RESUMEN
What do you do when your food is too big to chew, or worse, when you don't have a stomach at all? Richards and Talbot explain how osmotrophs get around the problem by digesting on the outside.
Asunto(s)
Hongos/fisiología , Oomicetos/fisiología , Streptomycetaceae/fisiología , Ingestión de Alimentos , Conducta Alimentaria , Interacciones Microbianas/fisiologíaRESUMEN
Streptomycetes, soil-dwelling mycelial bacteria, can form biofilms as indigenous components of the environment. The biofilms formed by streptomycetes exist in different ecological niches, in natural, medical, industrial environments. The biofilm-forming streptomycetes affect water quality, human health, associate with deterioration of artworks and historical monuments. The review should be of interest for researchers of the biofilm mode of streptomycetes growth.
Asunto(s)
Biopelículas/crecimiento & desarrollo , Streptomycetaceae/fisiología , Animales , HumanosRESUMEN
Streptomycetes or mycelial microorganisms are able to form biofilms under the natural, industrial and clinical conditions. The controlled use of biofilms in various industrial processes is much more efficient vs. the cultivation of plankton suspended cells. Optimization of biotechnological processes with the use of streptomycete biofilms is advisable in production of lactic acid and detoxication of the liquor in pyrolysis of plant biomass. Streptomycete biofilms are used in water purification systems. It is recommended to use biofilms for detoxication of wastes and bioremediation of soils contaminated with hard metals. The use of biofilms of streptomycetes producing biologically active substances is of special interest. High yields of.antibiotics and actinomycin D in particular was observed with. cultivation of antibioc-producing streptomycetes as biofilms in bioreactors of unique design.
Asunto(s)
Biopelículas , Biotecnología/métodos , Streptomycetaceae/fisiología , Purificación del Agua/métodos , Biodegradación Ambiental , BiomasaRESUMEN
Soil bacteria produce a diverse array of antibiotics, yet our understanding of the specific roles of antibiotics in the ecological and evolutionary dynamics of microbial interactions in natural habitats remains limited. Here, we show a significant role for antibiotics in mediating antagonistic interactions and nutrient competition among locally coexisting Streptomycete populations from soil. We found that antibiotic inhibition is significantly more intense among sympatric than allopatric Streptomycete populations, indicating local selection for inhibitory phenotypes. For sympatric but not allopatric populations, antibiotic inhibition is significantly positively correlated with niche overlap, indicating that inhibition is targeted toward bacteria that pose the greatest competitive threat. Our results support the hypothesis that antibiotics serve as weapons in mediating local microbial interactions in soil and suggest that coevolutionary niche displacement may reduce the likelihood of an antibiotic arms race. Further insight into the diverse roles of antibiotics in microbial ecology and evolution has significant implications for understanding the persistence of antibiotic inhibitory and resistance phenotypes in environmental microbes, optimizing antibiotic drug discovery and developing strategies for managing microbial coevolutionary dynamics to enhance inhibitory phenotypes.
Asunto(s)
Antibiosis , Evolución Biológica , Ecosistema , Microbiología del Suelo , Streptomycetaceae/fisiología , Antibacterianos/farmacología , Fenotipo , Streptomycetaceae/efectos de los fármacosRESUMEN
In the era when large whole genome bacterial datasets are generated routinely, rapid and accurate molecular systematics is becoming increasingly important. However, 16S ribosomal RNA sequencing does not always offer sufficient resolution to discriminate between closely related genera. The SsgA-like proteins are developmental regulatory proteins in sporulating actinomycetes, whereby SsgB actively recruits FtsZ during sporulation-specific cell division. Here, we present a novel method to classify actinomycetes, based on the extraordinary way the SsgA and SsgB proteins are conserved. The almost complete conservation of the SsgB amino acid (aa) sequence between members of the same genus and its high divergence between even closely related genera provides high-quality data for the classification of morphologically complex actinomycetes. Our analysis validates Kitasatospora as a sister genus to Streptomyces in the family Streptomycetaceae and suggests that Micromonospora, Salinispora and Verrucosispora may represent different clades of the same genus. It is also apparent that the aa sequence of SsgA is an accurate determinant for the ability of streptomycetes to produce submerged spores, dividing the phylogenetic tree of streptomycetes into liquid-culture sporulation and no liquid-culture sporulation branches. A new phylogenetic tree of industrially relevant actinomycetes is presented and compared with that based on 16S rRNA sequences.
