Activity of the natural algicide, cyanobacterin, on angiosperms

Cyanobacterin is a secondary metabolite produced by the cyanobacterium (blue-green alga) Scytonema hofmanni. The compound had previously been isolated and chemically characterized. It was shown to inhibit the growth of algae at a concentration of approximately 5 micromolar. Cyanobacterin also inhibited the growth of angiosperms, including the aquatic, Lemna, and terrestrial species such as corn and peas. In isolated pea chloroplasts, cyanobacterin inhibited the Hill reaction when p-benzoquinone, K₃Fe(CN)₆, dichlorophenolindophenol, or silicomolybdate were used as electron acceptors. The concentration needed to inhibit the Hill reaction in photosystem II was generally lower than the concentration of the known photosystem II inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethyl urea. Cyanobacterin had no effect on electron transport in photosystem I. The data indicate that cyanobacterin inhibits O₂ evolving photosynthetic electron transport in all plants and that the most probable site of action is in photosystem II.     

Effect of the natural algicide,cyanobacterin, on a herbicide-resistant mutant of anacystis nidulans R2

Cyanobacterin, a secondary metabolite produced by the cyanobacterium, Scytonema hofmanni, inhibits the growth of algae and plants. This compound is a potent inhibitor of photosynthetic electron transport and acts at a site in photosystem II (PS II). To further define the site of action of cyanobacterin, the effects of this natural product were investigated in a herbicide-resistant mutant of the cyanobacterium, Anacystis nidulans R2D2-X1. A. nidulans R2D2-X1 was reported to grow and maintain photosynthetic electron transport in the presence of 20 μM 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and 6.0 μM atrazine. Resistance was attributed to an altered 32 kDa (quinone-binding, QB) protein [6]. In the presence of Hill electron acceptors, K₃Fe(CN)₆ and dichlorophenol-indophenol (DCPIP), spheroplasts of A. nidulans R2D2-X1 were inhibited by cyanobacterin at the same concentration as wild type spheroblasts. Under these same conditions, spheroplasts of the mutant maintained their resistance to DCMU. Similar results were obtained with isolated thylakoid membranes. In contrast, silicomolybdate reduction, which is resistant to DCMU inhibition, was very sensitive to cyanobacterin. We conclude that cyanobacterin inhibits electron transport in PS II at a unique site which is different from that of DCMU.     

Site of action of the natural algicide,cyanobacterin, in the blue-green alga,Synechococcus sp.

Cyanobacterin is a secondary metabolite produced by the cyanobacterium, Scytonema hofmanni. Highly purified cyanobacterin was found to inhibit the growth of many cyanobacteria at a minimum effective dose of 2 g/ml (4.6 M). The antibiotic had no effect on eubacteria including the photosynthetic Rhodospirillum rubrum. The site of action of cyanobacterin was further investigated in the unicellular cyanobacterium, Synechococcus sp. Electron micrographs of antibiotic-treated Synechococcus cells indicated that cyanobacterin affects thylakoid membrane structure. The antibiotic also inhibited light-dependent oxygen evolution in Synechococcus cells and in spheroplasts. These data support our conclusion that cyanobacterin specifically inhibits photosynthetic electron transport. This activity is similar to herbicides such as 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU). The anhydro analog of cyanobacterin had no biological activity.Abbreviations DCMU 3-(3,4-dichlorophenyl)-1,1-dimethyl urea - DCPIP dichlorophenolindophenol     

Activity of the AIB factor observed in prokaryotic and eukaryotic microorganisms

Streptomyces cinnamonensis produces a new substance named AIB (for anti-isobutyrate) factor which, on a solid medium, efficiently counteracts toxic concentrations not only of isobutyrate but also of other salts of short-chain monocarboxylic acids. In the present study we demonstrate that the AIB factor activity is widely spread because this effect was positively detected in 25 of 31 randomly chosen microorganisms (streptomycetes, ascomycetes, zygomycetes and basidiomycetes). The AIB factor produced by the tested microorganisms on an agar media allows for germination, growth, and sporulation of the testingStreptomyces coelicolor on an agar medium containing 20 mmol/L acetate, propionate, butyrate, isobutyrate, valerate, isovalerate, and 2-methylbutyrate. The activity of the AIB factor from different sources towards these substances differs.     

