Quantification of the contribution of surface outgrowth to biocatalysis in sol-gels: oxytetracycline production by <Emphasis Type="Italic">Streptomyces rimosus</Emphasis>

A technique was developed for differentiating the activity of microbes solely within sol gels by using the contribution of biomass outgrowth. Streptomyces rimosus was immobilised in colloidal silica gels and biomass growth, oxytetracycline synthesis, pH and carbohydrate consumption were compared for UV surface-sterilised gels, untreated gels, and liquid cultures. Absolute and biomass specific oxytetracycline yields were higher for non-sterile gels than for liquid culture. Biomass solely within colloidal silica gels (1.7 mg ml^–1), and gels obtained from colloidal silica modified by addition of larger silica particles (1.2 mg ml^–1) yielded 27 and 21 g ml^–1 oxytetracycline compared with 97 and 104 g ml^–1 for unsterilised gels (3.6 and 5.2 mg ml^–1 biomass) displaying outgrowth. It was therefore apparent that biomass and antibiotic production within the gels was limited and that optimisation requires gel modification.     

Toxicity and moniliformin production by four recently described species of Fusarium and two uncertain taxa

Four recently described species, Fusarium nygamai, F. dlamini, F. beomiforme and F. napiforme and two uncertain taxa, F. nygamai from millet in Africa and Fusarium species from rice with Bakanae disease, were tested for toxicity and moniliformin production. Cultures grown on autoclaved corn were fed to groups of four one-day-old ducklings for 14 days. Isolates that caused the death of 3 or 4 out of 4 ducklings were considered to be toxic and analyzed for moniliformin. All 15 isolates of F. dlamini tested were nontoxic. The other taxa contained some isolates that were toxic to ducklings and produced moniliformin in corn cultures. This is the first report of moniliformin production by F. beomiforme (200–890 g/g), and F. napiforme (16–388 g/g), and by F. nygamai not obtained from millet in Africa (15–874 g/g). The highest production of moniliformin was obtained from the 19 isolates of F. nygamai from millet in Africa (4300–18200g/g) and the 15 isolates from rice with Bakanae disease (2300–19300 g/g). The taxonomic position of these two uncertain taxa should be re-evaluated.     

Oxytetracycline production by Streptomyces rimosus: gas and temperature patterns in a solid-state column reactor

During oxytetracycline production by Streptomyces rimosus TM-55 on sweet potato residue in a solid-state column reactor, the moisture content increased by between 2 and 5% (w/w) during incubation, from an initial content of 70 to 73%, and pH initially increased from 6.0 to 7.3, followed by a gradual decrease to 6.2. Appropriate aeration enhanced oxytetracycline production, while mixing only once daily decreased it. The temperatures in the centre and upper layers of each reactor were higher than elsewhere in static non-aerated cultures. The maximum CO₂ concentration ranged from 2.9 to 3.2% (v/v) and the minimum O₂ concentration was 11.0 to 17.2% (v/v) in static cultures. Under optimal conditions, each gram of dry substrate produced the equivalent potency of 12 mg oxytetracycline.The authors are with the Department of Agricultural Chemistry, National Taiwan University, Taipei, Taiwan 10617, Republic of China     

Toxicity in leaves of rice exposed to cadmium is due to hydrogen peroxide accumulation

The production of H₂O₂ in detached rice leaves of Taichung Native 1 (TN1) caused by CdCl₂ was investigated. CdCl₂ treatment resulted in H₂O₂ production in detached rice leaves. Diphenyleneiodonium chloride (DPI) and imidazole (IMD), inhibitors of NADPH oxidase (NOX), prevented CdCl₂-induced H₂O₂ production, suggesting that NOX is a H₂O₂-genearating enzyme in CdCl₂-treated detached rice leaves. Phosphatidylinositol 3-kinase inhibitors wortmanin (WM) or LY294002 (LY) inhibited CdCl₂-inducted H₂O₂ production in detached rice leaves. Exogenous H₂O₂ reversed the inhibitory effect of WM or LY, suggesting that phosphatidylinositol 3-phosphate is required for Cd-induced H₂O₂ production in detached rice leaves. Nitric oxide donor sodium nitroprusside (SNP) was also effective in reducing CdCl₂-inducing accumulation of H₂O₂ in detached rice leaves. Cd toxicity was judged by the decrease in chlorophyll content. The results indicated that DPI, IMD, WM, LY, and SNP were able to reduce Cd-induced toxicity of detached rice leaves. Twelve-day-old TN1 and Tainung 67 (TNG67) rice seedlings were treated with or without CdCl₂. In terms of Cd toxicity (leaf chlorosis), it was observed that rice seedlings of cultivar TN1 are Cd-sensitive and those of cultivar TNG67 are Cd-tolerant. On treatment with CdCl₂, H₂O₂ accumulated in the leaves of TN1 seedlings but not in the leaves of TNG67. Prior exposure of TN1 seedlings to 45^oC for 3 h resulted in a reduction of H₂O₂ accumulation, as well as Cd tolerance of TN1 seedlings treated with CdCl₂. The results strongly suggest that Cd toxicity of detached leaves and leaves attached to rice seedlings are due to H₂O₂ accumulation.     

