Discovery of Kebanmycins with Antibacterial and Cytotoxic Activities from the Mangrove-Derived Streptomyces sp. SCSIO 40068.

Mangrove derived actinomycetes are a rich reservoir of bioactive natural products and play important roles in pharmaceutical chemistry. In a screen of actinomycetes from mangrove rhizosphere sedimental environments, the isolated strain Streptomyces sp. SCSIO 40068 displayed strong antibacterial activity. Further fractionation of the extract yielded four new compounds kebanmycins A-D (1-4) and two known analogues FD-594 (5) and the aglycon (6). The structures of 1-6 were determined based on extensive spectroscopic data and single-crystal X-ray diffraction analysis. 1-3 featured a fused pyranonaphthaxanthene as an integral part of a 6/6/6/6/6/6 polycyclic motif, and showed bioactivity against a series of Gram-positive bacteria and cytotoxicity to several human tumor cells. In addition, the kebanmycins biosynthetic gene cluster (keb) was identified in Streptomyces sp. SCSIO 40068, and KebMT2 was biochemically characterized as a tailoring sugar-O-methyltransferase, leading to a proposed biosynthetic route to 1-6. This study paves the way to further investigate 1 as a potential lead compound.

Polyphasic Identification of Rhizomonospora bruguierae gen. nov., sp. nov., Isolated from Mangrove Rhizosphere Soil.

A novel yellowish-white actinobacterial strain, designated as TS60-4CT, was isolated from the rhizosphere soil of the mangrove Bruguiera gymnorhiza (L.) Lam. in Okinawa, Japan, and was subjected to a polyphasic assessment. The strain could grow at 0-3.0% NaCl concentrations (w/v), pH 6.0-10.0, and 20-37 °C. The 16S rRNA gene sequences-based phylogeny showed that the novel isolate belongs to the family Micromonosporaceae and that it shared the highest sequence similarity (98.4%) with Micromonospora craniellae LHW63014T. The hydrolysate of cell-wall of strain TS60-4CT contained alanine, glutamic acid, glycine, and meso-A2pm. The acyl type of muramic acid was N-glycolyl. The main (> 10%) fatty acids were anteiso-C17:0 (22.1%), iso-C16:0 (17.8%), iso-C15:0 (14.7%), and anteiso-C15:0 (10.3%) and the predominant menaquinones of the isolate were MK-9(H6) and MK-9(H4). The polar lipids of the isolate were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, an unidentified aminolipid, and three unidentified lipids. The genome size of strain TS60-4CT was 6.7 Mbp with a DNA G + C content of 72.4%. The average nucleotide identity, digital DNA-DNA hybridization, and average amino acid identity value could differentiate strain TS60-4CT from its closely related taxa. The genome of the strain had 22 putative biosynthetic gene clusters for secondary metabolites, indicating a significant potential as a producer of bioactive chemicals. Consequently, the strain is considered to represent a novel genus and a new species of the family Micromonosporaceae, for which the name Rhizomonospora bruguierae gen. nov., sp. nov. is proposed. The type species is R. bruguierae, with the type strain TS60-4CT (= NBRC 107566T = TBRC 2024T).

Chemical Constituents and Biological Activities of Bruguiera Genus and Its Endophytes: A Review.

The genus Bruguiera, a member of the Rhizophoraceae family, is predominantly found in coastal areas as a mangrove plant, boasting a rich and diverse community of endophytes. This review systematically compiled approximately 496 compounds derived from both the Bruguiera genus and its associated endophytes, including 152 terpenoids, 17 steroids, 16 sulfides, 44 alkaloids and peptides, 66 quinones, 68 polyketides, 19 flavonoids, 38 phenylpropanoids, 54 aromatic compounds, and 22 other compounds. Among these, 201 compounds exhibited a spectrum of activities, including cytotoxicity, antimicrobial, antioxidant, anti-inflammatory, antiviral, antidiabetic, insecticidal and mosquito repellent, and enzyme inhibitory properties, etc. These findings provided promising lead compounds for drug discovery. Certain similar or identical compounds were found to be simultaneously present in both Bruguiera plants and their endophytes, and the phenomenon of their interaction relationship was discussed.

