Ryosuke Fudou

Corynebacterium efficiens sp. nov., a glutamic-acid-producing species from soil and vegetables.

Three glutamic-acid-producing coryneform strains were isolated from soil and vegetable samples. Chemotaxonomic investigations indicated that these strains belonged to the genus Corynebacterium. Phylogenetic studies, based on 16S rDNA analysis, demonstrated that the three strains formed a distinct cluster within the genus Corynebacterium and that their nearest relatives were Corynebacterium glutamicum and Corynebacterium callunae, also known as glutamic-acid-producing species. The data from 16S rDNA sequence and DNA-DNA relatedness studies clearly indicated that the three isolates represented a new species within the genus Corynebacterium. All of the isolates could grow at 45 degrees C and produced acid from dextrin; these were the most significant characteristics differentiating the three isolates from their neighbours. On the basis of the data presented here, it is proposed that the three glutamic-acid-producing isolates together be classified as Corynebacterium efficiens sp. nov., the type strain of which is YS-314T (= AJ 12310T = JCM 11189T = DSM 44549T).

Cystothiazoles C-F, new bithiazole-type antibiotics from the myxobacterium Cystobacter fuscus

Abstract Bithiazole-type antifungal products, cystothiazoles C-F (3–6), have been isolated from a culture broth of the myxobacterium Cystobacter fuscus as minor components. These are structurally related to cystothiazole A (1), which was isolated as a cytotoxic antibiotic from the same microorganism in our previous work. The structures of these compounds were elucidated by spectroscopic analyses. These new compounds inhibit the phytopathogenic fungus, Phytophthora capsici, but are less active than 1.

Enhygromyxa salina gen. nov., sp. nov., a Slightly Halophilic Myxobacterium Isolated from the Coastal Areas of Japan

Six isolates of novel marine myxobacteria, designated strains SHK-1T, SMK-1-1, SMK-1-3, SMK-10, SKK-2, and SMP-6, were obtained from various coastal samples (mud, sands and algae) collected around Japan. All of the isolates had Gram-negative rod-shaped cells, motile by gliding and grew aerobically. They showed bacteriolytic action, fruiting body formation, and NaCl requirement for growth with an optimum concentration of 1.0-2.0% (w/v). In addition, divalent cationic components of seawater, such as Mg2+ or Ca2+, were also needed for growth. The major respiratory quinone was MK-7. The G+C content of genomic DNA ranged from 65.6 to 67.4 mol% (by HPLC). The isolates shared almost identical 16S rDNA sequences, and clustered with a recently described marine myxobacterium, Plesiocystis pacifica, as their closest relative on a phylogenetic tree (95.9-96.0% similarity). Physiological and chemotaxonomic differences between the new strains and strains of the genus Plesiocystis justify the proposal of a new genus. Therefore, we propose to classify the six isolates into a new taxon of marine myxobacteria with the name, Enhygromyxa salina gen. nov., sp. nov. The type strain is SHK-1(T) (JCM 11769(T) = DSM 15217(T) = AJ 110011(T)).

Miuraenamides A and B, Novel Antimicrobial Cyclic Depsipeptides from a New Slightly Halophilic Myxobacterium : Taxonomy, Production, and Biological Properties

A slightly halophilic myxobacterial strain, SMH-27-4, was isolated from nearshore soil and shown to belong to a new myxobacterium genus based on phylogenetic analysis. This slowly-growing myxobacterium produced the novel antibiotic depsipeptides miuraenamides A and B. Their physico-chemical properties and molecular formulas, C34H42N3O7Br and C34H42N3O7I, were determined. Miuraenamides A exhibited potent and selective inhibition against a phytopathogenic microorganism, Phytophthora sp., and moderate inhibition against some fungi and yeasts, but was ineffective against bacteria. Both of the metabolites inhibited NADH oxidase at IC50 values of 50 μM, suggesting, like β-methoxyacrylate-type antibiotics, the electron transfer system of the mitochondrial respiratory chain as the cellular target.

PCR Detection of Type I Polyketide Synthase Genes in Myxobacteria

ABSTRACT The diversity of type I modular polyketide synthase (PKS) was explored by PCR amplification of DNA encoding ketosynthase and acyltransferase domains in myxobacteria. The sequencing of the amplicons revealed that many PKS genes were distantly related to the published sequences. Thus, myxobacteria may be excellent resources for novel and diverse polyketides.

