Two New Fungi from Chinese Dead Wood Show Antibacterial and Antifungal Promise

Deep in the forests of northeast China, two previously unknown species of fungi have been quietly decomposing dead wood — and they may carry chemical weapons that could one day replace synthetic pesticides. Researchers collecting decaying woody litter in Changchun, Jilin Province, have formally described Chromolaenicola crataegicola and Paraphaeosphaeria fulva, two novel species belonging to the fungal family Didymosphaeriaceae. In preliminary laboratory tests, crude extracts from both organisms inhibited the growth of a dangerous human pathogen and several plant-disease fungi, hinting at a hidden reservoir of natural bioactive compounds.

The discovery, published in the journal MycoKeys, matters because Didymosphaeriaceae is no obscure branch of the fungal tree. It is a large and ecologically versatile family within the order Pleosporales, with members living as saprophytes that recycle dead plant matter, as endophytes that dwell harmlessly inside living tissues, and as pathogens that attack plants, animals and even humans. The family currently contains 39 recognised genera, distributed across virtually every habitat on Earth. Yet many of its type species lack molecular data, leaving the evolutionary relationships between several genera — such as Paraconiothyrium and Kalmusia — unresolved. Accurate identification therefore depends on multi-locus sequence analysis rather than appearance alone.

To place the new isolates firmly on the fungal family tree, the team extracted genomic DNA from pure cultures and amplified five genetic markers: the internal transcribed spacer region (ITS), the nuclear small and large ribosomal subunits (SSU and LSU), the translation elongation factor 1-alpha gene (tef1-α) and the second-largest subunit of RNA polymerase II (rpb2). These five loci were sequenced and compared against 165 reference strains retrieved from GenBank and recent literature, producing a combined dataset of 169 Didymosphaeriaceae taxa. Alignments were generated with MAFFT, and phylogenetic trees were constructed using both Maximum Likelihood and Bayesian Inference methods on the CIPRES computing portal, with Periconia didymospora, Byssothecium circinans and Massarina eburnea serving as outgroups to root the tree.

The results were unambiguous. The two strains of Chromolaenicola crataegicola formed a sister subclade to C. hongheensis with moderate statistical support (87% ML/0.99 BYPP), while the two strains of Paraphaeosphaeria fulva clustered with P. verruculosa and P. parmeliae with high support (99% ML/1 BYPP). Base-by-base comparison revealed measurable genetic divergence: C. crataegicola differs from its closest relative by 1.45% in ITS, 4.81% in rpb2 and 1.76% in tef1-α. Morphology reinforced the molecular separation. The conidiomata — the spore-producing structures — of C. crataegicola are notably larger than those of C. hongheensis, and its conidia turn dark reddish-brown at maturity with a single septum and internal cellular depression, whereas those of C. hongheensis become brown, guttulate and rough-walled.

Paraphaeosphaeria fulva earned its name — fulva means pale yellow — from the colour of its mature conidia, which are fusiform or reniform, initially hyaline and eventually turning pale yellow, partially curved in the middle with one to three septa. Its conidiogenous cells are hyaline, oblate or ampullate, lining the cavity of the conidiomata. These features distinguish it clearly from P. verruculosa, whose conidia are globose to ellipsoid with an orange-brown, verruculose wall, and from P. parmeliae, whose conidia are globose, brown, aseptate and thick-walled. Both new species were saprobic on dead twigs — C. crataegicola on hawthorn (Crataegus) branches, P. fulva on an unknown dead branch — and type specimens have been deposited in the Herbarium of Mycology at Jilin Agricultural University.

But taxonomy was only half the story. The team also fermented each fungus in liquid potato dextrose broth for 14 days at 28 °C and 150 rpm, then extracted the culture broth three times with ethyl acetate to obtain crude secondary metabolites. These complex chemical mixtures were tested against a panel of bacteria and fungi using two complementary assays: the paper disc diffusion method for antibacterial activity and the mycelial growth rate method for antifungal activity, each with three biological and three technical replicates.

The antibacterial results were striking. Both crude extracts inhibited Staphylococcus aureus, the bacterium behind everything from skin infections to life-threatening septicaemia, but showed no activity against Escherichia coli. The extract of C. crataegicola produced an inhibition zone of 8.38 ± 0.36 mm, significantly larger than the 7.09 ± 0.29 mm zone of P. fulva (p < 0.05). For comparison, streptomycin at 20 µg/ml produced a 7.26 mm zone. The researchers caution, however, that the crude extracts were tested at 20 mg/ml — a thousandfold higher concentration than the pure antibiotic — so the observed activity is modest relative to a refined drug at equivalent strength.

The antifungal results were equally compelling. Crude extract of P. fulva inhibited the grey mould pathogen Botrytis cinerea by 85.22 ± 2.99% and Trichoderma harzianum by 88.86 ± 1.14%, both significantly stronger than the C. crataegicola extract (81.00 ± 1.49% and 80.63 ± 2.65%, respectively, p < 0.05). Against Cladobotryum mycophilum, the causal agent of cobweb disease in mushroom cultivation, the two extracts were statistically indistinguishable (76.22 ± 5.49% vs. 77.13 ± 2.58%, p = 0.951). The positive control, the synthetic fungicide carbendazim at 20 mg/ml, achieved 100% inhibition against all three fungi.

These findings carry weight beyond the laboratory bench. With chemical pesticides posing mounting environmental risks, plant-associated microorganisms have become a critical resource for developing eco-friendly biopesticides. Prior antimicrobial pre-screening of four Chromolaenicola species from Thailand found none inhibited E. coli or Bacillus subtilis, and only weak activity against Mucor plumbeus in two species — making the antibacterial and antifungal potential of C. crataegicola a previously unrecognised trait within the genus. Meanwhile, Paraphaeosphaeria species are already known producers of bioactive secondary metabolites with antibacterial, antifungal and herbicidal activities; P. verruculosa, for instance, produces compounds effective against plant pathogens such as Colletotrichum gloeosporioides, Didymella glomerata and Nigrospora oryzae.

The authors emphasise that the crude extracts are complex mixtures, and the observed bioactivity cannot yet be attributed to specific compounds. Isolating and characterising the active molecules — and evaluating their potency, selectivity and safety — is the necessary next step before any agricultural or medicinal application. Still, the discovery enriches the known diversity of plant-associated ascomycetes in northeast China and underscores how much unexplored chemistry remains hidden in the world’s decaying wood. As the researchers conclude, Chromolaenicola and Paraphaeosphaeria represent underexplored sources for natural product discovery, with potential applications in biological control that are only beginning to come into focus.

Subject of Research: Taxonomy and bioactivity of two novel Didymosphaeriaceae fungal species from northeast China

Article Title: Additions to Didymosphaeriaceae : two novel species of Chromolaenicola crataegicola and Paraphaeosphaeria fulva with notes on antibacterial and antifungal activities

Article References: Su, W.-X., Tieliwadi, R., Zhang, B., Yuan, X.-H., & Li, X. (2026). Additions to Didymosphaeriaceae: two novel species of Chromolaenicola crataegicola and Paraphaeosphaeria fulva with notes on antibacterial and antifungal activities. MycoKeys, 137, 43-67. https://doi.org/10.3897/mycokeys.137.197035

Image Credits: AI Generated

DOI: 10.3897/mycokeys.137.197035

Keywords: Didymosphaeriaceae, Chromolaenicola crataegicola, Paraphaeosphaeria fulva, new fungal species, multi-locus phylogeny, antibacterial activity, antifungal activity, biopesticides, secondary metabolites, Pleosporales, northeast China, dead wood fungi