Isolation and characterization of chitinolytic Streptomyces sp. MT7 and its antagonism towards wood-rotting fungi

An actinomycetes isolate of Loktak Lake soil, designated as MT7, was characterized and identified as Streptomyces sp. based on fatty acid methyl ester and 16S ribosomal RNA gene analysis. Streptomyces sp. MT7 showed strong and broad spectrum antagonism towards seven out of eight tested wood-rotting fungi. Strain MT7 secretes three vital fungal cell wall lytic enzymes, i.e. chitinase, β-1,3-glucanase, and protease, and siderophores. Extracellularly produced mycolytic enzymes lost their antifungal activity completely after treatment with proteinase K and heat, indicating that the tested antifungal metabolites are heat-sensitive and proteinaceous in nature. Extracellular fluid (ECF) and its organic solvent extract also exhibited potential antagonism towards the tested wood-rotting fungi. Antifungal metabolites were characterized as polyene in nature. Biocontrol traits like co-production of cell wall lytic enzymes and antifungal secondary metabolites including siderophores by Streptomyces sp. MT7 suggests that it could be employed as a potential biocontrol agent against wood-rotting basidiomycetes.     

Actinomycetes from Moroccan habitats: isolation and screening for cytotoxic activities

In our screening for actinomycetes showing cytotoxic activities, 8 samples were collected from various Moroccan habitats, 136 isolates were tested for their capacity to produce antibacterial compounds against gram positive bacteria. Thirty-seven strains of these isolates were active against Gram-positive bacteria. Using the following steps of primary screening: antibacterial activity, confrontation between the isolates and toxicity to Artemia salina; fifteen different isolates were used for further investigation. The aqueous extracts of Streptomyces sp. T5 and Streptomyces sp. AS8 were selected for their cytotoxic activity against Hep2, BSR and P815 cell lines, and two active compounds were observed on HPLC. The two isolates exhibited high activity against human cancer cell lines and were inactive on PBMC cell lines. Furthermore, the Streptomyces sp. T5 extract showed a proliferative activity.     

大连海域沉积物中可培养海洋链霉菌活性及其多样性

以大肠杆菌、金黄色葡萄球菌和尖孢镰刀枯萎病菌作为测试靶目标,采用9种分离培养基从大连海域13个不同采样点的海洋沉积物样品中分离到165株海洋链霉菌。从165株海洋放线菌中筛选到对金黄色葡萄球菌具有抑制活性的菌株85株,占总菌株数的51.5%;对大肠杆菌具有抑制活性的菌株27株,占总菌株数的16.4%;对尖孢镰刀枯萎病菌具有抑制活性的菌株仅有6株,占总菌株数的3.6%。因此,海洋链霉菌的活性更多地表现为对细菌的抗性,尤其对革兰氏阳性细菌具有更高的抑制活性。对其中具有抑制活性或形态独特的菌株进行了16S r DNA序列分析,并构建系统发育树,显示活性海洋链霉菌具有丰富的种类多样性和广谱抗菌活性。同种海洋链霉菌与土壤链霉菌活性比较结果也表明,海洋链霉菌多表现抗革兰氏阳性细菌活性。     

Bioprospection and secondary metabolites profiling of marine Streptomyces levis strain KS46