Asunto(s)
Actinobacteria/clasificación , Proteínas Bacterianas/química , Proteínas Bacterianas/metabolismo , Actinobacteria/genética , Actinobacteria/fisiología , Secuencia de Aminoácidos , Proteínas Bacterianas/clasificación , Proteínas Bacterianas/genética , Evolución Molecular , Microbiología Industrial , Micromonospora/clasificación , Micromonospora/genética , Micromonospora/fisiología , Datos de Secuencia Molecular , Filogenia , ARN Ribosómico 16S/genética , Alineación de Secuencia , Homología de Secuencia de Aminoácido , Esporas Bacterianas/fisiología , Streptomycetaceae/clasificación , Streptomycetaceae/genética , Streptomycetaceae/fisiologíaRESUMEN
Among natural factors that permanently influence on the plants, the soil microorganisms play a special role for the growing of plants as habitants of their rhizosphere. Mainly they are the representatives of actinomycetes genus Streptomyces and fungal genus Penicillium and their metabolic products stimulate plant growth and inhibit the growth of pathogenic fungi and bacteria. The aim of our study was to determine the antagonism of actinomycetes and micromycetes isolated from soils of R. Moldova against the fungal pathogens of agricultural plants. The strains were isolated from 5 types of chernozem (black soil) from central zone of R. Moldova, with different concentration of humus. Most of micromycetes and streptomycetes were isolated from soil sample 1 (monoculture of maize) and soil sample 2 (Poltava road border) with similar humus content (2.4-2.6%). The antifungal activity of micromycetes strains was occurring mostly against Fusarium solani and Thelaviopsis basicola, at streptomycetes against Alternaria alternata and Botrytis cinerea. It was revealed the strains completely inhibit the growth of Alt. alternata (streptomycetes strains 23, 33, 37), B. cinerea (Streptomyces sp. 17), and F. solani (Penicillium sp. 104). Our results allow to consider the actinomycetes Streptomyces sp.9, Streptomyces sp. 12, Streptomyces sp. 17, Streptomyces sp. 37 Streptomyces sp. 66 and micromycetes Penicillium sp. 5, Penicillium sp. 65, Penicillium sp. 104 isolated from soils of R. Moldova, as prospective strains-antagonists against the phytopathogenic fungus, the causative agents of agricultural plants deseasis.
Asunto(s)
Hongos/fisiología , Penicillium/fisiología , Enfermedades de las Plantas/microbiología , Streptomycetaceae/fisiología , Control Biológico de Vectores , Microbiología del SueloRESUMEN
A polyphasic study was undertaken to establish the taxonomic positions of two isolates, SK15(T) and SK60(T), from soil samples that were found to have morphological and chemical properties consistent with Kitasatospora strains. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that strains SK15(T) and SK60(T) form novel evolutionary lineages within the radiation of the genus Kitasatospora and share the highest 16S rRNA gene sequences similarities with their closest relatives, Kitasatospora setae IAM 15325(T) (97.8%) and Kitasatospora mediocidica IAM 15162(T )(97.5%), respectively. However, the results of DNA-DNA hybridization experiment and phenotypic data demonstrated that strains SK15(T) and SK60(T) are distinct from their closest phylogenetic neighbors and other Kitasatospora species. For chemotaxonomic characteristics, the cell-wall peptidoglycan of strains contained both meso- and LL-diaminopimelic acids as the diamino acids, the predominant quinone system was MK-9(H(6)) and MK-9(H(8)), whole-cell hydrolysates were rich in galactose, mannose and ribose, and the major fatty acids were C(16:0), anteiso-C(15:0), iso-C(15:0) and iso-C(16:0). On the basis of both phenotypic and phylogenetic evidence, strains SK15(T) and SK60(T) were assigned to represent two novel species of the genus Kitasatospora, for which the names Kitasatospora saccharophila sp. nov. (type strain SK15(T)=JCM 14559(T)=KCTC 19566(T)) and Kitasatospora kazusanensis sp. nov. (type strain SK60(T)=JCM 14560(T)=KCTC 19565(T)) are proposed. It is also proposed that Streptomyces atroaurantiacus should be transferred to the genus Kitasatospora as Kitasatospora atroaurantiaca comb. nov. (type strain NBRC 14327(T)=DSM 41649(T)).
