Precautions for seafood consumers: An updated review of toxicity, bioaccumulation, and rapid detection methods of marine biotoxins.

Seafood products are globally consumed, and there is an increasing demand for the quality and safety of these products among consumers. Some seafoods are easily contaminated by marine biotoxins in natural environments or cultured farming processes. When humans ingest different toxins accumulated in seafood, they may exhibit different poisoning symptoms. According to the investigations, marine toxins produced by harmful algal blooms and various other marine organisms mainly accumulate in the body organs such as liver and digestive tract of seafood animals. Several regions around the world have reported incidents of seafood poisoning by biotoxins, posing a threat to human health. Thus, most countries have legislated to specify the permissible levels of these biotoxins in seafood. Therefore, it is necessary for seafood producers and suppliers to conduct necessary testing of toxins in seafood before and after harvesting to prohibit excessive toxins containing seafood from entering the market, which therefore can reduce the occurrence of seafood poisoning incidents. In recent years, some technologies which can quickly, conveniently, and sensitively detect biological toxins in seafood, have been developed and validated, these technologies have the potential to help seafood producers, suppliers and regulatory authorities. This article reviews the seafood toxins sources and types, mechanism of action and bioaccumulation of marine toxins, as well as legislation and rapid detection technologies for biotoxins in seafood for official and fishermen supervision.

Preparation and properties of polyvinyl alcohol/chitosan-based hydrogel with dual pH/NH3 sensor for naked-eye monitoring of seafood freshness.

To address the issue of food spoilage causing health and economic loss, we developed a pH/NH3 dual sensitive hydrogel based on polyvinyl alcohol/chitosan (PVA/CS) containing chitosan-phenol red (CP). The CP was synthesized via Mannich reaction and immobilized it in PVA/CS hydrogel through freezing/thawing method to prepare the final PVA/CS/CP hydrogel. The synthesis of CP was confirmed by 1H NMR, FT-IR, XRD, UV-vis, and XPS. The characteristics of hydrogel were evaluated by FT-IR, XRD, SEM, mechanical properties, thermal stability, leaching, and color stability tests. The PVA/CS/CP hydrogel showed distinctly different color at various pH and NH3 vapor levels (yellow to purple). The hydrogel exhibited obvious color changes (ΔE = 46.95) in response to shrimp spoilage, stored at 4 °C. It showed positive and strong correlation between the ΔE values of the indicator hydrogel and total volatile basic nitrogen (TVB-N) as (R2 = 0.9573) and with pH as (R2 = 0.8686), respectively. These results clearly show that the PVA/CS/CP hydrogel could be applied for naked-eye real-time monitoring of seafood freshness in intelligent packaging.

Okadaic Acid Detection through a Rapid and Sensitive Amplified Luminescent Proximity Homogeneous Assay.

Okadaic acid (OA), a marine biotoxin produced by microalgae, poses a significant threat to mariculture, seafood safety, and human health. The establishment of a novel, highly sensitive detection method for OA would have significant practical and scientific implications. Therefore, the purpose of this study was to develop an innovative approach for OA detection. A competitive amplified luminescent proximity homogeneous assay (AlphaLISA) was developed using the principle of specific antigen-antibody binding based on the energy transfer between chemiluminescent microspheres. The method was non-washable, sensitive, and rapid, which could detect 2 × 10-2-200 ng/mL of OA within 15 min, and the detection limit was 4.55 × 10-3 ng/mL. The average intra- and inter-assay coefficients of variation were 2.54% and 6.26%, respectively. Detection of the actual sample results exhibited a good correlation with high-performance liquid chromatography. In conclusion, a simple, rapid, sensitive, and accurate AlphaLISA method was established for detecting OA and is expected to significantly contribute to marine biotoxin research.

A Novel Multifunctional Crosslinking PVA/CMCS Hydrogel Containing Cyclic Peptide Actinomycin X2 and PA@Fe with Excellent Antibacterial and Commendable Mechanical Properties.

