Characterization of antifungal metabolite produced by a new strain Pseudomonas aeruginosa PUPa3 that exhibits broad-spectrum antifungal activity and biofertilizing traits

AIM: To study the antifungal activity and plant beneficial traits of a broad-spectrum antagonistic fluorescent pseudomonad strain, PUPa3. METHODS AND RESULTS: Strain PUPa3 was isolated from the rhizosphere soil of rice and identified as Pseudomonas aeruginosa on the basis of biochemical tests and by comparison of 16S rDNA sequences. This bacterium exhibits a broad-spectrum antifungal activity towards phytopathogenic fungi. The antifungal metabolite by PUPa3 was extracted, purified and characterized using nuclear magnetic resonance (NMR) and mass spectroscopy (MS). Production of indole-3-acetic acid (IAA), siderophores, phosphatase and protease in PUPa3 was determined. Strain PUPa3 did not produce hydrogen cyanide, cellulase and pectinase. CONCLUSION: The antifungal metabolite produced by PUPa3 has been identified as phenazine-1-carboxamide (PCN) on the basis of NMR and MS data. Strain PUPa3 showed a broad-spectrum antifungal activity towards a range of phytopathogenic fungi. This bacterium also showed several plant growth-promoting traits but did not show the traits attributed to deleterious rhizobacteria. SIGNIFICANCE AND IMPACT OF THE STUDY: Present study reports the production of PCN as well as IAA for the first time by a saprophytic P. aeruginosa strain PUPa3. Because of the production of siderophore, growth hormone, protease and phosphatase and its innate fungicidal potential, this strain can be used as biofertilizer and antagonist against a range of phytopathogenic fungi that infect rice, groundnut, tobacco, chili, mango, sugarcane, tea, cotton and banana.     

Cyclosporin C is the main antifungal compound produced by Acremonium luzulae.

A strain of Acremonium luzulae (Fuckel) W. Gams was selected in screening new microorganisms for biological control of fruit postharvest diseases, especially gray and blue mold diseases on apples and strawberries. This strain manifests a very strong activity against a large number of phytopathogenic fungi. In this work, the product responsible for this antifungal activity was isolated from modified Sabouraud dextrose broth cultures of A. luzulae. It was purified to homogeneity by reverse-phase column chromatography. On the basis of UV, infrared, and 1H and 13C nuclear magnetic resonance spectra, mass spectral analysis, and the amino acid composition of the acid hydrolysates, the antibiotic was determined to be cyclosporin C. Cyclosporin C showed a broad-spectrum activity against filamentous phytopathogenic fungi but no activity against bacteria or yeasts. Its antifungal activity is only fungistatic. In contrast to Tolypocladium inflatum, another cyclosporin-producing strain, A. luzulae, did not produce additional cyclosporins. This was confirmed by in vivo-directed biosynthesis.     

天山大峡谷原始森林黏细菌的分离鉴定及其抗菌活性

【背景】黏细菌是一类具有多细胞群体行为特征的高等原核生物,其对植物病原真菌和细菌的捕食特性使其在植物病害防治方面具有重要的应用潜力。【目的】探究乌鲁木齐天山大峡谷原始森林可培养黏细菌的多样性并分析其抗菌活性,为发掘黏细菌生防菌株奠定基础。【方法】以天山大峡谷原始森林采集的土样和腐木为分离材料,采用兔粪诱导法和被捕食菌诱导法从中分离纯化黏细菌菌株,结合形态学观察、生理生化测定和16S rRNA基因序列分析确定其分类地位,并以6种植物病原真菌[大丽轮枝菌(Verticillium dahliae)、尖孢镰刀菌萎蔫专化型(Fusarium oxysporum f. sp. vasinfectum)、拟轮枝链孢霉(Fusarium verticillioides)、立枯丝核菌(Rhizoctonia solani)、黄色镰刀菌(Fusarium culmorum)、细极链格孢菌(Alternaria tenuissima)]和1种植物病原细菌[梨火疫病菌(Erwinia amylovora)]为靶标菌,通过平板对峙法和菌苔捕食法测定其抗菌活性。【结果】从采集的样品中分离出70株菌株,经纯化后获得36株黏细菌纯培养物。经鉴定隶属于4个属,黏球菌属(Myxococcus) 30株、孢囊杆菌属(Cystobacter) 3株、珊瑚球菌属(Corallococcus) 2株和原囊菌属(Archangium) 1株。抗菌活性分析显示,本研究获得的36株黏细菌至少对2种植物病原真菌有抗菌活性,表现出广谱的抗真菌活性,初步筛选出一株菌株NSE37-1兼具广谱和高效抗真菌活性;供试的15株黏细菌对梨火疫病菌均具有捕食活性,初步筛选出一株对梨火疫病菌具有较强捕食能力的黏细菌菌株NSE25。【结论】天山大峡谷可培养黏细菌资源比较丰富,黏球菌属是该地区可培养黏细菌菌群中的优势菌。分离纯化出的黏细菌菌株均表现出广谱的抗植物病原菌活性,具有进一步研究和开发的潜在价值。     

