed that all samples could be significantly clustered into three major groups, according to the bacterial communities of origin. Four phyla, namely, Proteobacteria, Bacteroidetes, Chloroflexi, and Firmicutes, were abundant in the rhizoplane of the two salt marsh plants, whereas Cyanobacteria and Proteobacteria were the more abundant endophytic bacteria. Proteobacteria, Bacteroidetes, Chloroflexi, and Firmicutes in the rhizosphere bacteria of S. alterniflora accounted for 78.0%, 5.6%, 3.3%, and 1.6%, respectively. Members of the phyla Spirochaetes and Chloroflexi were found among the endophytic bacteria of S. alterniflora and K. obovata, respectively. Using linear discriminate analysis, we found some dominant rhizoplane and endophytic bacteria, including Pseudoalteromonadaceae, Vibrionaceae, Methylophilaceae, and Desulfovibrio, which could potentially affect the carbon, nitrogen, and sulfur cycles. Of interest was that endophytic bacteria were more sensitive to plant invasion than rhizosphere bacteria. Thus, the results provide evidence for the isolation of functional bacteria and the effects of root-associated microbial groups on S. alterniflora invasions. © 2018 Science Press. All rights reserved.     

Differences in the quality of steamed hull-less barley and wheat cakes北大核心CSCD

In this study, three different hull-less barley varieties were used to prepare steamed cakes, and their nutritional value, sensory qualities, textural properties, and in vitro starch hydrolysis were evaluated. The results showed that the contents of total dietary fiber (4.50%-5.12%), β-glucan (2.96%-3.96%), total flavonoids (12.56-38.73 mg/100 g), and γ-aminobutyric acid (5.08-9.53 mg/100 g) in the steamed hull-less barley cakes were significantly higher than that in the steamed wheat cake, which were 0.65%, 0.23%, 3.93 mg/(100 g), and 2.63 mg/(100 g), respectively. The sensory properties of steamed ordinary hull-less barley and wheat cakes were not significantly different, but the steamed 08-1127 (waxy hull-less barley) cake was softer and out of shape. The springiness, resilience, cohesiveness, gumminess, and adhesiveness of steamed ordinary hull-less barley cakes were similar to those of steamed wheat cake, while those of steamed 08-1127 cakes were significantly lower than those of steamed ordinary hull-less barley cakes. Steamed hull-less barley cake also showed a maximum starch hydrolysis rate (38.76%-42.74%) that was lower than that of steamed wheat cake (49.92%), and the contents of rapidly (11.58%-13.16%) and slowly digested starch (5.34%-7.56%) were lower than that of steamed wheat cake (17.21% and 15.97%, respectively). In addition, the glycemic (59.37-61.67) and hydrolysis indexes (35.82-40.00) were lower than those of steamed wheat cake (76.66 and 67.30, respectively), and the contents of resistant starch (2.74%-3.55%) were higher than those of wheat steamed cake (1.68%). Therefore, the steamed cakes of ordinary hull-less barley had a higher content of nutritional components than the steamed cake of wheat, and the in vitro starch hydrolysis parameters were better than those of steamed wheat cake. When it is necessary to consider both nutritional and sensory qualities, ordinary hull-less barley can be selected as the raw material for steamed cakes, but waxy hull-less barley is not suitable for making steamed cakes. © 2022 Science Press. All rights reserved.     

The diversity and floristic characteristics of mosses in Jiuzhaigou National Nature Reserve北大核心CSCD

苔藓是生态系统的重要组分和自然保护区的重点保护对象之一,在物种资源和生态系统功能维护中具有重要作用.通过野外标本采集和室内鉴定,对九寨沟国家级自然保护区的藓类植物的物种组成和分布特点进行研究.结果表明:(1)九寨沟共有藓类植物38科90属211种(含变种),其中优势科为青藓科(Brachytheciaceae)、丛藓科(Pottiaceae)、灰藓科(Hypnaceae)、金灰藓科(Pylaisiaceae)、提灯藓科(Mniaceae)、真藓科(Bryaceae)和羽藓科(Thuidiaceae);并且调查发现两种濒危级别的珍稀藓种.(2)九寨沟藓类植物的区系地理成分可划分为10个,优势成分为东亚分布,占34.2%,其次为北温带分布,占30.9%.(3)通过与西南地区5个自然保护区藓类植物的相似系数和区系谱主成分分析发现,九寨沟藓类植物种类与贡嘎山的共有种最多,达到94种,在区系成分上也与贡嘎山和王朗相近.本研究表明九寨沟高原喀斯特生境藓类植物物种资源丰富,虽然区系地理成分具有多样和复杂性,但主要还是以东亚分布和温带分布为主,在物种相似度和区系成分上与贡嘎山和王朗的藓类植物一致性更高.(图3表6参47)     