The quest for novel broad spectrum bioactive compounds is needed continuously because of the rapid advent of pathogenic multi drug resistant organisms. Actinomycetes, isolated from unexplored habitats can be a solution of this problem. The motive of this research work was isolation of actinomycetes having potential antimicrobial activities from unexplored regions of Devbag and Tilmati beach. The isolated actinomycetes were screened against pathogenic microbes for antimicrobial activities through cross streak method. Enzyme production activity was checked for these actinomycetes for amylase, protease, cellulase and lipase enzymes. Further antimicrobial activity of ethyl acetate extract of the potent strain KS46 was performed. The strain KS46 was identified with 16S rRNA gene sequencing and secondary structure was analysed. Gas chromatography–Mass spectrometry (GC–MS) profiling was conducted to ascertain the presence of bioactive metabolites in the ethyl acetate extract. The collected samples were pre-treated and 70 actinomycetes were isolated. The Streptomyces sp. strain KS46 showed the best antimicrobial activity in primary screening. Ethyl acetate extract of the strain KS46 revealed antimicrobial activity against S. aureus, B. subtilis, B. cereus, E. faecalis, K. pneumoniae, E. coli, S. flexneri, C. albicans and C. glabrata. The 16S rRNA gene sequencing identified the strain KS46 as Streptomyces levis strain KS46. The GC–MS metabolite profiling of the ethyl acetate extract revealed the availability of 42 compounds including fatty acid esters, fatty acid anhydrides, alkanes, steroids, esters, alcohols, carboxylic ester, etc. having antibacterial, antifungal, antiproliferative, antioxidant activities. This study indicated that Devbag and Tilmati beaches being untapped habitats have enormous diversity of promising antimicrobial metabolite producing actinomycetes. Therefore, further exploration should be carried out to characterize the potential actinomycetes, which can be optimistic candidates for generation of novel antimicrobial drugs.     

Bioactive compounds from marine <Emphasis Type="Italic">Streptomyces</Emphasis> sp. VITPSA as therapeutics

Background

Marine actinomycetes are efficient producers of new secondary metabolites that show different biological activities, including antibacterial, antifungal, anticancer, insecticidal, and enzyme inhibition activities.

Methods

The morphological, physiological, and biochemical properties of the strain Streptomyces sp. VITPSA were confirmed by conventional methods. Antibacterial, anti-oxidant, anti-inflammatory, anti-diabetic, and cytotoxic activities of Streptomyces sp. VITPSA extract were determined. The media were optimized for the production of secondary metabolites. Characterization and identification of secondary metabolites were conducted by high-performance liquid chromatography, gas chromatography-mass spectroscopy, and Fourier transform infrared spectroscopy analysis.

Results

The strain showed significant antibacterial, anti-oxidant, and cytotoxic activities, moderate anti-inflammatory activity, and no satisfactory anti-diabetic activity. The ethyl acetate extract of Streptomyces sp. VITPSA showed maximum antibacterial activity against two gram-positive and gram-negative bacteria at 0.5 mg/mL. The antioxidant potential of the crude extract exhibited strong reducing power activity at 0.5 mg/mL with 95.1% inhibition. The cytotoxic effect was found to be an IC₅₀ of 50 μg/mL on MCF-7 cell lines. Experimental design of optimization by one-factor analysis revealed the most favorable sucrose, yeast extract, pH (7.25), and temperature (28°C) conditions for the effective production of secondary metabolites.

Conclusion

This study revealed that Streptomyces sp. VITPSA is an excellent source of secondary metabolites with various bioactivities.

     

Bioactive potential of Streptomyces associated with marine sponges

The present work deals with isolation of Streptomyces associated with marine sponges and its bioactive potential. Streptomyces sp. were isolated from the marine sponges Callyspongia diffusa, Mycale mytilorum, Tedania anhelans and Dysidea fragilis. From the initial screening, 94 cultures of Streptomyces were obtained and from these 58 cultures exhibited antagonism against bacteria, 36 strains against fungi and 27 strains exhibited broad spectrum activity against both. The submerged culture extracts of the 58 anti-bacterial isolates were analysed and of these 58 strains, 37 strains showed positive inhibition against Bacillus subtilis, 43 against Staphylococcus aureus, 10 against Vibrio cholerae and 10 against Escherichia coli. The antifungal activities of the 36 strains were also evaluated and 27 strains showed positive inhibition against Aspergillus niger, 23 against Saccharomyces cerevisiae and 16 against Candida albicans. The production of polyene substances from the active extracts was confirmed by UV spectral analysis by the absorbance peaks that ranged from 225 to 262 nm and the TLC (R _f values) ranging from 0.40 to 0.78. The results indicate that Streptomyces strains isolated from marine sponges produce potential antibacterial, antifungal and broad spectrum antibiotic compounds.     

