Bacteriophage Lambda Lysogenic Cycle Biology Essay

Bacteriophage Lambda Lysogenic Cycle Biology Essay Viruses are tiny agents that cause infections in a wide range of hosts including animals, plants, bacteria and other viruses. In particular, viruses that infect bacteria are called bacteriophages, bacterio meaning â€Å"bacteria† in Greek and phage meaning â€Å"to eat†. Bacteriophages are able to undergo lytic and lysogenic cycle to replicate; however, most undergo one or the other cycle to replicate. An example of a bacteriophage that is able to undergo both cycles is bacteriophage lambda (phage lambda). Bacteriophage lambda infects only the bacterium Escherichia coli strain k-12. Phage lambda is unique in its ability to turn replication genes on or off depending on the host’s condition. When E. coli is infected with phage lambda and the cell dies due to an environmental factor, the phage will switch from the lysogenic to the lytic replication cycle. Bacteriophage lambda was discovered by Esther Lederberg in 1950 while she was working in a laboratory with E. c oli strain k-12. Lederberg is considered a pioneer of bacterial genetics; she was also an immunologist and microbiologist. She flourished academically, receiving a doctorate from the University of Wisconsin where she worked with many other pioneers of microbiology, genetics and immunology, including: Andre Lwoff, Edward Lawrie Tatum, George Wells Beadle, Frances Crick and James Watson. While at the University of Wisconsin, Lederberg was using ultraviolet light on E. coli strain k-12 to mutagenize that specific strain of the bacteria. After prolonged exposure to the ultraviolet light, the bacteria stopped growing and its condition slowly began to deteriorate. An hour and a half after the exposure to the ultraviolet light ceased, the bacteria began to lyse (burst). This led Lederberg to the discovery of bacteriophage lambda. The E. coli sample that Lederberg was using was infected with bacteriophage lambda. The phage was not detected because it was in the lysogenic cycle, which meant that the phage was a prophage, and thus that the phage genome was integrated within the bacterial genome. Bacteriophage lambda sensed that the bacteria was about to die, so it switched its replication genes on and converted to lytic replication, therefore causing the cell to lyse and release the phage into the environment. Lederberg is also accredited with the discovery of induction; the process of when the lysogenic cycle is terminated and the lytic cycle is activated due to adverse conditions caused by ultraviolet light. Lederberg, along with her team of researchers, was awarded the Pasteur award in 1956. Viruses have many different anatomical structures depending on what kind of cells they infect. The anatomical feature that is similar throughout all bacteriophage is the capsid. The capsid or head is a shell made out of protein that contains DNA or RNA, depending on the virus. The capsid also contains some internal proteins. The capsid can have many different configurations, from a polygon-shaped sphere, like an icosahedral, or a rod-shaped helix. The main functions of the capsid are that it allows the virion to attach to its host via special sites on the surface, contains the internal proteins that allows the virus to penetrate the host cell membrane, which enables it to inject the infectious DNA or RNA into the host cell’s cytoplasm, and that it provides protection for the nucleic acid from the environment and digestion by enzymes. The capsid has structural subunits called capsomers that may contain one or many polypeptide chains. Some viruses have a secondary structure that protects the capsid itself, this is called an envelope. Not all viruses have an envelope; the envelope is made up of glyco-proteins and surrounds the entire capsid for optimum protection. The envelope has two lipid layers intermingled with protein molecules, a lipoprotein bi-layer, and also has a mixture of material that consist of the viral origin and some material from the me mbrane of the host cell. Besides a capsid, some viruses also contain a tail that is attached to the capsid which helps the virus penetrate the host cell’s outer membrane and allows the virus to inject the DNA or RNA into the host cell. The tail consists of two main structures: the tail fibers and a tail sheath. The tail fibers are tiny leg like formations that help the phage attach on to the bacterial cell by clinging on to the surface receptors. The tail sheath is a tube like structure that runs from the capsid to the tail fibers; the tail sheath digs into the cell membrane of the host and the DNA or RNA travels down the sheath and into the cytoplasm of the host and the infectious cycle begins. For viruses without tails, specialized spikes are protruding directly from the capsid that play a similar role to that of tails; the spikes are made up of proteins and help the virus invade the host cell. Bacteriophage lambda has a capsid with an icosahedral configuration that is 55 n anometers in diameter that contains 350-575 capsomers or subunits of 37,000 Daltons; the capsomers are positioned in groups of 5 and 6 subunits or pentamers and hexamers. The tail is 180 micrometers long and contains a single tail fiber that is 25 nanometers long. Bacteriophage lambda does not possess an enveloped capsid.

Business Management Proposal Essay Example | Topics and Well Written Essays - 1500 words

Business Management Proposal - Essay Example (Rigby, 2005) The basic aim of the proposal would be to develop a modification of law based on the marketing plan for Visual Management Systems Ltd for expansion into the southern States of the country. Apart form this central theme it would also be looked upon there should be enough opportunity and specified methods to penetrate and expand market segments for the company in relation to the use and capability of the CCTV related security technology from the parameters of marketing and for this aspects too your moral and legislative help is extremely needed. The world is in the midst of an all-purpose technological revolution based on CCTV related security technology, defined here as visual security, software related surveillance techniques, and CCTV related security equipment. The macroeconomic benefits of the CCTV related security technology revolution are already apparent in some economies, especially the United States and United Kingdom. Historical experience has shown that such revolutions have often been accompanied by financial booms and busts, and the CCTV related security technology revolution has been no exception. But, while spending on CCTV related security technology goods is likely to remain stable ... While technological change is an ongoing process, there are periods during which technological progress is especially rapid, resulting in new products and falling prices of existing products that have widespread uses in the rest of the economy. Such periods are generally identified with CCTV related security technology revolutions. (Hood, 2003) Earlier examples include textiles production and steam power in the industrial revolution, railroads in the nineteenth century, and electricity in the early twentieth century (the automobile could also be included, but its development was relatively gradual). The effects of such revolutions have generally occurred in three (often overlapping) main stages. First, technological change raises productivity growth in the innovating sector; second, falling prices encourage capital deepening; and, finally, there can be significant reorganization of production around the capital goods that embody the new technology. (Hall, 2006) The growth of the CCTV related security technology sector in the 1980s was an important development for the economy, but it spurred relatively little policy or media interest. True, CCTV related security technology was recognized as a driver of comparative advantage for the US and the UK and there were a few initiatives involving industrial policy and military preparedness, CCTV related security technology was of interest primarily to specialists. (Prawer, 2005) A unique confluence of forces certainly came together in the 1990s: rapid technological advances in the technology sector; widespread recognition that security could be used to comparative advantage as well as process it; the rapid

Nurse Roles & Functions Essay Example | Topics and Well Written Essays - 250 words

Nurse Roles & Functions - Essay Example Alternatively, nurses also play instrumental roles in CQI by ensuring that they follow the prescribed rules and systems set by the healthcare organization. Nurses must also improve their service provision approaches to avoid errors experienced in the workplace. The various types of organizational hazards encountered while working at a local hospital entail injuries, accidents, inadequate equipment and congestion (Vincent, 2010). The preventive strategies that should be implemented to prevent workplace-related injuries include the provision of safety gears like gloves, cleaning the wards and the procurement of more equipment. The safety issues in health care, such as prevention of blood borne illnesses is to ensure that nurses use gloves when attending to patients (Vincent, 2010). The prevention of needle stick equipment is by disposing all the used syringes at the correct dump bins where children and other people cannot access them. The prevention of back injury can be handled by avoiding carrying of heavy items or placing medical equipment at places where others cannot overstretch to reach them (Vincent,