Activity of Nemathorin,natural product and bioproducts against root-knot nematodes on tomatoes

An experimental study was carried out in pots to investigate the activity of Nemathorin, natural product and biopesticides against root-knot nematodes (RKNs) on tomatoes. Fosthiazate and abamectin proved to be the most effective treatments which suppressed the RKN population by 82.1%. Furthermore, arbuscular mycorrhizal fungus 2 (AMF2) was the superior treatment that reduced galls/root system followed by abamectin with the values of 72.5% and 67.2%, respectively. In addition, fosthiazate, cadusafos and crustacean2 gave the highest increase in the root length with the values of 55.8%, 54.6% and 54.6%, respectively. AMF2 was the most effective treatment which increases the root weight by 43.9%, while azadirachtin decreased the rootweight by 12.2% compared to untreated check. AMF2, cadusafos and crustacean2 not only increased the shoot length but also increased the shoot weight. Azadirachtin recorded the minimum increase in shoot system length and weight.     

The natural herbicide, cyanobacterin, specifically disrupts thylakoid membrane structure in Euglena gracilis strain Z

Abstract Cyanobacterin is a natural product produced by the cyanobacterium (blue-green alga), Scytonema hofmanni . The compound has been chemically characterized and shown to inhibit electron transprot in photosystem II. Although the herbicide is lethal to photoautotrophs, photoheterotrophically-grown organisms such as Euglena gracilis can survive and grown in saturating concentrations of cyanobacterin. Electron micrographs of treated E. gracilis cells show extensive damage to the thylakoid membranes of the chloroplasts, similar to the effects observed with 3-(3, 4-dichlorophenyl)-1, 1-dimethyl urea (DCMU). Unlike the synthetic herbicide, cyanobacterin specifically disrupts thylakoid membranes and does not affect other cellular membranes or heterotrophic growth.     

Protectants used in the cryopreservation of microorganisms

The cryoprotective additives (CPAs) used in the frozen storage of microorganisms (viruses, bacteria, fungi, algae, and protozoa) include a variety of simple and more complex chemical compounds, but only a few of them have been used widely and with satisfactory results: these include dimethylsulfoxide (Me2SO), glycerol, blood serum or serum albumin, skimmed milk, peptone, yeast extract, saccharose, glucose, methanol, polyvinylpyrrolidone (PVP), sorbitol, and malt extract. Pairwise comparisons of the cryoprotective activity of the more common CPAs used in cryomicrobiology, based on published experimental reports, indicate that the most successful CPAs have been Me2SO, methanol, ethylene glycol, propylene glycol, and serum or serum albumin, while glycerol, polyethylene glycol, PVP, and sucrose are less successful, and other sugars, dextran, hydroxyethyl starch, sorbitol, and milk are the least effective. However, diols (as well as some other CPAs) are toxic for many microbes. Me2SO might be regarded as the most universally useful CPA, although certain other CPAs can sometimes yield better recoveries with particular organisms. The best CPA, or combination of CPAs, and the optimum concentration for a particular cryosensitive microorganism has to be determined empirically. This review aims to provide a summary of the main experimental findings with a wide range of additives and organisms. A brief discussion of mechanisms of CPA action is also included.     

Characterization of a mutant of Anacystis nidulans r2 resistant to the natural herbicide, cyanobacterin

Cyanobacterin, a secondary metabolite produced by the cysnobacterium, Scytonema hofmanni, inhibits electron transport at a site in photosystem II. It was previously shown that a DCMU-resistant mutant of A. nidulans R2 was still susceptible to cyanobacterin (Gleason et al., Plant Science, 46 (1986) 5–10). Apparently, cyanobacterin acts at a site different from that of DCMU and similar PS II inhibitors. To confirm this conclusion, a cyanobacterin-resistant strain of A. nidulans R2 was produced by nitrosoguanidine mutagenesis and selected by growth in the presence of 4.7 μM cyanobacterin. Hill activity in mutant thylakoids was compared to that of the wild type membranes in the presence of ferricyanide and silicomolybdate as electron acceptors. Photosynthetic electron transport in the mutant membranes shows a high degree of resistance to cyanobacterin in both reactions. In contrast, the mutant exhibits the same susceptibility to DCMU inhibition as the wild type R2. Cyanobacterin acts at a unique site, inhibiting electron flow from quinone-A to quinone-B.     

