Indothiazinone, an Indolyl Thiazolyl Ketone from a Novel Myxobacterium Belonging to the Sorangiineae

Indothiazinone (<b>1</b>), an indolyl thiazolyl ketone, was discovered in cultures of novel myxobacterial strain 706, recently isolated from compost in Germany. Molecular phylogenetic studies based on 16S rRNA gene sequences revealed strain 706 to be a representative of a new family of the Sorangiineae. A screening of the culture broth for antimicrobial metabolites followed by isolation and characterization of these compounds revealed six indole derivatives and a 1,4-naphthoquinone derivative. The structures were determined to be indothiazinone (<b>1</b>; 1<i>H</i>-indol-3-yl­(1,3-thiazol-2-yl)­methanone) and three 3-methylbuta-1,3-dien-1-yl-substituted indoles, indolyl ethanol <b>2</b> and the <i>E</i>- and <i>Z</i>-isomers of indolyl ethylidenehydroxylamine <b>4</b> and <b>5</b> by MS and NMR spectroscopic analyses. In the indolyl ethanol derivative <b>3</b> the unsaturated methylene group of the butadienyl residue was replaced by an oxygen atom to give the keto group of the butanone side chain. Further 1<i>H</i>-indol-3-ylacetonitrile (<b>6</b>) was identified, which was already known as a myxobacterial metabolite. 2-Hydroxyethyl-3-methyl-1,4-naphthoquinone (<b>7</b>) was recognized during dereplication as an antibiotic previously isolated from <i>Actinoplanes capillaceus</i>. Whereas <b>1</b>, <b>4</b>, <b>5</b>, and <b>7</b> showed weak activity against yeasts and filamentous fungi, isomers <b>4</b> and <b>5</b> were weakly active against Gram-positive bacteria and mouse fibroblasts. Compound <b>6</b> is volatile, and <b>2</b> and <b>3</b> showed no activity in a number of assays

Hyaladione, an <i>S</i>-Methyl Cyclohexadiene-dione from <i>Hyalangium minutum</i>

A bioassay-guided fractionation of the crude methanol extract of the myxobacterium <i>Hyalangium minutum</i>, strain NOCB-2^T (DSM 14724^T), led to the isolation of hyaladione (<b>1</b>), a novel <i>S</i>-methyl cyclohexadiene-dione. The structure of <b>1</b> was established by HRESIMS, NMR, and IR spectroscopy as well as X-ray crystallography. Compound <b>1</b> was active against growing mammalian cell lines, with IC₅₀ values ranging from 1.23 to 3.93 μM, in addition to a broad spectrum of antibacterial and antifungal activities, including inhibition of pathogenic methicillin-resistant <i>Staphylococcus aureus</i> and <i>Pseudomonas aeruginosa</i> with an MIC of 0.83 and 8.5 μg mL^–1, respectively

Hyafurones, Hyapyrrolines, and Hyapyrones: Polyketides from <i>Hyalangium minutum</i>

Seven new polyketides, for which the trivial names hyafurones A₁–B (<b>1</b>–<b>3</b>), hyapyrrolines A (<b>4</b>) and B (<b>5</b>), and hyapyrones A (<b>6</b>) and B (<b>7</b>) are proposed, were isolated from the fermentation broth of the myxobacteria <i>Hyalangium minutum,</i> strains NOCB-2^T and Hym-3. Their structures were elucidated from NMR and HRESIMS data, and their geometric configuration was assigned based on NOE and vicinal ¹H coupling data. Both hyafurone B (<b>3</b>) and hyapyrone B (<b>7</b>) inhibited growth of the Gram-positive bacterium <i>Nocardia flava</i>, while <b>7</b> showed antifungal activity against <i>Mucor hiemalis</i>

Diversity of Microscopic Green Algae (Chlorophyta) in Calcifying Biofilms of Two Karstic Streams in Germany

<div><p>For the first time the diversity of microscopic green algae (Chlorophyta) from calcified biofilms of karstic streams was analyzed using a combined approach based on pure cultures, i.e., 18S rRNA gene sequencing and microscopic analyses. Our study focused on two creeks in Germany. A considerable diversity of 34 species of green microalgae comprising three classes, the Trebouxiophyceae, Chlorophyceae and Ulvophyceae, was recovered. The biofilms of both streams were rather different in their species compositions which may reflect that they are exposed to differed hydrochemical conditions. The shallow Westerhöfer creek harbored predominantly Trebouxiophyceae and exhibited higher Mg²⁺ and SO₄²⁻ concentrations. In contrast, the deeper, longer and spatially more heterogeneous Deinschwanger creek harbored numerous species of Chlorophyceae. A lower number of species from the Ulvophyceae were spread on both studied streams. The closest relatives of the identified species were from other freshwater habitats, but mostly from phytoplankton. However, also several species we recovered from freshwater for the first time; so far they have been known from terrestrial habitats only. Less than half of the recovered species could be identified with names at the species level based on high sequence identities with available sequences from named reference strains. Most recovered species could not be identified with names to species level, i.e., they may represent species for which no 18S rRNA gene sequence have become available yet or which have been retrieved for the first time. The genus <i>Gongrosira</i> Kützing, often reported from freshwater tufa-stromatolites, was found to represent most likely a collective morphotype formed by several genera nested within the Ulvophyceae.</p></div

Cyanobacteria and Diatoms in Biofilms of Two Karstic Streams in Germany and Changes of Their Communities Along Calcite Saturation Gradients

<div><p>Biofilms microscopically dominated by cyanobacteria and diatoms of two CO₂ degassing karst-water creeks in Germany were investigated for their diversities along a gradient of calcification using SSU rRNA gene cloning and sequencing from environmental samples. The recovered totals of 731/413 cyanobacteria/diatom clones were grouped at 97/98% similarity levels into 28/29 molecular OTUs widely spread over their corresponding sequence phylogenies forming mostly monophyletic subclades. Sequence comparisons with named reference strains from NCBI/GenBank as well as newly determined references from the SAG culture collection left about half of the cyanobacteria OTUs still unidentified. Most of the diatom OTUs could be identified at least at the generic level. To improve identification also cultures of cyanobacteria and diatoms were established that allowed even species identification of some diatoms, but also revealed additional cyanobacteria hard to identify which were not recovered in the clone libraries. A significant correlation of the relative OTU abundances in clone libraries with values of SI_calcite was found and, therefore, redundancy analysis distinguished highly calcified sites far from the spring from those less calcified closer to the spring. The noncalcified spring sites were clearly distinct from all other sites by the presence of four cyanobacteria OTUs exclusively retrieved and that no diatoms could be recovered from there. Four cyanobacteria and three diatom OTUs were recovered whose increasing relative abundance per clone library was correlated with increasing calcification. This may indicate that not only cyanobacteria, but also diatoms are more directly involved in the biogenic impact on tufa formation than assumed previously.</p></div