Host metabolite producing endophytic fungi isolated from Hypericum perforatum

In the present study, endophytic fungi have been isolated from various parts of the medicinal herb Hypericum perforatum (St. John’s Wort), which is known as a source of medically important metabolites. The isolated strains were cultured in liquid media and their ability to synthesize hypericin, the secondary metabolite of the host and its suspected precursor, emodin was tested analyzing the extracts of the fermentation broth and the mycelia. The HPLC-UV analysis of the chloroform/methanol extracts of the mycelia revealed that three isolates were able to produce emodin (SZMC 23771, 19.9 ng/mg; SZMC 23772, 20.8 ng/mg; SZMC 23769, 427.9 ng/mg) and one of them also could synthesize hypericin (SZMC 23769, 320.4 ng/mg). These results were also confirmed via UHPLC-HRMS technique both in full scan and MS/MS mode. The strains producing only emodin belong to the section Alternata of the genus Alternaria, while the isolate producing both metabolites was identified as Epicoccum nigrum. The mycelial extracts of E. nigrum and the Alternaria sp. SZMC 23772 showed higher inhibitory activities in the antimicrobial tests against the six selected bacteria compared to the hypericin and emodin standards in the applied concentration (100 μg/mL), while in case of the Alternaria sp. SZMC 23771 lower inhibition activities were observed on Staphylococcus aureus and Streptomyces albus than the pure compounds.</div

Common cuckoos (<i>Cuculus canorus</i>) affect the bacterial diversity of the eggshells of their great reed warbler (<i>Acrocephalus arundinaceus</i>) hosts

<div><p>The common cuckoo (<i>Cuculus canorus</i>) is an avian brood parasite, laying its eggs in the nests of other bird species, where these hosts incubate the parasitic eggs, feed and rear the nestlings. The appearance of a cuckoo egg in a host nest may change the bacterial community in the nest. This may have consequences on the hatchability of host eggs, even when hosts reject the parasitic egg, typically within six days after parasitism. The present study revealed the bacterial community of cuckoo eggshells and those of the great reed warbler (<i>Acrocephalus arundinaceus</i>), one of the main hosts of cuckoos. We compared host eggs from non-parasitized clutches, as well as host and cuckoo eggs from parasitized clutches. As incubation may change bacterial assemblages on eggshells, we compared these egg types in two stages: the egg-laying stage, when incubation has not been started, and the mid-incubation stage (ca. on days 5–7 in incubation), where heat from the incubating female dries eggshells. Our results obtained by the 16S rRNA gene sequencing technique showed that fresh host and cuckoo eggs had partially different bacterial communities, but they became more similar during incubation in parasitized nests. Cluster analysis revealed that fresh cuckoo eggs and incubated host eggs in unparasitized nests (where no cuckoo effect could have happened) were the most dissimilar from the other groups of eggs. Cuckoo eggs did not reduce the hatchability of great reed warbler eggs. Our results on the cuckoo-great reed warbler relationship supported the idea that brood parasites may change bacterial microbiota in the host nest. Further studies should reveal how bacterial communities of cuckoo eggshells may vary by host-specific races (gentes) of cuckoos.</p></div

Plot of discriminant scores generated by Linear Discriminant Analysis, showing the bacterial community structure of cuckoo and great-reed warbler eggs.

<p>Plot of discriminant scores generated by Linear Discriminant Analysis, showing the bacterial community structure of cuckoo and great-reed warbler eggs.</p

Number of bacterial samples from cuckoo and great reed warbler eggshells.

<p>(Acronyms of categories used in the study: pcn = parasitized clutch, cuckoo egg, non-incubated; pci: parasitized clutch, cuckoo egg, incubated; pgn = parasitized clutch, great reed warbler egg, non-incubated; pgi = parasitized clutch, great reed warbler egg, incubated; ngn = non-parasitized clutch, great reed warbler egg, non-incubated; ngi = non-parasitized clutch, great reed warbler egg, incubated).</p

Dendrogram of agglomerative hierarchical cluster analysis.

<p>(Treatments: non-incubated clutches: ngn—non-parasitized great reed warbler egg, pgn—parasitized great reed warbler egg, pcn—parasitized cuckoo egg; incubated clutches: ngi—non-parasitized great reed warbler egg, pgi—parasitized great reed warbler egg, pci—parasitized cuckoo egg).</p

Relative abundance of bacterial genera on cuckoo and great reed warbler eggshells.

<p>Relative abundance of bacterial genera on cuckoo and great reed warbler eggshells.</p

Number and percent (in brackets) of eggshells of cuckoos and great reed warblers with corresponding detected bacterial genera.

<p>Number and percent (in brackets) of eggshells of cuckoos and great reed warblers with corresponding detected bacterial genera.</p

Classification results of LDA for eggshell bacterial communities.

<p>Classification results of LDA for eggshell bacterial communities.</p

Phylogenetic distribution of the coprinoid fruiting body type in the agaricoid clade (sensu [<b>17</b>]) shown on a Maximum Likelihood tree inferred from LSU sequences of all taxa of the agaricoid clade present in Genbank, supplemented with LSU sequences generated in this and a previous study ([<b>26</b>]).

<p>Phylogenetic distribution of the coprinoid fruiting body type in the agaricoid clade (sensu <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0056143#pone.0056143-Matheny1" target="_blank">[<b>17</b>]</a>) shown on a Maximum Likelihood tree inferred from LSU sequences of all taxa of the agaricoid clade present in Genbank, supplemented with LSU sequences generated in this and a previous study (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0056143#pone.0056143-Nagy1" target="_blank">[<b>26</b>]</a>).</p

50% Majority rule consensus phylogram showing the phylogenetic relationships in the Bolbitiaceae.

<p>Branch support values are MrBayes posterior probabilities, ML bootstrap values, BEAST posterior probabilities, in order. Nodes for which ancestral fruiting body type has been reconstructed are labeled nodes 1–5, corresponding to the Bolbitiaceae, <i>Bolbitius</i>+<i>Pholiotina</i> 1, <i>Bolbitius</i>, <i>Conocybe</i> 6 and section <i>Candidae</i>. Taxa with coprinoid combination of characters (pseudoparaphyses, ephemeral fruiting bodies which collapse upon maturity, plicate cap surface) are highlighted in blue. Relationships tested by constraint analyses are marked by dashed lines. The composition of stipe covering either as hairs only (open squares), lecythiform cystidia only (filled squares) and both types (fountain fill) is shown to the right of the tree. Note that ML bootstrap values and Bayesian posterior probabilities from the BEAST runs were obtained without the indel data.</p