Characterization of Tailoring Steps of Nargenicin A1 Biosynthesis Reveals a Novel Analogue with Anticancer Activities.

Nargenicin A1(1) is an antibacterial macrolide with effective activity against various Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus. Due to the promising properties of this compound in inhibiting cell proliferation, immunomodulation, and the cell protective effect, there has been significant interest in this molecule. Recently, the biosynthetic gene cluster (BGC) of 1 was reported from Nocardia argentinesis and Nocardia arthritidis. In addition, two crucial enzymes involved in the formation of the core decalin moiety and postmodification of the decalin moiety by an ether bridge were characterized. This study reports on the BGC of 1 from Nocardia sp. CS682. In addition, the direct capture and heterologous expression of nar BGC from Nocardia sp. CS682 in Streptomyces venezuelae led to the production of 1. Further metabolic profiling of wild type, Nocardia sp. CS682 in optimized media (DD media) resulted in the isolation of two acetylated derivatives, 18-O-acetyl-nodusmicin and 18-O-acetyl-nargenicin. The post-PKS modification pathway in biosynthesis of 1 was also deciphered by identifying intermediates and/or in vitro enzymatic reactions of NgnP1, NgnM, and NgnO3. Different novel analogues of 1, such as compound 6, compound 7, 23-demethyl 8,13-deoxy-nodusmicin (8), 23-demethyl 8,13-deoxynargenicin (9), 8,13-deoxynodusmicin (10), and 8,13-deoxynargenicin (11), were also characterized, which extended our understanding of key post-PKS modification steps during the biosynthesis of 1. In addition, the antimicrobial and anticancer activities of selected analogues were also evaluated, whereas compound 9 was shown to exhibit potent antitumor activity by induction of G2/M cell cycle arrest, apoptosis, and autophagy.

Production of a Novel Tetrahydroxynaphthalene (THN) Derivative from Nocardia sp. CS682 by Metabolic Engineering and Its Bioactivities.

Nargenicin A1 is major secondary metabolite produced by Nocardia sp. CS682, with an effective antibacterial activity against various Gram-positive bacteria. Most Nocardia spp. have metabolic ability to produce compounds of diverse nature, so one-strain-many-compounds (OSMAC) approach can be applied for obtaining versatile compounds from these strains. In this study, we characterized a novel 1, 3, 6, 8-tetrahydroxynaphthalene (THN) derivative by metabolic engineering approach leading to the inactivation of nargenicin A1 biosynthesis. By using genome mining, metabolite profiling, and bioinformatics, the biosynthetic gene cluster and biosynthetic mechanism were elucidated. Further, the antibacterial, anticancer, melanin formation, and UV protective properties for isolated THN compound were performed. The compound did not exhibit significant antibacterial and cytotoxic activities, but it exhibited promising UV protection effects. Thus, metabolic engineering is an effective strategy for discovering novel bioactive molecules.

Bioactive molecules from Nocardia: diversity, bioactivities and biosynthesis.

Nocardia spp. are catalase positive, aerobic, and non-motile Gram-positive filamentous bacteria. Many Nocarida spp. have been reported as unusual causes of diverse clinical diseases in both humans and animals. Therefore, they have been studied for a long time, primarily focusing on strain characterization, taxonomic classification of new isolates, and host pathophysiology. Currently, there are emerging interests in isolating bioactive molecules from diverse actinobacteria including Nocardia spp. and studying their biosynthetic mechanisms. In addition, these species possess significant metabolic capacity, which has been utilized for generating diverse functionalized bioactive molecules by whole cell biotransformation. This review summarizes the structural diversity and biological activities of compounds biosynthesized or biotransformed by Nocardia spp. Furthermore, the recent advances on biosynthetic mechanisms and genetic engineering approaches for enhanced production or structural/functional modification are presented.

TP53 codon 72 polymorphism and the risk of glaucoma in a north Indian cohort: A genetic association study.