Plasmid-borne resistance to arsenate, arsenite, cadmium, and chloramphenicol in a Rhodococcus species

Summary A primarily genetic approach was employed to obtain plasmids in Rhodococcus erythropolis ATCC 12674 which carried genes conferring increased resistance to sodium arsenate and arsenite, cadmium chloride, and chloramphenicol. The plasmids were large, migrating more slowly than chromosomal DNA in agarose gels, and were made up of resistance determinants from the host organism together with part of the genome of nocardiophage Q4. Purified plasmid was used to transform a suitable recipient to increased resistance to sodium arsenate, sodium arsenite, and cadmium chloride.     

Accumulation of cadmium by immobilizedZoogloea ramigera 115

Summary Zoogloea ramigera 115 was immobilized into beads of calcium-alginate and placed into batch air-bubbled column reactors. In the absence of any added nutrients the immobilized bacterium adsorbed Cd from solutions containing levels of 2 and 20 g ml^–1 per day, over a period of 21 and 20 days, respectively. Adsorption of Cd from solutions containing 20 g ml^–1 Cd was better than 90% for 16 days. Beads treated with Cd at 2 g ml^–1 never adsorbed less than 95% of the metal. Alginate adsorbed Cd as well, but inclusion of cells changed the effectiveness of adsorption. Of a 250 g ml^–1 Cd solution, alginate adsorbed 70.4% Cd in 60 min whereas alginate plus cells adsorbed 90.5% in the same time span. Temperature had no effect on adsorption by immobilized cells at levels of 2 and 10 g ml^–1 Cd. However at higher concentrations, binding was enhanced as temperature increased.Z. ramigera beads were stable during all treatments and for prolonged periods of time (21 days).     

Toxicity and biodegradation of fluometuron by selected cyanobacterial species

The Biodegradation capabilities of six selected cyanobacterial species for fluometuron, a phenylurea herbicide, as well as its inhibitory effect on chlorophyll a content were investigated. The selected species (three strains of Microcystis aeruginosa, Anabaena cylindrica, A. flos-aquae and A. spiroides) were subjected to three elevated concentrations of fluometuron (0.14, 0.7 and 1.4 mg/ml) for different exposure times (1–5 days). Results revealed that biodegradation of fluometuron is species-dependent and positively correlated with the exposure time, reaching maximum efficiency after 5 days at all the investigated concentrations. All the species tested showed generally great ability to degrade the compound even at the highest concentration with specific variations among them. Biodegradation efficiencies of fluometuron by the selected species were in the following ranges; 39.2–99.9; 87.5–100; and 93.2–100 at 0.14; 0.7 and 1.4 mg fluometuron/ml respectively. It was noticed that the gradual increase in the pesticide concentration enhances its biodegradability by the selected algal species. Variations according to species as well as exposure time were discussed. The highest fluometuron concentration (1.4 mg/l) showed the highest inhibition of chlorophyll a content in the tested species and toxicity was also species- and time-dependent.     

Molecular cloning of resistance genes and architecture of a linked gene cluster involved in biosynthesis of oxytetracycline by Streptomyces rimosus

Summary The isolation of mutants of Streptomyces rimosus which were blocked in oxytetracycline (OTC) production was described previously. The genes for the early steps of antibiotic biosynthesis mapped together. Genomic DNA fragments of S. rimosus which conferred resistance to OTC and complemented all of these non-producing mutants have been cloned. The cloned DNA is physically linked within approximately 30 kb of the genome of S. rimosus. The gene cluster is flanked at each end by a resistance gene each of which, independently, can confer resistance to the antibiotic. In OTC-sensitive strains of S. rimosus, the entire gene cluster including both resistance genes has been deleted. Complementation of blocked mutants by cloned DNA fragments in multi-copy vectors was often masked by a secondary effect of switching off antibiotic productions in strains othersise competent to produce OTC. This adverse effect on OTC production was not observed with recombinants using low copy-number vectors.     