Screening for Endophytic Fungi with Antitumour and Antifungal Activities from Chinese Medicinal Plants

Summary One hundred and thirty endophytic fungi isolated from 12 Chinese traditional medicinal plants collected at Yuanmou county and Dawei Mountain, Yunnan province, southwest China, were tested for antitumour and antifungal activities by MTT assay on human gastric tumour cell line BGC-823 and the growth inhibition test against 7 phytopathogenic fungi. The results showed that fermentation broths from 9.2% of the isolates exhibited antitumour activity and 30% exhibited antifungal activity, moreover, some of them exhibited broad-spectrum antifungal activity. The active isolates were identified to 32 taxa. The results indicate that the endophytic fungi of Chinese traditional medicinal plants are promising sources of novel bioactive compounds.     

Isolation and characterization of antagonistic Bacillus subtilis strains from the avocado rhizoplane displaying biocontrol activity

AIM: This study was undertaken to isolate Bacillus subtilis strains with biological activity against soil-borne phytopathogenic fungi from the avocado rhizoplane. METHODS AND RESULTS: A collection of 905 bacterial isolates obtained from the rhizoplane of healthy avocado trees, contains 277 gram-positive isolates. From these gram-positive isolates, four strains, PCL1605, PCL1608, PCL1610 and PCL1612, identified as B. subtilis, were selected on the basis of their antifungal activity against diverse soil-borne phytopathogenic fungi. Analysis of the antifungal compounds involved in their antagonistic activity showed that these strains produced hydrolytic enzymes such as glucanases or proteases and the antibiotic lipopeptides surfactin, fengycin, and/or iturin A. In biocontrol trials using the pathosystems tomato/Fusarium oxysporum f.sp. radicis-lycopersici and avocado/Rosellinia necatrix, two B. subtilis strains, PCL1608 and PCL1612, both producing iturin A, exhibited the highest biocontrol and colonization capabilities. CONCLUSIONS: Diverse antagonistic B. subtilis strains isolated from healthy avocado rhizoplanes have shown promising biocontrol abilities, which are closely linked with the production of antifungal lipopeptides and good colonization aptitudes. SIGNIFICANCE AND IMPACT OF THE STUDY: This is one of the few reports dealing with isolation and characterization of B. subtilis strains with biocontrol activity against the common soil-borne phytopathogenic fungi F. oxysporum f.sp. radicis-lycopersici and R. necatrix.     

Isolation,characterisation and antifungal activity of marine actinobacteria from Goa and Kerala,the west coast of India

In total, 53 marine actinobacteria were isolated from the soils of six different locations in Goa and Kerala, on the west coast of India. All the isolates were screened for their antifungal properties against some phytopathogenic fungi by dual culture experiments. Among the 53 actinobacterial isolates, five isolates inhibited the growth of phytopathogens, namely Colletotrichum falcatum, Thielaviopsis paradoxa and Fusarium semitectum. But none of them were effective against Aspergillus niger, Aspergillus candidus and Aspergillus flavus. The antifungal activity of the actinobacteria was tested by food poisoning techniques, using four different concentrations (0.5%, 1.0%, 1.5% and 2.0%) of cell-free culture filtrates, which showed promising activity (almost 100% inhibition) against three pathogenic and one non-pathogenic fungi at 2% extract concentration. A comparison of the antifungal activity of the actinobacteria was also made with three commercial fungicides, namely hexaconazole, thiophanate methyl and propiconazole. The identity of the antagonistic actinobacteria was confirmed based on the morphological, cultural, biochemical, chemo-taxonomical and physiological characteristics. Among 5 antagonistic isolates, three antagonistic isolates were assigned to the genus Streptomyces, Nocardiopsis (1) and Saccharopolyspora (1).     