BACKGROUND: The TP53 codon 72 Proline-Arginine polymorphism (TP53 P72R) is the most widely studied candidate among those evaluated for a putative association between impaired apoptosis and glaucoma. Considering the earlier findings about enhanced apoptotic potential by the Arg variant of TP53 P72R and the conflicting results about its association with glaucoma, we initiated a hospital-based case-control association study in a north Indian cohort to investigate the association of TP53 P72R with glaucoma. MATERIALS AND METHODS: We examined the status of TP53 P72R in 139 cases of primary open angle glaucoma (POAG) and in 111 cases of primary angle closure glaucoma (PACG) with respect to 218 controls using the polymerase chain reaction-restriction fragment length polymorphism method. Logistic regression analysis including age and gender as covariates was carried out to test the association of the polymorphism with overall glaucoma, POAG, and PACG cases. RESULTS: We observed significant differences between the genotypic distributions of combined glaucoma cases and controls in the recessive model. POAG cases with respect to controls did not exhibit any significant differences in the genotypic distributions. In contrast, the genotypic distributions as per the additive and recessive models in PACG cases were significantly different from those in controls. The two models suggested an increased risk of PACG in the Arg homozygotes of the investigated cohort. CONCLUSIONS: Ours is the first study demonstrating the association of TP53 P72R with the risk of PACG. It emphasizes that apart from narrow anterior chamber angle, impaired apoptotic mechanisms could also be an important contributor toward PACG.

Isolation and identification of Acinetobacter species with special reference to antibiotic resistance.

BACKGROUND: Acinetobacter is clinically important pathogen with widespread resistance to various antibiotics. We assessed the incidence of Acinetobacter infection at a tertiary care hospital, analyze their resistance pattern and identify the production of extended spectrum ß-lactamases (ESBLs) and metallo ß-lactamases (MBLs). MATERIALS AND METHODS: The study was conducted in tertiary care hospital, India over a period of 2 years. Acinetobacter species were isolated from various clinical samples received in Department of Microbiology. After identification, Acinetobacter isolates were speciated and antibiotic susceptibility was determined by the standard disc diffusion method. ESBL and MBL production was detected by the double disc synergy test and combined disc diffusion test respectively. RESULTS: Of 3298 infected samples, 111 (3.36%) were found to be Acinetobacter. The most predominant species was Acinetobacter calcoaceticus-A. baumannii (Acb) complex (72%). High incidence of resistance was recorded for piperacillin (55%), followed by ceftriaxone (46%) and ceftazidime (46%). Isolation rate and antibiotic resistance was higher in the Intensive Care Units (ICUs) of the hospital. ESBL and MBL production was detected in 31.5% and 14.4% of the isolates respectively. DISCUSSION AND CONCLUSION: A high level of antibiotic resistance was observed in our study and maximum isolation rate of Acinetobacter was in the ICUs. Acb complex was the most predominant and most resistant species. The analysis of susceptibility pattern will be useful in understanding the epidemiology of this organism in our hospital setup, which will help in treating individual cases and controlling the spread of resistant isolates to other individuals.

Micronutrients, antioxidants, and carcinoma of the gallbladder.

OBJECTIVES: Nutrient deficiency in developing countries can be considered a significant contributory factor modifying the multistage process of carcinogenesis. Studies from different parts of the world have shown the deficiency of various micronutrients to be significantly associated with cancer. This study was undertaken to test the above hypothesis in patients with carcinoma of the gallbladder. METHODS: Selenium (Se), zinc (Zn), copper (Cu), manganese (Mn), ascorbic acid (vitamin C), and alpha-tocopherol (vitamin E) were estimated in the serum, bile, and gallbladder tissue of 30 patients each of carcinoma of the gallbladder (group-I), cholelithiasis (group-II), and only in the serum of 30 age- and sex-matched healthy controls (group-III). The minerals were analyzed by atomic absorption spectrophotometer and vitamins by spectrophotometry. RESULTS: The mean serum levels of Se, Zn, Mn, vitamin E, and vitamin C were significantly lower (P < 0.001) in group-I when compared with groups II and III. The mean biliary levels of Se and Zn (0.29, 3.45 mg/L) were reduced significantly (P < 0.001) in group-I when compared with group II (0.51, 5.2 mg/L). Mean tissue levels of Se and Zn were also significantly lower (P < 0.001) in group I (2.75, 43.09 microg/g) compared to group II (3.90, 61.37 microg/g). However, no significant difference was observed in tissue concentration of Mn, vitamin C, and vitamin E. Cu levels and Cu/Zn ratio showed a highly significant (P < 0.001) increase in serum, bile, and gallbladder tissue in carcinoma of the gallbladder compared to the other two groups. CONCLUSIONS: The data supports an association between lower levels of Se, Zn, vitamin E, and risk of carcinoma of the gallbladder and suggest that Cu/Zn ratio could be a useful parameter in evaluating the patients of carcinoma of the gallbladder.