Prokaryotes-The+Start+of+Something+New

Bacteria have become more important today, even though they usually carry around a negative connotation. Bacteria fall into a much more broader category known as prokaryotes. Prokaryotes are grouped into four different categories due to their ability of obtaining energy and carbon. But how important can these cells really be, even when we know that many can cause disease? Many people may ask this question. According to many theories on evolution, life on Earth began with a single prokaryote. This gives rise to the cell theory that states all cells originate from previous, older cells.

General Information Prokaryotes are unicellular organisms that have diameters between the ranges of 0.5 to 1.0 micrometers and lengths between the ranges of 1.0 to 5.0 micrometers. Prokaryotes have several common shapes and among these shapes are a spherical and a rod shape. Spherical shapes known as cocci occur among the groups of independent cells while bacilli, the rod shaped prokaryotes occur as single rods or long chains. **//__Prokaryotic cells lack organelles of the cytoplasm such as nuclei, mitochondria, chloroplasts, endoplasmic reticules, Golgi apparatuses, and lysosomes__//**. Even though these cells do not have nuclei, they contain a nuclear area containing the hereditary information, DNA. In some prokaryotes, the plasma membrane could be folded inward. Cell walls are an important part of the prokaryotic cells as they help in maintaining the size and shape of the cells while stabilizing it. Flagella rotate counterclockwise causing a cell to move forward. Bacterium flagella do not have microtubules but consists of basal bodies, hooks and a single filament. The energy from ATP is used to pump protons out of the cell in a bacterium and these protons allow the spinning of the flagellum. In some prokaryotes, chemotaxis could be noticed. This is a process by which cells move due to a chemical stimulus present in the environment.

Prokaryotic DNA and the Transfer of Hereditary Information

Prokaryotes have circular DNA which has small amounts of protein associated with it. They are very successful organisms as they have an amazing ability to reproduce rapidly by the process of binary fission. This process of cell division occurs at a remarkable speed and under some conditions; the bacterial species could divide within 20 minutes. **//__Without any interference from any other factor, more than 1 billion bacteria could be produced by one bacterium within 10 hours at this rate!__//** Unfortunately, it is not possible for a bacterium to continue to reproduce at such an unimaginable rate! Budding and fragmentation are two other less common processes of sexual reproduction among bacteria.

Genetic material can be exchanged in prokaryotes just like eukaryotic organisms which results in genetic recombination. Sometimes an organism transfers genetic material to another organism that is not its offspring which is known as horizontal gene transfer. Three processes are involved to transfer genes among bacteria: Transformation, Transduction and Conjugation. During transformation, foreign DNA from a dead bacterium enters a host bacterium and DNA is exchanged by recombination. In transduction, a phage transfers bacteria DNA from one bacterium to another while during conjugation, two cells of different mating types transfer materials from one to the other. //E. coli// is the most common prokaryote found where conjugation has been mostly studied.


 * More information, including sources, are provided on the continuation of this page