Detection of Novel Secondary Metabolites

Franco, Christopher M. M.; Coutinho, Louis E. L.

doi:10.3109/07388559109069184

Cited by 38 publications

(19 citation statements)

References 561 publications

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“…In this case the advantage may take the form of a secondary metabolite produced by the endophyte, since actinobacteria are well known for their ability to produce a broad range of antibacterial, antifungal, and plant growth-regulatory metabolites (17). Further experiments to determine the role of these endophytes in the development of the host plant are ongoing in our laboratory (11).…”

Section: Discussionmentioning

confidence: 99%

Isolation and Identification of Actinobacteria from Surface-Sterilized Wheat Roots

Coombs

Franco

2003

Appl Environ Microbiol

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512

343

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This is the first report of filamentous actinobacteria isolated from surface-sterilized root tissues of healthy wheat plants (Triticum aestivum L.). Wheat roots from a range of sites across South Australia were used as the source material for the isolation of the endophytic actinobacteria. Roots were surface-sterilized by using ethanol and sodium hypochlorite prior to the isolation of the actinobacteria. Forty-nine of these isolates were identified by using 16S ribosomal DNA (rDNA) sequencing and found to belong to a small group of actinobacterial genera including Streptomyces, Microbispora, Micromonospora, and Nocardiodes spp. Many of the Streptomyces spp. were found to be similar, on the basis of their 16S rDNA gene sequence, to Streptomyces spp. that had been isolated from potato scabs. In particular, several isolates exhibited high 16S rDNA gene sequence homology to Streptomyces caviscabies and S. setonii. None of these isolates, nor the S. caviscabies and S. setonii type strains, were found to carry the nec1 pathogenicity-associated gene or to produce the toxin thaxtomin, indicating that they were nonpathogenic. These isolates were recovered from healthy plants over a range of geographically and temporally isolated sampling events and constitute an important plant-microbe interaction.The actinobacteria have been well characterized in the literature due to their economic importance as producers of two-thirds of the microbially derived antibiotics known today (6, 23). The actinobacteria are characterized by their grampositive nature and high guanine-plus-cytosine (GϩC) content in their genomes. Ecologically, actinobacteria and, particularly, the Streptomyces spp. are generally saprophytic, soil-dwelling organisms that spend the majority of their life cycles as semidormant spores (27). It has also been demonstrated that actinobacteria inhabit the rhizosphere of many plant species, including cereal crops such as wheat (13,15,30,37).Some actinobacteria are also known to form more intimate associations with plants and colonize their internal tissues. Within the order Actinomycetales there are examples of both endophytic and plant-pathogenic species. The best-characterized examples of the plant-pathogenic actinobacteria are the potato scab-causing Streptomyces scabies, S. acidiscabies, and S. turgidiscabies. Pathogenicity has been associated with the presence of a conserved and transmissible pathogenicity island (PAI) in their genomes (9, 21). This PAI encodes for the biosynthesis of a phytotoxin, thaxtomin, and also contains plant virulence factor genes such as nec1 (8,22,26). Actinorhizae (Frankia spp.) have been extensively researched as an endophytic association between a plant and an actinobacterium (for reviews, see references 3, 4, and 5). However, examples of actinobacteria other than Frankia inhabiting the root tissues of healthy plants as endophytes are rare. Sardi et al. (35) reported the presence of actinobacteria in root samples of crops and Italian native plants, with the majority of the isolates be...

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Section: Discussionmentioning

confidence: 99%

Isolation and Identification of Actinobacteria from Surface-Sterilized Wheat Roots

Coombs

Franco

2003

Appl Environ Microbiol

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512

343

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“…Actinobacteria are well known for their ability to produce a broad range of antibacterial, antifungal, and plant growth-regulatory metabolites VOL. 71, 2005 NON-FRANKIA ACTINOMYCETES FIX NITROGEN 465 (11).The ability to fix nitrogen by a select group of actinobacteria in addition to Frankia may be added to this list.…”

Section: Discussionmentioning

confidence: 99%

Non- Frankia Actinomycetes Isolated from Surface-Sterilized Roots of Casuarina equisetifolia Fix Nitrogen

