AP bio: Comparing Bacteria, Virus, Prion, and Protist

A typhoid bacterium.  (This picture is from: http://news.softpedia.com/news/Typhoid-Bacterium-Accompanied-Us-Along-Our-Evolution-41046.shtml.)

Bacteria

Bacteria can adapt very well to environment that change constantly because they have short generation spans.  During these short generation spans, they can undergo genetic recombination.  This way, so when they reproduce through various ways such as transformation, transduction, and conjugation, the new DNA will replicate along with their own original DNA.  These new, foreign DNA are expressed in the new strains of transformed bacteria.  This also lets each bacterium adapt their metabolic processes with the changes of their environment.

A diagram of the structure of a vius.  (This picture was from: http://www.armageddononline.org/viruses.html.)

Virus

Unlike bacteria, virus are not actually alive because they cannot survive outside a host.  They are basically just genes in a protective coat.  The parts of a virus includes its capsid, protein coat, viral envelope, and nucleic acid.  Bacteriophages are the group of viruses that can infect bacteria.  They reproduce through the lytic and lysogenic cycles.  In the lytic cycle, they attack the host cell and when the cell bursts, the new viruses move on to destroy other host cells.  In the lysogenic cycle, the virus may lie in wait in the host cell for a long time before the lytic cycle is activated and it destroys the host cell.

The structure of a prion.  (This picture was from: http://www.physorg.com/news153681509.html.)

Prion

Prions are simple infectious agents.  They are basically protein that are misfolded.  It has no genetic material.  Although they are proteins, they can reproduce on their own and become infectious agents.  In humans, they may have been linked with the Creutzfeldt-Jakob Disease (CJD) and the Gerstmann-Straussler-Scheinker Syndrome.

A microscopic view of a paramecium, a protist.  (This picture was from: http://www.mlms.loganschools.org/~ckircalli/homework/MATH_SCIENCE%20LINK%20PAGES/PROTIST%20INTERNET%20LESSON.html.)

Protist

Protists are eukaryotic microoorganisms.  They are classified in the Protista kingdom, which also includes unicellular organisms.  Sometimes, their behavior might make them pathogens that infect plants and animals.  Protists have a lot of different ways of feeding, such as filter feeding in flagellates and endocytosis (usually phagocytosis or cell-eating, but sometime pinocytosis or cell-drinking.)  Some reproduce sexually with gametes or asexually through binary fission.  Other protists are more complicated and have life cycles in which some forms of the organism reproduce sexually and others asexually.