New Secondary Metabolites of Mangrove-Associated Strains.

Positioned at the dynamic interface between terrestrial and marine realms, mangroves embody a vibrant tapestry of biodiversity, encompassing an array of plants, animals, and microorganisms. These microbial inhabitants of mangrove habitats have emerged as a pivotal resource for antimicrobials and a plethora of pharmaceutically valuable compounds, spanning enzymes, antineoplastic agents, pesticides, immunosuppressants, and immunomodulators. This review delves into the recent landscape (January 2021 to May 2024, according to the time of publication) of novel secondary metabolites isolated from mangrove-associated microorganisms, analyzing 41 microbial strains that collectively yielded 165 distinct compounds. Our objective is to assess the productivity and potential of natural products derived from microbial populations within mangrove ecosystems in recent times. Notably, fungi stand out as the preeminent contributors to the emergence of these novel natural products, underscoring their pivotal role in the bioprospecting endeavors within these unique environments.

Polyketide Derivatives from the Mangrove-Derived Fungus Penicillium sp. HDN15-312.

Four new polyketides, namely furantides A-B (1-2), talamin E (3) and arugosinacid A (4), and two known polyketides were obtained from the mangrove-derived fungus Penicillium sp. HDN15-312 using the One Strain Many Compounds (OSMAC) strategy. Their chemical structures, including configurations, were elucidated by detailed analysis of extensive NMR spectra, HRESIMS and ECD. The DPPH radicals scavenging activity of 3, with an IC50 value of 6.79 µM, was better than vitamin C.

Two C23-Steroids and a New Isocoumarin Metabolite from Mangrove Sediment-Derived Fungus Penicillium sp. SCSIO 41429.

Two new C23-steroids derivatives, cyclocitrinoic acid A (1) and cyclocitrinoic acid B (2), and a new isocoumarin metabolite, (3R,4S)-6,8-dihydroxy-3,4,5-trimethyl-7-carboxamidelisocoumarin (10), together with 12 known compounds (3-9, 11-15) were isolated from the mangrove-sediment fungus Penicillium sp. SCSIO 41429. The structures of the new compounds were comprehensively characterized by 1D and 2D NMR, HRESIMS and ECD calculation. All isolates were evaluated for pancreatic lipase (PL) inhibitory and antioxidant activities. The biological evaluation results revealed that compounds 2, 14 and 15 displayed weak or moderate inhibition against PL, with IC50 values of 32.77, 5.15 and 2.42 µM, respectively. In addition, compounds 7, 12 and 13 showed radical scavenging activities against DPPH, with IC50 values of 64.70, 48.13, and 75.54 µM, respectively. In addition, molecular docking results indicated that these compounds had potential for PL inhibitory and antioxidant activities, which provided screening candidates for antioxidants and a reduction in obesity.

New Naphthalene Derivatives from the Mangrove Endophytic Fungus Daldinia eschscholzii MCZ-18.

Five new naphthalene derivatives dalesconosides A-D, F (1-4, 6), a known synthetic analogue named dalesconoside E (5), and eighteen known compounds (7-24) were isolated from Daldinia eschscholzii MCZ-18, which is an endophytic fungus obtained from the Chinese mangrove plant Ceriops tagal. Differing from previously reported naphthalenes, compounds 1 and 2 were bearing a rare ribofuranoside substituted at C-1 and the 5-methyltetrahydrofuran-2,3-diol moiety, respectively. Their structures were determined by detailed nuclear magnetic resonance (NMR) and mass spectroscopic (MS) analyses, while the absolute configurations were established by theoretical electronic circular dichroism (ECD) calculation. Compounds 1, 3, 13-17 and 19 showed broad ranges of antimicrobial spectrum against five indicator test microorganisms (Enterococcus faecalis, Methicillin-resistant Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans); especially, 1, 16 and 17 were most potent. The variations in structure and attendant biological activities provided fresh insights concerning structure-activity relationships for the naphthalene derivatives.

