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.

Improved production of 1-deoxynojirymicin in Escherichia coli through metabolic engineering.

Azasugars, such as 1-deoxynojirymicin (1-DNJ), are associated with diverse pharmaceutical applications, such as antidiabetic, anti-obesity, anti-HIV, and antitumor properties. Different azasugars have been isolated from diverse microbial and plant sources though complicated purification steps, or generated by costly chemical synthesis processes. But the biosynthesis of such potent molecules using Escherichia coli as a heterologous host provides a broader opportunity to access these molecules, particularly by utilizing synthetic biological, metabolic engineering, and process optimization approaches. This work used an integrated approach of synthetic biology, enzyme engineering, and pathway optimization for rational metabolic engineering, leading to the improved production of 1-DNJ. The production of 1-DNJ in recombinant E. coli culture broth was confirmed by enzymatic assays and mass spectrometric analysis. Specifically, the pathway engineering for its key precursor, fructose-6-phosphate, along with optimized media condition, results in the highest production levels. When combined, 1-DNJ production was extended to ~ 273 mg/L, which is the highest titer of production of 1-DNJ reported using E. coli.

A Study on the Effect of Various Media and the Supplementation of Organic Compounds on the Enhanced Production of Astaxanthin from Haematococcus lacustris (Girod-Chantrans) Rostafinski (Chlorophyta).

Natural astaxanthin is in high demand due to its multiple health benefits. The microalga Haematococcus lacustris has been used for the commercial production of astaxanthin. In this study, we investigated the effects of six different media with and without a nitrogen source and supplementation with nine organic compounds on the growth and astaxanthin accumulation of H. lacustris. The highest astaxanthin contents were observed in cultures of H. lacustris in Jaworski's medium (JM), with a level of 9.099 mg/L in JM with a nitrogen source supplemented with leucine (0.65 g/L) and of 20.484 mg/L in JM without a nitrogen source supplemented with sodium glutamate (0.325 g/L). Six of the nine organic compounds examined (leucine, lysine, alanine, sodium glutamate, glutamine, and cellulose) enhanced the production of astaxanthin in H. lacustris, while malic acid, benzoic acid, and maltose showed no beneficial effects.

Effects of Four Organic Carbon Sources on the Growth and Astaxanthin Accumulation of Haematococcus lacustris.

The microalga Haematococcus lacustris has a complex life cycle and a slow growth rate, hampering its mass cultivation. Culture of microalgae with organic carbon sources can increase the growth rate. Few studies have evaluated the effects of organic carbon sources on H. lacustris. We compared the vegetative and inductive stages of H. lacustris under autotrophic and mixotrophic conditions using four organic carbon sources: sodium acetate, glycerol, sodium gluconate, and ribose, each at various concentrations (0.325, 0.65, 1.3, and 2.6 g/L). The cell density was increased by 1.3 g/L of glycerol in the vegetative stage. The rapid transition to the inductive stage under nitrogen-depletion conditions caused by 1.3 or 2.6 g/L sodium acetate promoted the accumulation of astaxanthin. The production of astaxanthin by H. lacustris in mass culture using organic carbon sources could increase profitability.

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.

Complete Genome Sequence of Nocardia sp. Strain CS682, a Producer of Antibacterial Compound Nargenicin A1.

Nocardia sp. strain CS682 is a rare actinobacterium with a promising ability to produce secondary metabolites such as nargenicin A1 (an effective antibacterial compound) and IBR-3 (a UV-protectant molecule). Here, we report the complete genome sequence of Nocardia sp. CS682, obtained by PacBio sequencing as a single contig with 8,919,230 bp (GC content, 63.3%).

Actinomadura Species: Laboratory Maintenance and Ribosome Engineering.

Actinomadura spp. are aerobic, Gram-positive, catalase-positive, non-acid fast, non-motile actinomycetes. Some species of Actinomadura are associated with opportunistic infections in humans. However, many bioactive compounds with pharmaceutical applications can be isolated from various Actinomadura spp. This unit includes general protocols for the laboratory maintenance of Actinomadura spp., including growth in liquid medium, growth on solid agar, long-term storage, and generation of a higher producing strain by ribosome engineering. Actinomadura hibisca P157-2 is used as a prototype for explaining the considerations for efficient laboratory maintenance of Actinomadura spp. © 2017 by John Wiley & Sons, Inc.