家白蚁中肠具有内切葡聚糖酶活性菌株的分离和鉴定

从家白蚁中肠分离得到了一株具有内切β-1,4-葡聚糖酶活性的细菌Streptomyces sp.Cf1,并经过16S rRNA和形态分析确定为属于链霉菌属(Streptomyces)一种.该菌具有内切β-1,4-葡聚糖酶活性但不具有糖苷酶活性.该菌所分泌的内切β-1,4-葡聚糖酶活性最大可达8.25 U/mg.菌株分泌酶活性的最适pH值为6～7,最适温度为60℃.从家白蚁中肠分离得到这一具内切葡聚糖酶活性的菌株表明,家白蚁中肠细菌可以通过分泌内切葡聚糖酶与白蚁内源性内切葡聚糖酶一道参与食物中纤维素的降解.     

Activity and efficacy of Bacillus subtilis strain NJ-18 against rice sheath blight and Sclerotinia stem rot of rape

A strain of Bacillus subtilis (NJ-18) with broad antimicrobial activity was screened in the laboratory and in the field. NJ-18 inhibited the in vitro radial extension of hyphae of the phytopathogenic fungi Rhizoctonia solani and Sclerotinia sclerotiorum. The bacterium apparently produced antifungal metabolites that diffused through the agar and caused abnormal swelling of hyphae. The in vitro data and observations indicated that one of the mechanisms of inhibition by NJ-18 is antibiosis. In field experiments for control of sheath blight of rice, fermentation of NJ-18 at 5.0 × 10⁷ cfu ml⁻¹ significantly reduced disease incidence and severity; NJ-18 alone or combined with 50% kresoxim-methyl treatment at 225 g ai ha⁻¹ provided better control than 50% kresoxim-methyl at 225 g ai ha⁻¹ or Jinggangmycin at 120 g ai ha⁻¹, and control by NJ-18 alone was as high as 100.0%. In field experiments for control of Sclerotinia stem rot of rape, fermentation of NJ-18 at 1.0 × 10⁷ cfu ml⁻¹ again significantly reduced disease incidence and severity; control by NJ-18 was as high as 77.1% and was comparable with control by 46% dimethachlon and better than control by 50% carbendazim at 750 g ai ha⁻¹. We conclude that strain NJ-18 of B. subtilis is a promising biological control agent and should be further studied and tested for control of sheath blight of rice, Sclerotinia stem rot of rape, and other diseases.     

MreB5 Is a Determinant of Rod-to-Helical Transition in the Cell-Wall-less Bacterium Spiroplasma

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Nickel Inhibition of the Growth of a Sulfur-oxidizing Bacterium Isolated from Corroded Concrete

A sulfur-oxidizing bacterium strain NB1-3 isolated from corroded concrete was a Gram negative, non-spore-forming, and rod-shaped bacterium (0.5–1.0x 1.5–2.0μm) with a polar flagellum. Strain NB1-3 had its optimum temperature and pH for growth at 30°C and 3.0–4.0, respectively. Strain NB1-3 had enzyme activities that oxidized elemental sulfur, thiosulfate, tetrathionate, and sulfide and the activity to incorporate ¹⁴CO₂ into the cells. The mean G+C content of the DNA was 52.9 mol%. These results indicate that strain NB1-3 is Thiobacillus thiooxidans. Since nickel has been known to protect concrete from corrosion, the effect of Ni on the growth of strain NB1-3 was studied. The cell growth on tiosulfate-, elemental sulfur-, or tetrathionate-medium was completely inhibited by 0.1% metal nickel or 5mM NiSO₄. Both cellular activities of elemental sulfur oxidation and CO₂ incorporation were strongly inhibited by 5mM NiSO₄. The amounts of Ni in cells with or without nickel treatment were 1.7 and 160.0 nmol/mg protein, respectively. These results indicate that nickel binds to strain NB1-3 cells and inhibits enzymes involved in sulfur oxidation of this bacterium, and as a result, inhibits cell growth.     

Characteristics of the Kabicidin Resistant Mutant of Fusarium sp. Having a High Productivity of Alkaline Protease

In order to elucidate the biochemical mechanism of the alkaline protease accumulation from n-paraffins by a kabicidin-resistant mutant of Fusarium sp., the cell constituents and the extracellular products of the mutant strain were compared with those of the parent strain. No prominent differences in the cell constituents were observed between the parent and the mutant. From the analysis of the extracellular products, however the mutant was found to have a high productivity of some hydrolytic enzymes, such as amylase and ribonuclease, and ergosterol which is a structural constituent of fungal cell membrane. The relationship of secretion of ergosterol, resistance to kabicidin and accumulation of alkaline protease is discussed.     