向日葵枯萎病拮抗芽胞杆菌的筛选与生防评价

目的筛选向日葵枯萎病拮抗芽胞杆菌菌株并研究其抗菌谱,探讨环境条件对菌株抑菌活性的影响并通过植物栽培完成生防评价。方法从向日葵根际土壤中选择性分离芽胞杆菌,通过5点对峙法确定1株高效拮抗菌株,进行鉴定后,测定其抑菌谱;单因素实验探讨环境条件对抑菌活性的影响;向日葵发芽实验完成生防评价。结果确定1株高效的枯萎病拮抗菌株WBFL-1,经鉴定为枯草芽胞杆菌,该菌对镰刀菌属具有广谱抗性,其抑菌活性的最佳条件是温度40℃,pH值7.0,接种量150μL,发酵时间48 h。生防评价表明该菌对枯萎病的拮抗效果显著。结论该菌可为农作物枯萎病的生物防治提供有效菌种储备。     

Characterization of CMR5c and CMR12a, novel fluorescent Pseudomonas strains from the cocoyam rhizosphere with biocontrol activity

AIM: To screen for novel antagonistic Pseudomonas strains producing both phenazines and biosurfactants that are as effective as Pseudomonas aeruginosa PNA1 in the biocontrol of cocoyam root rot caused by Pythium myriotylum. MATERIAL AND RESULTS: Forty pseudomonads were isolated from the rhizosphere of healthy white and red cocoyam plants appearing in natural, heavily infested fields in Cameroon. In vitro tests demonstrated that Py. myriotylum antagonists could be retrieved from the red cocoyam rhizosphere. Except for one isolate, all antagonistic isolates produced phenazines. Results from whole-cell protein profiling showed that the antagonistic isolates are different from other isolated pseudomonads, while BOX-PCR revealed high genomic similarity among them. 16S rDNA sequencing of two representative strains within this group of antagonists confirmed their relatively low similarity with validly described Pseudomonas species. These antagonists are thus provisionally labelled as unidentified Pseudomonas strains. Among the antagonists, Pseudomonas CMR5c and CMR12a were selected because of their combined production of phenazines and biosurfactants. For strain CMR5c also, production of pyrrolnitrin and pyoluteorin was demonstrated. Both CMR5c and CMR12a showed excellent in vivo biocontrol activity against Py. myriotylum to a similar level as Ps. aeruginosa PNA1. CONCLUSION: Pseudomonas CMR5c and CMR12a were identified as novel and promising biocontrol agents of Py. myriotylum on cocoyam, producing an arsenal of antagonistic metabolites. SIGNIFICANCE AND IMPACT OF THE STUDY: Present study reports the identification of two newly isolated fluorescent Pseudomonas strains that can replace the opportunistic human pathogen Ps. aeruginosa PNA1 in the biocontrol of cocoyam root rot and could be taken into account for the suppression of many plant pathogens.     

两株生防芽孢细菌筛选、鉴定及拮抗研究

【目的】筛选出广谱、高效的生防芽孢细菌,并对其拮抗作用进行研究。【方法】以8种植物病原真菌为靶标菌,通过皿内拮抗和发酵液拮抗能力的测定筛选出2株广谱性和高效性的芽孢细菌B06和B07。【结果】B06对8种植物病原真菌的R2/R1为0.4-1.8,无菌滤液对8种植物病原真菌的抑制率为66.7%-87.5%。B07对8种植物病原真菌的R2/R1为0.23-1.21,无菌滤液对8种植物病原真菌的抑制率为55.56%-81.25%。经16S rRNA序列鉴定,菌株B06和B07都被鉴定为解淀粉芽孢杆菌。【结论】芽孢细菌能够抑制多种植物病原真菌,具有较好的抑病作用。广谱和高效芽孢细菌的筛选在农业生物防治方面具有很大的开发和应用价值。     

Isolation of an antifungal Paenibacillus strain HT16 from locusts and purification of its medium-dependent antagonistic component