西沙石珊瑚共附生放线菌的分离培养及抗菌活性评价

【背景】珊瑚礁生态系统是海洋中一类极其重要的生态系统,健康珊瑚礁中丰富的共附生放线菌群体是珊瑚抵御各种致病菌的重要防线,因此,这类放线菌是寻找抗菌活性分子的重要资源,其药用潜力巨大。【目的】从西沙石珊瑚样品中分离共附生放线菌,并从中筛选具有良好抗菌活性的菌株。【方法】通过稀释涂布法分离珊瑚共附生放线菌,并根据16S rRNA基因序列构建系统发育树进行菌种鉴定;通过平板对峙法对放线菌进行抗菌活性筛选并确定目标菌株;将目标菌株涂布于不同氯化钠浓度的ISP2固体培养基上培养,测试其盐度耐受能力;通过平板对峙法对该菌株发酵产物的热稳定性和光稳定性进行测试;采用NanoPore和Illumina方法完成目标活性放线菌全基因组测序,并通过antiSMASH在线分析预测其次级代谢产物生物合成基因簇及其结构类型。【结果】从6份西沙石珊瑚样品中分离得到104株可培养放线菌,根据菌落形态和分离来源去重后对其中27株放线菌进行16S rRNA基因序列测序,通过序列比对和系统发育树分析将菌株初步鉴定为盐孢菌属(Salinispora)(25株)、链霉菌属(Streptomyces)(1株)和戈登菌属(Gord...     

Isolation and identification of Streptomyces sp. Act4Zk,a good producer of Staurosporine and some derivatives

In this study, strain Streptomyces sp. Act4Zk was isolated based on a method developed for the isolation of myxobacteria. Due to the low efficiency of the majority of conventional DNA extraction techniques, for molecular identification of the strain Streptomyces sp. Act4Zk, a new technique for DNA extraction of Actinobacteria was developed. In order to explore potential bioactivities of the strain, extracts of the fermented broth culture were prepared by an organic solvent (i.e. ethyl acetate) extraction method using. These ethyl acetate extracts were subjected to HPLC fractionation against standard micro-organisms, followed by LC/MS analysis. Based on morphological, physiological, biochemical and 16S rRNA gene sequence data, strain Streptomyces sp. Act4Zk is likely to be a new species of Streptomyces, close to Streptomyces genecies and Streptomyces roseolilacinus. Antimicrobial assay indicated high antifungal activity as well as antibacterial activity against Mycobacterium smegmatis and Gram-positive bacteria for the new strain. HPLC and LC/MS analyses of the extracts led to the identification of three different compounds and confirmed our hypothesis that the interesting species of the genus Streptomyces being a good producer of staurosporine and some derivatives.     

Studies on the microbial populations of the rhizosphere of big sagebrush (<Emphasis Type="Italic">Artemisia tridentata</Emphasis>)