Distribution and habitat characteristics of fishes in the Pearl River Estuary北大核心CSCD

To explore the current situation and distribution of fish in the eight major estuaries of the Pearl River Estuary in China, acoustic detection and water quality monitoring were conducted in 2018. The results showed that almost living in eight major estuaries were juvenile, the proportion of strong echo was higher in winter, and Jiaomen and Modaomen Estuary were relatively rich in adult fish. In winter, the Humen, Jiaomen, and Yamen Estuary had a high density relatively, for 46.05 (± 50.30), 33.12 (± 93), and 32 (± 78) ind/103 m3, respectively. However, the fish densities of the Hengmen, Modaomen, and Hutiaomen estuaries were higher in summer at 55.72 (± 83.23), 37.52 (± 55) and 36 (± 99) ind/103 m3, respectively. Thus, fish are mainly concentrated in the flood tidal estuary in winter and in the ebb tidal estuary in summer. In addition, fish density was higher in flood tide than in ebb tide, and the strong echo proportion was lower. In winter, the key water quality factors affecting the biodiversity of estuary fish Shannon were chlorophyll a (P < 0.05), while what affected the fish density were turbidity and salinity (P < 0.05). This study showed that the Pearl River estuary was still the main habitat for juvenile fish. However, habitat variability is obvious; hence, it is important to flexibly carry out the delimitation of estuarine fish reserves and ecological restoration. © 2022 Authors. All rights reserved.     

Effects of different concentrations of tetracycline and oxytetracycline on the growth and ecotoxicity in lettuce北大核心CSCD

四环素类抗生素(TCs)是目前我国应用广泛、用量最大的一类抗生素,畜禽粪便和土壤中存在TCs残留,影响蔬菜作物的生长发育. TCs因水溶性较高更容易被植物转运和积累,植物对TCs耐受性机理研究仍不足.为更全面探究土壤TCs对蔬菜的毒性作用,研究不同浓度四环素(TC)和土霉素(OTC)分别对生菜的抗生素残留、生长特征及抗氧化酶系统的影响.结果显示,在0(对照)、2、10、50、250 mg/kg 5个施用水平下,生菜叶片抗生素含量逐渐增加,且土霉素含量始终大于四环素含量.与对照相比,抗生素浓度在50 mg/kg以上时对生菜生长具有显著抑制作用,其中,株高、根长、地上部和地下部鲜重与叶片TC残留量具显著负相关.生菜叶片的脯氨酸含量随浓度增加呈先增加后降低的趋势,在10 mg/kg时达到最大.并且低浓度(2 mg/kg)促进抗氧化酶基因SOD、POD21和CAT的表达,高浓度抗生素(50、250 mg/kg)对其产生抑制作用,10 mg/kg的抗生素处理对SOD、POD21和CAT基因表达的影响在抗生素种类上存在差异.本研究表明抗生素浓度超过50 mg/kg对生菜生长产生抑制作用,脯氨酸和抗氧化酶SOD、POD、CAT的转录水平及其酶活性能快速响应抗生素胁迫,可作为生菜对抗生素抗性的辅助评价指标.(图8表3参19)     

Identification and expression analysis of the HvENOD93 gene family in barley北大核心CSCD

早期结瘤素93(ENOD93)蛋白在植物根瘤形成初期扮演着重要的角色.基于大麦基因组信息鉴定大麦ENOD93基因家族成员,分析其理化特性、进化关系、基因结构、蛋白质结构和启动子顺式作用元件;并分析ENOD93家族在不同组织和不同基因型(籽粒大小)的表达情况.结果显示,大麦ENOD93基因家族有16个成员,均含有ENOD93基因家族特有的保守结构域;编码区长度在207-627 bp之间,外显子数量有1-4个,平均2.75个,且大部分位于细胞膜上;进化树结果表明与水稻、小麦和玉米等禾本科植物ENOD93基因的亲缘关系较近;启动子顺式元件主要有植物生长发育响应元件、胁迫响应元件以及激素响应元件;大部分HvENOD93基因在灌浆期籽粒和大粒材料中表达量较高.推测大麦HvENOD93基因在籽粒大小形成中起关键性作用;另外,结合其他物种相关基因研究结果,共筛选出3个同源基因.(图4表2参45)     

Soil physi-chemical properties,biomass and nutrient contents of forest litter in mixed plantations of Eucalyptus grandis and three tree species北大核心CSCD