Deposition of anthropogenic compounds on monuments and their effect on airborne microorganisms

Monuments and buildings act as repositories of airborne organic and inorganic pollutants, which accumulate at the surfaces in zones protected from direct rainwater. This enriches the substratum and anthropogenic compounds may influence to a great extent the colonization and growth pattern of microorganisms in polluted urban environments. This paper reviews recent and ongoing research on the deposition of pollutants on building stones and their possible utilization by microorganisms.     

Degradation of carboxin and oxycarboxin by microorganisms

Summary Algae, protozoa and photosynthetic bacteria which occur in considerable number in wet soils were examined for their ability to degrade the fungicides in broth culture. Blue green algae, namely, species of Anabaena, Nostoc and Tolypothrix brought about extensive degradation of the fungicides as revealed by thin layer chromatography. Green alga,Chlorella vulgaris also degraded the fungicides. The photosynthetic bacteriumRhodospirillum sp., failed to degrade carboxin beyond sulphoxide stage but degraded oxycarboxin to a greater extent. A protozoan species, Colpoda on the other hand, brought about extensive degradation of carboxin but not of oxycarboxin. These organisms have not been examined before for the detoxification of either carboxin or oxycarboxin.Part of Ph.D. Thesis, submitted to USA, Bangalore-65 under the guidance of the second author.     

Mathematical model for apical growth, septation, and branching of mycelial microorganisms

A mathematical model for apical growth, septation, and branching of mycelial microorganisms is presented. The model consists of two parts: the determinstic part of the model is based on fundamental cellular and physical mechanisms; it represents the kinetics for growth of hyphal tips and septation of apical as well as intercalary compartments. In regard to random occurrences of hyphal growth and branching, the stochastic part deals with branching processes, tip growth directions, and outgrowth orientations of branches. The model can explain the morphological development of mycelia up to the formation of pellets. The results, as predicted by the model, correspond very closely to those observed in experiments. In addition, some unmeasured states can be ascertained, such as the distribution functions of hyphal length (biomass) and tips along pellet radii.     

长江三峡地区退化生态系统土壤微生物的初步研究*

通过对长江三峡地区4种退化生态系统类型,每一类型5个土壤样品中微生物的初步研究, 结果表明该地区土壤每克干土中真菌和细菌的数量分别为 8.62×10⁴ ～1.31×10⁵ cfu 及 1.547×10⁷～6.957×10⁷ cfu, 但不同退化生态系统类型下土壤微生物的数量有所不同,其中单位重量土壤真菌数量 (cfu/g)多少顺序为：栓皮栎林(Quercus variabilis forest)＞马尾松林( Pinus massoniana forest)＞马尾松-栓皮栎混交林( Pinus massoniana-Quercus variabilis forest)＞杉木林( Cunninghamia lanceolata forest),细菌数量顺序为：马尾松-栓皮栎混交林( Pinus massoniana-Quercus variabilis forest)＞栓皮栎林( Quercus　variabilis forest)＞马尾松林( Pinus massoniana forest)＞杉木林( Cunninghamia lanceolata forest)。真菌种类鉴定表明,青霉菌(Penicillium ssp.)、镰刀菌(Fusarium spp.)、木霉菌(Trihoderma spp.)和葡萄孢菌(Botrytis spp.)等是组成该地区土壤真菌的主要类群。     