Bacterial infected environments and resulting bacterial infections have been threatening the human health globally. Due to increased bacterial resistance caused by improper and excessive use of antibiotics, antibacterial biomaterials are being developed as alternatives to antibiotics in some cases. Herein, an advanced multifunctional hydrogel with excellent antibacterial properties, enhanced mechanical properties, biocompatibility and self-healing performance, was designed through freezing-thawing method. This hydrogel network is composed of polyvinyl alcohol (PVA), carboxymethyl chitosan (CMCS), protocatechualdehyde (PA), ferric iron (Fe) and an antimicrobial cyclic peptide actinomycin X2 (Ac.X2). The double dynamic bonds among protocatechualdehyde (PA), ferric iron (Fe) and carboxymethyl chitosan containing coordinate bond (catechol-Fe) as well as dynamic Schiff base bonds and hydrogen bonds endowed the hydrogel with enhanced mechanical properties. Successful formation of hydrogel was confirmed through ATR-IR and XRD, and structural evaluation through SEM analysis, whereas mechanical properties were tested with electromechanical universal testing machine. The resulting PVA/CMCS/Ac.X2/PA@Fe (PCXPA) hydrogel has favorable biocompatibility and excellent broad-spectrum antimicrobial activity against both S. aureus (95.3 %) and E. coli (90.2 %) compared with free-soluble Ac.X2, which exhibited subpar performance against E. coli reported in our previous studies. This work provides a new insight on preparing multifunctional hydrogels containing antimicrobial peptides as antibacterial material.

Preparation and Characterization of a Silk Fibroin/Polyurethane Fiber Blend Membrane Containing Actinomycin X2 with Excellent Mechanical Properties and Enhanced Antibacterial Activities.

Development of suitable antimicrobial biomaterials for hygienic wound dressing and healing is an important requirement for medical application. Durable mechanical properties increase the application range of biomaterial in different environmental and biological conditions. Due to the inherent brittleness of silk fibroin (SF), polyurethane fiber (PUF) was used to modify SF containing actinomycin X2 (Ac.X2) to prepare silk fibroin@actinomycin X2 /polyurethane fiber (ASF/PUF) blend membranes. The ASF/PUF blend membrane was developed by solution casting method. Incorporation of PUF improved the flexibility of material and introduction of Ac.X2 has increased antibacterial activity of materials. Excellent mechanical properties (tensile strength up to 25.7 MPa and elongation at break up to 946.5 %) of 50 % SF+50 % PUF blend membrane were proved by tensile testing machine. FT-IR spectra, TGA, contact angle and DMA were tested to prove the blend membrane's physico-chemical characteristics. ASF/PUF blend membrane displayed satisfactory antibacterial activity against S. aureus, and the cytotoxicity tests showed that the blend membrane has better biosafety compared to directly applied Ac.X2 in soluble form. These results suggest that the modification of SF through PUF for development of flexible antibacterial membranes has great potential application value in the field of silk-like material fabrication.

Actinomycin-X2-Immobilized Silk Fibroin Film with Enhanced Antimicrobial and Wound Healing Activities.

Actinomycin is a family of chromogenic lactone peptides that differ in their peptide portions of the molecule. An antimicrobial peptide, actinomycin X2 (Ac.X2), was produced through the fermentation of a Streptomyces cyaneofuscatus strain. Immobilization of Ac.X2 onto a prepared silk fibroin (SF) film was done through a carbodiimide reaction. The physical properties of immobilized Ac.X2 (antimicrobial films, AMFs) were analyzed by ATR-FTIR, SEM, AFM, and WCA. The findings from an in vitro study showed that AMFs had a more broad-spectrum antibacterial activity against both S. aureus and E. coli compared with free Ac.X2, which showed no apparent strong effect against E. coli. These AMFs showed a suitable degradation rate, good hemocompatibility, and reduced cytotoxicity in the biocompatibility assay. The results of in vivo bacterially infected wound healing experiments indicated that wound inflammation was prevented by AMFs, which promoted wound repair and improved the wound microenvironment. This study revealed that Ac.X2 transformation is a potential candidate for skin wound healing.

