水产养殖中使用氰化钠毒杀敌害生物对海洋生态环境影响的探讨

在水产养殖中,氰化物被用于毒杀敌害生物,但有关使用氰化物对海洋生态环境影响鲜有报道。本文从氰化钠在海洋环境中的迁移转化,对生物体的毒性效应,对生态系统的影响等方面进行探讨,研究表明:在水产养殖中合理使用氰化钠,对生态环境和人类健康不会造成有害的影响。     

Genomic analysis of antifungal metabolite production by <Emphasis Type="Italic">Pseudomonas fluorescens</Emphasis> Pf-5

The complete genomic sequences of several Pseudomonas spp. that inhabit the rhizosphere are now available, providing a new opportunity to advance knowledge of plant growth-promoting rhizobacteria (PGPR) through genomics. Among these is the biological control bacterium Pseudomonas fluorescens Pf-5. Nearly 6% of the 7.07 Mb genome of Pf-5 is devoted to the biosynthesis of secondary metabolites, including antibiotics toxic to soilborne fungi and Oomycetes that infect plant roots, and two siderophores involved in iron acquisition. Three orphan gene clusters, for which the encoded natural product was unknown, also were identified in the genome of Pf-5. The product synthesized from one of the orphan gene clusters was identified recently using a new ‘genomisotopic approach’, which employs a combination of genomic sequence analysis and isotope guided fractionation. Application of the genomisotopic approach to one orphan gene cluster in Pf-5 resulted in the discovery of orfamide A, founder of a new group of bioactive cyclic lipopeptides with a putative role in biological control of plant disease.     

添加麸皮与纤维素酶对笋壳青贮后氰甙含量的影响

[目的]研究添加麸皮与纤维素酶对笋壳青贮后氰甙含量的影响。[方法]采用异烟酸—吡唑啉酮比色法研究添加麸皮与纤维素酶对笋壳青贮后氰甙含量的影响。[结果]添加麸皮与纤维素酶均可降低笋壳青贮后的氰甙含量。麸皮添加水平越高,青贮笋壳毒性越低,当麸皮添加水平为15%时笋壳青贮后氰甙含量最低。[结论]该研究可为笋壳饲料的资源化利用提供理论依据。     

Plant microcosm studies demonstrating bioremediation of cyanide toxicity by Trichoderma and Fusarium spp.

The biodegradation of cyanide by Trichoderma and Fusarium spp. growing in association with plant roots in microcosms was investigated with CN^– at 50 or 100 mg/kg. Pea and wheat seeds germinated and plants grew only when seeds were inoculated with the fungi, probably because the plant/fungal association was capable of promoting cyanide catabolism. Inoculation by fungi also increased plant shoot lengths and the biomass of shoots and root compared with control plants without CN^– and fungi. Such plant/fungal association shows potential as a land remediation system.     

Replant diseases: Bacterial community structure and diversity in peach rhizosphere as determined by metabolic and genetic fingerprinting

Peach tree replant disease, though reported on in the literature for more than two centuries, has yet to have its causes clearly defined. Decline in peach productivity has been attributed to toxic agents, insects, nutritional disturbances, spray residues, fungi and nematodes. Bacteria has also been indicated as a contributing factor.Peach replant disease was reproduced by using two successive cultures on the same soil. Bacterial communities were isolated and characterized from healthy and diseased peach trees. The potential role of cyanide production by rhizobacteria in the replant problem of peaches was studied. Culture-dependent (evaluation of the number of culturable bacteria, metabolic activities, Biolog^® GN2) and independent (ribosomal intergenic spacer analysis, RISA) methods were used, in order to compare bacterial community structure and diversity in healthy and sick soils and to evaluate the possible role of cyanide.Bacterial densities were significantly increased in sick soils. Metabolic activities (Biolog^® GN2) and genetic structure, observed through RISA, were also significantly modified in sick soils. Changes in the composition of individual microbial groups in the rhizosphere of peach trees excavated from healthy or sick soil indicated the involvement of rhizobacteria in the etiology of the replant sickness of peach soil. More than 60% of the strains isolated from healthy soils corresponded to Pseudomonas sp. and 58% of the isolates from sick soils were Bacillus sp. This study determined that Bacillus were able to produce in vitro HCN. It also appeared that in sick soil, there was a shift in the structure of bacterial communities with an increase noted in phytotoxic microorganisms capable of producing HCN compounds.     

Reactivity of red palm oil and cyanide ion: Implications for the cyanogen content of palm oil-treated gari

Red palm oil was tested for the reactivity of its components with CN^-, and alkaline picrate as the color developing reagent. Palm oil components have a low-level absorbance at 490 nm which is reduced significantly (p0.01) after reaction with CN^-. Hydrolysis of palm oil components, and reaction of the hydrolysis products with CN^- significantly increased the absorbance at 490 nm. In contrast, after reaction of palm oil with alkaline picrate, the absorbance at 490 nm is very high; this is reduced significantly by reaction with CN^-, hydrolysis with 0.2 M NaOH , and reaction of the hydrolysis products with CN^- before treatment with alkaline picrate. The results indicate that palm oil component(s) sequester CN^- into a complex which may not be correctly estimated during cyanide quantification, resulting in the absence, or low levels of cyanide in palm oil-fried gari as earlier reported.     

Effect of traditional processing of cassava on the cyanide content of gari and cassava flour

Detoxification of cassava cultivars (30572 TMS and 30555 TMS) during their traditional methods of processing to produce gari and cassava flour has been investigated. The HCN quantitative determination was done using the enzymatic assay. Fermentation of cassava pulp for 96 hours during cassava processing for gari reduced the HCN by 22 ppm (52.4 percent) and 20 ppm (57.3 percent) for 30572 TMS and 30555 TMS respectively. There was no significant difference (P>0.05) in the HCN content of the two cultivars. Soaking of the sliced cassava tissue for 24 hours in cassava flour production prior to sundrying resulted in 16 ppm (38.1 percent) and 15 ppm (38.4 percent) HCN reduction for 30572 TMS and 30555 TMS respectively. HCN loss during sundrying was 6 ppm (14.3 percent) and 5 ppm (12.8 percent) for the two cultivars. There was significantly (P<0.05) higher HCN loss in processing of gari than cassava flour. The residual cyanide in gari was 12 ppm for 30572 TMS and 10 ppm for 30555 TMS and that in the flour was 20 ppm for 30572 and 19 ppm for 30555 TMS.     

Comparative effects of scopoletin and cyanide on rat brain, 1: Histopathology

Four week old male Wistar rats were used to study the effects of scopoletin and cyanide on the histopathology of rat brain. The rats were divided into a control and three experimental groups (2–4) and fed rations containing 0.07 g scopoletin/100 g, 0.07g scopoletin + 1.8 mg cyanide/100 g and 1.8 mg cyanide/100 g, respectively. These levels of scopoletin and cyanide corresponded to levels found in a processed cassava diet. The first group was fed the same ration as the others but without scopoletin and cyanide. The rats were fed these rations for twelve months. Rats from each group were sacrificed at the third, sixth, ninth and twelfth months; the relative brain weight of the rats (% of body weight) and histology of their brains were studied. The lipid peroxide levels of the rat brains were also studied at the twelfth month. The results showed that the relative brain weights of the rats fed scopoletin + cyanide were significantly (p<0.05) less than that of the control from the third month. There were no significant changes in the lipid peroxide levels of the rat brains in the various groups. Histological examination of the brains of the rats sugested that scopoletin is involved in the pathogenesis of the neuropathy seen in cassava consuming populations.