Identification and functional analysis of bacteria in sclerotia of Cordyceps militaris

Background Cordyceps militaris is a fungus that parasitizes insects. Compounds from C. militaris are valuable in medicine and functional food. There are many kinds of bacteria in the natural sclerotia of C. militaris. However, the community structure of microorganisms in samples from different places may be different, and the corresponding ecological functions require experimental verification. Results We used high-throughput sequencing technology to analyze bacterial 16S rRNA gene sequences in sclerotia of three samples of C. militaris from Liaoning Province, China. Pseudomonas, Pedobacter, Sphingobacterium, and Serratia were the dominant bacterial genera in the sclerotia. Pseudomonas and Pedobacter are heterotrophic, Sphingobacterium decomposes urea, and Serratia reduce nitrate. Two strains of bacteria, N-2 and N-26, were isolated from the sclerotia of the C. militaris, cultured, biochemically characterized, and identified as Stenotrophomonas maltophilia and Pseudomonas baetica, respectively. When these isolated strains were respectively cocultured with C. militaris, the mycelium biomass, mycelium pellet diameter, and cordycepin content decreased. Conclusions Bacteria in sclerotia have an important effect on the growth of C. militaris and the production of its metabolites.

Mulch removal time did not have significant effects on Tuber melanosporum mycelium biomass

Aim of study: We aimed to i) evaluate the effects of mulching on Tuber melanosporum mycelium biomass and seedling growth (i.e. root collar diameter and seedling height) and ii) unravel the relationship between growth in root collar diameter and mycelium abundance, in a T. melanosporum plantation.Area of study: The experimental plantation is located in the Pre-Pyrenees mountains in Catalonia, Spain.Material and methods: The experimental plantation was established in 2010 using one-year-old T. melanosporum inoculated Quercus ilex seedlings. Double-layered mulch materials were placed around the seedlings. The mulch materials were removed from randomly selected seedlings in 2015 and 2018. Soil samples were collected in 2018 at 40 and 80 cm distances from seedlings that had mulching during five and eight years, and T. melanosporum mycelium biomass was estimated by quantitative Polymerase Chain Reaction (qPCR). Seedling root collar diameter and height were measured simultaneously when mulch materials were removed.Main results: Mulch removal time did not have significant effects on T. melanosporum mycelium biomass or seedling growth. However, mycelium biomass at 40 cm distance tended to be higher on seedlings after eight-year mulching with 0.9 mg/g soil whereas mycelium biomass was 0.4 mg/g soil after five-year mulching. A positive relationship between mycelium biomass and seedling root collar diameter was also found.Research highlights: Mulching seems to have a positive effect on truffle mycelium biomass, with nearly two times higher quantity of mycelium after eight-years compared with five-years mulching usage. Seedling root collar diameter is a good indicator of mycelium expansion in the plantation.Keywords: Black truffle; Quercus ilex; mulching; tree growth; truffle cultivation.

Inhibitory Effects of Litsea cubeba Oil and Its Active Components on Aspergillus flavus

Aspergillus flavus (A. flavus) is a frequent harmful fungal pathogen. It can infect traditional Chinese medicine materials and release aflatoxin, to cause both economic and human health effects. By comparing the inhibitory potential of Litsea cubeba oil and its active components to A. flavus CGMCC 3.4408, citral was confirmed to be the main component that inhibits the growth of A. flavus CGMCC 3.4408, and the EC50 was 163.65 mg L−1. The inhibitory effect of citral on A. flavus CGMCC 3.4408 was studied for colony growth rate, mycelium biomass, aflatoxin production, and microstructure. Citral slowed down the growth rate of colonies and reduced mycelium biomass and toxin production. Moreover, citral altered the morphology of fungal spores and mycelium. In addition, citral also has the inhibitory effects on the isolates of A. flavus from moldy traditional Chinese medicinal materials. Thus, citral can be used as a potential agent to check the growth of A. flavus or related fungal strains.

Effect of tannin concentration on mycelial growth and development of Auricularia cornea

It is proved that the effect of tannin concentration on the mycelial growth of fungi. Auricularia cornea (white strain) were treated with different concentrations of tannins in petri-dishes and liquid shaking flasks. The growth rate of mycelium, the ratio of clamp connection, morphology of mycelium, biomass of mycelium and activity of antioxidant enzymes were determined. The results showed that different concentrations of tannin significantly decreased the rate of mycelium. However hign concentration of tannin stress increased the content of thiobarbituric acid in mycelia and had obvious time and concentration effects. Different antioxidant enzyme activities also had different responses to tannin stress. It provides theoretical basis for fungi to utilize and develop substrates containing tannin such as pine.

Effect of tannin concentration on mycelial growth and development of Auricularia cornea

It is proved that the effect of tannin concentration on the mycelial growth of fungi. Auricularia cornea (white strain) were treated with different concentrations of tannins in petri-dishes and liquid shaking flasks. The growth rate of mycelium, the ratio of clamp connection, morphology of mycelium, biomass of mycelium and activity of antioxidant enzymes were determined. The results showed that different concentrations of tannin significantly decreased the rate of mycelium. However hign concentration of tannin stress increased the content of thiobarbituric acid in mycelia and had obvious time and concentration effects. Different antioxidant enzyme activities also had different responses to tannin stress. It provides theoretical basis for fungi to utilize and develop substrates containing tannin such as pine.

Effect of Tannin Concentration on Mycelial Growth and Development of Auricularia Cornea

It is proved that the effect of tannin concentration on the mycelial growth of fungi. Auricularia cornea (white strain) were treated with different concentrations of tannins in Petri-dishes and liquid shaking flasks. The growth rate of mycelium, the ratio of clamp connection, morphology of mycelium, biomass of mycelium and activity of antioxidant enzymes were determined. The results showed that different concentrations of tannin significantly decreased the rate of mycelium. However hign concentration of tannin stress increased the content of thiobarbituric acid in mycelia and had obvious time and concentration effects. Different antioxidant enzyme activities also had different responses to tannin stress. It provides theoretical basis for fungi to utilize and develop substrates containing tannin such as pine.