Induction of Three New Secondary Metabolites by the Co-Culture of Endophytic Fungi Phomopsis asparagi DHS-48 and Phomopsis sp. DHS-11 Isolated from the Chinese Mangrove Plant Rhizophora mangle.

Co-cultivation is a powerful emerging tool for awakening biosynthetic gene clusters (BGCs) that remain transcriptionally silent under artificial culture conditions. It has recently been used increasingly extensively to study natural interactions and discover new bioactive metabolites. As a part of our project aiming at the discovery of structurally novel and biologically active natural products from mangrove endophytic fungi, an established co-culture of a strain of Phomopsis asparagi DHS-48 with another Phomopsis genus fungus DHS-11, both endophytes in mangrove Rhizophora mangle, proved to be very efficient to induce the production of new metabolites as well as to increase the yields of respective target metabolites. A detailed chemical investigation of the minor metabolites produced by the co-culture of these two titled fungal strains led to the isolation of six alkaloids (1-6), two sterols (7, 8), and six polyketides (9-14). In addition, all the compounds except 8 and 10, as well as three new metabolites phomopyrazine (1), phomosterol C (7), and phomopyrone E (9), were not present in discrete fungal cultures and only detected in the co-cultures. The structures were elucidated on the basis of spectroscopic analysis, and the absolute configurations were assumed by electronic circular dichroism (ECD) calculations. Subsequently, the cytotoxic, immunosuppressive, and acetylcholinesterase inhibitory properties of all the isolated metabolites were determined in vitro. Compound 8 exhibited moderate inhibitory activity against ConA-induced T and LPS-induced B murine splenic lymphocytes, with IC50 values of 35.75 ± 1.09 and 47.65 ± 1.21 µM, respectively.

Dereplication Tools for Rhizophora mangle Extracts from Different Mangrove Areas and their Potential Against Staphylococcus aureus.

Rhizophora extracts have several potential biological activities, and their metabolites can be used in the pharmaceutical industry. Extracts of Rhizophora species obtained from mangroves have shown prospective activity against Staphylococcus aureus. This study aimed to investigate the chemical profile of Rhizophora mangle leaves from fringe, basin, and transition mangrove zones and their bactericidal/bacteriostatic potential against S. aureus. R. mangle leaves were collected monthly in 2018 from litterfall in three different zones of the mangrove of Guaratiba State Reserve: fringe, basin, and transition. Extracts were prepared from the material collected in October and December for LC-HRMS/MS analysis, and dereplication was performed using a molecular library search and the classical molecular networking GNPS platform. The minimum inhibitory concentrations (MICs) of the aqueous extract of R. mangle against S. aureus were determined. No S. aureus growth was observed compared to the control for extracts collected from September to December. Different compounds were annotated in each region, yet a marked presence of phenolic compounds was noted, among them glycosylated flavonoid derivatives of quercetin and kaempferol. The results suggest bactericidal/bacteriostatic activity for extracts of R. mangle leaves collected in 2018 from three mangrove forest zones.

Biotechnological applications of mangrove plants and their isolated compounds in medicine-a mechanistic overview.

Mangrove plants, also known as halophytes, are ecologically important plants that grow in various tropical and subtropical intertidal regions. Owing to the extreme abiotic and biotic stressful conditions they thrive in, these plants produce unique compounds with promising pharmacological propensities. Mangroves are inhabited by an astronomical number of fungal communities which produce a diverse array of extracellular degradative enzymes, namely: amylase, cellulase, xylanase, pectinase, cholesterol oxidase, etc. Such enzymes can be isolated from the mangrove fungi and harnessed for different biotechnological applications, for example, as replacements for chemical catalysts. Mangrove microbes attract considerable attention as they shelter the largest group of marine microorganisms that are resistant to extreme conditions and can produce novel biogenic substances. Vaccines developed from mangrove microbes may promise a safe future by developing effective immunization procedures with a minimum of economic burden. Interestingly, mangroves offer an exciting opportunity for synthesizing nanoparticles in a greener way as these plants are naturally rich in phytochemicals. Rhizophora mucronata Lam., Avicennia officinalis L. and Excoecaria agallocha L. are capable of synthesizing nanoparticles which have evolved recently as an alternative in various industries and are used for their biomedical application. Besides, the phytoconstituents isolated from mangrove plants, such as: gallic acid, galactose, lupeol, catechins, carotenoids, etc., were explored for various biological activities. These compounds are used in the pharmaceutical and nutraceutical industries to produce antimicrobial, antioxidant, anticancer, antidiabetic, and other therapeutic agents. The present review provides information on the biotechnological potentials of mangrove plants and their bioactive compounds as a new source of novel drugs, enzymes, nanoparticles and therapeutically important microbial pigments. Thus, this review forms a base of support and hasten the urgent research on biomedical applications of mangroves.