Structures and Anti-Allergic Activities of Natural Products from Marine Organisms.

In recent years, allergic diseases have occurred frequently, affecting more than 20% of the global population. The current first-line treatment of anti-allergic drugs mainly includes topical corticosteroids, as well as adjuvant treatment of antihistamine drugs, which have adverse side effects and drug resistance after long-term use. Therefore, it is essential to find alternative anti-allergic agents from natural products. High pressure, low temperature, and low/lack of light lead to highly functionalized and diverse functional natural products in the marine environment. This review summarizes the information on anti-allergic secondary metabolites with a variety of chemical structures such as polyphenols, alkaloids, terpenoids, steroids, and peptides, obtained mainly from fungi, bacteria, macroalgae, sponges, mollusks, and fish. Molecular docking simulation is applied by MOE to further reveal the potential mechanism for some representative marine anti-allergic natural products to target the H1 receptor. This review may not only provide insight into information about the structures and anti-allergic activities of natural products from marine organisms but also provides a valuable reference for marine natural products with immunomodulatory activities.

Structure Elucidation of Two Intriguing Neo-Debromoaplysiatoxin Derivatives from Marine Cyanobacterium Lyngbya sp. Showing Strong Inhibition of Kv1.5 Potassium Channel and Differential Cytotoxicity.

Two aplysiatoxin derivatives, neo-debromoaplysiatoxin I (1) and neo-debromoaplysiatoxin J (2), were isolated from marine cyanobacterium Lyngbya sp. collected from the South China Sea. Their structures including absolute configurations were assigned by spectroscopic analysis, in combination with GIAO NMR shift calculation and DP4+ analysis. Structures of neo-debromoaplysiatoxin I and neo-debromoaplysiatoxin J contained a decahydro-5H-pyrano [2,3,4-de] chromen-5-one 6/6/6 ring skeleton and an intriguing peroxide bridge group, respectively, which are unprecedented structure scaffold and motif in aplysiatoxins. Two compounds displayed comparable inhibitory activities against Kv1.5 K+ channel with IC50 values of 2.59 ± 0.37 µM (1) and 1.64 ± 0.15 µM (2); however, they presented differential cytotoxic effects. It is worth noting that neo-debromoaplysiatoxin J, containing a peroxide bridge, showed remarkable cytotoxicity against four cancer cell lines including SW480, SGC7901, LoVo and PC-9 compared to the human normal cell line.

Improved 2α-Hydroxylation Efficiency of Steroids by CYP154C2 Using Structure-Guided Rational Design.

Cytochrome P450 enzymes are promising biocatalysts for industrial use because they catalyze site-selective C-H oxidation and have diverse catalytic reactions and a broad substrate range. In this study, the 2α-hydroxylation activity of CYP154C2 from Streptomyces avermitilis MA-4680T toward androstenedione (ASD) was identified by an in vitro conversion assay. The testosterone (TES)-bound structure of CYP154C2 was solved at 1.42 Å, and this structure was used to design eight mutants, including single, double, and triple mutants, to improve the conversion efficiency. Mutants L88F/M191F and M191F/V285L were found to enhance the conversion rates significantly (i.e., 8.9-fold and 7.4-fold for TES, 46.5-fold and 19.5-fold for ASD, respectively) compared with the wild-type (WT) enzyme while retaining high 2α-position selectivity. The substrate binding affinity of the L88F/M191F mutant toward TES and ASD was enhanced compared with that of WT CYP154C2, supporting the measured increase in the conversion efficiencies. Moreover, the total turnover number and kcat/Km of the L88F/M191F and M191F/V285L mutants increased significantly. Interestingly, all mutants containing L88F generated 16α-hydroxylation products, suggesting that L88 in CYP154C2 plays a vital role in substrate selectivity and that the amino acid corresponding to L88 in the 154C subfamily affects the orientation of steroid binding and substrate selectivity. IMPORTANCE Hydroxylated derivatives of steroids play essential roles in medicine. Cytochrome P450 enzymes selectively hydroxylate methyne groups on steroids, which can dramatically change their polarity, biological activity and toxicity. There is a paucity of reports on the 2α-hydroxylation of steroids, and documented 2α-hydroxylate P450s show extremely low conversion efficiency and/or low regio- and stereoselectivity. This study conducted crystal structure analysis and structure-guided rational engineering of CYP154C2 and efficiently enhanced the conversion efficiency of TES and ASD with high regio- and stereoselectivity. Our results provide an effective strategy and theoretical basis for the 2α-hydroxylation of steroids, and the structure-guided rational design of P450s should facilitate P450 applications in the biosynthesis of steroid drugs.

