Waters Yu (clavenic7)

Natamycin is a polyene macrolide antibiotic and widely used as a natural food preservative. Fungal elicitor had positive effects on the natamycin biosynthesis in Streptomyces natalensis HW-2. However, the global gene expression in response to fungal elicitor is not still reported. In the study, RNA-Seq was used to check the change of transcriptome by fungal elicitor in S. natalensis HW-2. The results showed that there were 1265 differential expression genes (DEGs) at 40 h and 2196 DEGs at 80 h. Most of the genes involved in natamycin biosynthesis were upregulated. KEGG pathway analysis showed that fungal elicitor had strong effects on the transcriptional levels of genes related to branch-chained amino acid (BCAA) metabolism. There were 23 upregulated or downregulated DEGs involved in BCAA biosynthesis and degradation at 40 h and 80 h. To confirm whether the improvement of BCAA biosynthesis could produce more natamycin, metabolic engineering was used to homologously overexpress the gene ilvH which encoded the regulatory subunit of acetolactate synthase (ALS) in S. natalensis. The results showed that overexpression of ilvH in S. natalensis HW-2 increased natamycin production to 1.25 g/L in the flask, which was a 32% increase compared with that of the parent strain. Real-time quantitative PCR analysis showed that the transcriptional level of ilvH in mutant strain S. natalensis ZS101 was significantly increased. Acetyl-CoA content was also raised. The results suggested that the fungal elicitor enhanced natamycin biosynthesis by improving precursor supply via BCAA metabolism. This study will open a new avenue for enhancing natamycin production by metabolic engineering and adding fungal elicitor. KEY POINTS • The fungal elicitor had strong effects on the transcriptional levels of genes related to branch-chained amino acid metabolism by RNA-Seq. • The homologous overexpression of gene ilvH increased natamycin production by 32% and acetyl-CoA content was raised in mutant strain S. natalensis ZS101.OBJECTIVES Detectability experiments performed to assess the diagnostic performance of computed tomography (CT) images should represent the clinical situation realistically. The purpose was to develop anatomically realistic phantoms with low-contrast lesions for detectability experiments. METHODS Low-contrast lesions were digitally inserted into a neck CT image of a patient. The original and the manipulated CT images were used to create five phantoms four phantoms with lesions of 10, 20, 30, and 40 HU contrast and one phantom without any lesion. Radiopaque 3D printing with potassium-iodide-doped ink (600 mg/mL) was used. The phantoms were scanned with different CT settings. Lesion contrast was analyzed using HU measurement. A 2-alternative forced choice experiment was performed with seven radiologists to study the impact of lesion contrast on detection accuracy and reader confidence (1 = lowest, 5 = highest). RESULTS The phantoms reproduced patient size, shape, and anatomy. Mean ± SD contrast values of the lo neck background. • Detectability experiments with anatomically realistic phantoms can assess CT image quality in a clinical context.OBJECTIVES To investigate whether breast MRI has comparable diagnostic performance as dedicated axillary MRI regarding assessment of node-negative and node-positive breast cancer. METHODS Forty-seven patients were included. All had undergone both breast MRI and dedicated axillary MRI, followed by surgery. All included breast MRI exams had complete field of view (FOV) of the axillary region. First, unenhanced T2-weighted (T2W) and subsequent diffusion-weighted (DW) images of both MRI exams were independently analyzed by two breast radiologists using a confidence scale and compared to histopathology. ADC values were measured by two researchers independently. Diagnostic performance parameters were calculated on a patient-by-patient basis. RESULTS T2W breast MRI had the