![]() This short generation time, coupled with mechanisms of genetic recombination and high rates of mutation, result in the rapid evolution of prokaryotes, allowing them to respond to environmental changes (such as the introduction of an antibiotic) very rapidly. Reproduction can be very rapid: a few minutes for some species. The DNA transferred can be in the form of a plasmid or as a hybrid, containing both plasmid and chromosomal DNA. In conjugation, DNA is transferred from one prokaryote to another by means of a pilus, which brings the organisms into contact with one another. Archaea are not affected by bacteriophages, but instead have their own viruses that translocate genetic material from one individual to another. Transduction results in a recombinant organism. In transduction, bacteriophages, the viruses that infect bacteria, sometimes also move short pieces of chromosomal DNA from one bacterium to another. If a nonpathogenic bacterium takes up DNA for a toxin gene from a pathogen and incorporates the new DNA into its own chromosome, it, too, may become pathogenic. In transformation, the prokaryote takes in DNA found in its environment that is shed by other prokaryotes. In (c) conjugation, DNA is transferred from one cell to another via a mating bridge that connects the two cells after the pilus draws the two bacteria close enough to form the bridge. In (b) transduction, a bacteriophage injects DNA into the cell that contains a small fragment of DNA from a different prokaryote. The DNA may remain separate as plasmid DNA or be incorporated into the host genome. In (a) transformation, the cell takes up prokaryotic DNA directly from the environment. Many endospore-producing bacteria are nasty pathogens, for example Bacillus anthracis, the cause of anthrax.\( \newcommand\): Modes of prokaryote reproduction: Besides binary fission, there are three other mechanisms by which prokaryotes can exchange DNA. This makes destroying them very difficult. These are dormant structures, which are extremely resistant to hostile physical and chemical conditions such as heat, UV radiation and disinfectants. That’s why we can quickly become ill when pathogenic microbes invade our bodies. After one more hour the number of bacteria will have risen to a colossal 16,777,216. This means that in just seven hours one bacterium can generate 2,097,152 bacteria. When conditions are favourable such as the right temperature and nutrients are available, some bacteria like Escherichia coli can divide every 20 minutes. Each daughter cell is a clone of the parent cell. The bacterial cell then elongates and splits into two daughter cells each with identical DNA to the parent cell. Binary fission begins when the DNA of the bacterium divides into two (replicates). In this process the bacterium, which is a single cell, divides into two identical daughter cells. Most bacteria reproduce by binary fission. © gaetan stoffel / iStockģD illustration of Escherichia coli How do bacteria reproduce? Relatively few bacteria are parasites or pathogens that cause disease in animals and plants. Some types cause food spoilage and crop damage but others are incredibly useful in the production of fermented foods such as yoghurt and soy sauce. Some bacteria live in the soil or on dead plant matter where they play an important role in the cycling of nutrients. A lot of these bacterial cells are found lining the digestive system. There are approximately 10 times as many bacterial cells as human cells in the human body. Some live in or on other organisms including plants and animals including humans. © ttsz / iStockīacteria are found in every habitat on Earth: soil, rock, oceans and even arctic snow. They can exist as single cells, in pairs, chains or clusters. For example it may contain a gene that makes the bacterium resistant to a certain antibiotic.īacteria are classified into five groups according to their basic shapes: spherical (cocci), rod (bacilli), spiral (spirilla), comma (vibrios) or corkscrew (spirochaetes). The plasmid often contains genes that give the bacterium some advantage over other bacteria. Some bacteria have an extra circle of genetic material called a plasmid rather than a nucleus. Their control centre, containing the genetic information, is contained in a single loop of DNA. Bacteria are microbes with a cell structure simpler than that of many other organisms.
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