Red Mangrove Propagule Bacterial Communities Vary With Geographic, But Not Genetic Distance.

Bacterial communities associated with plant propagules remain understudied, despite the opportunities that propagules represent as dispersal vectors for bacteria to new sites. These communities may be the product of a combination of environmental influence and inheritance from parent to offspring. The relative role of these mechanisms could have significant implications for our understanding of plant-microbe interactions. We studied the correlates of microbiome community similarities across an invasion front of red mangroves (Rhizophora mangle L.) in Florida, where the species is expanding northward. We collected georeferenced propagule samples from 110 individuals of red mangroves across 11 populations in Florida and used 16S rRNA gene (iTag) sequencing to describe their bacterial communities. We found no core community of bacterial amplicon sequence variants (ASVs) across the Florida range of red mangroves, though there were some ASVs shared among individuals within most populations. Populations differed significantly as measured by Bray-Curtis dissimilarity, but not Unifrac distance. We generated data from 6 microsatellite loci from 60 individuals across 9 of the 11 populations. Geographic distance was correlated with beta diversity, but genetic distance was not. We conclude that red mangrove propagule bacterial communities are likely influenced more by local environmental acquisition than by inheritance.

Description and genomic characterization of Gallaecimonas kandeliae sp. nov., isolated from the sediments of mangrove plant Kandelia obovate.

The genus Gallaecimonas, proposed by Rodríguez-Blanco et al. (Int J Syst Evol Microbiol 60:504-509, 2010), is mainly isolated from marine environments. So far, only three species have been identified and characterized in this genus. In this study, a new Gallaecimonas strain named Q10T was isolated from the sediments of mangrove plant Kandelia obovate taken from Dapeng district, Shenzhen, China. Strain Q10T was a Gram-stain-negative, non-motile, strictly aerobic, rod-shaped bacterium, and grew with 0-8.0% (w/v) NaCl, at 10-45 °C and at pH 5.5-8.5. Phylogenetic analysis indicated that strain Q10T and the three Gallaecimonas species formed a clade in the tree, with 16S rRNA gene sequence similarities ranging from 96.0 to 97.0%. The major respiratory quinone is Q8. The polar lipids comprised aminolipid, aminophospholipid, diphosphatidylglycerol, glycolipid, phosphatidylethanolamine, phosphatidylglycerol, glycophospholipid and phospholipid. The predominant fatty acids are C16:0, C17:1ω8c, summed feature 3 (C16:1ω7c/C16:1ω6c), and iso-C16:0. The complete genome of strain Q10T is 3,836,841 bp with a G+C content of 62.6 mol%. The orthologous proteins analysis revealed 55 unique proteins in strain Q10T related to important biological processes, especially three frataxins related to iron-sulfur cluster assembly, which may play a pivotal role in environmental adaptability of this species. Based on polyphasic taxonomic data, strain Q10T is considered to represent a novel species within the genus Gallaecimonas, for which the name Gallaecimonas kandelia sp. nov. is proposed. The type strain is Q10T (=KCTC 92860T=MCCC 1K08421T). These results contribute to a better understanding of general features and taxonomy of the genus Gallaecimonas.

A new chromone from Kandelia candel endophytic fungus Aspergillus sp. ZJ-68.