Culturable microorganisms from the earthworm digestive tract

The cultured aerobic copiotrophic bacteria and fungi from food-free digestive tracts of Aporrectodea caliginosa, Lumbricus terrestris, and Eisenia fetida earthworms, soil (compost), and fresh earthworm excrements were investigated. The microorganisms were isolated on nutrient media and identified by sequencing the fragments of bacterial 16S rRNA and fungal 28S rRNA (D1/D2 domain) gene sequences with subsequent phylogenetic analysis. Bacteria isolated from the digestive tracts of earthworms belonged to the families Aeromonadaceae, Comamonadaceae, Enterobacteriaceae, Flavobacteriaceae, Moraxellaceae, Pseudomonadaceae, and Sphingobacteriaceae (Bacteroidetes), as well as Actinobacteria. For five strains, namely Ochrobactrum sp. 341-2 (α-Proteobacteria), Massilia sp. 557-1 (β-Proteobacteria), Sphingobacterium sp. 611-2 (Bacteroidetes), Leifsonia sp. 555-1, and a bacterium from the family Microbacteriaceae, isolate 521-1 (Actinobacteria), the similarity to known 16S rRNA sequences was 93–97%; they therefore, probably belong to new species and genera. Bacterial groups isolated from the digestive tracts of earthworms were significantly different from those isolated from soil and excrements. Some bacterial taxa occurred in different sections of A. caliginosa intestine and in intestines of different earthworm species; however, the overall composition of bacterial communities in these objects is different. Existence of bacterial groupings symbiotically associated with intestines is proposed. Among the fungi, Bjerkandera adusta and Syspastospora parasitica were isolated from the cleaned digestive tracts as light-colored, sterile mycelium, as well as Geotrichum candidum, Acremonium murorum (A. murorum var. felina), Alternaria alternata, Aspergillus candidus, A. versicolor, Cladosporium cladosporioides, Rhizomucor racemosus, Mucor hiemalis, Fusarium (F. oxysporum, Fusarium sp.), and Penicillium spp. These fungi survive for a long time in the earthworm’s digestive environment. Investigation of the functional characteristics and role in the host organism is required to confirm the symbiotic status of the microorganisms associated with the earthworm digestive tract.     

Reaction of microorganisms to the digestive fluid of earthworms

The reaction of soil bacteria and fungi to the digestive fluid of the earthworm Aporrectodea caliginosa was studied. The fluid was obtained by centrifugation of the native enzymes of the digestive tract. The inhibition of growth of certain bacteria, spores, and fungal hyphae under the effect of extracts from the anterior and middle sections of the digestive tract of A. caliginosa was discovered for the first time. In bacteria, microcolony formation was inhibited as early as 20–30 s after the application of the gut extracts, which may indicate the nonenzymatic nature of the effect. The digestive fluid exhibited the same microbicidal activity whether the earthworms were feeding on soil or sterile sand. This indicates that the microbicidal agents are formed within the earthworm’s body, rather than by soil microorganisms. The effect of the digestive fluid from the anterior and middle divisions is selective in relation to different microorganisms. Of 42 strains of soil bacteria, seven were susceptible to the microbicidal action of the fluid (Alcaligenes faecalis 345-1, Microbacterium sp. 423-1, Arthrobacter sp. 430-1, Bacillus megaterium 401-1, B. megaterium 413-1, Kluyvera ascorbata 301-1, Pseudomonas reactans 387-2). The remaining bacteria did not die in the digestive fluid. Of 13 micromycetes, the digestive fluid inhibited spore germination in Aspergillus terreus and Paecilomyces lilacinus and the growth of hyphae in Trichoderma harzianum and Penicillium decumbens. The digestive fluid stimulated spore germination in Alternaria alternata and the growth of hyphae in Penicillium chrysogenum. The reaction of the remaining micromycetes was neutral. The gut fluid from the posterior division of the abdominal tract did not possess microbicidal activity. No relation was found between the reaction of microorganisms to the effects of the digestive fluid and the taxonomic position of the microorganisms. The effects revealed are similar to those shown earlier for millipedes and wood lice in the following parameters: quick action of the digestive fluid on microorganisms, and the selectivity of the action on microorganisms revealed at the strain level. The selective effect of the digestive gut fluid of the earthworms on soil microorganisms is important for animal feeding, maintaining the homeostasis of the gut microbial community, and the formation of microbial communities in soils.     

