Alkaliphilic soil actinomycetes

The actinomycete complex of alkaline soils was found to be dominated by alkaliphilic streptomycetes, which showed maximal radial rates of colony growth at pH 8. At pH values of 7 and 10, the growth of these streptomycetes was poor. Alkaliphilic streptomycetes can be morphologically differentiated from other actinomycetes based on their high radial rates of colony growth and increased spore formation in alkaline media as compared to neutral media.     

Antagonistic activity of soil acidophilic actinomycetes

It has been shown that soil acidophilic actinomycetes (mycelial prokaryotes with a growth optinum between pH 3 and 7) markedly differ from neutrophilic actinomycetes in antimicrobial activity: the former are more active against fungi and yeasts, whereas the latter effectively suppress Gram-positive bacteria. Acidophilic streptomycetes actively inhibit the growth of phytopathogenic fungi, especially on acidic media.     

Acidophilic and thermophilic Bacillus strains from geothermally heated antarctic soil

From soil enrichment culture of quinoline-4-carboxylic acid-degrading bacterium was isolated. The organism was identified as Microbacterium sp. Mutants were induced with N-methyl-N'-nitro-N-nitrosoguanidine. One mutant accumulated successively two metabolites which were identified as 2-oxo-1,2-dihydro-quinoline-4-carboxylic acid and 8-hydroxy-2-oxo-2H-1-benzopyran-4-carboxylic acid.     

Population dynamics of oligosporous actinomycetes in Chernozem soil

Investigation of the dynamics of an oligosporous actinomycete population in chernozem soil in the course of succession induced by soil wetting allowed us to reveal the time intervals and conditions optimal for the isolation of particular oligosporous actinomycetes. Saccharopolysporas and microbisporas proved to be best isolated in the early and late stages of succession, whereas actinomycetes of the subgroup Actinomadura and saccharomonosporas could be best isolated in the early and intermediate stages of succession.     

Isolation and characterization of alachlor-degrading actinomycetes from soil

Alachlor (2-cloro-N-(methoxymethyl)-N-(2,6-diethylphenyl)-acetamide) is an extremely toxic and highly mobile herbicide that is widely used for pre-emergence control of grasses and weeds in many commercial crops in Brazil. In order to select soil actinomycetes able to degrade this herbicide, fifty-three actinomycete strains were isolated from soil treated with alachlor using selective conditions and subjected to in vitro degradation assays. Sixteen isolates were shown to be tolerant to high concentrations of the herbicide (up to 720 mg L^-1), and six of these were able to grow and degrade 50 alachlor (72 mg L^-1) in mineral salts medium. Morphological and phylogenetic analysis enabled the assignment of the alachlor-degrading strains to the genus Streptomyces. Strain LS151 was related to the type strains of Streptomyces capoamus/Streptomyces galbus, whereas strains LS143 and LS153 were related to Streptomyces bikiniensis. The remaining strains, LS166, LS177 and LS182, were similar in morphological features and recovered in a single cluster based on 16S rDNA sequence analysis, but shown to be distinct on the basis of genomic fingerprint data (rep-PCR). Though a definitive taxonomic assignment of alachlor-degrading strains was not possible, these data indicate that ability to degrade this pesticide was detected in different Streptomyces taxa.     

Feeding trials ofAphelenchus avenae on soil bacteria and actinomycetes

Summary Aphelenchus avenae and various unidentified bacteria and actinomycetes were cultured from soil samples taken from a pine-forest and a wheat-field. The nematode failed to reproduce in significant numbers on cultures of these micro-organisms and was apparently unable to utilize them as food sources.     

Selective isolation of actinomycetes of the genus Actinomadura from soil

Some approaches to the selective isolation of actinomycetes of the genus Actinomadura from soil are described. The approach that involves thermal treatment of soil samples and their plating onto Gauze 1 medium with the antibiotics nystatin, nalidixic acid, and rubomycin provides for an increased amount of actinomaduras isolated from the soil actinomycete complex and for a decreased amount of streptomycetes.     

Acidophilic Soil Actinomycetes

A clear-cut dependence of the distribution of acidophilic actinomycetes on the pH value of soil was established. Acidophilic actinomycetes were found to be present in soils whose pH does not exceed 6.8 (acid forest soils, lowland peaty soil, and ordinary chernozem) and not in slightly alkaline soils (chestnut sodic and alluvial meadow soils). In acid lowland peaty soil, the species diversity of acidophilic streptomycetes was lesser than the species diversity of streptomycetes revealed in the same soil by using neutral medium.     

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.     

