The Vibrant Life of a Bacteria
For Streptomyces griseus there are many
interesting things to look at and discuss about its way of obtaining
nutrients and the complex life cycle that it progresses through.
Our bacteria and the fungi go after food in
similar ways. By that I mean that this bacteria will sense its
environment and then issue metabolites that will digest the food around it
so that the bacteria may absorb the nutrients and grow. These metabolites
can be thought of as exoenzymes (enzymes secreted to work outside the body
to digest the food). What is quite special about this bacteria is that it
has adopted to having the most optimal growth and thus optimal use of its
enzymes in alkaline soil of about a pH of 9. Living in the soil would also
be something most people are familiar with, the common
earthworm.
The
earth-like smell of soil comes from bacteria who live there! (Provided
by NASA)
Either way, after the food on the outside is digested, the
material the bacteria wants can be ingested. These food items can include
alcohols, amino acids, sugars and lastly aromatic compounds. Along with
this, if there is plenty of food for these bacteria it has been found in
some species ofStreptomyces that they store this excess as glycogen.
The life cycle of Streptomyces
griseus is much more complex then one would think. As the following
diagram shows the life cycle is almost exactly the same as a simple fungus.
The bacteria creates its vegetative mycelium until enough growth has
occurred that the bacteria colony can start creating structures called
conidia; during vegetative growth DNA is copied but the cells do not
split. These hold sporophores which are raised above the colony, which
create the spores directly. These spores are then released and start new
colonies themselves and the process is repeated.
Besides this, there really
does not seem to be anything that triggers the formation of spores except
for initial growth and then time for more spores to spread and start the
process over again.
To learn why this life cycle is similar to fungi check out these different
fungi to compare with the Streptomyces griseus life cycle. A
basidiomycota (phylum of mushroom) and its life
cycle are shown here. For comparison this is the orange peel fungus and is
instead an
ascomycota.
Now we'll look at why Streptomyces griseus would even excrete these drugs we classify as antibiotics, as we will soon see, it's not for our benefit!