Isolation and Biosynthetic Analysis of Haliamide, a New PKS-NRPS Hybrid Metabolite from the Marine Myxobacterium Haliangium ochraceum

Myxobacteria of marine origin are rare and hard-to-culture microorganisms, but they genetically harbor high potential to produce novel antibiotics. An extensive investigation on the secondary metabolome of the unique marine myxobacterium Haliangium ochraceum SMP-2 led to the isolation of a new polyketide-nonribosomal peptide hybrid product, haliamide (1). Its structure was elucidated by spectroscopic analyses including NMR and HR-MS. Haliamide (1) showed cytotoxicity against HeLa-S3 cells with IC50 of 12 μM. Feeding experiments were performed to identify the biosynthetic building blocks of 1, revealing one benzoate, one alanine, two propionates, one acetate and one acetate-derived terminal methylene. The biosynthetic gene cluster of haliamide (hla, 21.7 kbp) was characterized through the genome mining of the producer, allowing us to establish a model for the haliamide biosynthesis. The sulfotransferase (ST)-thioesterase (TE) domains encoded in hlaB appears to be responsible for the terminal alkene formation via decarboxylation.

Heterologous Production of the Marine Myxobacterial Antibiotic Haliangicin and Its Unnatural Analogues Generated by Engineering of the Biochemical Pathway.

Despite their fastidious nature, marine myxobacteria have considerable genetic potential to produce novel secondary metabolites. The marine myxobacterium Haliangium ochraceum SMP-2 produces the antifungal polyketide haliangicin (1), but its productivity is unsatisfactory. The biosynthetic gene cluster hli (47.8 kbp) associated with 1 was identified and heterologously expressed in Myxococcus xanthus to permit the production of 1 with high efficiency (tenfold greater amount and threefold faster in growth speed compared with the original producer), as well as the generation of bioactive unnatural analogues of 1 through gene manipulation. A unique acyl-CoA dehydrogenase was found to catalyse an unusual γ,δ-dehydrogenation of the diketide starter unit, leading to the formation of the terminal alkene moiety of 1. Biological evaluation of the analogues obtained through this study revealed that their bioactivities (anti-oomycete and cytotoxic activities) can be modified by manipulating the vinyl epoxide at the terminus opposite the β-methoxyacrylate pharmacophore.

A newly discovered Anaerococcus strain responsible for axillary odor and a new axillary odor inhibitor, pentagalloyl glucose

Skin surface bacteria contribute to body odor, especially axillary odor. We aimed to investigate anaerobic bacteria that had not been previously studied for axillary odor formation. A new anaerobic Anaerococcus sp. A20, that releases 3-hydroxy-3-metyl-hexanoic acid (HMHA, main component of axillary odor) from its glutamyl conjugate, was discovered from axillary isolates. This strain showed strong resistance to the antimicrobial agents, triclosan and 4-isopropyl-3-methylphenol; therefore, we screened plant extracts that inhibit the A20 strain. We discovered that pentagalloyl glucose (PGG) extracted from the Chinese Gall plant exhibited both antibacterial and inhibitory activities against HMHA release by the A20 strain. As the excellent antibacterial activity and inhibitory effect of PGG against HMHA release were seen in vitro, we conducted an open study to evaluate the deodorant effects of PGG on axillary odor. The sensory tests on odor strength showed that application of the PGG solution could reduce axillary odors in vivo. Although there was a small change in axillary microbiota, the microbial count of A20 significantly reduced. These results strongly indicate PGG as a new innovative deodorant material that only affects odor-releasing bacteria in the axillary microbiota.

Endocrocin and its derivatives from the Japanese mealybug Planococcus kraunhiae.

The Japanese mealybug, Planococcus kraunhiae, is suitable as a model insect for biosynthetic studies on mealybug pigments. Four yellow pigments, including two novel ones, were isolated from the mealybug bodies and characterized as endocrocin, a dicarboxylic acid named fujikonaic acid (1), emodin 1-O-β-D-glucopyranoside and 7-hydroxyemodin 1-O-β-D-glucopyranoside (2). The enzymatic activity of emodin 1-O-glucosyltransferase was observed in the extracts of insect bodies.

Articulospora sp. produces Art1, an inhibitor of bacterial histidine kinase.

A two-component system (TCS) comprising a histidine kinase (HK) sensor and a response regulator (RR) plays important roles in regulating the virulence of many pathogenic bacteria. We used a new screening method to isolate novel inhibitor Art1 against bacterial sensory HK from an acetone extract of solid cultures of Articulospora sp., an aquatic hypomycete. Art1 inhibited the ATP-dependent autophosphorylation of recombinant glutathione S-transferase-fusion protein SasA, a cyanobacterial HK, with an IC50 value of 9.5 μg/ml.