Treatment of allergy: Overview of synthetic anti-allergy small molecules in medicinal chemistry.

The prevalence of allergic diseases has been continuously increasing over the past few decades, affecting approximately 20-30% of the global population. Allergic reactions to infection of respiratory tract, digestive tract, and skin system involve multiple different targets. The main difficulty of anti-allergy research is how to develop drugs with good curative effect and less side effects by adopting new multi-targets and mechanisms according to the clinical characteristics of different allergic populations and different allergens. This review focuses on information concerning potential therapeutic targets as well as the synthetic anti-allergy small molecules with respect to their medicinal chemistry. The structure-activity relationship and the mechanism of compound-target interaction were highlighted with perspective to histamine-1/4 receptor antagonists, leukotriene biosynthesis, Th2 cytokines inhibitors, and calcium channel blockers. We hope that the study of chemical scaffold modification and optimization for different lead compounds summarized in this review not only lays the foundation for improvement of success rate and efficiency of virtual screening of antiallergic drugs, but also can provide valuable reference for the drug design of related promising research such as allergy, inflammation, and cancer.

Recent advances of anti-angiogenic inhibitors targeting VEGF/VEGFR axis.

Vascular endothelial growth factors (VEGF), Vascular endothelial growth factor receptors (VEGFR) and their downstream signaling pathways are promising targets in anti-angiogenic therapy. They constitute a crucial system to regulate physiological and pathological angiogenesis. In the last 20 years, many anti-angiogenic drugs have been developed based on VEGF/VEGFR system to treat diverse cancers and retinopathies, and new drugs with improved properties continue to emerge at a fast rate. They consist of different molecular structures and characteristics, which enable them to inhibit the interaction of VEGF/VEGFR, to inhibit the activity of VEGFR tyrosine kinase (TK), or to inhibit VEGFR downstream signaling. In this paper, we reviewed the development of marketed anti-angiogenic drugs involved in the VEGF/VEGFR axis, as well as some important drug candidates in clinical trials. We discuss their mode of action, their clinical benefits, and the current challenges that will need to be addressed by the next-generation of anti-angiogenic drugs. We focus on the molecular structures and characteristics of each drug, including those approved only in China.

Four clinical phenotypes of cow's milk protein allergy based on dairy product specific IgE antibody types in North China.

Background: Cow's milk protein allergy (CMPA) is a common allergy. Immunoglobulin E (IgE)-mediated cow's milk allergy is associated with a high mortality risk and poor prognosis. The study aims to investigate whether there are different clinically CMPA phenotypes in China and to explore the association between CMPA phenotypes and specific IgE (sIgE) antibodies against different dairy products. Methods: Serum sIgE against different animal milk and cow's milk products and different milk components was measured by an allergen array. Four CMPA classifications were identified by the presence of serum sIgE: boiled milk-positive, yogurt-positive, buttermilk-positive, and raw milk-positive. Results: Among the 234 participants included in the study, 9 were boiled milk sIgE-positive, 50 were yogurt sIgE-positive, 17 were buttermilk sIgE-positive, and 158 were only raw milk sIgE-positive. The boiled milk-positive group had the highest levels of raw milk sIgE and casein sIgE antibodies, followed sequentially by the yogurt-positive, buttermilk-positive, and raw milk-positive groups. The boiled milk group observed the highest levels of sIgE against raw milk, casein, α-lactalbumin, and ß-lactoglobulin. These levels differed significantly from those in the other three groups. Allergic symptoms were distributed differently among the four study groups. The percentages of allergic patients with gastrointestinal tract symptoms in the above mentioned four groups ranged from high to low, and the percentages of patients with skin symptoms in the four groups ranged from low to high, respectively. Conclusion: Based on dairy product sIgE antibody levels associated with different milk components and various clinical allergic symptom tendencies, we could distinguish four CMPA phenotypes.

