Bacteria are a lot like humans in the sense that they go about their daily business acquiring energy that is necessary to go on living. Like humans, they also get sick. They can become infected with other microorganisms, or non-organisms; whichever is the case.
Viruses are molecules that must infect an organism's cells in order to duplicate their genetic material. They cannot procreate on their own. It is for this reason that viruses are considered to be non-living by many scientists.
A particular type of virus infects bacteria: the bacteriophage, which literally means bacteria-eater. There are many strains of bacteriophages, but they share many similarities.
Bacteriophage Virus Structure
The typical bacteriophage is made up of protein with a head that contains either RNA or DNA. Many bacteriophages have a collar that attaches the head to a tail, much like the human neck attaches the head to the body. The hollow tail is used to transport the genetic material into the bacteria by contracting an outer sheath. The tail culminates into a base plate and projects many long tail fibers, like the legs of a spider.
The Bacteriophage Penetrates the Bacterial Cell Wall for Virus Reproduction
Like that of all cells, bacterial cell walls have receptors that react to specific molecules. Bacteriophages can use specific receptors to attach to bacterial cell walls, usually with the tail fibers. The base plate is then used to make a more permanent connection to the bacterium.
According to the University of South Carolina School of Medicine's Microbiology and Immunology On-line article, "Bacteriophage," (accessed May 7, 2010) by Dr. Gene Mayer, "Some phages have enzymes that digest various components of the bacterial envelope," but those with sheaths contract the sheaths to push "the hollow tail fiber…through the bacterial envelope."
Mayer further explains that once the bacteriophage accesses the inside of the bacterial cell, "the nucleic acid from the head passes through the hollow tail and enters the bacterial cell. Usually, the only phage component that actually enters the cell is the nucleic acid." The bacterial cell duplicates the viral genetic material and the proteins and assembles new bacteriophages.
Bacterial Cell Lysis by Osmosis Releases New Bacteriophages
Eventually, the bacterium bursts and releases the new bacteriophages. On his microbiology website, The Grapes of Staph, Dr. Gary E. Kaiser of the Community College of Baltimore County says in his September 7, 2007 notes, "Bacteriophage Life Cycles: The Lytic Life Cycle," (accessed May 7, 2010) that the bacteriophages release lysozymes that break down the peptidoglycan within the bacterial cell wall. This weakens the cell by allowing water to move into the cell creating a hypotonic, intracellular environment until it finally bursts, a process called osmotic lysis.
While bacteriophages and bacteria share similar names, they are quite different. The bacteriophage is not a bacterium, but a virus. It is parasitic to the bacterium in that it uses the cellular machinery of the bacterium to produce new bacteriophages. The new bacteriophages are released when the bacterium bursts.
Diane Ursu - Diane Ursu joined Suite101 as a contributing writer in August 2009 and became a Feature Writer in January 2010. She is a freelance writer ...
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