Asunto(s)
Microbiología del Suelo , Streptomyces/clasificación , Streptomycetaceae/clasificación , Técnicas de Tipificación Bacteriana , ADN Bacteriano/análisis , ADN Ribosómico/análisis , Japón , Datos de Secuencia Molecular , Hibridación de Ácido Nucleico , Fenotipo , Filogenia , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADN , Especificidad de la Especie , Streptomyces/genética , Streptomycetaceae/genética , Streptomycetaceae/aislamiento & purificación , Streptomycetaceae/fisiologíaRESUMEN
OBJECTIVE: Acidophilic filamentous acitnomycetes are active in the turnover of organic matter in acid litters and soils, and are a source of antifungal antibiotics and acid-stable enzymes. The aim of this study is to delineate the diversity of neutrotolerant acidophilic streptomycetes in acidic soil environment, and to investigate the resources of species. METHODS: 367 actinomycetes with cultural characteristics of streptomycetes were isolated from 14 acidic soil samples collected in Yunnan Province, China, using the method of DDC (dispersion and differential centrifugation) and a selective medium. The isolates were color grouped on the basis of their properties of aerial mycelium, substrate mycelium and diffusible pigments. 97 representative isolates were picked from the color groups for micromorphological observation and for the test of pH range for growth. Among the neutrotolerant acidophilic streptomycetes, 16 representatives were further selected and were subjected to a molecular systematic study based on almost complete 16S rRNA gene sequences and DNA-DNA relatedness. RESULTS: The isolates were assigned to 12 color groups, and 80% of them were neutrotolerant acidophilic streptomycetes. The 16 representative strains formed eight distinct subclades within the genus of Streptomyces, and probably represented at least eight new genotypic species of Streptomyces. CONCLUSION: The neutrotolerant acidophilic streptomycetes isolated in this study were placed in eight distinct evolutionary groups, indicating the good diversity and novelty of these microorganisms in acidic soils in Yunnan Province.
Asunto(s)
Biodiversidad , Microbiología del Suelo , Streptomycetaceae/aislamiento & purificación , Streptomycetaceae/fisiología , China , Genotipo , Concentración de Iones de Hidrógeno , Microscopía Electrónica , Filogenia , Pigmentación , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADN , Streptomycetaceae/genética , Streptomycetaceae/ultraestructura , TemperaturaRESUMEN
For soil-dwelling bacteria that usually live in a carbon-rich and nitrogen-poor environment, the ability to utilize chitin - the second most abundant polysaccharide on earth - is a decisive evolving advantage as it is a source for both elements. Streptomycetes are high-GC Gram-positive soil bacteria that are equipped with a broad arsenal of chitinase-degrading genes. These genes are induced when the streptomycetes sense the presence of chitooligosaccharides. Their expression is repressed as soon as more readily assimilated carbon sources become available. This includes for example glucose or N-acetylglucosamine, the monomer subunit of chitin. Historically, the first cis-acting elements involved in carbon regulation in streptomycetes were found more than a decade ago upstream of chitinase genes, but the transcriptional regulator had so far remained undiscovered. In this work, we show that these cis-acting elements consist of inverted repeats with multiple occurrences and are bound by the HutC/GntR type regulator DasR. We have therefore designated these sites as DasR-responsive elements (dre). DasR, which is also the repressor of the genes for the N-acetylglucosamine-specific phosphotransferase transport system, should therefore play a critical role in sensing the balance between the monomeric and polymeric forms of N-acetylglucosamine.