Isolation of actinomycetes from soil using extremely high frequency radiation

A new method employing extremely high frequencies (EHFs) is proposed for the selective isolation of actinomycetes from soil. The pretreatment of soil suspensions with EHF wavelengths of 5.6 and 7.1 mm led to a nonselective isolation of actinomycetes. At the same time, the irradiation of soil suspensions within wavelength bands of 3.8-5.8 and 8-11.5 mm considerably augmented the total number of isolated actinomycetes and increased the fraction of the isolated rare genera by 2 and 7 times, respectively. The rare actinomycete genera were represented by Actinomadura, Microtetraspora, Nonomuraea, Micromonospora, Amycolatopsis, Pseudonocardia, Saccharotrix, and Streptosporangium.     

Influence of agricultural crops on the actinomycetes flora in soil

Summary The influence of various crops on the actinomycetes flora was studied in different soil types. The influence of soil types on the numbers and species appeared to be more important than that of the crop grown. However, the crop did influence the actinomycetes, especially in the newly reclaimed soil of Oostelijk Flevoland. There it was found that were sugar beets had been grown the number of actinomycetes decreased; this was especially the case with the frequency of Streptomyces scabies. The actinomycetes flora of the rhizoplane differs from that of rhizosphere.     

土壤放线菌分离方法的初步研究

本文对土壤放线菌的一种新分离技术进行了研究。结果表明,用加有氟哌酸、青霉素、制霉菌素的培养基,可以选择性地从土壤中分离放线菌,０．０５％ＳＤＳ（十二烷基碘酸钠）在４０℃自理土壤样品,可以促进放线菌的孢子萌发而获得更多的放线菌株,进一步提高放线菌的分离效果。     

Fossilization of Acidophilic Microorganisms

This study examines fossil microorganisms found in iron-rich deposits in an extreme acidic environment, the Tinto River in SW Spain. Both electron microscopy (SEM and TEM) and non-destructive in situ microanalytical techniques (EDS, EMP and XPS) were used to determine the role of permineralization and encrustation in preserving microorganisms forming biofilms in the sediments. Unicellular algae were preserved by silica permineralization of their cell walls. Bacterial biofilms were preserved as molds by epicellular deposition of schwertmannite around them. In the case of fungi and filamentous algae, we observed permineralization of cell structures by schwertmannite in the sediments. The extracellular polymeric matrix around the cells was also preserved through permineralization of the fibrillar component. The process of permineralization and deposition of iron-rich precipitates present in the acidic waters of Rio Tinto served to preserve many microfossils in an oxidizing environment, in which organic compounds would not normally be expected to persist. Studies of microbial fossil formation mechanisms in modern extreme environments should focus on defining criteria to identify inorganic traces of microbial life in past environments on Earth or other planets.     

Antagonistic and plant growth promoting activities of endophytic and soil actinomycetes

The objective of this study was the isolation and screening of actinomycete isolates for antagonistic potential and plant growth promoting activities. A total of 321 isolates were recovered from different plants, their rhizospheric soils and non-rhizospheric soils of Punjab and Himachal Pradesh regions. Out of these, 62 were endophytic, 156 were rhizospheric and 103 were non-rhizospheric isolates. In primary screening (dual culture assay), 83 isolates antagonised one or more test phytopathogenic fungi. From these active isolates, 20 were found to be antagonistic in well diffusion assay (secondary screening) and most of them demonstrated broad spectrum inhibitory activity against five to six test fungi. Studies on plant growth promoting activities revealed that 12 showed abilities to produce indole acetic acid, 10 produced siderophores and 12 showed ammonia production. Phosphate solubilisation was observed in five isolates and four fixed atmospheric N₂. In addition, production of hydrolytic enzymes such as chitinase, amylase, cellulase and protease was demonstrated by five, twenty, eleven and eleven isolates, respectively. The results of this study indicate that these isolates may be used as biocontrol and plant growth promoting agents. Morphological and chemotaxonomic studies revealed that all the active isolates belonged to the genus Streptomyces     

Use of membrane filters for selective isolation of actinomycetes from soil

Abstract A method using membrane filters of appropriate pore size, to selectively isolate actinomycetes from a mixed population of soil microorganisms, is described.
The method is based on the ability of actinomycetes to propagate and pass through the pores of filters while bacteria and fungi are retained on the membrane surface.     

A new method for the selective isolation of actinomycetes from soil

Summary A coal-vitamin medium was developed to isolate actinomycetes from soil, which was superior to other currently used media. It increased the number of actinomycetes and inhibited the growth of other soil bacteria. The pretreatment of soil suspension with peptone (6%) and lauryl sulfate (0.05%) at 50°C for 10 min, also greatly increased the number of actinomycetes from soil prior to incubation with new medium.