Variety-Specific Actinomycete Complexes Associated with Barley Roots in Soddy Podzolic Soil

The root-colonizing actinomycete complexes of genotypically different barley plants grown in soddy podzolic soil were found to contain streptomycetes of the sections Cinereus (series Chromogenes, Achromogenes, and Aureus) and Roseus (series Fradiae), dominant being streptomycetes of the section Cinereus ser. Chromogenes. The abundance and diversity of soil streptomycetes in the barley rhizoplane increased in the order: var. 999-93 < var. Kumir < var. Novichok < var. 889-93. Experiments revealed functional specificity in the root-associated actinomycete complexes of different barley varieties. The actinomycete complex colonizing the barley var. 999-93 roots was distinguished by a wide range of utilizable root exudate metabolites and a low occurrence rate of antagonistic species.     

Competing Factors of Compost Concentration and Proximity to Root Affect the Distribution of Streptomycetes

Streptomycetes are important members of soil microbial communities and are particularly active in the degradation of recalcitrant macromolecules and have been implicated in biological control of plant disease. Using a streptomycetes-specific polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (PCR-DGGE) methodology coupled with band excision and sequence analysis, we examined the effect of grape marc compost amendment to soil on cucumber plant–associated streptomycetes community composition. We observed that both compost amendment and proximity to the root surface influenced the streptomycetes community composition. A strong root selection for a soil-derived Streptomycete, most closely related to Streptomyces thermotolerans, S. iakyrus, and S. thermocarboxydus, was independent of compost amendment rate. However, while the impact of compost amendment was mitigated with increasing proximity to the root, high levels of compost amendment resulted in the detection of compost-derived species on the root surface. Conversely, in rhizosphere and non-rhizosphere soils, the community composition of streptomycetes was affected strongly even by modest compost amendment. The application of a streptomycetes-specific PCR primer set combined with DGGE analysis provided a rapid means of examining the distribution and ecology of streptomycetes in soils and plant-associated environments.     

Isolation of Endophytic Actinomycetes From Roots and Leaves of Banana (Musa Acuminata) Plants and Their Activities Against Fusarium oxysporumf. sp. cubense

Two hundred and forty-two actinomycete strains were isolated from the interior of leaves and roots of healthy and wilting banana plants. Most of them were streptomycetes, Streptomyces griseorubiginosus-like strains were the most frequently isolated strains. Community analysis demonstrated increased actinomycete diversity in wilting leaves compared to that in healthy leaves, similar actinomycete communities were found in wilting and healthy roots. Screening of the isolates for antagonistic activity against Fusarium oxysporumf. sp. cubenserevealed that the proportion of antagonistic streptomycetes in healthy roots was higher than that in wilting roots (P < 0.01), but no difference was found between antagonistic strains isolated from healthy and wilting leaves. The potential biological control of Panama disease of banana by endophytic streptomycetes, especially Streptomyces griseorubiginosus-like strains was discussed.     

Experimental studies on the ecological role of antibiotic production in bacteria

Summary Genetically well-characterized strains of antibiotic-producing soil bacteria (Streptomyces griseus andStreptomyces coelicolor) were used to examine the ecological role of antibiotic production. Streptomycetes were competed against sensitive and resistantBacillus subtilis, another soil bacterium, on surface (agar) culture. The ecological role of antibiotics was examined in three levels of competition. (1) Capacity of antibiotics to allow invasion of producing organisms (B. subtilis established and streptomycetes added later). (2) Capacity of antibiotics to mediate competition between established populations (B. subtilis and streptomycetes co-inoculated). (3) Capacity of antibiotics to prevent invasion by competitors (streptomycetes established andB. subtilis added later). Antibiotic production was found to play a significant role in preventing the invasion of competitors in these experiments. Antibiotic production did not improve the ability of producers to invade a population of sensitive cells nor did it play a strong role in mediating competition between established populations. Antibiotic production also selected for antibiotic-resistant bacteria among invading competitors.     

WD-repeat protein encoding genes among prokaryotes of theStreptomyces genus

Southern hybridization with probes designed for detection of WD-repeats coding sequences gave positive results in 21 streptomycete strains indicating that WD-repeats encoding genes are massively spread among streptomycetes. One of them, thewdlA gene ofStreptomyces lincolnensis, codes for a 971 amino acid protein with seven WD-repeats in its C-terminus, two transmembrane domains and an ATP/GTP binding site upstream of the WD-repeat region.     