One chromone (1), together with four known alkaloids, were isolated from the mangrove endophytic fungus Aspergillus sp. ZJ-68. Their structures were elucidated by a combination of HRESIMS and NMR spectroscopic analyses. Compound 1 showed strong anti-inflammatory activity in vitro by inhibiting nitric oxide (NO) production in lipopolysaccharide-activated RAW264.7 cells with an IC50 value of 4.094 ± 0.8 µM, which was better than positive drug indomethacin (IC50=35.8 ± 0.5 µM).

New Isocoumarin and Pyrone Derivatives from the Chinese Mangrove Plant Rhizophora mangle-Associated Fungus Phomopsis sp. DHS-11.

Mangrove-associated fungi are important sources for the discovery of new bioactive natural products. Three new isocoumarins (1-3) and one new pyrone derivative (4) were isolated from the ethyl acetate extract of the fermentation broth of the mangrove endophytic fungus Phomopsis sp. DHS-11. Nuclear magnetic resonance (NMR) spectroscopy (one-dimensional and two-dimensional) and mass spectrometry were used to determine the structures of these new compounds. The absolute configurations for the new isocoumarins 1-3 were determined by comparing their experimental and calculated electronic circular dichroism (ECD) spectra, while the configuration for the new pyrone-derivative 4 was tentatively solved by comparison of its 13C NMR data with reported data. In the biological activity test, compounds 1 and 3 showed cytotoxic activity against HeLa cells with IC50 values of 11.49 ± 1.64 µM and 8.70 ± 0.94 µM, respectively. The initial structure and activity relationship (SAR) analysis revealed that the length of the side chain at C-3 for isocoumarin-type compounds 1-3 could affect the cytotoxicity against HeLa cells. Compound 4 exhibited cytotoxic activities against human hepatoma cells HepG2 with an IC50 value of 34.10 ± 2.92 µM. All compounds have no immunosuppressive activity.

Metabacillus kandeliae sp. nov., isolated from the rhizosphere soil of a decayed mangrove plant Kandelia candel.

In this study, we isolated a novel Gram-stain-positive, aerobic, motile, rod-shaped bacterium, named GX 13764T, from the rhizosphere soil of a decayed mangrove plant Kandelia candel collected from Beihai, Guangxi, PR China, and characterized using a polyphasic taxonomic approach. The strain exhibited yellow-orange, round, convex, shiny, smooth, opaque and 2-3 mm diameter colonies on marine agar 2216 media after 3 days of incubation at 30 °C and was capable of growth at 4-45 °C (optimum, 30 °C), pH 5.0-9.0 (optimum, pH 7.0) and 0-4 % NaCl (w/v; optimum, 2 %). The strain was positive for catalase and negative for the oxidase. The main cellular fatty acid was anteiso-C15:0, iso-C15:0, iso-C16:0 and iso-C14:0. The cell-wall peptidoglycan comprised meso-diaminopimelic acid and the main menaquinone was MK-7. The polar lipids included one diphosphatidylglycerol, one phosphatidylglycerol, two glycolipids, two unidentified phospholipids and three unidentified lipids. Based on 16S rRNA gene analysis, GX 13764T presented the highest sequence similarity to Metabacillus mangrovi KCTC 33872T (97.04 %). The DNA G+C content of the type strain was 44.2 mol%. The average nucleotide identity values between GX 13764T and M. mangrovi KCTC 33872T, Metabacillus idriensis DSM 19097T and Metabacillus indicus LMG 22858T were 69.39, 68.87 and 68.95 %, respectively, with digital DNA-DNA hybridization values of 19.9, 19.5 and 19.5 %, respectively. Based on the polyphasic data, strain GX 13764T should be nominated as a novel species of the genus Metabacillus, for which the name Metabacillus kandeliae sp. nov. is proposed. The type strain is GX 13764T (=MCCC 1K06654T=KCTC 43366T).

Nocardioides mangrovi sp. nov., a novel endophytic actinobacterium isolated from root of Kandelia candel.

