Aeromicrobium halocynthiae sp. nov., a taurocholic acid-producing bacterium isolated from the marine ascidian Halocynthia roretzi

Taxonomic descriptions of Aeromicrobium duanguangcaii sp. nov., Aeromicrobium wangtongii sp. nov. and Aeromicrobium senzhongii sp. nov

Six Gram-stain-positive, facultative anaerobic, nonmotile and rod-shaped strains, designated zg-Y50T, zg-Y1362, zg-Y1379T, zg-Y869, zg-629T and zg-Y636, were isolated from the intestinal contents of Marmota himalayana in Qinghai Province, PR China. Strains zg-Y50T, zg-Y1379T and zg-629T exhibited the highest 16S rRNA gene sequence similarities of 99.2, 98.9 and 98.8 % to Aeromicrobium choanae 9 H-4T, Aeromicrobium ginsengisoli JCM 14732T and Aeromicrobium flavum TYLN1T, respectively. Phylogenetic and phylogenomic analyses based on the 16S rRNA gene and genomic sequences, respectively, revealed that the six strains formed three distinct clades within the genus Aeromicrobium. The genome sizes of strains zg-Y50T, zg-Y1379T and zg-629T were 3.1-3.7 Mb, with DNA G+C contents of 69.6-70.4 mol%. Average nucleotide identity and digital DNA-DNA hybridization values between each novel strain and available members of the genus Aeromicrobium were all below species thresholds. All novel strains contained MK-9 (H4) as the major menaquinone and diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol as the polar lipids. The predominant fatty acid of the six isolates was C18 : 1  ω9c. The cell-wall peptidoglycan contained ʟʟ-diaminopimelic acid as the diagnostic diamino acid. Based on the results from this polyphasic taxonomic study, three novel species in the genus Aeromicrobium are proposed, namely, Aeromicrobium duanguangcaii sp. nov. (zg-Y50T=GDMCC 1.2981T=KCTC 49764T), Aeromicrobium wangtongii sp. nov. (zg-Y1379T=GDMCC 1.2982T=KCTC 49765T) and Aeromicrobium senzhongii sp. nov. (zg-629T=CGMCC 1.17414T=JCM 33888T).

Bioassay-Guided Fractionation Leads to the Detection of Cholic Acid Generated by the Rare Thalassomonas sp

Bacterial symbionts of marine invertebrates are rich sources of novel, pharmaceutically relevant natural products that could become leads in combatting multidrug-resistant pathogens and treating disease. In this study, the bioactive potential of the marine invertebrate symbiont Thalassomonas actiniarum was investigated. Bioactivity screening of the strain revealed Gram-positive specific antibacterial activity as well as cytotoxic activity against a human melanoma cell line (A2058). The dereplication of the active fraction using HPLC-MS led to the isolation and structural elucidation of cholic acid and 3-oxo cholic acid. T. actiniarum is one of three type species belonging to the genus Thalassomonas. The ability to generate cholic acid was assessed for all three species using thin-layer chromatography and was confirmed by LC-MS. The re-sequencing of all three Thalassomonas type species using long-read Oxford Nanopore Technology (ONT) and Illumina data produced complete genomes, enabling the bioinformatic assessment of the ability of the strains to produce cholic acid. Although a complete biosynthetic pathway for cholic acid synthesis in this genus could not be determined based on sequence-based homology searches, the identification of putative penicillin or homoserine lactone acylases in all three species suggests a mechanism for the hydrolysis of conjugated bile acids present in the growth medium, resulting in the generation of cholic acid and 3-oxo cholic acid. With little known currently about the bioactivities of this genus, this study serves as the foundation for future investigations into their bioactive potential as well as the potential ecological role of bile acid transformation, sterol modification and quorum quenching by Thalassomonas sp. in the marine environment.

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.

Symbiotic Associations in Ascidians: Relevance for Functional Innovation and Bioactive Potential

Associations between different organisms have been extensively described in terrestrial and marine environments. These associations are involved in roles as diverse as nutrient exchanges, shelter or adaptation to adverse conditions. Ascidians are widely dispersed marine invertebrates associated to invasive behaviours. Studying their microbiomes has interested the scientific community, mainly due to its potential for bioactive compounds production-e.g., ET-73 (trabectedin, Yondelis), an anticancer drug. However, these symbiotic interactions embrace several environmental and biological functions with high ecological relevance, inspiring diverse biotechnological applications. We thoroughly reviewed microbiome studies (microscopic to metagenomic approaches) of around 171 hosts, worldwide dispersed, occurring at different domains of life (Archaea, Bacteria, Eukarya), to illuminate the functions and bioactive potential of associated organisms in ascidians. Associations with Bacteria are the most prevalent, namely with Cyanobacteria, Proteobacteria, Bacteroidetes, Actinobacteria and Planctomycetes phyla. The microbiomes of ascidians belonging to Aplousobranchia order have been the most studied. The integration of worldwide studies characterizing ascidians' microbiome composition revealed several functions including UV protection, bioaccumulation of heavy metals and defense against fouling or predators through production of natural products, chemical signals or competition. The critical assessment and characterization of these communities is extremely valuable to comprehend their biological/ecological role and biotechnological potential.