Prolonged use of broad-spectrum antibiotics has led to the emergence of drug-resistant pathogens, both in medicine and in agriculture. New threats such as biological warfare have increased the need for novel and efficacious antimicrobial agents. Natural habitats not previously examined as sources of novel antibiotic-producing microorganisms still exist. One such habitat is the rhizosphere of desert shrubs. Here, we show that one desert shrub habitat, the rhizosphere of desert big sagebrush (Artemisia tridentata) is a source of actinomycetes capable of producing an extensive array of antifungal metabolites. Culturable microbial populations from both the sagebrush rhizosphere and nearby bulk soils from three different sites were enumerated and compared, using traditional plate-count techniques and antibiotic activity bioassays. There were no statistical differences between the relative numbers of culturable non-actinomycete eubacteria, actinomycetes and fungi in the rhizosphere versus bulk soils, but PCR amplification of the 16S rRNA gene sequences of the total soil DNA and denaturing gradient gel electrophoresis showed that the community structure was different between the rhizosphere and the bulk soils. A high percentage of actinomycetes produced antimicrobials; and the percentage of active producers was significantly higher among the rhizosphere isolates, as compared with the bulk soil isolates. Also, the rhizosphere strains were more active in the production of antifungal compounds than antibacterial compounds. 16S rRNA gene sequence analysis showed that sagebrush rhizospheres contained a variety of Streptomyces species possessing broad spectrum antifungal activity. Scanning electron microscopy studies of sagebrush root colonization by one of the novel sagebrush rhizosphere isolates, Streptomyces sp. strain RG, showed that it aggressively colonized young sagebrush roots, whereas another plant rhizosphere-colonizing strain, S. lydicus WYEC108, not originally isolated from sagebrush, was a poor colonizer of the roots of this plant, as were two other Streptomyces isolates from forest soil. These results support the hypothesis that the rhizosphere of desert big sagebrush is a promising source of habitat-adapted actinomycetes, producing antifungal antibiotics.     

Nature’s combinatorial biosynthesis and recently engineered production of nucleoside antibiotics in <Emphasis Type="Italic">Streptomyces</Emphasis>

Modified nucleosides produced by Streptomyces and related actinomycetes are widely used in agriculture and medicine as antibacterial, antifungal, anticancer and antiviral agents. These specialized small-molecule metabolites are biosynthesized by complex enzymatic machineries encoded within gene clusters in the genome. The past decade has witnessed a burst of reports defining the key metabolic processes involved in the biosynthesis of several distinct families of nucleoside antibiotics. Furthermore, genome sequencing of various Streptomyces species has dramatically increased over recent years. Potential biosynthetic gene clusters for novel nucleoside antibiotics are now apparent by analysis of these genomes. Here we revisit strategies for production improvement of nucleoside antibiotics that have defined mechanisms of action, and are in clinical or agricultural use. We summarize the progress for genetically manipulating biosynthetic pathways for structural diversification of nucleoside antibiotics. Microorganism-based biosynthetic examples are provided and organized under genetic principles and metabolic engineering guidelines. We show perspectives on the future of combinatorial biosynthesis, and present a working model for discovery of novel nucleoside natural products in Streptomyces.     

Biodiversity of Actinomycetes Associated with Caribbean Sponges and Their Potential for Natural Product Discovery

Marine actinomycetes provide a rich source of structurally unique and bioactive secondary metabolites. Numerous genera of marine actinomycetes have been isolated from marine sediments as well as several sponge species. In this study, 16 different species of Caribbean sponges were collected from four different locations in the coastal waters off Puerto Rico in order to examine diversity and bioactive metabolite production of marine actinomycetes in Caribbean sponges. Sediments were also collected from each location, in order to compare actinomycete communities between these two types of samples. A total of 180 actinomycetes were isolated and identified based on 16S rRNA gene analysis. Phylogenetic analysis revealed the presence of at least 14 new phylotypes belonging to the genera Micromonospora, Verruscosispora, Streptomyces, Salinospora, Solwaraspora, Microbacterium and Cellulosimicrobium. Seventy-eight of the isolates (19 from sediments and 59 from sponges) shared 100 % sequence identity with Micromonospora sp. R1. Despite having identical 16S rRNA sequences, the bioactivity of extracts and subsequent fractions generated from the fermentation of both sponge- and sediment-derived isolates identical to Micromonospora sp. R1 varied greatly, with a marked increase in antibiotic metabolite production in those isolates derived from sponges. These results indicate that the chemical profiles of isolates with high 16S rRNA sequence homology to known strains can be diverse and dependent on the source of isolation. In addition, seven previously reported dihydroquinones produced by five different Streptomyces strains have been purified and characterized from one Streptomyces sp. strain isolated in this study from the Caribbean sponge Agelas sceptrum.     

