Phases of the Bacterial Growth Curve

Bacteria are prokaryotic organisms that most commonly replicate by the asexual process of binary fission. These microbes reproduce rapidly at an exponential rate under favorable conditions. When grown in culture, a predictable pattern of growth in a bacterial population occurs. This pattern can be graphically represented as the number of living cells in a population over time and is known as a bacterial growth curve. Bacterial growth cycles in a growth curve consist of four phases: lag, exponential (log), stationary, and death. Key Takeaways: Bacterial Growth Curve The bacterial growth curve represents the number of live cells in a bacterial population over a period of time.There are four distinct phases of the growth curve: lag, exponential (log), stationary, and death.The initial phase is the lag phase where bacteria are metabolically active but not dividing.The exponential or log phase is a time of exponential growth.In the stationary phase, growth reaches a plateau as the number of dying cells equals the number of dividing cells.The death phase is characterized by an exponential decrease in the number of living cells. Bacteria require certain conditions for growth, and these conditions are not the same for all bacteria. Factors such as oxygen, pH, temperature, and light influence microbial growth. Additional factors include osmotic pressure, atmospheric pressure, and moisture availability. A bacterial populations generation time, or time it takes for a population to double, varies between species and depends on how well growth requirements are met. Phases of the Bacterial Growth Cycle The bacterial growth curve represents the number of living cells in a population over time. Michal Komorniczak/Wikimedia Commons/CC BY-SA 3.0 In nature, bacteria do not experience perfect environmental conditions for growth. As such, the species that populate an environment change over time. In a laboratory, however, optimal conditions can be met by growing bacteria in a closed culture environment. It is under these conditions that the curve pattern of bacterial growth can be observed. The bacterial growth curve represents the number of live cells in a bacterial population over a period of time. Lag Phase: This initial phase is characterized by cellular activity but not growth. A small group of cells are placed in a nutrient rich medium that allows them to synthesize proteins and other molecules necessary for replication. These cells increase in size, but no cell division occurs in the phase.Exponential (Log) Phase: After the lag phase, bacterial cells enter the exponential or log phase. This is the time when the cells are dividing by binary fission and doubling in numbers after each generation time. Metabolic activity is high as DNA, RNA, cell wall components, and other substances necessary for growth are generated for division. It is in this growth phase that antibiotics and disinfectants are most effective as these substances typically target bacteria cell walls or the protein synthesis processes of DNA transcription and RNA translation.Stationary Phase: Eventually, the population growth experienced in the log phase begins to decline as the available nutrients become depl eted and waste products start to accumulate. Bacterial cell growth reaches a plateau, or stationary phase, where the number of dividing cells equal the number of dying cells. This results in no overall population growth. Under the less favorable conditions, competition for nutrients increases and the cells become less metabolically active. Spore forming bacteria produce endospores in this phase and pathogenic bacteria begin to generate substances (virulence factors) that help them survive harsh conditions and consequently cause disease.Death Phase: As nutrients become less available and waste products increase, the number of dying cells continues to rise. In the death phase, the number of living cells decreases exponentially and population growth experiences a sharp decline. As dying cells lyse or break open, they spill their contents into the environment making these nutrients available to other bacteria. This helps spore producing bacteria to survive long enough for spore producti on. Spores are able to survive the harsh conditions of the death phase and become growing bacteria when placed in an environment that supports life. Bacterial Growth and Oxygen Campylobacter jejuni, shown here, is a microaerophilic organism requiring reduced levels of oxygen. C. jejuni is the bacterium which causes gastroenteritis. Henrik Sorensen/The Image Bank/Getty Images Bacteria, like all living organisms, require an environment that is suitable for growth. This environment must meet several different factors that support bacterial growth. Such factors include oxygen, pH, temperature, and light requirements. Each of these