Aeromicrobium terrae sp. nov., isolated from a maize field

A polyphasic taxonomic approach was used to characterize a Gram-stain-positive bacterium, designated strain CC-CFT486^T, isolated from soil sampled in a maize field in Taiwan. Cells of strain CC-CFT486^T were short rods, motile with polar flagella, catalase-positive and oxidase-positive. Optimal growth occurred at 30 °С, pH 8 and 1 % NaCl. Phylogenetic analyses based on 16S rRNA genes revealed a distinct taxonomic position attained by strain CC-CFT486^T associated with Aeromicrobium panacisoli (97.0 % sequence identity), Aeromicrobium lacus (97.0 %), Aeromicrobium erythreum (96.8 %) and Aeromicrobium alkaliterrae (96.8 %), and lower sequence similarity values to other species. Average nucleotide identity (ANI) values were 70.6-77.8 % (n=11) compared within the type strains of the genus Aeromicrobium. Strain CC-CFT486^T contained C_16 : 0, C_17 : 0, C_17 : 1  ω8c and C_18 : 1  ω9c as the predominant fatty acids. The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, two unidentified aminophospholipids and three unknown phospholipids. The cell wall peptidoglycan of strains CC-CFT486^T contained ll-diaminopimelic acid (ll-DAP) and the major polyamine was spermidine. The DNA G+C content was 70.6 mol% and the predominant quinone was menaquinone 9 (MK-9). Based on its distinct phylogenetic, phenotypic and chemotaxonomic traits together with results of comparative 16S rRNA gene sequence and ANI analyses, strain CC-CFT486^T is proposed to represent a novel Aeromicrobium species, for which the name Aeromicrobium terrae sp. nov. (type strain CC-CFT486^T=BCRC 81217^T=JCM 33499^T).

Draft genome and description of Aeromicrobium phoceense strain Marseille-Q0843T sp. nov., a new bacterium isolated from human healthy skin

In 2019, by culturing a skin swab sample from the back of the hand of a 61-year-old healthy woman and assessing it via the culturomics method, we isolated the new bacterial strain Marseille-Q0843^T (= CSUR-Q0843). Matrix-assisted desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) failed to identify this isolate. Analysis of the 16S ribosomal RNA gene and genome-to-genome comparison suggested that this taxon belongs to a novel bacterial species within the family in Nocardioidaceae in the phylum Actinobacteria. We describe here the main phenotypic characteristics, genome sequence and annotation of Aeromicrobium phoceense strain Marseille-Q0843^T, a new member of the Aeromicrobium genus, which we propose as the type strain.

Aeromicrobium piscarium sp. nov., isolated from the intestine of Collichthys lucidus

A Gram-stain-positive, rod-shaped, whitesmoke-coloured and aerobic bacterium, designated strain Co35T, was isolated from the intestine of Collichthys lucidus collected from the Jiangmen Guangdong Chinese White Dolphin Provincial Nature Reserve. Strain Co35T was able to grow at 15–35 °C (optimal 28 °C), at pH 7.0–8.5 (optimal 8.0) and with 0–9 % (w/v) NaCl (optimal 0.5–1 %). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain Co35T was a member of the genus Aeromicrobium within the family Nocardioidaceae . The genomic DNA G+C content of strain Co35T was 68.4 mol%. Chemotaxonomic analysis showed that the sole respiratory quinone was menaquinone 9 (MK-9), and the major fatty acids included 10-methyl C18 : 0. The polar lipids were found to consist of phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE), phosphatidylinositol (PI), two unidentified phospholipids (PL1–2) and two unidentified glycolipids (GL1–2). On the basis of its phylogenetic, phenotypic, chemotaxonomic, genotypic and genomic characteristics presented in this study, strain Co35T represents a novel species in the genus Aeromicrobium , for which the name Aeromicrobium piscarium sp. nov. is proposed. The type strain is Co35T (=KCTC 49280T=MCCC 1K03754T).