Aims:  To isolate an antagonist for use in the biological control of the phytopathogenic fungus Penicillium expansum and purify the antifungal component produced by the antagonist.
Methods and Results:  An antifungal strain HT16 was isolated from locusts, showing strong inhibition to Pen. expansum . Based on its in vitro effectiveness, HT16 was characterized as a strain of Paenibacillus polymyxa by phenotypic tests and 16S rDNA sequence analysis. It was found that the antifungal component HT16 secreted was only induced by Poria cocos sclerotium (PCS), and it remained active after sterilization at 121°C for 15 min. The protein was purified by ammonium sulfate precipitation, heating process, and ultrafiltration using a 10 kDa cut-off membrane. The molecular weight of the purified antifungal protein, which was determined by mass spectrometry, was 4517 Da.
Conclusions:  A novel bacterial strain HT16 antagonistic to Pen. expansum was isolated from locusts and identified as Pae. polymyxa . The antifungal protein of 4517 Da was purified, and its production needed the inducer PCS in the fermentation medium.
Significance and Impact of the Study:  The antagonistic protein from Pae. polymyxa showed strong antifungal activity against phytopathogenic fungus Pen. expansum . This strain HT16 and the antifungal metabolite are therefore strong candidates for the biocontrol of phytopathogens in agriculture.     

Biological properties of the wild rhizosphere strain Pseudomonas fluorescens 2137 and its derivatives marked with the gusA gene

The natural wild rhizosphere strain P. fluorescens 2137 was marked with the beta-glucuronidase gene gusA. The introduction of this gene influenced the viability of the wild strain, as well as its certain physiological parameters, such as cultural characteristics, biochemical properties, and antagonistic activity against the phytopathogenic fungi Fusarium culmorum, F. oxysporum, F. graminearum, and Verticillum nigrescens. The gusA-marked derivative strains that deviate the least from the wild strain in biological properties can be used to monitor populations of P. fluorescens 2137 cells in the plant rhizosphere.     

Isolation and characterization of a co-producer of fengycins and surfactins, endophytic Bacillus amyloliquefaciens ES-2, from Scutellaria baicalensis Georgi

An endophytic bacterium was isolated from Chinese medicinal plant Scutellaria baicalensis Georgi. The phylogenetic and physiological characzterization indicated that the isolate, strain ES-2, was Bacillus amyloliquefaciens, which produced two families of secondary metabolites with broad-spectrum antibacterial and antifungal activities. Culture filtrate of ES-2 displayed antagonism against some phytopathogenic, food-borne pathogenic and spoilage bacteria and fungi owing to the existence of antimicrobial compounds. A HPLC-MS analysis showed two series of ion peaks from the culture filtrate. A further electrospray ionization/collision-induced dissociation spectrum revealed that the two series ion peaks represented different fengycin homologues and surfactin homologues, respectively, which had a potential for food preservation and the control of several fungal plant diseases.     

Antimicrobial activity of Paenibacillus peoriae strain NRRL BD-62 against a broad spectrum of phytopathogenic bacteria and fungi

AIMS: To investigate the potential antagonistic activity of Paenibacillus peoriae strain NRRL BD-62 against phytopathogenic micro-organisms and to determine the physiological and biochemical characteristics of the antimicrobial compound produced by this strain. METHODS AND RESULTS: Strain NRRL BD-62 showed a broad inhibition spectrum with activity against various phytopathogenic bacteria and fungi. Physico-chemical characterization of the antimicrobial activity showed that it was stable during heat treatment and was retained even after autoclave at 121 degrees C for 10 min. The compound was also stable after the treatment with organic solvents, hydrolytic enzymes and its activity was preserved at a wide range of pH. The partial purification carried out by Sephadex G25 gel filtration showed two profiles of inhibition against the indicator strains tested, suggesting at least two different substances with distinct molecular weight. CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report on the production of antimicrobial substances in P. peoriae. Besides the antimicrobial inhibition capability, the strain NRRL BD-62 is also able to effectively fix molecular nitrogen, and produce chitinases and proteases as well, suggesting that further studies should be addressed to use P. peoriae strain NRRL BD-62 as a plant growth promoter and/or as a biocontrol agent in field experiments.     