Asunto(s)
Proteínas Bacterianas/fisiología , Quitina/metabolismo , Quitinasas/fisiología , Streptomycetaceae/fisiología , Proteínas Bacterianas/genética , Secuencia de Bases , Quitinasas/genética , Secuencia de Consenso , Regulación Bacteriana de la Expresión Génica , Elementos de Respuesta , Streptomycetaceae/genéticaRESUMEN
A total of 131 endophytic actinomycete strains were successfully isolated from surface-sterilized banana roots. These isolates belonged to Streptomyces (n=99), Streptoverticillium (n=28), and Streptosporangium (n=2) spp. The remaining 2 isolates were not identified. About 18.3% of the isolates inhibited the growth of pathogenic Fusarium oxysporum f. sp. cubense on banana tissue extract medium. The most frequently isolated Streptomyces sp. strain S96 was similar to Streptomyces griseorubiginosus. About 37.5% of the S. griseorubiginosus strains were antagonistic to F. oxysporum f. sp. cubense. The antagonism of strain S96 was lost when FeCl(3) was introduced into the inhibition zone. In vivo biocontrol assays showed that the disease severity index (DSI) was significantly (P=0.05) reduced and mean fresh weight increased (P=0.001) in plantlets treated with strain S96 compared to those grown in the absence of the biocontrol strain. These findings indicate the potential of developing siderophore-producing Streptomyces endophytes for the biological control of fusarium wilt disease of banana.
Asunto(s)
Fusarium/crecimiento & desarrollo , Musa/microbiología , Raíces de Plantas/microbiología , Streptomycetaceae/aislamiento & purificación , Antibiosis , China , Cloruros , Compuestos Férricos/metabolismo , Control Biológico de Vectores/métodos , Enfermedades de las Plantas/microbiología , Sideróforos/fisiología , Streptomycetaceae/clasificación , Streptomycetaceae/fisiologíaRESUMEN
The taxonomic position of a rhizosphere isolate, strain 52108a(T), was determined using a polyphasic approach. The strain was found to have chemical and morphological properties consistent with its assignment to the genus Kitasatospora. An almost complete 16S rRNA gene sequence determined for the strain was aligned with corresponding sequences of representatives of the genus Kitasatospora and related taxa using three tree-making algorithms. The organism formed a distinct phyletic line within the Kitasatospora clade and was most closely related to Kitasatospora arboriphila (98.9 %), Kitasatospora kifunensis (99.0 %), Kitasatospora paracochleata (98.4 %) and Kitasatospora terrestris (98.2 %), but was readily distinguished from representatives of these species using a combination of phenotypic properties. The combined genotypic and phenotypic data show that the strain should be classified in the genus Kitasatospora as a novel species. The name proposed is Kitasatospora viridis sp. nov., with the type strain 52108a(T) (=AS 4.1878(T)=DSM 44826(T)).
Asunto(s)
Camellia/microbiología , Raíces de Plantas/microbiología , Microbiología del Suelo , Streptomycetaceae/clasificación , China , ADN Bacteriano/análisis , ADN Ribosómico/análisis , Genes de ARNr , Genotipo , Datos de Secuencia Molecular , Fenotipo , Filogenia , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADN , Streptomycetaceae/genética , Streptomycetaceae/aislamiento & purificación , Streptomycetaceae/fisiologíaRESUMEN
A polyphasic study was carried out to establish the taxonomic positions of six strains isolated from diverse soil samples and provisionally assigned to the genus Kitasatospora. The isolates were found to have chemical and morphological properties consistent with their classification as Kitasatospora strains. Direct 16S rRNA gene sequence data confirmed the taxonomic position of the strains following the generation of phylogenetic trees by using three tree-making algorithms. Five of the isolates were considered to merit species status using complementary genotypic and phenotypic data. These organisms were designated Kitasatospora arboriphila sp. nov. (HKI 0189(T)=2291-120(T)=DSM 44785(T)=NCIMB 13973(T)), Kitasatospora gansuensis sp. nov. (HKI 0314(T)=2050-015(T)=DSM 44786(T)=NCIMB 13974(T)), Kitasatospora nipponensis sp. nov. (HKI 0315(T)=2148-013(T)=DSM 44787(T)=NCIMB 13975(T)), Kitasatospora paranensis sp. nov. (HKI 0190(T)=2292-041(T)=DSM 44788(T)=NCIMB 13976(T)) and Kitasatospora terrestris sp. nov. (HKI 0186(T)=2293-012(T)=DSM 44789(T)=NCIMB 13977(T)). The remaining organism, isolate HKI 0316 (=2122-022=DSM 44790=NCIMB 13978), was considered to be a strain of Kitasatospora kifunensis on the basis of 16S rRNA gene sequence, DNA-DNA relatedness and phenotypic data.