Pseudomonas fluorescens HYK0210-SK09 offers species-specific biological control of winter algal blooms caused by freshwater diatom Stephanodiscus hantzschii

Aims:  The study of an algicidal activity and mechanism of the isolated Pseudomonas fluorescens HYK0210-SK09 (SK09) against a winter bloomed harmful diatom, Stephanodiscus hantzschii.
Methods and Results:  SK09 was isolated from the Paldang reservoir, Korea and used to biological control of S. hantzschii . The inoculation of SK09 at the final density of 5 × 10⁶ cells ml⁻¹ caused degradation of >90% of S. hantzschii cells within 5 days. The algal cell lysis was achieved by a direct attack of the bacteria to the diatom cells, and the algicidal compound was located in the cytoplasm of the cell. As SK09 did not suppress Microcystis aeruginosa , Anabaena cylindrica , Coelastrum astroideum or Cyclotella meneghiniana , it appeared to attack S. hantzschii in a species-specific manner. Testing in an indoor mesocosms confirmed that SK09 effectively reduced S. hantzschii cells by 88% within 9 days.
Conclusions:  This bacterium is useful in regulating blooms of S. hantzschii . However, it should be studied in the future that their impact in shaping phytoplankton community and their activity in natural environments.
Significance and Impact of the Study:  The bacterium enabled us to develop a new strategy, to understand the interaction for anthropogenic control of harmful algal blooms in nature.     

Characteristics of an endophytic pyrene-degrading bacterium of Enterobacter sp. 12J1 from Allium macrostemon Bunge

One pyrene-degrading endophytic bacterium was isolated from plants grown in polycyclic aromatic hydrocarbon-contaminated soils and identified as Enterobacter sp. 12J1 based on the 16S rDNA gene sequence analysis. Heavy metal and antibiotic resistance, degradation of pyrene, solubilization of inorganic phosphate and cell surface hydrophobicity characteristics of the isolate were further characterized. The isolate was also evaluated for promoting plant growth of wheat and maize and pyrene removal from pyrene-amended soil in pot experiments. High-performance liquid chromatograph (HPLC) analysis showed that the degradation rate of pyrene (5 mg l⁻¹) by the endophytic bacterial strain 12J1 was 83.8% under 28 °C for 7 days. The Enterobacter sp. 12J1 could produce indole acetic acid (IAA), siderophore and solubilize inorganic phosphate. The Enterobacter sp. 12J1 also has a cell surface hydrophobicity. In the live bacterial inoculation experiment, an increase in pyrene removal varying from 60% to 107% was observed in the planted soils treated with 100 mg kg⁻¹ of pyrene compared with the unplanted soils. The rate of pyrene removal increased by 43–65% in the live bacterium-inoculated planted soils compared with the dead bacterium-inoculated planted soils. Although there were no significant differences in the total culturable bacterial numbers between live and dead bacterial inoculation, the numbers of pyrene-degrading bacteria were significantly greater in the live bacterium-inoculated planted or unplanted soils. The isolate could colonize the tissue (root and stem) interiors and rhizosphere soils of wheat and maize after root inoculation.     

A novel anti-plant viral protein from coelomic fluid of the earthworm Eisenia foetida: purification, characterization and its identification as a serine protease

A novel protein showing strong antiviral activities against cucumber mosaic virus (CMV) and tomato mosaic virus (TMV) was purified from the coelomic fluid of the earthworm Eisenia foetida. The protein was characterized as a cold-adapted serine protease. Its molecular weight was estimated to be 27,000 by SDS-PAGE. The enzyme was most active at pH 9.5 and 40–50 °C. The protease activity at 4 °C was 60% of that obtained at the optimal temperature. The activity was suppressed by various serine protease inhibitors. Partial N-terminal amino acid sequence of the enzyme showed homology with serine proteases of earthworms, E. foetida and Lumbricus rubellus previously studied. Our results suggest that the enzyme can be applicable as a potential antiviral factor against CMV, TMV, and other plant viruses.     

Cryoprotective properties and preliminary characterization of exopolysaccharide (P-Arcpo 15) produced by the Arctic bacterium Pseudoalteromonas elyakovii Arcpo 15

Twenty-two bacterial strains that secrete exopolysaccharides (EPS) were isolated from marine samples obtained from the Chukchi Sea in the Arctic Ocean; of these, seven strains were found to be capable of producing cryoprotective EPS. The ArcPo 15 strain was isolated based on its ability to secrete large amounts of EPS, and was identified as Pseudoalteromonas elyakovii based on 16S rDNA analysis. The EPS, P-ArcPo 15, was purified by protease treatment and gel filtration chromatography. The purified EPS (P-ArcPo 15) had a molecular mass of 1.7 × 10⁷ Da, and its infrared spectrum showed absorption bands of hydroxyl and carboxyl groups. The principal sugar components of P-ArcPo 15 were determined to be mannose and galacturonic acid, in the ratio of 3.3:1.0. The cryoprotective properties of P-ArcPo 15 were characterized by an Escherichia coli viability test. In the presence of 0.5% (w/v) EPS, the survival percentage of E. coli cells was as high as 94.19 ± 7.81% over five repeated freeze–thaw cycles. These biochemical characteristics suggest that the EPS P-ArcPo 15 may be useful in the development of cryoprotectants for biotechnological purposes, and we therefore assessed the utility of this novel cryoprotective EPS.     

我国海洋细菌新物种鉴定与资源研发进展

近年来国际上对海洋微生物资源的发掘方兴未艾。本文综述了2000年以来我国在海洋细菌新物种鉴定与资源研发方面的进展,统计分析了国内相关单位海洋细菌新物种鉴定发表的数量及多样性,介绍了国内相关科研机构在海洋细菌系统学方面的工作进展,以及国内海洋微生物资源保藏与开发现状。比较了世界范围内海洋细菌系统学研究进展,并探讨了海洋细菌分离培养的主要方法,最后小结了我国海洋细菌资源研究领域存在的问题及未来发展的前景,为其进一步研发利用提供参考。