外生菌根真菌对‘NL-895杨’光合作用的影响

以‘NL-895杨’(Populus×euramericanacv.Nanlin 895)幼苗为材料,研究6种外生菌根真菌接种对其幼苗光合作用的影响.结果显示:接种60 d后‘NL-895杨’叶片的叶绿素a和b含量、PSⅡ最大光能转化效率(Fv/Fm)比对照极显著提高,其中叶绿素a和b的增加幅度分别为28.16%～68.03%和69.29%～138.26%,并以接种劣味乳菇的‘NL-895杨’Fv/Fm最高,且与对照差异极显著.各处理菌根苗培养150 d时‘NL-895杨’的净光合速率表现为美味牛肝菌>红绒盖牛肝菌>劣味乳菇>彩色豆马勃2号>紫金蜡蘑>彩色豆马勃1号>对照;菌根真菌处理对‘NL-895杨’叶片胞间CO2浓度影响较小,但其蒸腾速率显著高于对照,而且能促进总糖的合成与积累,并以接种彩色豆马勃2号的‘NL-895杨’苗总糖含量最高.研究表明,接种菌根真菌可以有效提高‘NL-895杨’对光能资源的利用率,增加其光合产物积累,显著促进其生长.     

云南嵩明大哨天然虫生真菌及其内生真菌的分离鉴定与抑菌活性分析

【背景】云南存在着丰富的虫草资源,天然虫草群落中蕴藏多样的真菌资源,是挖掘新型抑菌活性化合物的潜在来源。【目的】了解云南嵩明大哨天然虫生真菌及其内生真菌的物种多样性,并从中筛选具有抑菌活性的菌株。【方法】采用组织分离法对所采集的野生虫草样本进行虫生真菌及其内生真菌的分离,并通过形态观察和ITS联合nrSSU、nrLSU、tef-1α、rpb1、rpb2多基因测序进行物种鉴定及多样性分析;通过平板对峙法以7株病原细菌、5株植物病原真菌为病原指示菌进行抑菌活性测试。【结果】共采集86份天然虫草样本,经鉴定隶属于3科5属7种,包括虫草科（Cordycipitaceae）虫草属（Cordyceps）（1种）、白僵菌属（Beauveria）（2种）、鳞翅虫草属（Samsoniella）（2种）、麦角菌科（Clavicipitaceae）泛普可尼亚属（Metapochonia）（1种）,以及线虫草科（Ophiocordycipitaceae）线虫草属（Ophiocordyceps）（1种）。同时,从采集到的虫草样本中分离得到26株内生真菌,分属于9科9属,其中木霉属（Trichoderma）（38%）和镰刀菌属（Fusarium）（19%）为此次分离得到的优势菌属。对所分离保存的真菌按其分离源及种类归属,从虫生真菌和内生真菌菌株中共挑取20株代表性菌株进行抑菌活性筛选,有11株真菌对2株及以上病原指示细菌具有不同程度的抑菌活性,13株真菌对1株以上植物病原真菌具有不同程度拮抗能力;其中Trichoderma sp.Y3-1和Fusarium sp.WZ3-1具有广谱抑菌活性。【结论】云南嵩明大哨分布有丰富的虫生真菌及内生真菌资源,分离所得的真菌对多种病原菌具有不同程度的抑制作用。本研究丰富了云南虫草资源多样性,为云南省虫草及其内生真菌资源的开发利用提供了数据支持,也为下一步从虫草及其相关真菌资源中挖掘抑菌活性物质提供了菌株资源。     

热带太平洋深海微生物抗肿瘤活性的初步研究

以４个人体癌细胞株为模型、利用四甲基偶氮唑盐（Methyl Thiazolyl blue Tetrazolium bromide,MTT）比色法和磺酰罗丹明（SulfoRhodamine B,SRB）染色法对55株来自于热带太平洋深海微生物（细菌和霉菌）的培养液的乙酸乙酯抽提物以及菌体的甲醇提取物进行了细胞毒活性筛选,并主要采用分子生物学方法鉴定了该批菌株. 结果表明,55株微生物发酵样品共１１０个提取物中,９０％样品表现出细胞毒活性;其中13株微生物的活性较强（提取物有效抑制浓度≤16μg/ml）,具有较好的开发应用前景。同时还发现,菌体中检测到的活性菌株数大于发酵液中检测到的活性菌株数, 细菌的筛选得率高于霉菌的筛选得率.鉴定结果显示, 50株微生物分属于21属、29种,其中１３个较高活性菌株来源于８个属。本文为我国深海微生物资源的开发利用,提供了探索性研究信息。