Extracellular metalloendopeptidase of Streptomyces rimosus

Metalloendopeptidase was isolated from Streptomyces rimosus culture filtrates in a homogeneous form. It was determined to be a 15 kDa basic protein, most active around pH 7.5, and susceptible to inhibition by chelating agents, N-bromosuccinimide, thiorphan, and 10⁻⁴ M zinc. The enzyme was highly specific for phenylalanine at the N-side of endopeptide bonds. Determination of amino acid sequence of the enzyme’s NH₂-part allowed the recognition of its structure homology with isolated and predicted metallopeptidases from several Streptomyces species. The data contribute to the definition of M7 family of metalloendopeptidases in streptomycetes.     

Classification of novel soil streptomycetes as Streptomyces aureus sp. nov., Streptomyces laceyi sp. nov. and Streptomyces sanglieri sp. nov

The taxonomic positions of soil isolates known as Streptomyces groups A, B and C were clarified. Comparative 16S rDNA sequence studies indicated that representatives of all three taxa formed distinct phyletic lines within the Streptomyces tree though the group A strains were shown to be related to Streptomyces griseus and associated validly described species. The taxonomic integrity of all three groups was highlighted by DNA:DNA relatedness and ribotype data though the group A strains encompassed a higher degree of genetic variation than the group B and C strains. In light of these and earlier phenotypic data it is proposed that Streptomyces groups A, B and C be given species status as Streptomyces sanglieri sp. nov., Streptomyces aureus sp. nov. and Streptomyces laceyi sp. nov., respectively. This revised version was published online in June 2006 with corrections to the Cover Date.     

The growth and some physiological responses of rice to Cd toxicity as affected by nitrogen form

A hydroponic experiment was conducted to examine the effect of Cd stress on anti-oxidative enzyme activities at heading stage, yield components, root exudation and Cd and N uptake of rice plants grew in different N source i.e. (NH₄)₂SO₄, NH₄NO₃ and Ca(NO₃)₂. The results show that the effect of Cd stress on all measured parameters were N source dependent. Cd stress (1 μM) caused a remarkable reduction in grain yield and shoot biomass, an increase in root exudation, glutathione content, Cd concentration and catalase (CAT) and peroxidase (POD) activities of rice plants. In the plants under the control (without Cd addition) N source had no distinctive effect on the above measured parameters, but the differences among the three N forms in these parameters became significant when plants were exposed to Cd stress. Cd stress significantly increased POD and CAT activities, and gultathione content, with Ca(NO₃)₂-fed plants having the greatest POD and CAT activities and lowest glutathione content, and (NH₄)₂SO₄-fed plants being just opposite. Moreover, organic acid exudation varied also with N form for the Cd-stressed plants. In comparison with other two N forms, (NH₄)₂SO₄,-treated plants had higher grain yield, N concentration and lower Cd concentration in plants. The current results indicated that (NH₄)₂SO₄ is a better fertilizer for use in Cd contaminated soil.     

慈姑属4种同域分布植物的人工种间杂交

泽泻科（Alismataceae）是现存最原始的单子叶植物类群之一,慈姑属（Sagittaria）是泽泻科相对进化的分类群,地域分布广泛,其物种大多集中分布于北温带,且有种间同域分布现象。为了探究同域分布物种之间的杂交可能性,我们通过选取同域分布且在系统进化树上具有代表性的冠果草（S.guayanensis subsp. lappula）、小慈姑（S. potamogetonifolia）、利川慈姑（S. lichuanensis）和野慈姑（S. trifolia）为研究对象,调研中国数字植物标本馆（CVH）的标本信息和已有文献,分析这4种慈姑的地理分布格局,并分别以这4种慈姑为母本进行人工授粉实验以检验种间杂交的可能性。基于对1 172份4种慈姑属腊叶标本的分析,表明这4种慈姑在福建省武夷山地区存在同域分布情况。通过对4种慈姑之间的人工授粉实验结果分析表明,冠果草、小慈姑、利川慈姑和野慈姑异种授粉后均出现心皮膨大现象,所有异种授粉产生的种子均不可育,败育胚种子比例各不相同,且该比例与父本和母本在系统进化树上的位置有关。     

