RESUMEN

Daptomycin is a cyclolipopeptide antibiotic produced by Streptomyces roseosporus. It is widely used to treat drug-resistant bacterial infections; however, daptomycin yield in wild strains is very low. To improve the daptomycin production by the strain BNCC 342432, a modified method of ribosome engineering with superposition of streptomycin resistance was adopted in this study. The highest-yield mutant strain SR-2620 was obtained by increasing streptomycin resistance of BNCC 342432, and achieved daptomycin production of 38.5 mg/l in shake-flask fermentation, 1.79-fold higher than the parent strain and its heredity stability was stable. The morphological characteristics of the two strains were significantly different, and the 440th base G of the rpsL gene in the mutant strain was deleted, which resulted in a frameshift mutation. Our results demonstrate that gradually increasing strain resistance to streptomycin was an effective breeding method to improve daptomycin yield in S. roseosporus.

Asunto(s)

Daptomicina , Antibacterianos/farmacología , Daptomicina/farmacología , Fermentación , Estreptomicina/farmacología

RESUMEN

Two strains representing a novel yeast species were isolated from plant leaves collected in the Baotianman Nature Reserve in Henan Province, central China. Phylogenetic analysis based on the concatenated sequences of the internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2) and the D1/D2 domain of the large subunit rRNA gene revealed that the novel species belonged to the genus Hyphopichia, although the formation of ascospores was not observed. The novel species was related most closely to Hyphopichia paragotoi CBS 13913T but they differed by 0.9 % sequence divergence (five substitutions) in the D1/D2 domain and by 3.7 % sequence divergence (seven substitutions and eight gaps) in the ITS region. Furthermore, the novel species can also be differentiated from the closely related species in some biochemical and physiological characteristics. The species name of Hyphopichia xiaguanensis f.a., sp. nov. (Holotype CBS 16668, Mycobank MB 842425) is proposed to accommodate strains NYNU 20899T and NYNU 20914.

Asunto(s)

Ácidos Grasos , Saccharomycetales , Técnicas de Tipificación Bacteriana , Composición de Base , ADN Bacteriano/genética , ADN de Hongos/genética , ADN Espaciador Ribosómico/genética , Ácidos Grasos/química , Técnicas de Tipificación Micológica , Filogenia , Hojas de la Planta , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADN

RESUMEN

Two strains of a novel ascomycetous yeast species were isolated from rotting wood samples collected in Jiuxi Mountain Forest Park in Yunnan Province, southwest China. Both strains formed one or two spherical ascospores in persistent asci. Phylogenetic analysis of the concatenated sequences of the internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2) and the D1/D2 domain of the large subunit rRNA gene revealed that the novel strains represented a phylogenetically distinct species belonging to the genus Torulaspora. This novel species differed from the type strains of the closest known species, Torulaspora nypae and Torulaspora maleeae, by 0.9 and 1.2 % nucleotide substitutions in the D1/D2 domain and 5.3 and 6 % nucleotide substitutions in the ITS region, respectively. The novel species can also be distinguished from T. nypae and T. maleeae in terms of the ability to assimilate ribitol, succinate and citrate, and its ability to grow at 37 °C. The species name of Torulaspora jiuxiensis sp. nov. is proposed with holotype CBS 16004T (Mycobank MB 844535).

Asunto(s)

Ascomicetos , Saccharomycetales , Torulaspora , Madera , Filogenia , ADN Espaciador Ribosómico/genética , China , ADN de Hongos/genética , Análisis de Secuencia de ADN , Técnicas de Tipificación Micológica , Composición de Base , ARN Ribosómico 16S/genética , ADN Bacteriano/genética , Técnicas de Tipificación Bacteriana , Ácidos Grasos/química , Ascomicetos/genética