In the present study, we compared the soil physical and chemical properties, biomass of forest litter and nutrient contents in three-and-half-year plantations of E. grandis mixed with Toona ciliate, Alnus formosana, Sassafras tzumu. The results indicated that mixing T. ciliate and A. formosana with E. grandis mitigated soil acidification. In E. grandis × S. tzumu plantations, the soil bulk density decreased, but the moisture capacity and porosity increased. The mixed plantations of E. grandis × S. tzumu significantly increased the soil total C, N, P and K content, by 64.7%, 41.9%, 28.6% and 7.7%, respectively. The mixed plantations of E. grandis × A. formosana also significantly increased the soil total C, N and P content, by 15.2%, 27.9% and 47.6%, respectively. Compared with the pure plantations, the mixed plantations had significantly lower soil hydrolysis N and higher available P content. Only the E. grandis × A. formosana plantations had higher soil available K content. Compared with that in pure plantations, the biomass of branch litter and leaf litter was significantly higher in E. grandis × A. formosana plantations but significantly lower in E. grandis × A. formosana and E. grandis × A. formosana plantations; the biomass of leaf litter and total biomass of litter of E. grandis × S. tzumu were 9.8% and 9.3% respectively lower. The litter C content in three kinds of mixed forest was significantly lower and the litter N content was significantly higher than that in the pure plantations. Only the mixed plantations of E. grandis × A. formosana plantations would increase the content of litter P. The mixed plantations of E. grandis × S. tzumu would increase the content of litter K. In general, S. tzumu is the optimal tree species to mix with E. grandis, followed by A. formosana, but T. ciliate is unsuitble for mixed plantation with E. grandis.     

Field tests to study the dynamics of weed inhibition of allelopathic rice and microbial physiological traits of rice rhizospheric soils北大核心CSCD

The weed inhibition of allelopathic rice PI312777 and nonallelopathic rice Lemont, allelopathic potential of rice rhizospheric soils, as well as the microbial physiological traits of rice rhizospheric soils, were studied by field tests after weedremoving and weed treatments. The results showed that the inhibitory rate of PI312777 at the 7-leaf stage on paddy weeds was 85.82%. Results of the Soil-Agar Sandwich method revealed that the allelopathic potential of PI312777 rhizospheric soils on the inhibitory rate of plant dry weight of barnyard grass was significantly higher at the 5-leaf stage than that at the 3-leaf stage, and increased by 20.16% from the 3-leaf stage to the 5-leaf stage after weed treatment. When at the same leaf stage, the soil microbe biomass carbon and soil respiration, the number of soil bacteria, and activity of soil enzymes (urease, protease, and sucrase) were significantly higher in PI312777 rhizospheric soils than in Lemont rhizospheric soils; they were also higher after the weed-removing treatment than after weed treatment. The largest increase of soil allelopathic potentials and soil microbial physiological indexes in PI312777 rhizospheric soils appeared from the 3-leaf stage to the 5-leaf stage. In case of weed treatment, the allelopathic potential of PI312777 rhizospheric soils on the soil microbe biomass carbon, soil respiration, the number of soil bacteria, activity of urease, activity of protease, and activity of sucrase increased by 53.11%, 51.56%, 38.97%, 44.83%, 60.00%, and 41.92%, respectively, from the 3-leaf stage to the 5-leaf stage. These results indicated that rice allelopathy had a close relationship with the activity of rhizospheric soils. Rice allelochemicals lead to the change of soil microbes; rice allelopathy is a process based on plant-soil interaction. © 2018 Science Press. All rights reserved.     

Screening and characterization of extremophiles in spacecraft assembly environment北大核心CSCD

Spacecrafts need to strictly control microorganisms before entering space flight. The Spacecraft Assembly, Integration, and Test Center (AITC) is an important environmental source for spacecrafts to carry microorganisms. The assembly clean room has characteristics of ventilation, dryness, and lack of nutrients that are not conducive to the growth and reproduction of microorganisms, except for extremophiles. In this study, based on the internal air and surface environment of the AITC in China, 13 strains of bacteria were identified by plate culture and 16S sequence analysis, and their extreme environmental tolerance, antibiotic resistance, and film-forming ability were tested. All these bacteria belonged to the Firmicutes and Proteobacteria phyla, and nine strains belonged to the Bacillus genus. All 13 strains of bacteria were salt-tolerant, acid-tolerant, and alkali-tolerant, and 69.2% of the bacteria survived heat shock at 80 ℃. Among these, one strain of Sphingomonas sp. JCM7513 isolated from the surface environment was insensitive to all the tested antibiotics and had strong drug resistance, while the other 12 strains were sensitive to most β-lactam antibiotics but had strong resistance to tetracyclic antibiotics and erythromycin. Most of the isolated bacteria exhibited strong biofilm-forming abilities. The study showed that there are a certain number of extremophiles in the spacecraft assembly environment. To protect spacecrafts from biological corrosion and planetary protection forward pollution, more effective monitoring and elimination methods are needed. © 2022 Science Press. All rights reserved.     

