00:01
Another important property of fungi is that
they can be dimorphic. This largely applies
to the filamentous fungi. They can display
one of two growth forms. They can grow as
a yeast, a single cell organism, shown on
the right of this slide which divides by budding,
or they can grow as a mold, depending on the
environment. So that's dimorphism, they can
grow with one of two forms. And so here we're
showing on the left of the slide, growth as
a mycelium, on the right of the slide, growth
as a yeast form, and the switch between the
two forms, we typically observe when a free
living organism infects a living host, so
free living molds for example, the mycelium
on the left, they exist in the woods, we can
inhale mold spores, within as they begin to
grow as the yeast form. So here is an emphasis
of that, the yeast is typically the systemic
form, that means the form that grows within
us, the mold is found in the environment and
we inhale the mold, typically as spores, it
converts to a yeast form within us. And in
this illustration we're showing the mold on
a fruit, growing on a tree, but certainly
the mold can be anywhere, it could be on the
wood of the trunk, it could be on the forest
floor, it could be on rotting wood. Molds
grow everywhere in the environment.
01:26
There are a few unusual examples where the
form that grows systemically within us is
actually a mycelial form, this is an example
of a pathogen, we'll talk about a fungal pathogen
Candida albicans, which exist as a yeast form
and in some individuals, transform to a mycelial
form in tissues and as you might imagine the
mycelial forms are invasive and these can
be problematic as we'll talk. Now there are
a number of categories of the human infections