Antimicrobial and antiviral activities of an actinomycete (Streptomyces sp.) isolated from a Brazilian tropical forest soil

A promising producer of bioactive compounds isolated from a Brazilian tropical soil was tested for its range of antimicrobial activities. Strain 606, classified as Streptomyces sp., could not be identified up to species level, suggesting a possible new taxon. The supernatant and 10 extracts and fractions, obtained by extraction and chromatographic techniques, presented antimicrobial activity using antibiograms. The methanolic fraction was highly active against pathogenic bacteria, phytopathogenic fungi and the human pathogenic yeast Candida albicans. It also possessed high antiviral activity inhibiting the propagation of an acyclovir-resistant herpes simplex virus type 1 strain on HEp-2 cells at non-cytotoxic concentration. The strong cytotoxic effect suggests an antitumour action. This revised version was published online in August 2006 with corrections to the Cover Date.     

Cyclosporine A from a nonpathogenic Fusarium oxysporum suppressing Sclerotinia sclerotiorum

AIMS: To evaluate the antagonistic activity of Fusarium oxysporum nonpathogenic fungal strain S6 against the phytopathogenic fungus Sclerotinia sclerotiorum and to identify the antifungal compounds involved. METHODS AND RESULTS: The antagonistic activity of Fusarium oxysporum strain S6 was determined in vitro by dual cultures. The metabolite responsible for the activity was isolated by chromatographic techniques, purified and identified by spectroscopic methods as cyclosporine A. The antifungal activity against the pathogen was correlated with the presence of this metabolite by a dilution assay and then quantified. Cyclosporine A caused both growth inhibition and suppression of sclerotia formation. In a greenhouse assay, a significant increase in the number of surviving soybean (Glycine max) plants was observed when S. sclerotiorum and F. oxysporum (S6) were inoculated together when compared with plants inoculated with S. sclerotiorum alone. CONCLUSION: Fusarium oxysporum (S6) may be a good fungal biological control agent for S. sclerotiorum and cyclosporine A is the responsible metabolite involved in its antagonistic activity in vitro. SIGNIFICANCE AND IMPACT OF THE STUDY: Cyclosporine A has not been previously described as an inhibitor of S. sclerotiorum. Its minimum inhibitory concentration (MIC) of 0.1 microg disc(-1) makes it suitable to use as a biofungicide. In vivo experiments showed that F. oxysporum (S6) is a good candidate for the biocontrol of S. sclerotiorum in soybean.     

Biocontrol of avocado dematophora root rot by antagonistic Pseudomonas fluorescens PCL1606 correlates with the production of 2-hexyl 5-propyl resorcinol

A collection of 905 bacterial isolates from the rhizospheres of healthy avocado trees was obtained and screened for antagonistic activity against Dematophora necatrix, the cause of avocado Dematophora root rot (also called white root rot). A set of eight strains was selected on the basis of growth inhibitory activity against D. necatrix and several other important soilborne phytopathogenic fungi. After typing of these strains, they were classified as belonging to Pseudomonas chlororaphis, Pseudomonas fluorescens, and Pseudomonas putida. The eight antagonistic Pseudomonas spp. were analyzed for their secretion of hydrogen cyanide, hydrolytic enzymes, and antifungal metabolites. P. chlororaphis strains produced the antibiotic phenazine-1-carboxylic acid and phenazine-1-carboxamide. Upon testing the biocontrol ability of these strains in a newly developed avocado-D. necatrix test system and in a tomato-F oxysporum test system, it became apparent that P. fluorescens PCL1606 exhibited the highest biocontrol ability. The major antifungal activity produced by strain P. fluorescens PCL1606 did not correspond to any of the major classes of antifungal antibiotics produced by Pseudomonas biocontrol strains. This compound was purified and subsequently identified as 2-hexyl 5-propyl resorcinol (HPR). To study the role of HPR in biocontrol activity, two Tn5 mutants of P. fluorescens PCL1606 impaired in antagonistic activity were selected. These mutants were shown to impair HRP production and showed a decrease in biocontrol activity. As far as we know, this is the first report of a Pseudomonas biocontrol strain that produces HPR in which the production of this compound correlates with its biocontrol activity.     