Biosystematic studies on novel streptomycetes from soil

Members of three putatively novel Streptomyces species, designated Streptomyces groups A, B and C, were repeatedly isolated from environmental samples taken from four hay meadow plots at Cockle Park Experimental Farm, Northumberland (UK). Representative isolates were found to have properties consistent with their classification in the genus Streptomyces and were recovered in three taxa using different phenotypic criteria, namely morphological and pigmentation properties, rapid enzyme tests, and whole-organism fatty acid, protein electrophoretic and pyrolysis mass-spectrometric data. The isolates were rapidly characterised as three taxonomic groups using pyrolysis mass spectrometry. The three taxa were also distinguished from one another and from validly described species of Streptomyces using rapid enzyme tests based on the fluorophores 7-amino-methylcoumarin and 4-methylumbelliferone, and computer-assisted identification procedures. The results indicate that selective isolation and rapid characterisation of streptomycetes using pyrolysis mass spectrometry provide a practical way of determining the phenotypic species diversity of streptomycetes in natural habitats. The experimental data also indicate that representative sampling of cultivable streptomycetes from soil can best be achieved using a multi-step extraction procedure coupled with the use of selective isolation procedures.     

Biosystematics of alkaliphilic streptomycetes isolated from seven locations across a beach and dune sand system

Alkaliphilic streptomycetes were isolated from composite sand samples collected from six out of seven locations across a beach and dune sand system using starch-casein-nitrate agar supplemented with cycloheximide and buffered to pH 10.5. The isolates had colonial and chemotaxonomic properties consistent with their classification in the genus Streptomyces. They were assigned to 49 multimembered and 114 single-membered colour-groups given their ability to produce pigments on oatmeal and peptone-yeast-extract-iron agars and to corresponding taxa based on whole-genome rep-PCR banding patterns. Twenty-four isolates representing the colour and rep-PCR groups grew well from pH 5 to 11, and optimally at pH 9, as did phylogenetically close members of the Streptomyces griseus 16S rRNA gene clade. One hundred and twelve representative alkaliphilic streptomycetes formed a heterogeneous but distinct clade in the Streptomyces 16S rRNA gene tree. A 3-dimensional representation of 16S rRNA sequence data showed that the alkaliphilic streptomycetes formed a distinct group in multidimensional taxospace. It is evident that alkaliphilic streptomycetes are common in the beach and dune sand system and that representatives of this community form new centers of taxonomic variation within the genus Streptomyces that can be equated with species. GenBank accession numbers for the 16S rRNA gene sequences for the strains of the alkaliphilic streptomycetes Bd 095, Bd 064, Bd 077, Bd 013, Bd 108, Bd 088, Bd 012, Bd 187, Bd 128, Bd 174, Bd 167, Lt 005, Lt 006, Fd 015, Bd 099, Bd 059, Bd 159, Ht 015, Md 005, Ht 020, Bd 205, Md 063, Fd 004, Md 039 and Bd 092 are EU477215, EU477216, EU477217, EU477218, EU477219, EU477220, EU477221, EU477222, EU477223, EU477224, EU477225, EU477226, EU477227, EU477228, EU477229, EU477230, EU477231, EU477232, EU477233, EU477234, EU477235, EU477236, EU477237, EU477238 and EU477257, respectively.     

链霉菌最新研究进展

链霉菌(streptomycetes)因其产生的抗生素广泛应用于医疗与制药领域而闻名,是放线菌门中最为庞大且极富物种多样性的分支。链霉菌经过多年来系统且深入的研究,在系统分类学、多样性以及天然产物资源勘探等领域都取得了巨大进展。本文综述了链霉菌3个主要方向的研究近况,阐述了目前研究面临的机遇与挑战,并对未来的研究工作进行了展望。     

Identification of glucose kinase‐dependent and ‐independent pathways for carbon control of primary metabolism,development and antibiotic production in Streptomyces coelicolor by quantitative proteomics

Members of the soil‐dwelling prokaryotic genus Streptomyces are indispensable for the recycling of complex polysaccharides, and produce a wide range of natural products. Nutrient availability is a major determinant for the switch to development and antibiotic production in streptomycetes. Carbon catabolite repression (CCR), a main signalling pathway underlying this phenomenon, was so far considered fully dependent on the glycolytic enzyme glucose kinase (Glk). Here we provide evidence of a novel Glk‐independent pathway in Streptomyces coelicolor, using advanced proteomics that allowed the comparison of the expression of some 2000 proteins, including virtually all enzymes for central metabolism. While CCR and inducer exclusion of enzymes for primary and secondary metabolism and precursor supply for natural products is mostly mediated via Glk, enzymes for the urea cycle, as well as for biosynthesis of the γ‐butyrolactone Scb1 and the responsive cryptic polyketide Cpk are subject to Glk‐independent CCR. Deletion of glkA led to strong downregulation of biosynthetic proteins for prodigionins and calcium‐dependent antibiotic (CDA) in mannitol‐grown cultures. Repression of bldB, bldN, and its target bldM may explain the poor development of S. coelicolor on solid‐grown cultures containing glucose. A new model for carbon catabolite repression in streptomycetes is presented.     