Valdés¹,

Pérez²,

Santos

et al. 2005

Appl Environ Microbiol

115

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Based on partial 16S sequences, we previously described a novel group of nonsymbiotic, acetylene reduction activity-positive actinomycetes which were isolated from surface-sterilized roots of Casuarina equisetifolia growing in Mexico. An amplified rRNA restriction analysis confirmed that these actinomycetes are distinct from Frankia, a finding substantiated by a 16S rRNA gene phylogenetic analysis of two of the Mexican isolates. Further support for these actinomycetes being separate from Frankia comes from the very low DNA-DNA homology that was found. Nevertheless, the Mexican isolates may be diazotrophs based not only on their ability to grow in N-free medium and reduce acetylene to ethylene but also on the results from 15 N isotope dilution analysis and the finding that a nifH gene was PCR amplified. A comparison of the nifH sequences from the various isolates showed that they are closely related to nifH from Frankia; the similarity was 84 to 98% depending on the host specificity group. An analysis of complete 16S rRNA gene sequences demonstrated that the two strains analyzed in detail are most closely related to actinobacteria in the Thermomonosporaceae and the Micromonosporaceae.In the course of isolating Frankia from surface-sterilized root nodules of Casuarina equisetifolia growing in Mexico, additional filamentous bacteria were obtained (13). The filaments of these bacteria are smaller in diameter than Frankia hyphae, the filaments do not develop typical nitrogen-fixing diazovesicles ex planta under aerobic conditions, and the strains are unable to reinfect Casuarina or other tested actinorhizal plants upon reinoculation (20). In addition, of 24 fatty acids examined, only 7 were shared by Frankia and the Mexican isolates (17). Based on an analysis of a partial sequence of the 16S rRNA gene, we proposed that these bacteria lie outside of the Frankia clade (20).In this report, we examined the possibility that these nonFrankia Mexican actinomycetes have nitrogen-fixing genes based on their previously discovered abilities to reduce acetylene to ethylene, an indicator of nitrogenase activity, and to grow in N-free medium (13, 36). Nitrogenase, which catalyzes the reduction of dinitrogen to ammonia, is encoded by the genes of the nifHDK operon and is universally found in diazotrophs. Preliminary results with Southern blot analysis suggested that nifH-and nifD-like sequences were present in some of the Mexican isolates, but the bands weakly hybridized to a Klebsiella pneumoniae nifHD probe (unpublished results).Weak hybridization to DNA isolated from two Mexican strains (L4 and 7702B) was also observed when a Frankia CcI3 nifH probe was used (19).Because nif genes are conserved among a broad spectrum of bacteria, the use of universal primers has enabled the amplification and analysis of nifH sequences from very different microorganisms and environmental samples (21,38,40). However, when we used the universal degenerate primers Zf and Zr (39), the expected nifH gene products were not amplified. Instead, a PCR fra...

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“…The ft species were found to be the quinone form of the corresponding a components. The ft components are distinguished from the antibiotic naphthyridinomycin by the presence of a second oxazolidine ring in a region of the molecule [6] Staphylococcus hemolyticus [1 ] Streptococcus pyogenes [ 1] Streptococcus agalactiae [1] Streptococcus pneumoniae [ 1 ] Enterococcus faecalis VS [4] Enterococcus faecium VR [2] Bacillus cereus [1] analogous to quinocarcin (Fig. 4).…”

Section: Isolation and Structure Elucidationmentioning

confidence: 99%

Bioxalomycins, new antibiotics produced by the marine Streptomyces sp. LL-31F508. Taxonomy and fermentation.

Bernan¹,

Montenegro²,

Korshalla³

et al. 1994

J. Antibiot.

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An actinomycete strain designated LL-3 1F508 was isolated from an intertidal sediment sample collected in Key West, Florida. Culture LL-31F508 was assigned to the Streptomyces genus based on the presence of LL-diaminopimelic acid (DAP)in the cell wall and observations of spiny spores using scanning electron microscopy (SEM). Excellent antimicrobial activity against Staphyloccoccus and Enterococcusspp. weredetected in both the supernatant and cell extract samples from fermentations of culture LL-31F508. Production of antibiotic activity peaked at 48~50 hours and closely paralleled cell growth, during which time glucose was more rapidly assimilated than dextrin. A series of new antibiotics called the bioxalomycins was identified as the antibacterial products from fermentations of this culture. Fermentation conditions for production of bioxalomycin a differed substantially from those required for production of a related compound, naphthyridinomycin, by the reference culture Streptomyces lusitanus NRRL8034.

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Detection of Novel Secondary Metabolites

Cited by 38 publications

References 561 publications

Isolation and Identification of Actinobacteria from Surface-Sterilized Wheat Roots

Isolation and Identification of Actinobacteria from Surface-Sterilized Wheat Roots

Non- Frankia Actinomycetes Isolated from Surface-Sterilized Roots of Casuarina equisetifolia Fix Nitrogen

Bioxalomycins, new antibiotics produced by the marine Streptomyces sp. LL-31F508. Taxonomy and fermentation.

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