Isolation of rhizospheric and roots endophytic actinomycetes from Leguminosae plant and their activities to inhibit soybean pathogen, Xanthomonas campestris pv. glycine

In this study, actinomycetes from roots and rhizospheric soils of leguminous plants were isolated using starch casein agar supplemented with antifungal and antibacterial antibiotics. Three hundred and seventeen actinomycetes were isolated with 77 isolates obtained from plant roots and 240 isolates from rhizospheric soils. Analysis of whole-organism hydrolysates showed that 289 strains were rich in the LL-isomer of diaminopimelic acid, a result consistent with their assignment to the streptomycetes. The remaining 28 strains were assigned to non-streptomycetes based on the presence of meso-isomer of diaminopimelic acid in cell wall. Sixty-four isolates (20.2 %) showed antagonistic activity against soybean pathogen Xanthomonas campestris pv. glycine by agar overlay method. Isolate RM 365 showed the highest activity with an inhibition ratio of 3.79, with no inhibitory activity on the growth of Rhizobium japonicum TISTR 079, Rhizobium sp. TISTR 061 and Rhizobium sp. TISTR 063. The 16S rRNA gene sequence analysis revealed that isolate RM 365 shared 99.28 % similarity to Streptomyces caeruleatus GIMN4^T (GQ329712). In addition, isolates which contained meso-DAP were also identified by 16S rRNA gene sequence analysis. The results showed that they were members of the genus Amycolatopsis, Isoptericola, Micromonospora, Microbispora, Nocardia, Nonomuraea, Promicromonospora and Pseudonocardia.     

Biodiversity,Anti-Trypanosomal Activity Screening,and Metabolomic Profiling of Actinomycetes Isolated from Mediterranean Sponges

Marine sponge–associated actinomycetes are considered as promising sources for the discovery of novel biologically active compounds. In the present study, a total of 64 actinomycetes were isolated from 12 different marine sponge species that had been collected offshore the islands of Milos and Crete, Greece, eastern Mediterranean. The isolates were affiliated to 23 genera representing 8 different suborders based on nearly full length 16S rRNA gene sequencing. Four putatively novel species belonging to genera Geodermatophilus, Microlunatus, Rhodococcus and Actinomycetospora were identified based on a 16S rRNA gene sequence similarity of < 98.5% to currently described strains. Eight actinomycete isolates showed bioactivities against Trypanosma brucei brucei TC221 with half maximal inhibitory concentration (IC₅₀) values <20 μg/mL. Thirty four isolates from the Milos collection and 12 isolates from the Crete collection were subjected to metabolomic analysis using high resolution LC-MS and NMR for dereplication purposes. Two isolates belonging to the genera Streptomyces (SBT348) and Micromonospora (SBT687) were prioritized based on their distinct chemistry profiles as well as their anti-trypanosomal activities. These findings demonstrated the feasibility and efficacy of utilizing metabolomics tools to prioritize chemically unique strains from microorganism collections and further highlight sponges as rich source for novel and bioactive actinomycetes.     

Marine actinomycete Streptomyces sp. ISP2-49E,a new source of Rhamnolipid

Marine derived actinomycetes were isolated from sediment samples of Galveston Bay, Texas and screened for production of bioactive metabolites. Streptomyces sp. ISP2-49E, identified by 16s rDNA, produced a previously described Rha-Rha-C10-C10 rhamnolipid; however, this is the first report of a rhamnolipid produced by a Streptomyces sp. This organism was isolated from hydrocarbon contaminated sediment and further supports the trend of rhamnolipid production as a potential adaptation to this environment.     

