Mycelium

About: Mycelium is a research topic. Over the lifetime, 8923 publications have been published within this topic receiving 170993 citations.

Hyphal differentiation in the exploring mycelium of Aspergillus niger

Abstract: Mycelial fungi play a central role in element cycling in nature by degrading dead organic material such as wood. Fungal colonization of a substrate starts with the invasion of exploring hyphae. These hyphae secrete enzymes that convert the organic material into small molecules that can be taken up by the fungus to serve as nutrients. Using green fluorescent protein (GFP) as a reporter, we show for the first time that exploring hyphae of Aspergillus niger differentiate with respect to enzyme secretion; some strongly express the glucoamylase gene glaA, while others hardly express it at all. When a cytoplasmic GFP was used, 27% of the exploring hyphae of a 5-day-old colony belonged to the low expressing hyphae. By fusing GFP to glucoamylase and by introducing an ER retention signal, this number increased to 50%. This difference is due to cytoplasmic streaming of the reporter in the former case, as was shown by using a photo-activatable GFP. Our findings indicate that a fungal mycelium is highly differentiated, especially when taking into account that hyphae in the exploration zone were exposed to the same nutritional conditions.

Day/night and circadian rhythm control of con gene expression in Neurospora.

Abstract: In the filamentous fungus Neurospora crassa, several events in the process of conidiation are influenced by light. Two genes, con-6 and con-10, which were previously shown to be transcriptionally activated during conidiation and by exposure to light, were found to be unexpressed in mycelium maintained in constant darkness or in constant light. However, when mycelium was shifted from darkness to light, transcripts of both genes appeared and were abundant. Upon further illumination both transcripts disappeared--i.e., their continued production was light repressed. When dark-grown mycelium was exposed to a light pulse and reincubated in the dark, expression of con-6 and con-10 exhibited a 20-hr circadian periodicity. Both genes were photoinducible throughout the stages of the circadian cycle. In the mutant strains bd and bd;frq9, con-6 and con-10 were light inducible but were not normally light repressible. Mutant genes such as acon-2, acon-3, and fl that block developmental expression of con-6 and/or con-10 did not prevent their photoinduction.

Decolourisation of Orange II by a Wood-Rotting Fungus

Abstract: The decolourisation of Orange II by a wood-rotting fungus has been studied. It was found that Fungus F29 could effectively decolourise Orange II especially when grown as pelleted mycelia under agitated conditions. Many factors affecting the decolourisation process in nitrogen-limited media (NLM) were studied, including: concentration of glucose, NH4+, Mn(II) and veratryl alcohol; initial pH; amount of mycelium; mycelial age; Orange II concentration; temperature. Results showed that the media containing Orange II at 1000 mg dm−3 (or higher) could be decolourised by 98% of the initial colour (A480 nm) in 2 days, in most conditions tested, and that the mycelia could be repeatedly reused. © 1997 SCI.

Enzyme production by endophytes of Brucea javanica

Abstract: Twenty-one endophytic isolates from Brucea javanica were tested for their ability to produce extracellular cellulase and extracellular and intracellular amylase, ligninase, pectinase and xylanase. The same fungi were tested for their ability to cause weight loss in wood blocks. All fungi produced amylase and cellulase, while only one sterile mycelium produced ligninase and no isolates produced pectinase. The enzyme tests indicate that most endophytes are degraders of the simpler sugars and cellulose available in recently dead leaves and possibly wood. Only one slow growing species of sterile mycelium however, appeared to be capable of degrading lignin that would be available in dead wood. No fungi appeared to be latent pathogens. A discussion of enzyme production in relation to possible roles of endophytes is provided.

Characterization of a CuZn superoxide dismutase gene in the arbuscular mycorrhizal fungus Glomus intraradices.

Abstract: To gain further insights into the mechanisms of redox homeostasis in arbuscular mycorrhizal fungi, we characterized a Glomus intraradices gene (GintSOD1) showing high similarity to previously described genes encoding CuZn superoxide dismutases (SODs). The GintSOD1 gene consists of an open reading frame of 471 bp, predicted to encode a protein of 157 amino acids with an estimated molecular mass of 16.3 kDa. Functional complementation assays in a CuZnSOD-defective yeast mutant showed that GintSOD1 protects the yeast cells from oxygen toxicity and that it, therefore, encodes a protein that scavenges reactive oxygen species (ROS). GintSOD1 transcripts differentially accumulate during the fungal life cycle, reaching the highest expression levels in the intraradical mycelium. GintSOD1 expression is induced by the well known ROS-inducing agents paraquat and copper, and also by fenpropimorph, a sterol biosynthesis inhibitor (SBI) fungicide. These results suggest that GintSOD1 is involved in the detoxification of ROS generated from metabolic processes and by external agents. In particular, our data indicate that the antifungal effects of fenpropimorph might not be only due to the interference with sterol metabolism but also to the perturbation of other biological processes and that ROS production and scavenging systems are involved in the response to SBI fungicides.