A novel species of endophytic actinobacterium, designated strain GBK3QG-3T, was isolated from surface-sterilized root of Kandelia candel collected from Beilun Estuary, Guangxi Zhuang Autonomous Region, PR China. Cells of strain GBK3QG-3T were Gram-stain-positive, aerobic, non-spore-forming and rod-shaped. Growth of GBK3QG-3T was observed at 10-40 °C (optimum, 30 °C), pH 5.0-9.0 (optimum, pH 7.0) and in the presence of 0-3 % (w/v) NaCl (optimum, 0 %). The G+C content of genomic DNA was determined to be 72.2 mol%. On the basis of 16S rRNA gene sequence analysis, strain GBK3QG-3T was most related to the type strain of Nocardioides agrisoli CCTCC AB 2017058T (97.7 % 16S rRNA gene sequence similarity), followed by Nocardioides ginkgobilobae SYP-A7303T (97.0 %) and Nocardioides aquiterrae GW-9T (96.9 %). Average nucleotide identity and digital DNA-DNA hybridization values between strain GBK3QG-3T and some strains of the genus Nocardioides with publicly available genomes were below 84.3 and 30.0 %, respectively. The cell-wall peptidoglycan contained ll-diaminopimelic acid. The polar lipids comprised diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, an unknown phospholipid and an unknown lipid. The major menaquinone was identified as MK-8(H4), and the major fatty acids were identified as iso-C16 : 0, iso-C17 : 0 and anteiso-C17 : 0. Based on evidence collected from the phenotypic, genotypic and phylogenetic analyses, we propose a novel species named Nocardioides mangrovi sp. nov. The type strain is GBK3QG-3T (=CGMCC 4.7708T=JCM 34553T).

Stakelama flava sp. nov., a novel endophytic bacterium isolated from a branch of Kandelia candel.

A Gram-stain-negative, aerobic, motile, non-spore-forming, short-rod-shaped strain that did not produce diffusible pigment, designated CBK3Z-3T, was isolated from a branch of Kandelia candel, collected from the Beilun Estuary National Nature Reserve in Guangxi Zhang Autonomous Region, PR China, and investigated by a polyphasic approach to determine its taxonomic position. Strain CBK3Z-3T grew at pH 5.0-10.0 (optimum, pH 8.0), 20-37 °C (optimum, 25-30 °C) and with 0-10 % (w/v) NaCl (optimum, 2-3 %). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain CBK3Z-3T was closely related to species of genus Stakelama and had the highest 16S rRNA gene sequence similarity of 98.7 % to Stakelama pacifica CGMCC 1.7294T. The DNA G+C content value of strain CBK3Z-3T was 62.6 mol%. The diagnostic diamino acid in the cell-wall peptidoglycan was meso-diaminopimelic acid and the polar lipids comprised diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, sphingoglycolipid, an unidentified aminolipid and an unidentified lipid. The major fatty acids were C18 : 1 ω7c and C16 : 0. The average nucleotide identity, estimated digital DNA-DNA hybridization and average amino acid identity values between strain CBK3Z-3T and the type strain of Stakelama pacifica CGMCC 1.7294T were 80.4, 23.1 and 81.5 %, respectively. Based on the phylogenetic, phenotypic and chemotaxonomic data, strain CBK3Z-3T should be designated as a novel species of the genus Stakelama, for which the name Stakelama flava sp.nov. is proposed. The type strain is CBK3Z-3T (=JCM 34534T=CGMCC 1.18972T).

Bisabolanoic acid A, a new polychiral sesquiterpene with AChE inhibitory activity from a mangrove-derived fungus Colletotrichum sp.

A new polychiral bisabolane sesquiterpene, bisabolanoic acid A (1), was isolated from the mangrove-derived fungus Colletotrichum sp. SCSIO KcB3-2. Its planar structure was identified on the basis of spectroscopic data analysis (HRESIMS, 1D, and 2D NMR), and the absolute configurations of three chiral carbons were determined by experimental and calculated electronic circular dichroism (ECD) and optical rotatory dispersion (ORD), together with Mo2(OAc)4-induced ECD methods. Bisabolanoic acid A (1) showed moderate inhibitory activity against acetylcholinesterase (AChE) with IC50 value of 2.2 µM, and the in silico molecular docking was also performed.