factors may be different for different bacteria and limit the types of microbes that populate a particular environment. Bacteria can be categorized based on their oxygen requirement or tolerance levels. Bacteria that can not survive without oxygen are known as obligate aerobes. These microbes are dependent upon oxygen, as they convert oxygen to energy during cellular respiration. Unlike bacteria that require oxygen, other bacteria can not live in its presence. These microbes are called obligate anaerobes and their metabolic processes for energy production are halted in the presence of oxygen. Other bacteria are facultative anaerobes and can grow with or without oxygen. In the absence of oxygen, they utilize either fermentation or anaerobic respiration for energy production. Aerotolerant anerobes utilize anaerobic respiration but are not harmed in the presence of oxygen. Microaerophilic bacteria require oxygen but only grow where oxygen concentration levels are low. Campylobacter jejuni is an example of a microaerophilic bacterium that lives in the digestive tract of animals and is a major cause of foodborne illness in humans. Bacterial Growth and pH Helicobacter pylori are microaerophilic bacteria found in the stomach. They are neutrophiles that secrete an enzyme that neutralizes stomach acid. Science Picture Co/Getty Images Another important factor for bacterial growth is pH. Acidic environments have pH values that are less that 7, neutral environments have values at or near 7, and basic environments have pH values greater than 7. Bacteria that are acidophiles thrive in areas where the pH is less than 5, with an optimal growth value close to a pH of 3. These microbes can be found in locations such as hot springs and in the human body in acidic areas such as the vagina. The majority of bacteria are neutrophiles and grow best in sites with pH values close to 7. Helicobacter pylori is an example of a neutrophile that lives in the acidic environment of the stomach. This bacterium survives by secreting an enzyme that neutralizes stomach acid in the surrounding area. Alkaliphiles grow optimally at pH ranges between 8 and 10. These microbes thrive in basic environments such as alkaline soils and lakes. Bacterial Growth and Temperature New Zealands Champagne Pool is a hot spring that contains a community of thermophilic and acidophilic microorganisms whose distribution relates to the temperature and chemical environment. Simon Hardenne/Biosphoto/Getty Images Temperature is another important factor for bacterial growth. Bacteria that grow best in cooler environments are called psycrophiles. These microbes prefer temperatures ranging between 4 °C and 25 °C (39 °F and 77 °F). Extreme psycrophiles thrive in temperatures below 0 °C/32 °F and can be found in places such as arctic lakes and deep ocean waters. Bacteria that thrive in moderate temperatures (20-45 °C/68-113 °F) are called mesophiles. These include bacteria that are part of the human microbiome which experience optimum growth at or near body temperature (37 °C/98.6 °F). Thermophiles grow best in hot temperatures (50-80 °C/122-176 °F) and can be found in hot springs and geothermal soils. Bacteria that favor extremely hot temperatures (80 °C-110 °C/122-230 °F) are called hyperthermophiles. Bacterial Growth and Light Cyanobacteria (blue) are photosynthesizing bacteria that are found in most habitats where water is present. Several spores (pink) are also seen. Steve Gschmeissner/Science Photo Library/Getty Images Some bacteria require light for growth. These microbes have light-capturing pigments that are able to gather light energy at certain wavelengths and convert it to chemical energy. Cyanobacteria are examples of photoautotrophs that require light for photosynthesis. These microbes contain the pigment chlorophyll for light absorption and oxygen production through photosynthesis. Cyanobacteria live in both land and aquatic environments and can also exist as phytoplankton living in symbiotic relationships with fungi (lichen), protists, and plants.   Other bacteria, such as purple and green bacteria, do not produce oxygen and utilize sulfide or sulfur for photosynthesis. These bacteria contain bacteriochlorophyll, a pigment capable of absorbing shorter wavelengths of light than chlorophyll. Purple and green bacteria inhabit deep aquatic zones. Sources Jurtshuk, Peter. Bacterial Metabolism. National Center for Biotechnology Information, U.S. National Library of Medicine, 1 Jan. 1996, www.ncbi.nlm.nih.gov/books/NBK7919/. Parker, Nina, et al. Microbiology. OpenStax, Rice University, 2017.Preiss, et al. Alkaliphilic Bacteria with Impact on Industrial Applications, Concepts of Early Life Forms, and Bioenergetics of ATP Synthesis. Frontiers in Bioengineering and Biotechnology, Frontiers, 10 May 2015, www.frontiersin.org/articles/10.3389/fbioe.2015.00075/full.