Aeromicrobium chenweiae sp. nov. and Aeromicrobium yanjiei sp. nov., isolated from Tibetan antelope (Pantholops hodgsonii) and plateau pika (Ochotona curzoniae), respectively

Four novel strains (592^T, S592, MF47^T and SMF47) were isolated from Tibetan antelopes (Pantholops hodgsonii) and plateau pikas (Ochotona curzoniae), respectively. The cells were aerobic, non-motile, Gram-stain- and catalase-positive, rod-shaped bacteria. The 16S rRNA gene sequences of the four strains showed highest similarities to Aeromicrobium fastidiosum DSM 10552^T (98.1, 98.6, 98.7 and 98.7 %, respectively), and the phylogenetic analyses based on 16S rRNA gene and genomic sequences indicated that strains 592^T and MF47^T represent two novel species. The four isolates produced acid from l-rhamnose, d-xylose and cellobiose, but were unable to reduce nitrate. The DNA G+C contents of strains 592^T and MF47^T were 70.3 and 69.8 mol%, respectively. The digital DNA-DNA hybridization value between strains 592^T and MF47^T was 32.6 %, lower than the threshold of 70 %, indicating they belong to different species. The four strains' genomes displayed less than 24.6 % DNA-DNA relatedness with all available genomes of the genus Aeromicrobium in the NCBI database, including Aeromicrobium fastidiosum NBRC 14897^T and Aeromicrobium ginsengisoli JCM 14732^T. The major fatty acids of the four strains were C_18 : 1  ω9c and C_18 : 0 10-methyl, and the main polar lipids were diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol. The predominant respiratory quinones were MK-9(H₄) and MK-8(H₄). The cell-wall peptidoglycan contained ll-diaminopimelic acid. Based on these genotypic, phenotypic and biochemical analyses, it is proposed that the four unidentified bacteria be classified as two novel species, Aeromicrobium chenweiae sp. nov. and Aeromicrobium yanjiei sp. nov. The type strains are 592^T (=CGMCC1.16526^T=DSM 106289^T) and MF47^T (=CGMCC 1.17444^T=JCM 33790^T), respectively.

Origins and Bioactivities of Natural Compounds Derived from Marine Ascidians and Their Symbionts

Marine ascidians are becoming important drug sources that provide abundant secondary metabolites with novel structures and high bioactivities. As one of the most chemically prolific marine animals, more than 1200 inspirational natural products, such as alkaloids, peptides, and polyketides, with intricate and novel chemical structures have been identified from ascidians. Some of them have been successfully developed as lead compounds or highly efficient drugs. Although numerous compounds that exist in ascidians have been structurally and functionally identified, their origins are not clear. Interestingly, growing evidence has shown that these natural products not only come from ascidians, but they also originate from symbiotic microbes. This review classifies the identified natural products from ascidians and the associated symbionts. Then, we discuss the diversity of ascidian symbiotic microbe communities, which synthesize diverse natural products that are beneficial for the hosts. Identification of the complex interactions between the symbiont and the host is a useful approach to discovering ways that direct the biosynthesis of novel bioactive compounds with pharmaceutical potentials.

Aeromicrobium endophyticum sp. nov., an endophytic actinobacterium isolated from reed (Phragmites australis)

A Gram-staining-positive, motile and short-rod-shaped actinobacterium designated 9W16Y-2^T was isolated from surface-sterilized leaves of reed (Phragmites australis) collected from Taklamakan Desert in Xinjiang Uygur Autonomous Region, China. Colonies were pale greenish yellow, circular, smooth, and convex. The 16S rRNA gene sequence of strain 9W16Y-2^T exhibited highest sequence similarities with Aeromicrobium camelliae CGMCC 1.12942^T (99.0%) and Aeromicrobium erythreum NRRL B-3381^T (97.2%). Phylogenetic analyses based on 16S rRNA gene sequences and single-copy phylogenetic marker genes (pMGs) showed that strain 9W16Y-2^T belonged to the genus Aeromicrobium and formed a monophyletic clade with Aeromicrobium camelliae CGMCC 1.12942^T. Furthermore, average nucleotide identity (ANI) and DNA-DNA hybridization (DDH) clearly separated strain 9W16Y-2^T from the other species of the genus Aeromicrobium with values below the thresholds for species delineation. The G+C content of the genomic DNA is 68.9 mol%. The diagnostic diamino acid of the cell-wall peptidoglycan was LL-diaminopimelic acid. The predominant menaquinone was MK-9(H₄). The major fatty acids (> 10% of the total fatty acids) were C_18:0 10-methyl (TBSA) (28.2%), C_16:0 (21.0%), C_16:0 2-OH (20.8%) and C_18:1ω9c (12.8%). The polar lipid profile comprised diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylinositol, an unidentified aminophospholipid and an unidentified lipid. Based on the phylogenic, phenotypic and chemotaxonomic features, strain 9W16Y-2^T represents a novel species of the genus Aeromicrobium, for which the name Aeromicrobium endophyticum sp. nov. is proposed. The type strain is 9W16Y-2^T (= CGMCC 1.13876^T = JCM 33141^T).