The Use of Phase Inversion Temperature (PIT) Microemulsion Technology to Enhance Oil Utilisation during <Emphasis Type="Italic">Streptomyces rimosus</Emphasis> Fed-batch Fermentations to Produce Oxytetracycline

The use of a rapeseed oil emulsion feed, produced by a phase inversion temperature (PIT) process, produced more biomass, gave a 3-fold increase in oil utilisation and a higher oxytetracycline titre but a higher residual oil concentration when compared to a conventional fed-batch Streptomyces rimosus process fed with crude rapeseed oil. Importantly, microbial utilisation of the surfactant was confirmed for the first time.     

Partial resistance to late blight (Phytophthora infestans) in hybrid progenies of four South American Solanum species crossed with diploid S. tuberosum

Resistant genotypes of the diploid tuber-bearing South American species Solarium arnezii x hondelmannii, S. berthaultii, S. leptophyes and S. microdontum were crossed with three diploid genotypes of S. tuberosum that varied in resistance and maturity type. The progenies were field tested for 2 years for resistance to a complex race of Phytophthora infestans. A wealth of genetic variation for resistance was found in most of the progenies. At least two susceptibility groups could be distinguished in some progenies of S. microdontum. This could be explained by the presence of several major resistance genes in the wild parent and, unexpectedly, in the susceptible parent SH 82-44-111. In most of the wild parents and in the susceptible parent SH 77-114-2988 there appeared to be minor resistance genes. General combining ability effects were predominant; small specific combining ability effects were detected in some crosses of S. microdontum. Gene action appeared dominant in some crosses.     

Honeydew feeding in the solitary bee Osmia bicornis as affected by aphid species and nectar availability

Like honey bees (Apis mellifera), non-Apis bees could exploit honeydew as a carbohydrate source. In addition to providing carbohydrates, this may expose them to potentially harmful plant products secreted in honeydew. However, knowledge on honeydew feeding by solitary bees is very scarce. Here we determine whether the polylectic solitary bee Osmia bicornis (=O. rufa) collects honeydew under semi-field conditions, and whether this is affected by aphid species and presence of floral nectar. Bees were provided with oilseed rape plants containing flowers and/or colonies of either Myzus persicae or Brevicoryne brassicae. We used the total sugar level of the bee crop as a measure of the individual's nutritional state and the oligosaccharide erlose as indicator for honeydew consumption. Erlose was present in honeydews from both aphid species, while absent in oilseed rape nectar, nor being synthesized by O. bicornis. When bees were confined to a single honeydew type as the only carbohydrate source, consumption of M. persicae honeydew was confirmed for 47% of the bees and consumption of B. brassicae honeydew for only 3%. Increased mortality in the latter treatment provided further evidence that B. brassicae honeydew is an unsuitable food source for O. bicornis. All bees that were given the choice between honeydew and floral nectar showed significantly increased total sugar levels. However, the fact that no erlose was detected in these bees indicates that honeydew was not consumed when suitable floral nectar was available. This study demonstrates that honeydew exploitation by O. bicornis is dependent on honeydew type and the presence of floral nectar.     

Interference by S-nitroso compounds with the measurement of nitrate in methods requiring reduction of nitrate to nitrite by cadmium

Various methods suited for the measurement of nitrate require its reduction to nitrite by cadmium under acidic or alkaline conditions. N^G-Nitroarginine analogs have been shown to interfere with the measurement of nitrate by such assays. In the present work we show by gas chromatography−mass spectrometry that under alkaline reduction conditions the S-nitroso compounds S-nitrosoglutathione and S-nitrosohomocysteine but not S-nitroso-N-acetylcysteine and S-nitroso-N-acetylpenicillamine can considerably contribute to nitrate and thus interfere with its measurement. Our results suggest that S-nitroso compounds may interfere with the measurement of nitrate in methods requiring cadmium-catalyzed reduction of nitrate to nitrite.     