Asunto(s)
Microbiología del Suelo , Streptomycetaceae/clasificación , Streptomycetaceae/aislamiento & purificación , Antibacterianos/farmacología , Técnicas de Tipificación Bacteriana , ADN Bacteriano/química , ADN Bacteriano/aislamiento & purificación , ADN Ribosómico/química , ADN Ribosómico/aislamiento & purificación , Ácidos Grasos/análisis , Ácidos Grasos/aislamiento & purificación , Genes de ARNr/genética , Concentración de Iones de Hidrógeno , Japón , Microscopía Electrónica , Datos de Secuencia Molecular , Filogenia , ARN Bacteriano/genética , ARN Ribosómico 16S/genética , Solución Salina Hipertónica , Análisis de Secuencia de ADN , Streptomycetaceae/citología , Streptomycetaceae/fisiología , TemperaturaRESUMEN
Although antibiotic production may contribute significantly to microbial fitness, there is limited information on the ecology of antibiotic-producing microbial populations in soil. Indeed, quantitative information on the variation in frequency and intensity of specific antibiotic inhibitory and resistance abilities within soil microbial communities is lacking. Among the streptomycetes, antibiotic production is highly variable and resistance to antibiotics is highly specific to individual microbial strains. The objective of this work was to genetically and phenotypically characterize a reference collection of streptomycetes for use in distinguishing inhibition and resistance phenotypes of field-collected microbes. Specifically, we examined inhibition and resistance abilities of all isolates in all possible pairwise combinations, genetic relatedness using BOX-PCR and 16S rDNA sequence analyses, nutrient utilization profiles, and antibiotic induction among all possible three-way combinations of isolates. Each streptomycete isolate possessed a unique set of phenotypic and genetic characteristics. However, there was little correspondence between phenotypic and genetic traits. This collection of reference isolates provides the potential for distinguishing 1024 inhibition and resistance phenotypes in field-collected microbes. Relationships between the genetic and phenotypic characteristics examined may provide preliminary insight into the distinct strategies that microbes use in optimizing their fitness in natural environments.
Asunto(s)
Antibacterianos/farmacología , Antibiosis , Farmacorresistencia Bacteriana , Streptomycetaceae/genética , Streptomycetaceae/fisiología , Antibacterianos/biosíntesis , Técnicas de Tipificación Bacteriana , Análisis por Conglomerados , Dermatoglifia del ADN , ADN Bacteriano/química , ADN Bacteriano/aislamiento & purificación , ADN Ribosómico/química , ADN Ribosómico/aislamiento & purificación , Genes de ARNr/genética , Genotipo , Pruebas de Sensibilidad Microbiana , Datos de Secuencia Molecular , Fenotipo , Filogenia , Reacción en Cadena de la Polimerasa , Polimorfismo Genético , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADN , Microbiología del Suelo , Streptomycetaceae/efectos de los fármacos , Streptomycetaceae/aislamiento & purificaciónRESUMEN
Ninety-three wild-type isolates identified as actinomycetes were tested against 11 organochlorine pesticides (OPs): aldrin, chlordane, DDD, DDE, DDT, dieldrin, heptachlor, and heptachlor epoxides, lindane, and methoxychlor. Qualitative screening agar assays displayed 62-78% tolerance of strains to OPs. Four strains designed M4, M7, M9 and M15 were selected based on multi-OP-tolerance, and identified as members of the streptomycetes group. Different growth profiles were observed in cultures of the four selected streptomycetes cultured in synthetic medium containing 5-50 microg x l(-1) aldrin or chlordane or lindane. Increase of aldrin removal by the selected microorganisms was concomitant with the 4.8-36.0 microg x l(-1) pesticide concentration range. After 72 h of streptomycete M7 growth in synthetic medium containing 48.0 microg x l(-1) aldrin, the remaining OP concentration in the supernatant was approximately 10% of the initial concentration. Also, in stationary growth phase less than 2.5 microg x l(-1) aldrin residual concentration was detected in the medium.