Screening and identification of novel isolate Streptomyces sp., NLKPB45 from Nellore costal region for its biomedical applications

Actinobacteria, which are the prolific producers of antibiotics and significant suppliers to the pharmaceutical industry, can produce a wide variety of bioactive metabolites. An actinomycete strain designated NLKPB45 was isolated from mangrove soils samples of Nellore coastal regions Andhra Pradesh and assessed for antibiotic production and activity against pathogenic bacteria. From a total of 9 mangrove soil samples, 143 acinomycetes were isolated. Among the isolated them 6 actinomycetes strains showed potential antibacterial activity against at two tested pathogens gram positive and gram negative bacteria E. coli and S. aureus. The potent strain NLKPB45 was identified by 16S gene isolation and sequencing to the Streptomyces genus. The ethyl acetate extracts also as shown excellent antimicrobial activity against Salmonella sp., staphylococcus aureus, E. coli, and B. subtilus were detected in both the supernatant extract samples from fermentations of culture NLKPB45. The anticancer activity of extracts in the HeLa with IC₅₀ value of 37.1924 μg/ml, MCF-7 IC₅₀ value of 40.9177 μg/ml and HT 29 IC₅₀ value of 43.3758 μg/ml.     

Screening of nonpolyenic antifungal metabolites produced by clinical isolates of actinomycetes

The purpose of this work was to screen clinical isolates of actinomycetes producing nonpolyenic antifungals. This choice was made to limit the problem of rediscovery of well-known antifungal families, especially polyenic antifungals. One hundred and ten strains were tested, using two diffusion methods and two test media, against three yeast species and three filamentous fungi. Among 54 strains (49%) showing antifungal activity, five strains belonging to the genus Streptomyces were active against all test organisms and appeared promising. These results indicate that clinical and environmental isolates of actinomycetes could be an interesting source of antifungal bioactive substances. The production of nonpolyenic antifungal substances by these five active isolates was investigated using several criteria: antibacterial activity, ergosterol inhibition, and UV-visible spectra of active extracts. One active strain responded to all three selection criteria and produced potentially nonpolyenic antifungal metabolites. This strain was retained for further investigation, in particular, purification, structure elucidation, and mechanism of action of the active product.     

Antimicrobial properties of endophytic actinomycetes isolated from <Emphasis Type="Italic">Combretum latifolium</Emphasis> Blume,a medicinal shrub from Western Ghats of India

Endophytic actinomycetes were isolated from Combretum latifolium Blume (Combretaceae),Western Ghats of Southern India and identified by its characteristic culture morphology and molecular analysis of 16S rRNA gene sequences. In this survey of endophytic actinomycetes, a total of 117 isolates representing 9 different genera of endophytic actinomycetes were obtained using four different isolation media and several of them seemed to be novel taxa. Streptomyces genera (35%) was the most frequently isolated strains, followed by Nocordiopsis (17%) and Micromonospora (13%). ISP-4 medium recovered more isolates (47%) when compared to rest of the media used. Preliminary antibacterial activity of the isolates was carried out by confrontation test. Ethyl acetate fraction of selected isolates in disc diffusion assay exhibited broad spectrum antimicrobial activity against test human pathogens. All Streptomyces spp. strains displayed significant antimicrobial activity against test pathogens. Strain CLA-66 and CLA-68 which are Nocordipsis spp. inhibited both bacterial and fungal pathogens where as other isolates inhibited atleast three test human pathogens in disc diffusion assay. Antimicrobial screening of endophytic actinomycetes from this host may represent a unique potential niche for antimicrobial compounds of industrial and pharmaceutical applications. This work is the first comprehensive report on incidence of potential endophytic actinomycetes inhabiting C. latifolium Blume.     

