The carotenoids of flexibacteria. 2. A new xanthophyll from Saprospira grandis

Bioactive natural products from Bacteroidetes

Covering: up to end of January 2022Bacteria representing the phylum Bacteroidetes produce a diverse range of natural products, including polyketides, peptides and lactams. Here, we discuss unique aspects of the bioactive compounds discovered thus far, and the corresponding biosynthetic pathways if known, providing a comprehensive overview of the Bacteroidetes as a natural product reservoir.

Marine Bacteria versus Microalgae: Who Is the Best for Biotechnological Production of Bioactive Compounds with Antioxidant Properties and Other Biological Applications?

Natural bioactive compounds with antioxidant activity play remarkable roles in the prevention of reactive oxygen species (ROS) formation. ROS, which are formed by different pathways, have various pathological influences such as DNA damage, carcinogenesis, and cellular degeneration. Incremental demands have prompted the search for newer and alternative resources of natural bioactive compounds with antioxidant properties. The marine environment encompasses almost three-quarters of our planet and is home to many eukaryotic and prokaryotic microorganisms. Because of extreme physical and chemical conditions, the marine environment is a rich source of chemical and biological diversity, and marine microorganisms have high potential as a source of commercially interesting compounds with various pharmaceutical, nutraceutical, and cosmeceutical applications. Bacteria and microalgae are the most important producers of valuable molecules including antioxidant enzymes (such as superoxide dismutase and catalase) and antioxidant substances (such as carotenoids, exopolysaccharides, and bioactive peptides) with various valuable biological properties and applications. Here, we review the current knowledge of these bioactive compounds while highlighting their antioxidant properties, production yield, health-related benefits, and potential applications in various biological and industrial fields.

Pink- and orange-pigmented Planctomycetes produce saproxanthin-type carotenoids including a rare C45 carotenoid

Planctomycetes are ubiquitous and environmentally important Gram-negative aquatic bacteria with key roles in global carbon and nitrogen cycles. Many planctomycetal species have a pink or orange colour and have been suggested to produce carotenoids. Potential applications as food colorants or anti-oxidants have been proposed. Hitherto, the planctomycetal metabolism is largely unexplored and the strain pigmentation has not been explored. For a holistic view of the complex planctomycetal physiology, we analysed carotenoid profiles of the pink-pigmented strain Rhodopirellula rubra LF2^T and of the orange strain Rubinisphaera brasiliensis Gr7. During LC-MS/MS analysis of culture extracts, we could identify three saproxanthin-type carotenoids including a rare C₄₅ carotenoid. These compounds, saproxanthin, dehydroflexixanthin and 2'-isopentenyldehydrosaproxanthin, derive from the common carotenoid precursor lycopene and are characterized by related end groups, namely a 3-hydroxylated β-carotene-like cyclohexene ring as one end group and simple hydration on the other end of the molecule. Based on the observed molecule structure we present putative pathways for their biosynthesis. Results support Planctomycetes as a promising, yet mostly untapped source of carotenoids.

Exploring the Valuable Carotenoids for the Large-Scale Production by Marine Microorganisms

Carotenoids are among the most abundant natural pigments available in nature. These pigments have received considerable attention because of their biotechnological applications and, more importantly, due to their potential beneficial uses in human healthcare, food processing, pharmaceuticals and cosmetics. These bioactive compounds are in high demand throughout the world; Europe and the USA are the markets where the demand for carotenoids is the highest. The in vitro synthesis of carotenoids has sustained their large-scale production so far. However, the emerging modern standards for a healthy lifestyle and environment-friendly practices have given rise to a search for natural biocompounds as alternatives to synthetic ones. Therefore, nowadays, biomass (vegetables, fruits, yeast and microorganisms) is being used to obtain naturally-available carotenoids with high antioxidant capacity and strong color, on a large scale. This is an alternative to the in vitro synthesis of carotenoids, which is expensive and generates a large number of residues, and the compounds synthesized are sometimes not active biologically. In this context, marine biomass has recently emerged as a natural source for both common and uncommon valuable carotenoids. Besides, the cultivation of marine microorganisms, as well as the downstream processes, which are used to isolate the carotenoids from these microorganisms, offer several advantages over the other approaches that have been explored previously. This review summarizes the general properties of the most-abundant carotenoids produced by marine microorganisms, focusing on the genuine/rare carotenoids that exhibit interesting features useful for potential applications in biotechnology, pharmaceuticals, cosmetics and medicine.

Identification of polyunsaturated fatty acid and diterpenoid biosynthesis pathways from draft genome of Aureispira sp. CCB-QB1

The genus Aureispira consisting of two species, Aureispira marina and Aureispira maritima is an arachidonic acid-producing bacterium and produces secondary metabolites. In this study, we isolated a new Aureispira strain, Aureispira sp. CCB-QB1 from coastal area of Penang, Malaysia and the genome sequence of this strain was determined. The draft genome of this strain is composed of 185 contigs for 7,370,077 bases with 35.6% G+C content and contains 5911 protein-coding genes and 76 RNA genes. Linoleoyl-CoA desaturase, the key gene in arachidonic acid biosynthesis, is present in the genome. It was found that this strain uses mevalonate pathway for the synthesis of geranylgeranyl diphosphate (GGPP), which is precursor of diterpenoid, and novel pathway via futalosine for the synthesis of menaquinones. This is the first draft genome sequence of a member of the genus Aureispira.

