Using Batch And Continuous Cultures Biology Essay

Using Batch And Continuous Cultures Biology Essay Microbial growth causes an increase in a microorganisms size and population number and can be studied using batch and continuous culture mediums (Lansing M. Prescott et al. 1990, 1993, p. 112) Batch cultures: Nutrient consumption and build up of toxic by-products slow down and stop the growth of bacteria. One method to avoid this is to use batch culture system. This involves culturing bacteria in liquid medium within a closed system where no fresh medium is added during the incubation period and hence the nutrient concentration declines and waste products accumulate during the growth of bacteria (Slonczewski Foster 2009, p. 137). The microorganisms reproduce by binary fission and their growth can be expressed as the logarithm of cell number and can be plotted against incubation time. This result in a curve that has 4 distinct phases as shown in Figure 1: (Lansing M. Prescott et al. 1990, 1993, p. 113) Figure 1: Curve showing phases of growth for batch cultures (taken from Tortora et al. 1992) Lag Phase- when microorganisms are introduced into fresh culture medium no increase in cell number or mass occurs. This marks the beginning of the Lag Phase which is necessary as the cells may be old and depleted of ATP, certain essential cofactors and ribosome, the medium may be different from the one that the microorganism was growing in previously, or the microorganism may have suffered injuries and may need time to recover (Lansing M. Prescott et al. 1990, 1993, p. 113). Length of the Lag Phase varies depending on factors such as age of culture, temperature changes and differences between old and new media. When cells are transferred from a complex medium to a fresh complex medium lag phase is very short, whereas when cells are transferred from complex medium into a minimally defined medium, lag phase is protracted (Slonczewski Foster 2009, p. 137). Exponential Phase- during this phase the rate of growth of microorganisms is constant and they divide and become double in number at regular intervals and at the maximal rate possible given their genetic potential, nature of the medium and the conditions of growth (Lansing M. Prescott et al. 1990, 1993, p. 113).As batch cultures are not synchronous every cell has an equal generation time and each cell divides at a different moment, as hence the cell number rises smoothly. When the medium is abruptly changed nutritional downshifts or nutritional upshifts cause cells experiencing balanced exponential growth to be thrown into metabolic chaos that is unbalanced growth (Slonczewski Foster 2009, p. 138). Exponential phase cultures are used in biochemical and physiological studies as the population is most uniform in terms of chemical and physiological characteristics during this phase (Lansing M. Prescott et al. 1990, 1993, p. 113). Stationary Phase- during this phase the growth curve becomes horizontal as growth of the population ceases. Bacteria enter this phase at a population level of around cells per ml. The total number of viable organisms remains constant due to a balance between cell division and cell death or because the population ceases to divide but still remains metabolically active. Microbial populations enter the stationary phase due to reasons such as nutrient limitations, oxygen availability and accumulation of toxic waste products (Lansing M. Prescott et al. 1990, 1993, p. 114). Death Phase- characteristic feature of this phase is decline in the number of viable cells due to nutrient deprivation and buildup of toxic wastes. The death of a microbial population is logarithmic. The extended survival of particularly resistant cells may reduce the death rate (Lansing M. Prescott et al. 1990, 1993, p. 114). In this phase the number of cells that die during a given time period is proportional to the number of cells that existed at the beginning of the time period (Slonczewski Foster 2009, p. 138). Advantages of using batch cultures: They allow versatility and can be used for many different reactions (Nielsen Villadsen 1994, p. 344). They are safe and do not pose a threat of strain mutation (Nielsen Villadsen 1994, p. 344). They ensure complete conversion of substrate (Nielsen Villadsen 1994, p. 344). The changing conditions during the use of batch cultures affect the physiology and growth of bacteria and hence highlight the ability of bacteria to adapt to its environment (Slonczewski Foster 2009, p. 137). Disadvantages of using batch cultures: Use of batch cultures requires highly skilled labor thus increasing labor costs (Nielsen Villadsen 1994, p. 344). Use of batch cultures is time consuming (Nielsen Villadsen 1994, p. 344). According to Xuezhen Kang (2000) changing concentrations of products and reactants, varying pH and oxidation-reduction potential makes interpretation of results difficult. According to Xuezhen Kang (2000) complicated mix of growing, dying and dead cells also makes interpretation difficult. Continuous cultures: In a continuous culture system the microorganisms are grown in an open system where constant environmental conditions are maintained through continuous provisions for new nutrients and removal of waste. This allows the microbial population to remain in exponential growth phase and at a constant biomass concentration for an extended period of time (Lansing M. Prescott et al. 1990, 1993, p. 120). 2 main types of continuous culture systems: Chemostat- this system ensures that sterile medium containing essential nutrients in limiting quantities is fed into the culture vessel at the same rate as the medium containing the microorganism is removed (Lansing M. Prescott et al. 1990, 1993, p. 120). The growth rate of microorganisms is determined by the rate at which new medium is fed into the growth chamber. The final cell density depends on the concentration of the limiting nutrient (Lansing M. Prescott et al. 1990, 1993, p. 120). Dilution rate D is used to express the rate of nutrient exchange and is defined as the rate at which medium flows through the culture vessel relative to the vessel volume. f represents flow rate and V represents volume of the vessel (Lansing M. Prescott et al. 1990, 1993, p. 120). D=f/V f (ml/hr) and V(ml)(Lansing M. Prescott et al.1990, 1993, p. 120) Microbial population levels and generation time depend on the dilution rate. As the dilution rate increases generation time shortens and growth rate rises. Under these conditions the limiting nutrient will be almost completely depleted and it begins to rise at higher dilution rates as there are fewer microorganisms present to use it. At low dilution rate a rise in both cell density and growth rate occur (Lansing M. Prescott et al. 1990, 1993, p. 120). Turbidostat- involves a photocell that measures the turbidity of the culture in the growth vessel. The rate of flow of the media through the growth vessel is automatically regulated to maintain a predetermined turbidity. Here the dilution rate remains constant and there is no limiting nutrient in the culture. The turbidostat operates best at high rates of dilution (Lansing M. Prescott et al. 1990, 1993, p. 120). Advantages of using continuous cultures: They allow good utilization of the bioreactor and ensure low labor costs (Nielsen Villadsen 1994, p. 344). They are efficient and ensure high and constant productivity due the autocatalytic nature of microbial reaction taking place (Nielsen Villadsen 1994, p. 344). They allow detailed analysis of microbial physiology at different growth rates as all cells of the population achieve a steady state and hence has significant industrial and research applications (Slonczewski Foster 2009, p. 139). The situation in a chemostat resembles the growth of bacteria in nature where the growth rates are very low (Slonczewski Foster 2009, p. 140). According to Xuezhen Kang (2000) their use eliminates the lag the organism experiences before going into high productivity. Disadvantages of using Continuous Cultures: Sometimes they fail to produce results due to infection and mutations of microorganisms that result in production of non producing strains (Nielsen Villadsen 1994, p. 344). Use of these cultures requires downstream equipments to be designed for low volumetric rates and continuous operation (Nielsen Villadsen 1994, p. 344). In conclusion, we see that both culture mediums have their advantages and disadvantages and while using either one, these should be kept in mind.