Endophytic Bacteria from Ocimum sanctum and Their Yield Enhancing Capabilities

Endophytes are beneficial microbes that reside intercellularly inside the plants. Interaction of endophytes with the host plants and their function within their host are important to address ecological relevance of endophyte. Four endophytic bacteria OS-9, OS-10, OS-11, and OS-12 were isolated from healthy leaves of Ocimum sanctum. These isolated microbes were screened in dual culture against various phytopathogenic fungi viz. Rhizoctonia solani, Sclerotium rolfsii, Fusarium solani, Alternaria solani, and Colletotrichum lindemuthianum. Of these, strain OS-9 was found to be antagonistic to R. solani, A. solani, F. solani, and C. lindemuthianum while OS-11 was found antagonistic against A. solani only. The growth-promoting benefits of the endophytes were initially evaluated in the glasshouse by inoculated seeds of O. sanctum. Treatment with endophytes OS-10 and OS-11 resulted in significant enhancement of growth as revealed by increase in fresh as well as dry weight. Further, field trials involving two genotypes OS Purple and CIM-Angana were conducted with strains OS-10 and OS-11. The growth-promoting effect was visible on both the genotypes tested as the endophytes significantly enhanced fresh herbage yield (t/ha). Interestingly, these endophytes increased the content of essential oil particularly in cultivar OS Purple and thereby increasing the total oil yields. Molecular characterization of strain OS-11 indicated the strain to be highly related to the type strain of Bacillus subtilis.     

人参内生细菌ge21菌株的鉴定及抑菌活性测定

从人参根内分离到一株细菌ge21,经形态特征观察、生理生化特性测定和16SrDNA序列分析,表明该菌株同已知菌Paenibacillus granivorans的相似性最高,为96.89%,初步认定为类芽孢杆菌属的一个潜在新种。抑菌试验结果表明,该菌株对尖孢镰刀菌(Fusarium oxysporium)、寄生疫霉菌(Phytophthora parasitica)、剑麻炭疽病菌(Colletotrichum agaves)、烟草赤星病菌(Alternaria longipes)、稻瘟病菌(Pyricularia oryzae)、人参立枯病菌(Rhizoctonia solani)、人参疫病菌(Phytophthora cactorum)和人参菌核病菌(Sclerotinia schinseng)均有一定的抑菌活性。     

Biological control of collar rot disease with broad-spectrum antifungal bacteria associated with groundnut

Bacteria associated with 6 habitats of groundnut were evaluated for their broad-spectrum antifungal activity and suppression of collar rot (Aspergillus niger) of groundnut. Three hundred and ninety-three strains were tested against 8 fungal pathogens of groundnut including 5 necrotrophic fungi, Aspergillus flavus, A. niger, Rhizoctonia bataticola, Rhizoctonia solani, and Sclerotium rolfsii, and 3 biotrophic fungi, Cercospora arachidicola, Phaeoisariopsis personata, and Puccinia arachidis. Pseudomonas sp. GRS 175, Pseudomonas aeruginosa GPS 21, GSE 18, GSE 19, and GSE 30, and their cell-free culture filtrates were highly antagonistic to all the test fungi. The cell-free culture filtrates of these bacteria were fungicidal and induced mycelial deformations including hyphal bulging and vacuolization in necrotrophic fungi. The cell-free culture filtrates at 10% (v/v) concentration significantly inhibited the spore germination of biotrophic fungi. In the greenhouse, P. aeruginosa GSE 18 emerged as an effective biocontrol agent of collar rot closely followed by P. aeruginosa GSE 19. The bacterium applied as a seed treatment reduced the pre-emergence rotting and postemergence wilting by > 60%. Pseudomonas aeruginosa GSE 18 effectively colonized the groundnut rhizosphere, both in native and in A. niger infested potting mixtures. Ninety-day-old peat formulation of P. aeruginosa GSE 18 had biocontrol ability comparable with the midlog-phase cells. Pseudomonas aeruginosa GSE 18, tolerant to thiram, in combination with the fungicide had an improved collar rot control. The present study was a successful attempt in selection of broad-spectrum and fungicide tolerant biocontrol agents that can be a useful component of integrated management of collar rot.     

Isolation, characterization and antifungal activity of Streptomyces sampsonii GS 1322

For new antifungal antibiotics from actinomycetes, a strain of Streptomyces GS 1322 was isolated from a sample of garden soil. The strain was found to possess antagonistic activity against four fungi i.e., Candida albicans, Aspergillus niger, Microsporum gypseum and Trichophyton sp. The strain was identified as Streptomyces sampsonii and the antifungal compound produced by it was found to be the heptaene group of polyene antibiotics.