Biological and Chemical Diversity of Ascidian-Associated Microorganisms

Ascidians are a class of sessile filter-feeding invertebrates, that provide unique and fertile niches harboring various microorganisms, such as bacteria, actinobacteria, cyanobacteria and fungi. Over 1000 natural products, including alkaloids, cyclic peptides, and polyketides, have been isolated from them, which display diverse properties, such as antibacterial, antifungal, antitumor, and anti-inflammatory activities. Strikingly, direct evidence has confirmed that ~8% of natural products from ascidians are actually produced by symbiotic microorganisms. In this review, we present 150 natural products from microorganisms associated with ascidians that have been reported up to 2017.

Taste and smell in aquatic and terrestrial environments

The review summarizes results up to 2017 on chemosensory cues occurring in both aquatic and terrestrial environments.

Biofilm Formation and Detachment in Gram-Negative Pathogens Is Modulated by Select Bile Acids

Biofilms are a ubiquitous feature of microbial community structure in both natural and host environments; they enhance transmission and infectivity of pathogens and provide protection from human defense mechanisms and antibiotics. However, few natural products are known that impact biofilm formation or persistence for either environmental or pathogenic bacteria. Using the combination of a novel natural products library from the fish microbiome and an image-based screen for biofilm inhibition, we describe the identification of taurine-conjugated bile acids as inhibitors of biofilm formation against both Vibrio cholerae and Pseudomonas aeruginosa. Taurocholic acid (1) was isolated from the fermentation broth of the fish microbiome-derived strain of Rhodococcus erythropolis and identified using standard NMR and MS methods. Screening of the twelve predominant human steroidal bile acid components revealed that a subset of these compounds can inhibit biofilm formation, induce detachment of preformed biofilms under static conditions, and that these compounds display distinct structure-activity relationships against V. cholerae and P. aeruginosa. Our findings highlight the significance of distinct bile acid components in the regulation of biofilm formation and dispersion in two different clinically relevant bacterial pathogens, and suggest that the bile acids, which are endogenous mammalian metabolites used to solubilize dietary fats, may also play a role in maintaining host health against bacterial infection.

Aeromicrobium camelliae sp. nov., isolated from Pu′er tea

A novel Gram-reaction-positive, aerobic and non-spore-forming rod-shaped bacterial strain, YS17T, was isolated from ripened Pu′er tea. Growth of the strain was observed at 15–50 °C (optimum 30–37 °C) and at pH 5.5–10.5 (optimum 6.0–9.5). Phylogenetic analysis of 16S rRNA gene sequences indicated that the strain represented a member of the genus Aeromicrobium. The strains most closely related to YS17T were Aeromicrobium erythreum DSM 8599T, Aeromicrobium alkaliterrae JCM 13518T and Aeromicrobium ginsengisoli JCM 14732T, with 16S rRNA gene sequence similarities of 96.8, 96.8 and 96.7 %, respectively. DNA–DNA hybridization of YS17T with the type strains of the most closely related species, A. erythreum DSM 8599T, A. alkaliterrae JCM 13518T and A. ginsengisoli JCM 14732T, yielded reassociation values of 10.9, 16.8 and 10.9 %, respectively. The diagnostic diamino acid of the cell wall peptidoglycan was ll-diaminopimelic acid. The predominant menaquinones were menaquinone MK-9(H4) (76 %) and MK-8(H4) (17 %). The major fatty acids were C16 : 0, 10-methyl C18 : 0 and C18 : 1ω9c. The DNA G+C content of YS17T was 66 mol%. YS17T could be differentiated from recognized species of the genus Aeromicrobium on the basis of phenotypic characteristics, chemotaxonomic differences, phylogenetic analysis and DNA–DNA hybridization data. On the basis of evidence from the polyphasic analyses performed as part of this study a novel species, Aeromicrobium camelliae sp. nov., is proposed, with strain YS17T ( = CGMCC 1.12942T = JCM 30952T) as the type strain.