Kabuki : A Japanese Form Essay -- essays research papers fc

Japan’s dances and dramas as they are seen today contain 1300 years of continuous uninterrupted history. This prodigious feat of conservation, theatrically speaking, makes Japan an extraordinary and unique country. In all of Asia, where tradition generally is sanctified and change eschewed, Japan stands as the only country whose theatre is its entirety has never suffered an eclipse nor undergone any drastic revivification or renovation. The most traditional form of Japanese theatre is kabuki. Its origin goes back to the latter part of the 16th century and, with extensive and continuous evolution, it has now been perfected into a state of classical refinement. Though not as flourishing as it once was, the kabuki theatre retains wide popularity among the people, and is in fact drawing quite large audiences even now. During the period generally referred to as the Edo Era, during which much of the development of kabuki took place, distinctions between the warrior class and the commoners was more rigidly observed than at any other time in Japan's history. Mainly the merchants cultivated the art of kabuki in those days. They had become increasingly powerful economically, but had to remain socially inferior as they belonged to the commoner class. To them kabuki was most significant as the artistic means by which to express their emotions under the prevailing conditions. Thus, the fundamental themes of kabuki plays are conflicts between humanity and the feudalistic system. It is largely due to this humanistic quality of the art that it gained such an enduring popularity among the general public of those days and remains this way today. A unique feature of the kabuki art, and possibly the most significant detail and in keeping with the kabuki spirit of unusualness, is the fact that it has no actresses whatsoever (Bowers 325). Male impersonators known as onnagata play all female parts. The players of the kabuki drama in its primitive stage were principally women, and with the increasing popularity of kabuki, many of the actresses began to attract undue attention from male admirers. The authorities felt that this would lead to a serious demoralization of the public and in 1629 the theatrical appearance of women was officially banned. However, since the public already accepted kabuki, men immediately took over and have continued performing to the present. The ban on... ...e curtain is open and serve also as prompters. They are not characters in the play and the audience is supposed to disregard them. â€Å"A review of theatrical history of the world shows that an ancient dramatic art, once its form has been stabilized in a near perfect state, has been capable of surviving the test of time even when its literary elements were no longer contemporary.† (Hsu, 123) The truth of this statement is born out by the present state of kabuki. It does not depict contemporary life in Japan, a country whose whole civilization has undergone a great degree of Westernization, yet it enjoys wide popularity. A principal reason for this lies in the fact that it is now a crystallized form. Kabuki has thus retained, and seems destined to retain, a place in the nation's pride and affection. Works Cited 1.  Ã‚  Ã‚  Ã‚  Ã‚  Bowers, Faubion. Theatre in the East. New York. Grove Press, Inc., 1993 2.  Ã‚  Ã‚  Ã‚  Ã‚  Hsu, Tao-Ching. The Japanese Conception of the Theatre. Seattle. University of Washington Press, 1985. 3.  Ã‚  Ã‚  Ã‚  Ã‚  Mackerras, Colin. The Japanese Theatre in Modern Times. Amherst. University of Massachusetts Press, 1975.