The 16α-Hydroxylation of Progesterone by Cytochrome P450 107X1 from Streptomyces avermitilis.

Cytochrome P450 enzymes (CYPs or P450s) are ubiquitous heme-dependent enzymes that catalyze the monooxygenation of non-activated C-H bonds to modify the structure of the substrate. In this study, we heterologously expressed CYP107X1 from Streptomyces avermitilis and conducted in vitro substrate screening using the alternative redox partners putidaredoxin and putidaredoxin reductase. CYP107X1 catalyzed the 16α-hydroxylation of progesterone with regio- and stereoselectivity. The spectroscopic analyses showed that CYP107X1 bound progesterone with a relatively high Kd value of 65.3±38.9 µM. The Km and kcat values for progesterone were estimated to be 47.7±12.0 µM and 0.30 min-1 , respectively. Furthermore, a crystal structure was obtained of CYP107X1 bound with glycerol from the buffer solution. Interestingly, a conserved threonine was replaced with asparagine in CYP107X1, indicating that it may adopt an unnatural proton transfer process and play a crucial role in its catalytic activity.

Erythrobacter aurantius sp. nov., isolated from intertidal seawater in Taizhou.

A Gram-stain-negative, aerobic, chemoheterotrophic and rod-shaped strain, designated as C5T, was isolated from intertidal surface seawater in Taizhou, Zhejiang Province, PR China and characterized using a polyphasic taxonomic approach. Strain C5T could produce carotenoids and bacteriochlorophyll a. Growth was observed at 20-45 °C, at pH 6.0-9.0 and with 0-8.0 % (w/v) NaCl. The 16S rRNA gene sequence identity analysis revealed that strain C5T was the most closely related to Qipengyuania nanhaisediminis CGMCC 1.7715T (98.8%) and Erythrobacter litoralis DSM 8509T (98.7%). The phylogenetic reconstruction based on core genes demonstrated that strain C5T was clustered into the members of the genus Erythrobacter. The average nucleotide identity and digital DNA-DNA hybridization values between strain C5T and Erythrobacter type strains were lower than 76 and 25 %, respectively. The predominant and minor respiratory quinones were identified as ubiquinone-10 and ubiquinone-9. The major fatty acids were summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c) and iso-C18 : 0. Polar lipids included phosphatidylethanolamine, phosphatidylglycerol, a glycosphingolipid and an unidentified aminolipid. Based on the genetic, chemotaxonomic and phenotypic data, strain C5T is concluded to represent a novel species in the genus Erythrobacter, for which the name Erythrobacter aurantius sp. nov. is proposed. The type strain is C5T (=MCCC 1K05108T=KCTC 92307T).

Halomonas populi sp. nov. isolated from Populus euphratica.