New and rare carotenoids isolated from marine bacteria and their antioxidant activities

Marine bacteria have not been examined as extensively as land bacteria. We screened carotenoids from orange or red pigments-producing marine bacteria belonging to rare or novel species. The new acyclic carotenoids with a C₃₀ aglycone, diapolycopenedioc acid xylosylesters A-C and methyl 5-glucosyl-5,6-dihydro-apo-4,4'-lycopenoate, were isolated from the novel Gram-negative bacterium Rubritalea squalenifaciens, which belongs to phylum Verrucomicrobia, as well as the low-GC Gram-positive bacterium Planococcus maritimus strain iso-3 belonging to the class Bacilli, phylum Firmicutes, respectively. The rare monocyclic C₄₀ carotenoids, (3R)-saproxanthin and (3R,2'S)-myxol, were isolated from novel species of Gram-negative bacteria belonging to the family Flavobacteriaceae, phylum Bacteroidetes. In this review, we report the structures and antioxidant activities of these carotenoids, and consider relationships between bacterial phyla and carotenoid structures.

Rare carotenoids, (3R)-saproxanthin and (3R,2′S)-myxol, isolated from novel marine bacteria (Flavobacteriaceae) and their antioxidative activities

We isolated three orange or yellow pigment-producing marine bacteria, strains 04OKA-13-27 (MBIC08261), 04OKA-17-12 (MBIC08260), and YM6-073 (MBIC06409), off the coast of Okinawa Prefecture in Japan. These strains were classified as novel species of the family Flavobacteriaceae based on their 16S rRNA gene sequence. They were cultured, and the major carotenoids produced were purified by chromatographic methods. Their structures were determined by spectral data to be (3R)-saproxanthin (strain 04OKA-13-27), (3R,2'S)-myxol (strain YM6-073), and (3R,3'R)-zeaxanthin (strains YM6-073 and 04OKA-17-12). Saproxanthin and myxol, which are monocyclic carotenoids rarely found in nature, demonstrated significant antioxidative activities against lipid peroxidation in the rat brain homogenate model and a neuro-protective effect from L-glutamate toxicity.

New neoverrucosane diterpenoids produced by the marine gliding bacterium Saprospira grandis

Chemical examination of the culture broth extracts of the marine gliding bacterium Saprospira grandis (ATCC 23116) has resulted in the isolation of four new diterpenoids of the neoverrucosane class. The structures of the new diterpenoids, compounds 1-4, were assigned by combined spectroscopic methods emphasizing 2D NMR experiments. The relative stereochemistry of 1 was determined by 2D ROESY NMR methods, while the absolute stereochemistry was assigned by application of the modified Mosher method. This study adds to the rare observation of terpene production by prokaryotic microorganisms and suggests that marine gliding bacteria may be a significant source for new terpenoid secondary metabolites.

A method for the machine detection of near equivalence of major substructures in a molecule

The use of the concept of near equivalence of substructures in a computer program concerned with organic synthesis requires a concrete definition of «nearness» and an efficient method for implementing the concept. Such a method has been devised and its use is described and examples are given.

Carotenoid pigments of facultatively anaerobic spirochetes

Carotenoid pigments were purified from a previously undescribed, red, halophilic spirochete (spirochete RS1), and from Spirochaeta aurantia strain J1. Both spirochetes are facultative anaerobes and produce pigments when growing aerobically. The major pigments of the two spirochetes were identified by means of chromatographic analysis, absorption spectroscopy, hydride reduction, acetylation and silylation experiments, and mass spectrometry. It was concluded that the major pigment from spirochete RS1 was 4-keto-1',2'-dihydro-1'-hydroxytorulene. This conclusion was further supported by infrared spectroscopy and additional analytical data. The evidence showed that the major pigment from S. aurantia was 1',2'-dihydro-1'-hydroxytorulene. Chromatographic and spectrophotometric evidence indicated that this pigment was also present, as a minor carotenoid component, in spirochete RS1. These pigments have been previously detected almost exclusively in gliding bacteria, such as species of Flexibacter, Stigmatella, and Myxococcus. The occurrence of 4-keto-1',2'-dihydro-1'-hydroxytorulene and 1',2'-dihydro-1'-hydroxytorulene in both spirochetes and gliding bacteria may have significance with respect to the evolutionary development of these organisms.

Fatty acids and polar lipids of extremely thermophilic filamentous bacterial masses from two Yellowstone hot springs

The fatty acid composition of filamentous bacterial masses from two very hot Yellowstone Park springs is not unusual despite the extreme environment. Both populations have a series of C(14) to C(20) straight-chain acids with a maximum at C(18), and a series of saturated iso acids with a maximum at C(17) in one case and C(19) in the other. The fatty acid pattern of this anomalous group of organisms is like that of bacteria but not of blue-green algae. Both populations have similar polar lipids and identical carotenoids. It is speculated that these organisms may be adapted to their high-temperature environment by means of stable lipoprotein membrane systems.