Ethical Issues in Businesses Today Essay

Ethical issues in businesses today There are a million ethical issues in today’s businesses and unfortunately there is no perfect decision measurement for all these ethical issues in business. The ethical issues in international businesses are much more complicated and much more delicate, along with being tenfold in numbers. According to Wiley (1995), â€Å"ethics is concerned with moral obligation, responsibility, and social Justice. † She goes on to say that â€Å"ethics reflects the character of the individual and more con temporarily per haps, the character of the business firm, which is a collection of individuals. Mauro et all, 1999) It is evident that ethics play such a crucial role in businesses if we consider the instances like the â€Å"Enron company’s ethical break down†. Not only in â€Å"Enron†, but Dilemmas involving discrimination, harassment, fraud, contractual breaches, favouritism and consistent policies regarding pay, rewards and discipline are common occurrences in many organizations. (Hartel, C. E. J, Fujimoto, Y, 2010) â€Å"Industry Wide Ethical Issues in Business Following is a list of industry wide ethical issues in businesses. The problem with these ethical issues in business is that they are not only really routine and frequent ut they are also more wide-spread Bribing powerful officials in order to get bids and tenders accepted and bribing competitor employees to get informational leaks is a serious ethical issue in business. In fact, it is a crime that is legally punishable in most countries today. Labor related issues like gender discrimination at workplace, employee harassment, minority community participation, working conditions and child labor are also some general ethical issues in busines