Resistance ofStreptomyces felleus to the herbicide bromoxynil

A soil strain ofStreptomyces felleus resistant to the herbicide bromoxynil (BX) and capable of supporting growth of sensitive streptomycetes on a BX-containing medium, was found to decrease the concentration of BX in the medium to one half after 10 d of incubation. Physicochemical methods showed that a co-metabolic process without any accumulation of the degradation products similar to BX was involved. Mutation experiments carried out with the strain suggest a nonchromasomal control of the resistance to BX.     

PCR Detection of Oxytetracycline Resistance Genes otr(A) and otr(B) in Tetracycline-Resistant Streptomycete Isolates from Diverse Habitats

A range of European habitats was screened by PCR for detection of the oxytetracycline resistance genes otr(A) and otr(B), found in the oxytetracycline-producing strain Streptomyces rimosus. Primers were developed to detect these otr genes in tetracycline-resistant (Tc^R) streptomycete isolates from environmental samples. Samples were obtained from bulk and rhizosphere soil, manure, activated sludge and seawater. The majority of Tc^R streptomycetes originated from bulk and rhizosphere soil. Fewer Tc^R streptomycetes were isolated from manure and seawater and none from sewage. By PCR, three out of 217 isolates were shown to contain the otr(A) gene and 13 out of 217 the otr(B) gene. Surprisingly, these genes were detected in taxonomic groups not known as tetracycline-producing strains. The majority of the otr gene–carrying strains was assigned to S. exfoliatus or S. rochei and originated from all habitats from which Tc^R streptomycetes were obtained. Our results indicated that the occurrence of otr(A) and otr(B) genes in natural environments was limited and that otr(B), in comparison to otr(A), seemed to be more common.     

Use of polyvalent phage for reduction of streptomycetes on soil dilution plates

D.I. KURTBÖKE, C.F. CHEN AND S.T. WILLIAMS. 1992. An isolation method was developed in which prior to inoculation soil suspensions were exposed to suspensions of polyvalent phage isolated to Streptomyces spp. The phage susceptibility of streptomycetes provided a selective means of reducing streptomycetes on isolation plates subsequent to inoculation, and this reduction was persistent after long incubation periods. The efficiency and applicability of the method developed were checked with different samples from a range of sources. The increased chances of development of other genera after the reduction of streptomycetes on soil dilution plates were assessed.     

Characteristics ofStreptomyces globisporus strain 0234A forming endospores in submerged cultures

Thermosensitive submerged endospores formed byStreptomyces globisporus 0234 and its natural variant A resembled those of thermoresistant actinomycetes not only in their morphology and ultrastructure, but also in the content of dipicolinic acid. The production of endospores containing this substance is unusual inStreptomyces while other features of the strain indicate relatedness to other streptomycetes. Chemotaxonomic analysis of variant A revealed the cell wall to be of chemotype I and fatty acid content typical ofStreptomyces. Most characteristics of surface cultures of variant A coincided with those of the original strain 0234 and its endosporeless variant B. Both the strain 0234 and its variants A and B produced identical antibiotics and pesticidal compounds.     

Isolation of Endophytic Actinomycetes from Different Cultivars of Tomato and their Activities Against Ralstonia solanacearum in Vitro

The populations of endophytic actinomycetes from healthy and wilting tomato plants (tomato cultivars resistant and susceptible to Ralstonia solanacearum) grown in three different sites from Guangzhou, Guangdong Province, South China were investigated by cultivation methods. Most of the isolates belonged to streptomycetes. The Aureus group of Streptomyces was the most frequently isolated group. The population composition of Streptomyces varied according to tomato cultivars, physiological status and soil types. The proportions of antagonistic Streptomyces strains from healthy plants were higher than that from wilting plants (P < 0.05), although the difference among the proportions of antagonistic Streptomyces strains from different cultivars of healthy tomato was not significant, the similar result was found from wilting plants. No significant difference was found in the proportions of siderophere-producing Streptomyces strains from the same site (P > 0.05), but the difference was found from the different sampling sites (P < 0.05). The percentage of bacterial cell wall-degrading streptomycetes from wilting tomato was higher than that from healthy plants (P < 0.05). These results indicated that the cultivar of the host plant, physiological status and sampling sites would influence the proportion of endophytic streptomycetes with different physiological traits. Diversity of endophytic Streptomyces and their physiological diversity should be involved in developing potential biocontrol agents.     