Mumia flava gen. nov., sp. nov., an actinobacterium of the family Nocardioidaceae

A novel actinobacterial strain, designated MUSC 201T, was isolated from a mangrove soil collected from Kuantan, the capital city of Pahang State in Malaysia. The taxonomic status of this strain was determined using a polyphasic approach. Comparative 16S rRNA gene sequence analysis revealed that strain MUSC 201T represented a novel lineage within the class Actinobacteria. Strain MUSC 201T formed a distinct clade in the family Nocardioidaceae and was most closely related to the members of the genera Nocardioides (16S rRNA gene sequence similarity, 91.9-95.1%), Aeromicrobium (92.7-94.6%), Marmoricola (92.5-93.1%) and Kribbella (91.5-92.4%). The cells of this strain were irregular coccoid to short rod shaped. The peptidoglycan contained ll-diaminopimelic acid as diagnostic diamino acid and the peptidoglycan type was A3γ. The peptidoglycan cell wall contained ll-diaminopimelic acid, glycine, glutamic acid and alanine in a molar ratio of 1.5:0.9:1.0:1.5. The cell-wall sugars were galactose and rhamnose. The predominant menaquinone was MK-9(H4). The polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphoglycolipid, glycolipid and four unknown phospholipids. The major cellular fatty acids were C18:1ω9c (30.8%), C16:0 (24.1%), and 10-methyl C18:0 (13.9%). The DNA G+C content was 72.0±0.1 mol%. On the basis of phylogenetic and phenotypic differences from members of the genera of the family Nocardioidaceae, a novel genus and species, Mumia flava gen. nov., sp. nov. are proposed. The type strain of Mumia flava is MUSC 201T (=DSM 27763T=MCCC 1A00646T=NBRC 109973T).

Genome sequence and description of Aeromicrobium massiliense sp. nov

Aeromicrobium massiliense strain JC14^Tsp. nov. is the type strain of Aeromicrobium massiliense sp. nov., a new species within the genus Aeromicrobium. This strain, whose genome is described here, was isolated from the fecal microbiota of an asymptomatic patient. Aeromicrobium massiliense is an aerobic rod-shaped gram-positive bacterium. Here we describe the features of this organism, together with the complete genome sequence and annotation. The 3,322,119 bp long genome contains 3,296 protein-coding and 51 RNA genes.

Two new cholic acid derivatives from the marine ascidian-associated bacterium Hasllibacter halocynthiae

The investigation of secondary metabolites in liquid cultures of a recently discovered marine bacterium, Hasllibacter halocynthiae strain KME 002^T, led to the isolation of two new cholic acid derivatives. The structures of these compounds were determined to be 3,3,12-trihydroxy-7-ketocholanic acid (1) and 3,3,12-trihydroxy-7-deoxycholanic acid (2) through HRFABMS and NMR data analyses.

Hasllibacter halocynthiae gen. nov., sp. nov., a nutriacholic acid-producing bacterium isolated from the marine ascidian Halocynthia roretzi

A Gram-negative, aerobic, ovoid to rod-shaped bacterial strain, KME 002(T) was isolated from a marine ascidian, Halocynthia roretzi, off the coast of Gangneung, Korea. Phylogenetic analyses based on 16S rRNA gene sequences showed that this strain belonged to the family Rhodobacteraceae in the class Alphaproteobacteria and was closely related to the type strains of Dinoroseobacter shibae, Roseovarius crassostreae and Pseudoruegeria aquimaris with 95.0, 94.7 and 94.5% 16S rRNA gene sequence similarities, respectively. KME 002(T) was an obligately halophilic bacterium requiring 1 to 5% (w/v) NaCl, with an absolute requirement for magnesium chloride for growth. Cells were motile by means of a single polar flagellum and showed budding fission. The predominant cellular fatty acid of the isolate was C(18:1)ω7c and Q-10 was the major ubiquinone. The DNA G+C content of the strain was 71.6 mol%. The major secondary metabolites from cultures in liquid medium were cholic acid derivatives, including 3α,12α-hydroxy-3-keto-glycocholanic acid, 12-hydroxy-3-keto-glycocholanic acid, nutriacholic acid and deoxycholic acid. These characteristics determined in this polyphasic study suggest that strain KME 002(T) represents a novel species in a new genus of the family Rhodobacteraceae. The name Hasllibacter halocynthiae gen. nov., sp. nov. is proposed for this isolate, and the type strain is KME 002(T) (=JCM 16214(T)=KCCM 90082(T)).