Martelella alba sp. nov., isolated from mangrove rhizosphere soil within the Beibu Gulf.

Strain BGMRC 2036T was isolated from rhizosphere soil of Bruguiear gymnorrhiza collected from the Beibu Gulf of China. Optimum growth occurred at 28 °C, pH 7.0, and under the conditions of 3-5% (w/v) NaCl. The phylogenetic comparisons of 16S rRNA gene sequences displayed that strain BGMRC 2036T was closely related to Martelella limonii NBRC109441T (96.6% sequence similarity), M. mediterranea CGMCC 1.12224T (96.5%), M. lutilitoris GH2-6T (96.5%), M. radicis BM5-7T (96.2%), and M. mangrove BM9-1T (95.9%), M. suaedae NBRC109440T (95.8%). The phylogenomic tree based on the up-to-date bacterial core gene set indicated that the strain BGMRC 2036T form a clade formed with members of the genera Martelella. The major polar lipids include phosphatidylmethylethanolamine, phosphatidylglycerol, phosphatidylcholine, phosphotidylinositol, two unidentified phospholipids, and three unidentified ninhydrin positive phospholipids. The major respiratory quinone is Q-10, which is similar to those of genera Martelella. The main cellular fatty acids are C18:1 ω7c, C16:0, and C12:0 aldehyde. Genome sequencing revealed a genome size of 4.99 Mbp and a G + C content of 62.3 mol%. Pairwise comparison of the genomes of the new strain BGMRC 2036T and the three reference strains M. endophytica YC 6887T, M. mediterranea CGMCC 1.12224T, and M. mangrovi USBA-857 indicated that gANI value was lower than 81% and a digital DNA-DNA hybridization value was lower than 27%. The strain BGMRC 2036T possessed genes putatively encoding riboflavin synthesis and flavodoxin A polyphasic taxonomic study suggested that strain BGMRC 2036T represented a novel species belonging to the genus Martelella, and it was named Martelella alba sp. nov. The type strain is BGMRC 2036T (=KCTC 52121T =NBRC 111908T).

Kaustia mangrovi gen. nov., sp. nov. isolated from Red Sea mangrove sediments belongs to the recently proposed Parvibaculaceae family within the order Rhizobiales.

We isolated a novel strain, R1DC25T, described as Kaustia mangrovi gen. nov. sp. nov. from the sediments of a mangrove forest on the coast of the Red Sea in Saudi Arabia. This isolate is a moderately halophilic, aerobic/facultatively anaerobic Gram-stain-negative bacterium showing optimum growth at between 30 and 40 °C, at a pH of 8.5 and with 3-5 % NaCl. The genome of R1DC25T comprises a circular chromosome that is 4 630 536 bp in length, with a DNA G+C content of 67.3 mol%. Phylogenetic analyses based on the 16S rRNA gene sequence and whole-genome multilocus sequence analysis of 120 concatenated single-copy genes revealed that R1DC25T represents a distinct lineage within the family Parvibaculaceae in the order Rhizobiales within the class Alphaproteobacteria. R1DC25T showing 95.8, 95.3 and 94.5 % 16S rRNA gene sequence identity with Rhodoligotrophos appendicifer, Rhodoligotrophos jinshengii and Rhodoligotrophos defluvii, respectively. The predominant quinone was Q-10, and the polar lipids were phosphatidylglycerol, phosphatidylcholine, diphosphatidylglycerol, as well as several distinct aminolipids and lipids. The predominant cellular fatty acids were C19 : 0 cyclo ω8c, a combination of C18 : 1ω7c and/or C18 : 1ω6c and C16 : 0. On the basis of the differences in the phenotypic, physiological and biochemical characteristics from its known relatives and the results of our phylogenetic analyses, R1DC25T (=KCTC 72348T;=JCM 33619T;=NCCB 100699T) is proposed to represent a novel species in a novel genus, and we propose the name Kaustia mangrovi gen. nov., sp. nov. (Kaustia, subjective name derived from the abbreviation KAUST for King Abdullah University of Science and Technology; mangrovi, of a mangrove).