Three yellow-pigmented, Gram-stain-negative, aerobic, motile by flagella and rod-shaped strains, designated as MCT, PC and RC, were isolated from stems of Populus euphratica. Growth of those three strains occurs at 4-40 °C, pH 6.0-10.0 and with 0.5-18.0% (w/v) NaCl. Respiratory quinones contained ubiquinone-9 and ubiquione-8 as major and minor components, respectively. Major fatty acids (> 10%) were summed feature 8 (C18:1ω6c and/or C18:1ω7c), summed feature 3 (C16:1ω6c and/or C16:1ω7c) and C16:0. Polar lipids included diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, two unidentified phospholipids, one unidentified aminolipid, one unidentified glycolipid and four unidentified lipids. Strains MCT, PC and RC shared pairwise 16S rRNA gene sequence similarities of 99.9-100.0%, and showed higher similarities of 98.4-98.5% with Halomonas songnenensis NEAU-ST10-39T and 98.3-98.4% with Halomonas nanhaiensis YIM M 13059T than to other Halomonas type strains. Genomic comparisons revealed that those three strains had the pan-genome consisting of 4446 orthologous clusters, among which 676 orthologous clusters were absent in other Halomonas type strains. Phylogenomic tree indicated that strains MCT, PC and RC formed an independently stable clade with Halomonas nanhaiensis YIM M 13059T and Halomonas songnenensis NEAU-ST10-39T. The average nucleotide identity and digital DNA-DNA hybridization values between those three strains and other Halomonas type strains were < 89.9% and < 39.3%, respectively. Based upon phenotypic, chemotaxonomic, phylogenetic and genomic results, strains MCT, PC and RC represent a novel species in the genus Halomonas, for which the name Halomonas populi sp. nov. is proposed. The type strain is MCT (= JCM 33545T = MCCC 1K03942T).

Natural Products from Actinomycetes Associated with Marine Organisms.

The actinomycetes have proven to be a rich source of bioactive secondary metabolites and play a critical role in the development of pharmaceutical researches. With interactions of host organisms and having special ecological status, the actinomycetes associated with marine animals, marine plants, macroalgae, cyanobacteria, and lichens have more potential to produce active metabolites acting as chemical defenses to protect the host from predators as well as microbial infection. This review focuses on 536 secondary metabolites (SMs) from actinomycetes associated with these marine organisms covering the literature to mid-2021, which will highlight the taxonomic diversity of actinomycetes and the structural classes, biological activities of SMs. Among all the actinomycetes listed, members of Streptomyces (68%), Micromonospora (6%), and Nocardiopsis (3%) are dominant producers of secondary metabolites. Additionally, alkaloids (37%), polyketides (33%), and peptides (15%) comprise the largest proportion of natural products with mostly antimicrobial activity and cytotoxicity. Furthermore, the data analysis and clinical information of SMs have been summarized in this article, suggesting that some of these actinomycetes with multiple host organisms deserve more attention to their special ecological status and genetic factors.

Absolute Structure Determination and Kv1.5 Ion Channel Inhibition Activities of New Debromoaplysiatoxin Analogues.

Potassium channel Kv1.5 has been considered a key target for new treatments of atrial tachyarrhythmias, with few side effects. Four new debromoaplysiatoxin analogues with a 6/6/12 fused ring system were isolated from marine cyanobacterium Lyngbya sp. Their planar structures were elucidated by HRESIMS, 1D and 2D NMR. The absolute configuration of oscillatoxin J (1) was determined by single-crystal X-ray diffraction, and the absolute configurations of oscillatoxin K (2), oscillatoxin L (3) and oscillatoxin M (4) were confirmed on the basis of GIAO NMR shift calculation followed by DP4 analysis. The current study confirmed the absolute configuration of the pivotal chiral positions (7S, 9S, 10S, 11R, 12S, 15S, 29R and 30R) at traditional ATXs with 6/12/6 tricyclic ring system. Compound 1, 2 and 4 exhibited blocking activities against Kv1.5 with IC50 values of 2.61 ± 0.91 µM, 3.86 ± 1.03 µM and 3.79 ± 1.01 µM, respectively. However, compound 3 exhibited a minimum effect on Kv1.5 at 10 µM. Furthermore, all of these new debromoaplysiatoxin analogs displayed no apparent activity in a brine shrimp toxicity assay.

Marinomonas vulgaris sp. nov., a marine bacterium isolated from seawater in a coastal intertidal zone of Zhoushan island.