Axillary bud development of passionfruit as affected by ethylene precursor and inhibitors

Summary The effects of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) and two inhibitors, silver thiosulfate (STS) and aminoethoxyvinylglycine (AVG), were tested in yellow passionfruit (Passiflora edulis f. flaricarpa Degener) acillary cultured in vitro. The organogenic responses were assessed by the number of buds per explant, mean leaf area per explant, and shoot length. ACC-supplemented medium significantly inhibited all evaluated responses at both concentrations tested. When ethylene action and biosynthesis were inhibited, a significant increase in the number of developed buds and average leaf area was observed. Accumulated ethylene and its accumulation rate were significantly greater at 10 μM ACC, with a maximum production rate deteeted: at the 14th day and a decline at the 21st day. The results suggest beneficial effects of ethylene inhibitors on in vitro development of axillary buds and their reliability for use as an alternative approach to evaluate sensitivity of Passiflora species to ethylene. Even though shoot elongation did not differ from that of the control, the inhibition of the ethylene action and its biosynthesis by AVG and STS, respectively, significantly enhanced the number of buds per explant and leaf area.     

镉在土壤-香根草系统中的迁移及转化特征

以无植物组处理为对照,采用盆栽试验方式探讨不同Cd浓度胁迫条件下香根草根际土壤中重金属Cd的积累、迁移及转化特征。土壤Cd处理设4个浓度梯度,分别为0、2、20、80 mg/kg土壤干重。结果表明:(1)香根草可以显著降低土壤中生物有效态Cd和总Cd含量。(2)香根草各部分Cd积累量随处理浓度的增加和处理时间的延长而增加,90 d时80 mg/kg处理组地上部分和根的Cd积累量分别高达180.42 mg/kg和241.54 mg/kg。(3)各浓度Cd处理下,富集系数随着Cd处理浓度的增加而显著降低,随处理时间的延长而升高。(4)香根草地上部分Cd含量小于根部,各处理转移系数均小于1。随着处理时间的延长,中低浓度处理组的转移系数稍有降低,高浓度处理组的转移系数则显著上升。(5)种植香根草使其根际土中残渣态的Cd转化为生物有效态Cd,提高Cd清除效率。研究结果表明,香根草能够有效地吸收土壤中的Cd,降低土壤中总Cd含量,提高土壤安全性,可作为Cd污染地区植物修复的备选物种。     

Subcellular compartmentalisation of cadmium in white lupins determined by energy-dispersive X-ray microanalysis

The microlocalisation of cadmium (Cd) at the tissue-cellular level in Lupinus albus L. cv. Multolupa was determined by energy-dispersive X-ray microanalysis (EDXMA). Experimental plants were grown on Cd-treated (0 and 150 microM) perlite for 35 days. In leaves, Cd was found inside cells (cytoplasm or vacuoles), especially in the vascular bundle cells. Cd-induced damage of the chloroplast structure was also detected. EDXMA of the roots showed the cell wall to be the main area of Cd binding at the cellular level; only a small amount of Cd was found in the vacuoles. At the tissue level, a decreasing Cd gradient was seen from the outer to the inner root cortical parenchyma. Cd and S were found co-localised in the vascular cylinder.     

Nitrogen uptake from prey and substrate as affected by prey capture level and plant reproductive status in four carnivorous plant species

Uptake of nitrogen from prey and substrate and partitioning of prey-derived nitrogen were studied in the carnivorous plant species Pinguicula alpina, P. villosa, P. vulgaris and Drosera rotundifolia in a subarctic environment. Efficiency in nitrogen uptake from prey was evaluated by tracing ¹⁵N from ¹⁵N-enriched Drosophila flies fed to the plants. The in situ uptake efficiency differed somewhat between species and ranged from 29 to 41% of prey N. This efficiency was not affected by different feeding levels or plant reproductive status (flowering or non-flowering). A test of the amount of N absorbed from prey caught on flower stalks of Pinguicula villosa and P. vulgaris showed that both species took up little of what was available in prey (2.5% or less). The uptake efficiency found in greenhouse grown plants was higher than in plants in situ (40–50% vs. 30–40% respectively). This could probably best be explained by the absence of rain and a higher temperature in the greenhouse. The prey-derived ¹⁵N was traced to reproductive organs and winter buds. Non-flowering individuals allocated 58–97% of the N derived from prey to their winter buds. Flowering individuals allocated 17–43% of the N income from prey to reproduction, while 34–71% were allocated to buds. Root uptake of nitrogen was stimulated by increased prey capture. This increase in uptake of nitrogen from the substrate was larger than the potential direct uptake of nitrogen from captured prey.