Reclassification of Streptomyces cinnamonensis as a later heterotypic synonym of Streptomyces virginiae

We studied the taxonomic relationship between Streptomyces cinnamonensis and Streptomyces virginiae . These type strains shared the same 16S rRNA gene sequence. Phylogenomic analysis supported them being closely related. Digital DNA–DNA relatedness and average nucleotide identity using whole genome sequences indicated that the two species represent the same genomospecies. They shared similar phenotypic characteristics and harboured the same set of secondary metabolite-biosynthetic gene clusters for polyketides and nonribosomal peptides in the genomes. Therefore, according to Rule 24b of the Bacteriological Code, S. cinnamonensis Okami 1952, 572AL (Approved Lists 1980) should be reclassified as a later heterotypic synonym of S. virginiae Grundy et al. 1952, 399AL (Approved Lists 1980) emend. Nouioui et al. 2018. Although 16S rRNA gene sequences were identical among type strains of Streptomyces xanthophaeus , Streptomyces spororaveus and Streptomyces nojiriensis and between those of Streptomyces vinaceus and Streptomyces cirratus , respectively, digital DNA–DNA relatedness indicated that these species are not synonymous.

Regulatory Patterns of Crp on Monensin Biosynthesis in Streptomyces cinnamonensis

Monensin, produced by Streptomyces cinnamonensis, is a polyether ionophore antibiotic widely used as a coccidiostat and a growth-promoting agent in agricultural industry. In this study, cyclic AMP receptor protein (Crp), the global transcription factor for regulation of monensin biosynthesis, was deciphered. The overexpression and antisense RNA silencing of crp revealed that Crp plays a positive role in monensin biosynthesis. RNA sequencing analysis indicated that Crp exhibited extensive regulatory effects on genes involved in both primary metabolic pathways and the monensin biosynthetic gene cluster (mon). The primary metabolic genes, including acs, pckA, accB, acdH, atoB, mutB, epi and ccr, which are pivotal in the biosynthesis of monensin precursors malonyl-CoA, methylmalonyl-CoA and ethylmalonyl-CoA, are transcriptionally upregulated by Crp. Furthermore, Crp upregulates the expression of most mon genes, including all PKS genes (monAI to monAVIII), tailoring genes (monBI-monBII-monCI, monD and monAX) and a pathway-specific regulatory gene (monRI). Enhanced precursor supply and the upregulated expression of mon cluser by Crp would allow the higher production of monensin in S. cinnamonensis. This study gives a more comprehensive understanding of the global regulator Crp and extends the knowledge of Crp regulatory mechanism in Streptomyces.

Detección espectrofotométrica de sobredosis de monensina en piensos para bovinos

<p>La creciente presión de la agricultura, así como la búsqueda de mayor eficiencia en los sistemas anaderos, ha conducido al aumento del empleo de productos farmacológicos como estrategias para mejorar la rentabilidad de la ganadería. La monensina (MN) es un antibiótico poliéter del grupo de los ionóforos elaborado a partir del hongo <em>Streptomyces cinnamonensis. </em>En este trabajo se describe la puesta a punto de un método espectrofotométrico sencillo y eficaz para la determinación de MN en muestras de piensos para ganado bovino. Se evaluaron alimentos con diferentes concentraciones de MN conocidas e incógnitas, recolectadas en las provincias de Córdoba y La Pampa (Argentina). Los resultados muestran que el método espectrofotométrico es apropiado para medir MN en piensos a dosis normales y en sobredosificaciones, siendo útil para revelar presuntas intoxicaciones de origen alimentario. Comparada con otros métodos, la técnica revela bajo costo en insumos y equipamiento, aunque requiere cierta laboriosidad. Los resultados del trabajo señalan la idoneidad del método para efectuar la vigilancia farmacológica de MN, dado que brinda un rápido y efectivo diagnóstico en casos de intoxicación, de gran utilidad en laboratorios de baja complejidad. </p>

Intermediates in monensin biosynthesis: A late step in biosynthesis of the polyether ionophore monensin is crucial for the integrity of cation binding

Polyether antibiotics such as monensin are biosynthesised via a cascade of directed ring expansions operating on a putative polyepoxide precursor. The resulting structures containing fused cyclic ethers and a lipophilic backbone can form strong ionophoric complexes with certain metal cations. In this work, we demonstrate for monensin biosynthesis that, as well as ether formation, a late-stage hydroxylation step is crucial for the correct formation of the sodium monensin complex. We have investigated the last two steps in monensin biosynthesis, namely hydroxylation catalysed by the P450 monooxygenase MonD andO-methylation catalysed by the methyl-transferase MonE. The corresponding genes were deleted in-frame in a monensin-overproducing strain ofStreptomyces cinnamonensis. The mutants produced the expected monensin derivatives in excellent yields (ΔmonD: 1.13 g L−1dehydroxymonensin; ΔmonE: 0.50 g L−1demethylmonensin; and double mutant ΔmonDΔmonE: 0.34 g L−1dehydroxydemethylmonensin). Single crystals were obtained from purified fractions of dehydroxymonensin and demethylmonensin. X-ray structure analysis revealed that the conformation of sodium dimethylmonensin is very similar to that of sodium monensin. In contrast, the coordination of the sodium ion is significantly different in the sodium dehydroxymonensin complex. This shows that the final constitution of the sodium monensin complex requires this tailoring step as well as polyether formation.