RESUMO
An actinomycete strain, isolated from a Mata Atlântica soil sample, showing cellulolytic activity was subjected to polyphasic taxonomic characterization to determine its identity. Strain M7aT presented morphological and chemotaxonomic characteristics consistent with its assignment to the genus Streptomyces. Phylogenetic analysis of its 16S rDNA sequence revealed that the strain differed from described streptomycetes available in the public databases; the most closely related species was Streptomyces laceyi, with 98.4% nucleotide similarity. It also differed from other cellulolytic strains in its phenotypic characteristics. It is therefore proposed that strain M7aT, a cellulolytic strain with biotechnological potential, represents a novel species, named Streptomyces drozdowiczii sp. nov. The type strain is M7aT (=CBMAI 0498T=CIP 107837T=NRRL B-24297T).
Assuntos
Celulose/metabolismo , Microbiologia do Solo , Streptomyces/classificação , Streptomyces/isolamento & purificação , Aminoácidos/análise , Técnicas de Tipagem Bacteriana , Brasil , Parede Celular/química , DNA Bacteriano/química , DNA Ribossômico/química , Ácidos Graxos/análise , Genes de RNAr , Dados de Sequência Molecular , Filogenia , RNA Bacteriano/genética , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Homologia de Sequência , Streptomyces/citologia , Streptomyces/metabolismoRESUMO
Actinomycetes have been isolated from three Brazilian tropical soils. The dispersion and differential centrifugation procedure revealed count values 1.5 to 5.0 times greater than those obtained by the conventional dilution plate technique for all soils and media tested. Eighteen strains, promising for biotechnological applications, were submitted to chemotaxonomic procedures and numerical taxonomy for identification. Two were identified as Amycolatopsis orientalis, one as Streptomyces misakiensis, and two tentatively included or associated to S. chromofuscus and S. griseoruber. The others, all belonging to the Streptomyces genus, could not be fitted into any known species, and were arranged by the UPGMA analysis for classification, as an isolated group. This suggests that the actinomycetes in tropical soils may represent a vast unexplored resource for biotechnology.
Assuntos
Actinomycetales/isolamento & purificação , Microbiologia do Solo , Actinomycetales/química , Actinomycetales/classificação , Brasil , Carboidratos , Parede Celular/química , Centrifugação , Ácidos MicólicosRESUMO
AIMS: The chitinolytic activity of an actinomycete, isolated from a tropical acidic ferrasol (FAO) under cerrado (savanna) vegetation, is reported. METHODS AND RESULTS: Selection of the strain was based on spot inoculation on solid colloidal chitin medium. The use of chemotaxonomic, morphological and physiological procedures placed it in the Streptomyces genus, but identification to species level could not be achieved. A protein with endochitinase activity was isolated and purified from the supernatant fluid by concentration, precipitation, hydrophobic interaction, gel filtration and adsorption procedures. The molecular size of the purified chitinase was estimated by gel filtration to be 70 kDa, and its pI was 6.1. The enzyme had temperature and pH optima of 40 degrees C and 8.0, respectively, and showed thermal (30-70 degrees C) and pH (4-9) stabilities. Antifungal activity of the selected strain was observed following in vitro experiments using growing cells, crude extract or the purified endochitinase, and by detecting growth inhibition of the tested phytopathogenic fungi. CONCLUSION: Strain Streptomyces RC 1071 could not be placed into any known species, suggesting a new taxon. The purified endochitinase presented similar molecular weight, optimum temperature and pH activity, and stability of other endochitinolytic enzymes reported in the literature. In all three in vitro experiments performed, inhibition of growth of the phytopathogenic fungi used as test organisms was observed. SIGNIFICANCE AND IMPACT OF THE STUDY: Some of the endochitinase characteristics such as thermal stability, as well as pH tolerance, are very interesting for biotechnological purposes. In addition, due to its antifungal activity, Streptomyces RC 1071 seems promising for use in biological control.
Assuntos
Quitinases/isolamento & purificação , Streptomyces/enzimologia , Aspergillus/efeitos dos fármacos , Extratos Celulares/farmacologia , Eletroforese , Estabilidade Enzimática , Temperatura Alta , Doenças das Plantas/microbiologia , Microbiologia do SoloRESUMO
Two Streptomyces strains, M7a and M23, from a Brazilian forest soil were evaluated for the cellulase production of their supernatants after growth in a microcrystalline cellulose medium, using carboxymethylcellulose and filter paper as substrates at different temperatures and pH values. Endoglucanase and exoglucanase activities were compared to a commercial Trichoderma reesei cellulase using fluorogenic conjugated substrates. Similar specific activities were observed for the enzyme preparations of strain M23 and T. reesei. For M7a the activities were about seven times higher than those obtained for T. reesei. Extracellular or cell-associated cellobiase activities were not detected in both strains.
Assuntos
Celulase/metabolismo , Microbiologia do Solo , Streptomyces/enzimologia , Brasil , Carboximetilcelulose Sódica , Fermentação , Cinética , Papel , Streptomyces/isolamento & purificação , Especificidade por Substrato , Trichoderma/enzimologiaRESUMO
The crude enzyme extracts from five actinomycetes selected from a cerrado soil presented very good endochitinolytic activity when compared to a commercial chitinase. Exochitinase and chitobiase activities were also detected. They were identified as Streptomyces, but could not be characterized to species level, probably corresponding to new ones. The crude extracts, obtained from growth on fungal mycelium plus chitin of three of the strains, have shown a very pronounced activity against phytopathogenic fungi. In tests using growing cells, all five strains were active. These data suggest that these strains are potential biocontrol agents.