The Effects Of Sleep Deprivation On Memory - 1055 Words

Sleep is essential for optimal human function. In fact, a lack of sleep can actually affect important cognitive functions, like memory. A 2007 study added to the already substantial evidence that even acute total sleep deprivation impairs attentiveness, working memory, and reaction time in various tasks (Alhola, Polo-Kantola). One such way to further this investigation of the effects of sleep deprivation on memory is through the Memory Interference Test, or MIT. MIT is a program designed by Gaston Pfluegl, Ph.D., and Enrique Lopez, Psy. D., at UCLA to test the memory of students. Along with a memory test, the MIT also anonymously collected the physical states, mental states, and demographics of each student test subject, providing a substantial database through which students can test hypotheses, such as the connection between sleep deprivation and memory. Since the MIT requires short-term memory recall, the hours of sleep a student had before taking the test could have a noticeable effect on his or her performance. An unprecedented study this year found that sleep deprivation may actually even induce false memories, which would certainly impact a student taking the MIT because the test requires the subject to recognize images that have been previously presented to them (Frenda, et al). The hypothesis is that students who slept 8 hours before the test will perform better on the MIT than students who only slept 4 hours. The null hypothesis is that students who had adequateShow MoreRelatedThe Effects Of Sleep Deprivation On Memory1605 Words   |  7 Pagesstudy investigated the effects of sleep deprivation on memory. A sample of 17 Long-Evans rats was deprived of water except for a 15-minute exposure. Day one just water was administered, day two grape juice was administered followed by a LiCl injection and day three both water and grape juice were administered. Half of the rats were sleep deprived on day two and taste aversion was calculated on day three. The gr oups gave unexpected results but the results were significant. Sleep has been a widely controversialRead MoreThe Effects Of Sleep Deprivation On Prospective Memory Essay1353 Words   |  6 PagesThe Effects of Sleep Deprivation on Prospective Memory Sleep is one of the key essentials for cognitive performance, yet it is accounted that most people do not receive a sufficient amount. The Center for Disease Control and Prevention reported in 2016 that on average, 50-70 million Americans do not receive the proper amount of sleep per night. This concept is more commonly referred to as sleep deprivation. By definition, sleep deprivation is simply not getting enough or the lack of sleep. As theRead MoreSleep Deprivation Is A Wide Spread Phenomenon1277 Words   |  6 PagesSleep is one of our most basic physiological needs and getting enough of it is paramount to keeping our bodies and minds functioning at optimal performance. The amount of sleep needed varies and decreases by age. From 12-18 hours needed by a newborn to 7-9 hours needed by a health adult. The basal sleep need varies by individual with some people requiring more or less sleep than others (Czeisler 2014). When an individual does not get enough sleep they enter a state o f sleep deprivation. Sleep deprivationRead MoreSleep Deprivation Persuasive Speech1577 Words   |  7 PagesChronic Sleep Deprivation Introduction: A. Attention Getting Opening: Over the past ten to twenty years, academic demands placed upon college students have increased significantly, this has lead to an increase in workload and amount of time needed to study for a specific course. Today, college students represent the most sleep-deprived division of the population in the U.S. (Sleep and Memory). According to Gayla Martindale, 63% percent of the students who attend college do not get enough sleep, whichRead MoreEssay On Sleep Deprivation801 Words   |  4 Pagesthe world sleep deprivation could be detrimental to people lives and health. Without sleep Im a angry person I get real snappy and grumpy. I would like to know more about the effects of the lack of sleep that effects people’s lives. I know that without sleep you can’t function properly. Why do people choose to push themselves to the limit when they are tired? Who do sleep issues mainly effect? These are some of the questions that I have pertaining to sle ep deprivation. Sleep deprivation is a globalRead MoreSleep Deprivation Essay1183 Words   |  5 PagesSleep is a necessity that people require to live a healthy lifestyle, and to partake in daily activities. Sleep is something that improves concentration, physical health, and provides energy. Steve Jobs once said, â€Å"For you to sleep well at night, the aesthetic, the quality, has to be carried all the way through.† Steve Jobs is proclaiming that to receive the full benefits of sleep, people must sleep the recommended hours. College students continue to undergo a lack of sleep as they persist throughRead MorePsychology947 Words   |  4 PagesLack of sleep ages body s systems. The basic claim of the article is that sleep deprivation has various harmful effects on the body. The reported effects include decreased ability to metabolize glucose (similar to what occurs in diabetes) and increased levels of cortisol (a stress hormone involved in memory and regulation of blood sugar levels). The article also briefly alludes (in the quote at the bottom of page 1) to unspecified changes in brain and immune functioning with sleep deprivationRead MoreThe Effects Of Sleep Deprivation On Stress1352 Words   |  6 PagesSleep is very important for proper human functioning. Sleep deprivation occurs the body does not get an adequate amount of sleep regularly. The lack of sleep can affect many aspects of life. This topic affects many Americans especially college students. American culture values being very busy and cramming in many activities to daily schedules in which often requires sacrificing sleep. Different age groups reactions to sleep deprivation was investigated. Physical effects of lack of sleep were examinedRead MoreCause And Effect Of Sleep Deprivation984 Words   |  4 Pagesand Effect Lack of sleep has been known to make a person grumpy and foggy, but those are not the only things resulted for sleep deprivation. The effects of not getting more than seven or more hours of sleep can also impact a person s memory, sex life, looks, health, and even weight. Staying up all night may seem like a good idea, however, a person might want to realize the true consequences of staying up late and reconsider depriving themselves of their sleep. Accidents are a huge effect of lackRead MoreThesis Statement : Sleep Deprivation1414 Words   |  6 PagesEng 112.0004 Mrs. B. Peterson October 13, 2017 Sleep deprivation Thesis Statement: Sleep deprivation is harmful to college students because it hinders student learning and jeopardizes their safety while driving. I. Learning a. Memory b. Lack of attention II. Safety a. Fatigue b. Decision making Sleep is one of the unavoidable daily-living activities and it is one of the most important factors contributing to a person’s health. A quality sleep is essential for the physical, cognitive and