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.  


A very complex life cycle for a bacteria!  (Provided by Microbe Wiki)

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!

The Grim Reaper of the Soil