Effect of protein phosphorylation on the activity of RNA polymerase in streptomycetes

RNA polymerase was isolated fromStreptomyces granaticolor and protein kinase was partially purified fromStreptomyces albus. When RNA polymerase was treated with protein kinasein vitro the activity of RNA polymerase was markedly enhanced. Furthermore, a protein ofM=65 kDa was isolated which, after being phosphorylated, stimulated RNA polymerase activityin vitro. Because neither the β-subunits nor the α-subunits of RNA polymerase were phosphorylated it is assumed that phosphorylation of the 65 kDa protein may regulate the activity of RNA polymerase in streptomycetes.     

Use of polyvalent phage for reduction of streptomycetes on soil dilution plates.

An isolation method was developed in which prior to inoculation soil suspensions were exposed to suspensions of polyvalent phage isolated to Streptomyces spp. The phage susceptibility of streptomycetes provided a selective means of reducing streptomycetes on isolation plates subsequent to inoculation, and this reduction was persistent after long incubation periods. The efficiency and applicability of the method developed were checked with different samples from a range of sources. The increased chances of development of other genera after the reduction of streptomycetes on soil dilution plates were assessed.     

Recognition and degradation of chitin by streptomycetes

Chitin is the second most abundant renewable polysaccharide, as it is a component of the exoskeleton of many organisms and of the cell walls of numerous fungi. Most streptomycetes secrete a number of chitinases, hydrolyzing chitin to oligomers, chitobiose or N-acetylglucosamine which can be utilized as carbon or nitrogen source. The chitinases of several streptomycetes have been shown to have a modular arrangement comprising catalytic, substrate binding as well as linker domains. Moreover, during growth in the presence of chitin-containing substrates, many Streptomycesstrains have been shown to secrete formerly unknown, small (about 200 aa) chitin binding proteins (CHBs) which lack enzymatic activity and specifically target and invade chitin. Several motifs, including the relative location and spacing of four tryptophan residues, are conserved in the investigated CHB types, CHB1 and CHB2. The affinity of CHB1 to crab shell chitin is two times higher than that of CHB2. Comparative studies of various generated mutant CHB1 proteins led to the conclusion that it is one of the exposed tryptophan residues that directly contributes to the interaction with chitin. On the basis of immunological, biochemical and physiological studies, it can be concluded that the CHBs act like a glue with which streptomycetes target chitin-containing samples or organisms. The ecological implications of these findings are discussed.     

Expression of polyketide biosynthesis and regulatory genes in heterologous streptomycetes

Summary There are now several examples showing that hybrid secondary metabolites can be produced as a result of interspecies cloning of antibiotic biosynthesis genes in streptomycetes. This paper reviews examples of hybrid secondary metabolite production, and examines the underlying biochemical and regulatory principles leading to the formation of hybrid anthraquinones by recombinant anthracycline-producing streptomycetes carrying actinorhodin biosynthesis genes. An anthraquinone, aloesaponarin II, was produced by cloning theactI, actIII, actIV, andactVII genes (pANT12) of actinorhodin biosynthesis pathway fromStreptomyces coelicolor in anthracycline producing streptomycetes.Streptomyces galilaeus strains 31 133 and 31 671, aclacinomycin and 2-hydroxyaklavinone producers, respectively, formed aloesaponarin II as their major polyketide product when transformed with pANT12. Subcloning experiments indicated that a 2.8-kbXhoI fragment containing only theactI andactVII loci was necessary for aloesaponarin II biosynthesis byS. galilaeus 31 133. WhenS. galilaeus 31 671 was transformed with theactI, actVII, andactIV genes, however, the recombinant strain produced two novel anthraquinones, desoxyerythrolaccin and 1-0-methyldesoxyerythrolaccin. WhenS. galilaeus 31671 was transformed with only the intactactIII gene (pANT45), aklavinone was formed exclusively. These experiments indicate a function for theactIII gene, which is the reduction of the keto group at C-9 from the carboxyl terminus of the assembled polyketide to the corresponding secondary alcohol. The effects of three regulatory loci,dauG, dnrR1, andasaA, on the production of natural and hybrid polyketides were also shown.     

Anti-Fusarium activity of cyanobacteria and actinomycetes in soil and rhizosphere

The effect of cyanobacteria (Nostoc linckia, N. commune, and Microchaeta tenera) and streptomycetes on the pathogenic micromycete Fusarium was studied in laboratory simulation experiments. Interpopulational relationships in the rhizosphere of spring wheat (Triticum aestivum L.) and in soddy-podzolic soil were investigated.