A Marinomonas-like, Gram-stain-negative, strictly aerobic and rod to ovoid-shaped bacterium, designated as strain A79T, was isolated from the seawater mixtures of oyster shells and brown algae in a coastal intertidal zone of Zhoushan, China. The strain was positive for oxidase and catalase. Colonies grown on marine agar for 48 h were round, milky white, smooth and moist with the diameter of 2-3 mm. Growth was observed at 15-30 °C (optimum, 25℃), pH 5.5-9.5 (optimum, pH 8.5) and with 0.5-8% (w/v) NaCl (optimum, 2-2.5%). The G + C content based on the genome sequence was 46.0%. The only respiratory quinone was Q-8. The main polar lipids contained phosphatidylglycerol, phosphatidylethanolamine, unidentified glycolipids, unidentified phospholipid and three unidentified lipids. The major fatty acids (> 10%) were C16:0, Summed feature 3 (comprising C16:1 ω6c and/or C16:1 ω7c) and summed feature 8 (comprising C18:1 ω6c and/or C18:1 ω7c). The 16S rRNA gene sequence similarity between strain A79T and Marinomonas pollencensis IVIA-Po-185T was 97.4%, the similarities with other type strains of the genus Marinomonas were 93.8-96.7%. Based on the results, Marinomonas vulgaris sp. nov. was proposed as a novel species. The type strain is A79T (= MCCC 1K05799T = KCTC 82519T = JCM 34473T).

Complete genome sequence of marine Roseobacter lineage member Monaibacterium sp. ALG8 with six plasmids isolated from seawater around brown algae.

Monaibacterium sp. ALG8 (=MCCC 1 K04733) was isolated from seawater around brown algae. The genome of Monaibacterium sp. ALG8 was sequenced, one circular 3,036,380 bp chromosome and six circular plasmids ranging from 12,229 to 151,263 bp were found after assembly. The results of genomic annotation showed that Monaibacterium sp. ALG8 lacks the ability to degrade alginate, indicating its ecological role may not be directly related to the degradation of brown algae. The comparison of genomic features in the plasmids showed that almost all of these plasmids, except pALG4, were horizontally recruited from donors, not ancestors. Based on predicted functions, the existence of plasmids may provide strain ALG8 with advantages including nitrate reduction, tolerance of osmotic stress via glycine betaine, resistance to heavy metal stress such as mercury and cobalt, degradation of benzoate metabolites such as p-cumate, transformation of the swim-or-stick lifestyle and improvement of the immune system with two CRISPR-Cas systems. This study provides evidence for the carbon metabolic patterns of Monaibacterium sp. ALG8 and predicts the functions and donors of six plasmids in this strain, broadening our understanding of the ecological roles of bacteria in the environment around brown algae and the functions and evolutionary patterns of plasmids in marine Roseobacter lineage members.

Hydroxylation, Epoxidation, and Dehydrogenation of Capsaicin by a Microbial Promiscuous Cytochrome P450 105D7.

Cytochrome P450 enzymes (P450s) are versatile biocatalysts, which insert a molecular oxygen into inactivated C-H bonds under mild conditions. CYP105D7 from Streptomyces avermitilis has been reported as a bacterial substrate-promiscuous P450 which catalyzes the hydroxylation of 1-deoxypentalenic acid, diclofenac, naringenin, compactin and steroids. In this study, CYP105D7 catalyzes hydroxylation, epoxidation and dehydrogenation of capsaicin, a pharmaceutical agent, revealing its functional diversity. The kinetic parameters of the CYP105D7 oxidation of capsaicin were determined as Km =311.60±87.30 µM and kcat =2.01±0.33 min-1 . In addition, we conducted molecular docking, mutagenesis and substrate binding analysis, indicating that Arg81 plays crucial role in the capsaicin binding and catalysis. To our best knowledge, this study presents the first report to illustrate that capsaicin can be catalyzed by prokaryotic P450s.