Lincomycin A (Lin-A) is a widely used antibacterial antibiotic fermented by Streptomyces lincolnensis. However, the transcriptional regulatory mechanisms underlying lincomycin biosynthesis have seldom been investigated. Here, we first identified a TetR family transcriptional regulator (TFR), SLCG_2919, which negatively modulates lincomycin biosynthesis in S. lincolnensis LCGL. SLCG_2919 was found to specifically bind to promoter regions of the lincomycin biosynthetic gene cluster (lin cluster), including 25 structural genes, three resistance genes, and one regulatory gene, and to inhibit the transcription of these genes, demonstrating a directly regulatory role in lincomycin biosynthesis. Furthermore, we found that SLCG_2919 was not autoregulated, but directly repressed its adjacent gene, SLCG_2920, which encodes an ATP/GTP binding protein whose overexpression increased resistance against lincomycin and Lin-A yields in S. lincolnensis. The precise SLCG_2919 binding site within the promoter region of SLCG_2920 was determined by a DNase I footprinting assay and by electrophoretic mobility shift assays (EMSAs) based on base substitution mutagenesis, with the internal 10-nucleotide (nt) AT-rich sequence (AAATTATTTA) shown to be essential for SLCG_2919 binding. Our findings indicate that SLCG_2919 is a negative regulator for controlling lincomycin biosynthesis in S. lincolnensis. The present study improves our understanding of molecular regulation for lincomycin biosynthesis. IMPORTANCE TetR family transcriptional regulators (TFRs) are generally found to regulate diverse cellular processes in bacteria, especially antibiotic biosynthesis in Streptomyces species. However, knowledge of their function in lincomycin biosynthesis in S. lincolnensis remains unknown. The present study provides a new insight into the regulation of lincomycin biosynthesis through a TFR, SLCG_2919, that directly modulates lincomycin production and resistance. Intriguingly, SLCG_2919 and its adjoining gene, SLCG_2920, which encodes an ATP/GTP binding protein, were extensively distributed in diverse Streptomyces species. In addition, we revealed a new TFR binding motif, in which SLCG_2919 binds to the promoter region of SLCG_2920, dependent on the intervening AT-rich sequence rather than on the flanking inverted repeats found in the binding sites of other TFRs. These insights into transcriptional regulation of lincomycin biosynthesis by SLCG_2919 will be valuable in paving the way for genetic engineering of regulatory elements in Streptomyces species to improve antibiotic production.
Background:Unilateral and bilateral percutaneous balloon kyphoplasty (PKP) are 2 main approaches for the treatment of patients with osteoporotic vertebral compression fractures (OVCFs). Numerous published systematic reviews and meta-analyses evaluating the effectiveness of 2 approaches remain inconclusive. In order to propose a significant principle to make decisions for comparing clinical safety and efficacy of unilateral versus bilateral PKP for treating OVCFs patients based on the currently best available evidence, a systematic review of overlapping meta-analysis was conducted.Methods:Three electronic databases, Pubmed/Medline, Embase2 and the Cochrance Library, were searched systematically to retrieve and identify all eligible systematic reviews and meta-analyses comparing unilateral and bilateral PKP for the treatment of patients with OVCFs. Only systematic reviews or meta-analyses with an exclusively pooled analysis of randomized controlled trials (RCTs) met the minimum eligibility criteria in this investigation. The Oxford Levels of Evidence, Jadad algorithm and Assessment of Multiple Systematic Reviews (AMSTAR) instrument were adopted for evaluation of the methodological quality for each included literature to select currently best available evidence.Results:Screening determined that out of 2159, 9 meta-analyses with level II or III of evidence met the inclusion criteria in the systematic review of overlapping meta-analyses. The multiple systematic reviews scores ranged from 8 to 9 with a mean of 8.55 (median 8.5). According to the search process and selection strategies of the Jadad algorithm, a meta-analysis by Feng et al with the best available evidence (12 RCTs and an AMSTAR score of 9) demonstrated that unilateral and bilateral PKP are both nice choices for the treatment of patients with OVCFs, and no significant differences were revealed in clinical scores, radiological outcomes, and quality of life with long-term follow-up. However, compared with bilateral PKP, unilateral PKP produced a shorter surgery time, smaller dosage of cement, lower risk of cement leakage, and relieved a higher degree of intractable pain at short-term follow-up after surgery.Conclusion:Unilateral percutaneous balloon kyphoplasty is more advantageous and superior to bilateral percutaneous kyphoplasty, and should be considered an effective option for the treatment of patients with osteoporotic vertebral compression fractures.
Streptomyces lincolnensis is generally utilized for the production of lincomycin A (Lin-A), a clinically useful antibiotic to treat Gram-positive bacterial infections. Three methylation steps, catalyzed by three different S-adenosylmethionine (SAM)-dependent methyltransferases, are required in the biosynthesis of Lin-A, and thus highlight the significance of methyl group supply in lincomycin production. In this study, we demonstrate that externally supplemented SAM cannot be taken in by cells and therefore does not enhance Lin-A production. Furthermore, bioinformatics and in vitro enzymatic assays revealed there exist two SAM synthetase homologs, MetK1 (SLCG_1651) and MetK2 (SLCG_3830) in S. lincolnensis that could convert L-methionine into SAM in the presence of ATP. Even though we attempted to inactivate metK1 and metK2, only metK2 was deleted in S. lincolnensis LCGL, named as ΔmetK2. Following a reduction of the intracellular SAM concentration, ΔmetK2 mutant exhibited a significant decrease of Lin-A in comparison to its parental strain. Individual overexpression of metK1 or metK2 in S. lincolnensis LCGL either elevated the amount of intracellular SAM, concomitant with 15% and 22% increase in Lin-A production, respectively. qRT-PCR assays showed that overexpression of either metK1 or metK2 increased the transcription of lincomycin biosynthetic genes lmbA and lmbR, and regulatory gene lmbU, indicating SAM may also function as a transcriptional activator. When metK1 and metK2 were co-expressed, Lin-A production was increased by 27% in LCGL, while by 17% in a high-yield strain LA219X.
Objective: To explore the safety and efficacy of percutaneous pedicle screw fixation combined with vertebroplasty for the treatment of stage III Kümmell disease. Methods:The clinical data and follow-up results of 22 patients with Kümmell disease who were admitted to our department from 2014 to 2018 were analyzed. There were 14 females and eight males, and the Age range was 58-81 years. All patients were followed up for 24 months. The treatment method was percutaneous pedicle screw fixation combined with vertebroplasty. The patient general information such as age, gender, bedrest time and location of fracture vertebrae were recorded. The clinical symptoms and imaging data of visual analogue scale (VAS), bone cement leakage, Oswestry Disability Index (ODI), Cobb angle, anterior, middle and posterior height of the diseased vertebral body, and complications were recorded before operation and during follow-up.Results: For patients enrolled, no bone cement leakage was observed during the operation; no patients developed infections after operation. The operation was safe and resulted in a short bedrest time. The VAS score and ODI index at 3 and 24 months postoperative (2.86 AE 0.83, 31.68% AE 6.21%; 3.0 AE 0.82, 32.78% AE 6.05%) were significantly lower than that recoded preoperatively (7.59 AE 0.59, 71.5% AE 8.84%) (P < 0.05). Additionally, there was no significant difference between the records at 3 and 24 months after operation (P > 0.05). Imaging data showed that the bone cement and screws were in good position and did not move during postoperative and follow-up. The anterior, middle and posterior height of the diseased vertebral body measured 2 days after surgery (23.46
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