Prokaryotic Cells

Morphology

All are UNICELLULAR organisms Although one group of bacteria that lives in soil, called the MYXOBACTERIA form aggregates (“swarms” or “packs”) that move together and are capable of forming a “fruiting body” meant to survive until nutrients are more plentiful. The fruiting process is thought to ensuring that cell growth is resumed with a group of bacteria, rather than as isolated cells.

Prokaryotic cells are generally smaller than eukaryotic cells

There are two main types of prokaryotic cells: Eubacteria (true bacteria) Archaea

Individual Cells are Either:

Under a electron microscope, there are a number of characteristic structures visible:

Cell membrane (plasma membrane) Controls passage of materials into and out of the cell May be infolded (called mesosome)

Cytoplasm Fluid portion of the cell Location of cellular metabolism (For these reasons we can think of it as a nutrient soup!)

Ribosomes Float freely in the cytoplasm The site of protein synthesis.

Some scary facts! Bacteria live on or in just about every material and environment on Earth from soil to water to air, and from your house to arctic ice to volcanic vents. Each square centimeter of your skin averages about 100 000 bacteria. A single teaspoon of top soil contains more than a billion (1 000 000 000) bacteria. A shovel full has as many bacteria as there are people on the Earth. You may find this one appetizing!. A gram of the toxin from this organism is a lethal dose for 200 000 mice. A cup of this toxin in pure form would be capable of depopulating the entire Earth. This organism is Clostridium botulinum, the organism responsible for Botulism. The toxin, called botulin works like nerve gas  causing respiratory failure, paralysis and death in as little as 4 hours. It can be found  in improperly prepared canned foods. Bacteria thrive in warm, moist  environments. Wearing headphones for just one hour will increase the amount of bacteria in your ear by 700 times. This is Streptococcus pyogenes, which is the organism responsible for Strep Throat, Rheumatic Fever and Impetigo  (also known as FLESH EATING BACTERIA!)  It has been with us for centuries and looks like it will continue to be, but it is not a major concern for the entire human race as some of the tabloids might have you believe

Prokaryotic cells do not have membrane bound organelles

Nucleoid Contains the DNA molecule and therefore controls the activity of the cell. The DNA is in a circle and is not supported by proteins as in eukaryotic cells (termed “naked DNA”).

Plasmid A small circle of DNA that exists and replicates independently of the main DNA in the nucleoid. Contain genetic instructions for certain cell activities such as resistance to antibiotics.

Some Prokaryotes have a cell wall Exception is a genus called mycoplasma Gives shape, support and protection to the plasma membrane and cytoplasm of the cell. Made of peptidoglycan* (protein-sugar molecules). *different than plant cell walls, which are made of cellulose

Flagellum Some bacteria have one or more Used for motility.

Pili Short fibers projecting from the cell wall found on some bacteria. They may help the bacteria cling to surfaces.

Capsule A special mucus-like protective coating found on some disease-producing bacteria.

What can you remember?