Fungi forming mold on food are
hazardous. Fungi supplying antibiotics are beneficial. Fungi may be harmful
pathogens. On the other hand, they are used for the production of food or
medicine and in bioengineering. In either case, it is required to precisely
understand their growth mechanism. Researchers have now taken a big step
forward: Using high-performance light microscopy, they watched mold fungi as
they grew in the cell.
Like most fungi, mold fungi are hyphal
fungi. They consist of filamentous cells, hyphae, which may form large
networks, mycelia. The hyphae of about 3 µm in thickness exclusively grow by
directed extension of their tips. They grow very rapidly, by about 1.5 mm per
day. An important objective of biological fundamental research is to understand
this growth on the molecular level, as hyphal growth plays an important role in
both health-damaging effects and beneficial applications of fungi.
For their studies, the researchers
tagged a key enzyme required for building the chitin-containing cell wall with
a fluorescent protein and observed the latter in the living cell with the help
of high-resolution microscopy (nanoscopy). Use of ultrasensitive cameras in the
microscope enabled high-speed imaging of tip growth and of the transport of
individual vesicles. These images resemble small movies and allow to precisely
determine transport speed of the vesicles. They reveal how building materials
are packed into smallest vesicles and transported along the fiber structures of
the cell skeleton to the cell tip by transport vehicles, the motor proteins.
Motor proteins are very small nanomotors that dock to the fiber structures with
two small "feet" and walk on these structures. Using genetically
modified fungi, the scientists also identified the motor proteins responsible
for the transports.
From their observations, the researchers
of the Institute of Applied Physics and the Institute for Applied Biosciences
of KIT derived a first comprehensive model to describe how the rapidly growing
hyphal tip is supplied with construction material. This is an important step
towards complete molecular understanding of directed cell growth processes,
Professor Gerd Ulrich Nienhaus of KIT's Institute of Applied Physics says.
"The findings made in hyphal fungi are of general relevance to biology, as
they can be transferred to other cells and organisms. On the other hand, they
open up new opportunities to specifically influence fungal growth, which is
important to the mitigation of pathogenic species in medicine."
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Posted by Dr. Tim Sandle
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Pharmaceutical Microbiology