Selective Isolation and Ansamycin-Targeted Screenings of Commensal Actinomycetes from the “Maytansinoids-Producing” Arboreal <Emphasis Type="Italic">Trewia nudiflora</Emphasis>

To verify the hypothesis on the involvement of commensal actinomycetes in the biosynthesis of plant maytansinoids that belong to the ansamycin family, selective isolation and targeted screenings were conducted. In total, 164 endophytic actinomycetes isolates were obtained from the roots, twigs, seeds, callus, and germ-free seedlings of “maytansinoids-producing” Trewia nudiflora Linn. by selective isolation methods. Crude extracts of the isolates were screened by antifungal bioassay against Penicillium avellaneum UC-4376, thin-layer chromatography, and liquid chromatography–mass spectrometry detection according to the bioactivity as well as structural characteristics of maytansinoids. Respectively, 25.0%, 64.8%, and 26.7% of the extracts were positive in corresponding screenings. Ten isolates showed positive results in all three different screenings. To confirm on a genetic level, 28 representative isolates from 20 morphological groups were screened by polymerase chain reaction with 3-amino-5-hydroxybenzoic acid synthase gene and carbamoyltransferase gene primers, both of which were involved in the biosynthesis of ansamycins. According to the results of the targeted screenings, two isolates Streptomyces sp. 5B and Streptomyces sp. M27m3 might have the potential of producing ansamycins, which further enhanced the hypothesis that endophyte(s) might be involved in the biosynthesis of plant maytansinoids.     

内生链霉菌SAT1转录组分析和抑菌代谢产物的鉴定

【背景】植物内生链霉菌Streptomyces sp.SAT1分离自药用植物荠苨根部,对多种植物病原真菌和病原细菌具有强抑菌活性,在农林业生物防治领域应用潜力巨大。【目的】揭示该菌在不同培养基条件下的抑菌效果和抑制细菌的活性物质类型,为该菌生物防治应用提供理论基础和技术支撑。【方法】通过测定发酵液和菌体萃取物的抑菌活性,研究培养基成分对抑菌活性物质生物合成的影响;选择抑制细菌活性高和无抑菌活性的培养基进行发酵,通过转录组测序分析差异表达基因的功能,并利用紫外吸收光谱和UPLC-MS/MS鉴定活性物质的成分。【结果】所选用的7种链霉菌常用发酵培养基中,无论发酵液还是菌体萃取物,TSB、GS和R5培养基无抑制细菌活性;PDB、ISP2、MS和H有较强的抑菌活性。对PDB、ISP2和TSB发酵菌体进行转录组测序分析,共发现差异表达基因3 567个,KEGG富集分析发现差异基因多集中在global and overview maps、氨基酸代谢和碳水化合物代谢等通路上,而且与TSB比,PDB和ISP2分别有18个和5个上调基因定位于moenomycin类物质的生物合成基因簇上。以标准品为对照,...     

Endophytic actinomycetes from Pinus thunbergii and their antifungal activity against Cylindrocladium sp.

The inside of Pinus thunbergii could be a reliable screening source for a useful agent in controlling plant disease. Isolation of endophytic actinomycetes from P. thunbergii and their potential as biocontrol agents against the plant pathogen Cylindrocladium sp. were investigated. Two endophytic actinomycetes, Streptomyces sp. and Microbispora sp., were isolated from surface-sterilised root tissues of P. thunbergii seedlings. The recovery test of these two endophytic actinomycetes from pine seedling showed that Streptomyces sp. was isolated from only roots, but Microbispora sp. was isolated from both roots and leaves. Thus, Microbispora sp. is able to move to leaves from roots. Moreover, we evaluated the potential of both strains as biocontrol agents against Cylindrocladium sp. Two weeks after inoculation of Cylindrocladium sp. alone, pine seedlings showed a 50% mortality rate. Co-inoculation of Cylindrocladium sp. and Microbispora sp. did not affect seedling mortality rate. However, inoculation with both Cylindrocladium sp. and Streptomyces sp. reduced seedling mortality to 12%. Streptomyces sp. could be a useful agent in controlling pine disease caused by Cylindrocladium sp. Thus, it seems that Streptomyces sp. may induce a local host defence reaction and Microbispora sp. systemically spreads to aerial parts through the transpiration stream.