The interaction of heat shock proteins and some components of plant viruses北大核心CSCD

Considerable research has indicated that heat shock proteins (Hsp), as molecular chaperones, carry out many biological activities of plant viruses by folding, transporting, translocating, assembling, or degrading client proteins. It is fundamental to develop resistant plant varieties and novel anti-viral agents by determining the interaction mechanisms between plant viruses and hosts. In this study, we first reviewed the classification, gene and protein structure, and biological significances. We then analyzed the assembling mechanism of Hsp70 or Hsp90, plant host cofactors, and RNA-dependent RNA polymerases in a viral replicase complex, and the mechanism of interaction and subcellular localization between Hsp70 and some plant virus components. We highlighted the mechanism of interaction and movement between Hsp70 and some plant virus components and the effect of Hsp expression of plant hosts or viruses. The results indicated where the mechanism occurred, the participating factors, energy supply, and material conversion between Hsps and the plant virus components for the course of the intracellular movement, local movement between cells, and long-distance movement, and showed the Hsp type specificity and the law of dynamic Hsp expression in plant hosts infected by viruses. The studies mainly focused on the two Hsp factors and the plant viral components, indicating limited coordination mechanisms among many nucleic acids, proteins, and polysaccharides in macromolecular protein complexes (MRC). Future research should analyze the translocation mechanism between client proteins and Hsps, the coordination mechanism between Hsps and MRC components, and the relation between MRC and the plant tissue structure. © 2018 Science Press. All rights reserved.     

Identification of Bacillus methylotrophicus and its application in preventing fly maggot production in the environment北大核心CSCD

This research aimed to screen Bacillus spp. to prevent the production of fly maggot on kitchen wastes from soil in the experimental bases of the South China Agricultural University. A nutrient-rich medium was used to isolate the Bacillus spp. with high temperature treatment. The seventeen Bacillus strains were obtained and assigned to three groups by using Insertion Sequence based PCR (IS-PCR) DNA fingerprinting patterns. The homology of the 16S rDNA gene was 100% between Group I and Bacillus methylotrophicus CBMB 205T, 99.61% between Group II and Bacillus aerophilus 28KT, and 99.87% between Group III and Bacillus cereus ATCC 14579T. The results of kitchen waste tests proved that the representative bacteria of Group I RF2 had the ability to prevent fly maggot production on kitchen wastes. Furthermore, the results of physiological and biochemical tests, carbon utilization tests, and antagonists against plant pathogen tests showed that the bacteria from Group I RF2 had the ability to decompose glucose into pyruvate and then decarboxylate pyruvate to diacetyl under alkaline conditions, convert ammonia to intracellular amino acids or other kinds of nitrogenous compounds, use many kinds of carbon source for self-growth, and be antagonistic against plant pathogenic rice sheath blight disease, banana fusarium wilt, and Fusarium oxysporum. Besides, the bacteria from RF2 could secret organic acids to dissolve insoluble phosphate [Ca3(PO4)2] for its own growth by decreasing the pH. Group I RF2 was a strong plant-promotion bacterium, and had good prospects of application for preventing fly maggot production on kitchen wastes. © 2018 Science Press. All rights reserved.     

Effects of glucose dehydrogenase gene knock-out in Acetobacter sp. On the metabolism of carbon sources and the synthesis of 3-hydroxypropionic acid北大核心CSCD

3-Hydroxypropionic acid (3-HP) is an emerging platform chemical with a high added-value. Resting cells of Acetobacter sp. can efficiently catalyze 1,3-propanediol (1,3-PDO) to 3-HP. Glucose is oxidized by the membrane-bound dehydrogenase, resulting in an acidic environment that inhibits cell growth and reduces the biomass. We deleted the gdh gene for glucose dehydrogenase (GDH), and investigated the effects on cell growth, carbon metabolism, and 3-HP production. The gdh gene knocked-out showed a 1.72-fold increase in biomass in the mixed medium containing glucose and glycerol. A carbon flux analysis showed that glucose was converted to gluconic acid by GDH, followed by an oxidation to 2-ketogluconic acid. In addition, a small percentage of the gluconic acid was degraded via the pentose phosphate pathway. Glycerol was phosphorylated and entered the central pathway (gluconeogenesis). Results indicate that the deletion of gdh can effectively promote higher cell densities and improve the catalytic performance for the production of 3-HP, and thus provide a theoretical reference for improving the carbon source utilization and the catalytic performance of acetic acid bacteria. © 2018 Science Press. All rights reserved.