Asunto(s)
Hidrocarburos Clorados , Insecticidas/metabolismo , Streptomycetaceae/fisiología , Purificación del Agua/métodos , Biodegradación Ambiental , Streptomycetaceae/aislamiento & purificaciónRESUMEN
Five actinomycete strains, SK-3255T, SK-3406T, SK-3412, SK-3421 and OM-5023, were isolated using a novobiocin-containing agar medium from soil samples. These strains produced long spore chains on aerial mycelium and contained LL- and meso-diaminopimelic acids (DAPs) in the cell wall. On the basis of morphological and chemotaxonomic characteristics and phylogenetic analysis, these five strains were classified into the genus Kitasatospora. DNA-DNA hybridization and comparison of physiological characteristics revealed that strains SK-3255T and SK-3406T differed from known species. Strains SK-3406T, SK-3412 and SK-3421 were regarded as the same species. Strain OM-5023 was identified as Kitasatospora griseola. Therefore, two novel species are proposed, Kitasatospora cineracea sp. nov. and Kitasatospora niigatensis sp. nov., with the type strains K. cineracea SK-3255T (= IFO 16452T = JCM 10915T = NRRL B-23134T) and K. niigatensis SK-3406T (= IFO 16453T = JCM 10916T = NRRL B-24135T).
Asunto(s)
ARN Ribosómico 16S/genética , Análisis de Secuencia de ADN , Microbiología del Suelo , Streptomycetaceae/clasificación , Streptomycetaceae/aislamiento & purificación , Pared Celular/química , ADN Ribosómico/análisis , Ácido Diaminopimélico/análisis , Datos de Secuencia Molecular , Hibridación de Ácido Nucleico , Filogenia , Streptomycetaceae/genética , Streptomycetaceae/fisiología , Streptomycetaceae/ultraestructuraRESUMEN
A strain of Streptoverticillium cinnamoneum produced a peptide antibiotic named lanthiopeptin, which contained four unusual amino acids, erythro-beta-hydroxyaspartic acid, mesolanthionine, threo-beta-methyllanthionine and lysinoalanine. Lanthiopeptin showed antiviral activity against herpes simplex virus type 1 KOS strain infection in Vero cells by cytopathic effect reduction assay. The structure of lanthiopeptin is similar to that of ancovenin.
Asunto(s)
Antibacterianos , Antibacterianos/aislamiento & purificación , Antivirales/aislamiento & purificación , Péptidos/aislamiento & purificación , Simplexvirus/efectos de los fármacos , Streptomycetaceae/metabolismo , Secuencia de Aminoácidos , Aminoácidos/análisis , Animales , Antibacterianos/análisis , Antibacterianos/biosíntesis , Antibacterianos/farmacología , Antifúngicos/análisis , Antifúngicos/biosíntesis , Antifúngicos/aislamiento & purificación , Antifúngicos/farmacología , Antivirales/análisis , Antivirales/biosíntesis , Antivirales/farmacología , Bacterias/efectos de los fármacos , Cromatografía en Gel , Efecto Citopatogénico Viral/efectos de los fármacos , Fermentación , Espectroscopía de Resonancia Magnética , Datos de Secuencia Molecular , Biosíntesis de Péptidos , Péptidos/análisis , Péptidos/farmacología , Péptidos Cíclicos , Microbiología del Suelo , Solubilidad , Esporas Bacterianas , Streptomycetaceae/crecimiento & desarrollo , Streptomycetaceae/fisiología , Células VeroRESUMEN
Changes in the DNA content were studied in the spores of Streptoverticillium mycoheptinicum. The content of DNA increased in the spores when they were incubated in a liquid nutrient medium at 28 degrees C for 5 hours. Changes in the DNA content during germination of spores corresponded to individual stages: at the stage of activation, the replication of DNA only commenced; at the stage of initiation, the content of DNA doubled in the majority of spores in the population. The rate of DNA synthesis varied among different spores of the actinomycete.
Asunto(s)
ADN Bacteriano/análisis , Streptomycetaceae/análisis , Medios de Cultivo , Cinética , Esporas Bacterianas/análisis , Streptomycetaceae/fisiología , Factores de TiempoRESUMEN
The lethal and mutagenic effects of the DNA-tropic antibiotic mithomycin C and UV-light on Streptoverticillium mycoheptinicum during the period of the spore replication were studied. The spores were more stable to the effect of the mutagens during DNA replication after 120 minutes of incubation. The mutagenic activity of mithomycin C and UV-light was closely connected with the quantitative changes in the genetic material of the pores. During DNA replication the rate of the morphological mutants was the highest. With respect to production of mycoheptin the spores were most mutable under the effect of mithomycin C during the period of DNA replication, while under the effect of UV-light they were most mutable at the lag-phase.