The Preface By William Lloyd Garrison - 3512 Words

The preface by William Lloyd Garrison describes the encounter between Frederick Douglass and Garrison, at an anti-slavery convention. It tells about how this encounter led to a long partnership between the two as well as Douglass’ involvement in the Anti-Slavery Society. At the convention the people noticed his appearance as well as his intellectual side. The crowd seemed to respond well to the idea of protecting Douglass against his owners. In the convent Garrison says Douglass’ testimony made the audience question their ideas about black being inferior. Garrison then goes on to talk about how any inferior ideas about a race are the cause of slavery. He describes the events where a shipwrecked whites where held as slaves by blacks in Africa because they were seen as inferior. He then goes on to point of that many slaves have endured a much harsher life then Douglass, and he points out how murder of slaves was not being investigated. In the preface there was a letter to Douglass from a Wendell Phillips, addressing Douglass as a friend. He says that he is happy the writing of former slaves is now being published and able to be but into history. The prior history of slave owning was by slave owners themselves and they left out very important details. He then goes on to say that he was astounded at the harsh ways he was treated in an area that was considered a less harsh area. He then goes on to talk about how since he put the real names of himself and of his masters he hasShow MoreRelatedThe Preface Starts Off By William Lloyd Garrison1695 Words   |  7 PagesThe preface starts off by William Lloyd Garrison describing his encounter with Frederick Douglass at an anti-slavery convention in Nantucket. Garrison tells us that Frederick Douglass made an escape from the southern prison house of bondage and that his speech at the convention was a memorable one. Frederick Douglass’s had eloquence and a skill of persuading. Connecting people’s minds and hearts to his words of description about the reality of slavery. The audience responded with great attentionRead MoreThe Narrative Of The Life Of Frederick Douglass941 Words   |  4 Pagesanti-slavery abolitionists, William Lloyd Garrison and Wendell Phillips. In the preface of the narrative, William Lloyd Garrison credits Douglass by describing in detail Douglass’ impact on slavery and liberation. Garrison describes, â€Å"Whose minds he has enlightened on the subject of slavery, and who have been melted to tears by his pathos, or roused to virtuous indignation by his stirring eloquence against the enslavers of men!† (Douglass v). In this illustration, William Lloyd Garrison credits Douglass asRead MoreThe Abolition Movement Of The 1800s1547 Words   |  7 Pagesbecoming important, and crucial to the abolishment of slavery. The American Anti-Slavery Society played key roles in the abolition of slavery. The Anti-Slavery Society is what began the abolitionist movement. It was founded in Philadelphia by William Lloyd Garrison, Arthur and Lewis Tappan, and a few others. This ensemble issued the Declaration of the Anti-Slavery Convention; the Declaration of the Anti-Slavery Convention announced the reasons for formation of the society and establishing its goalsRead MoreThe Anti Slavery Movement By William Lloyd Garrison, Arthur And Lewis Tappan1580 Words   |  7 PagesThe Anti-Slavery Movement began to take shape in 1833. William Lloyd Garrison, Arthur and Lewis Tappan, and other members gathered in Philadelphia and formed the American Anti-Slavery Society. The group was created to provide perspective into slavery. Through the use of almanacs containing poems, drawings, essays, and other material, the Anti-Slavery Society was able to illustrate the horrors slavery. Through the distribution of these alm anacs, people were shown the types of struggles and horrorsRead MoreA Brief Look at Frederick Douglass737 Words   |  3 Pagesstatement of his success was made evident in the preface and afterward, which was written by white abolitionists. William Lloyd Garrison and Wendell Phillips were abolitionists before meeting Douglass, but upon hearing his story encountered and even deeper and greater aspect of the importance of abolition. Upon having Douglass on the abolitionist’s side, they also received a face and a story to give evidence to the injustices they were talking about. Garrison and Phillips who were noteworthy people atRead MoreFrederick Douglasss Narrative and Its Influence1209 Words   |  5 Pagesrights movement, Frederick Douglass. In 1845, many white people did not consider that a slave was able to write their own autobiography. However, William Lloyd Garrisons preface is an evidence for Douglass that he wrote the book by himself. 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This little story plays to the audienceRead MoreThe Narrative Of The Life Of Frederick Douglass Essay1765 Words   |  8 Pagesrepresentation of Christianity from Douglass’ Narrative are who Douglass would call â€Å"true Christians† are William Lloyd Garrison and Wendell Phillips. William Lloyd Garrison is the founder of the American Anti-Slavery Society. Garrison and Douglass met at an abolitionist convention in Nantucket in 1841. Garrison employs Douglass for the abolitionist cause after he hears Douglas speak at the convention. Garrison s tated, â€Å"I shall never forget his first speech at the convention- the extraordinary emotion itRead MoreNarrative Of The Life Of Frederick Douglass Rhetorical Analysis1050 Words   |  5 Pagescountless occasions throughout his autobiography, Douglass uses vivid, grotesque and gory imagery to make us feel pain for the slaves. In chapter one, he recounts the time is aunt Hester was whipped â€Å"until her red blood dripped to the floor† by Colonel Lloyd. Using pathos, Douglass also is able to establish parts of his tone. When describing the whippings and how slaves were treated like animals, any reasonable person would expect Douglass to be enraged. He likely was, but he kept a calm, cool, collectedRead MoreSelfdom in Slavedom: Gustavus Vassa1503 Words   |  7 Pagessettled life. On the other hand, Jacobs is born into slavery and raised by her grandmother. We see influences of her family throughout her life, from â€Å"looking up to [her grandmother] with a respect bordering upon awe† to relying on her brother, William, while she waits in the attic to desperately searching for just a view of her children to remind her why she must gain her freedom. Economic developments of the South that led to the reliance on slavery in general and reproduction to further the

The Effectiveness of the Young Shakespeare Award free essay sample

Research Questions To do this, the research questions – how effective is the Young Shakespeare Award in Jamaaluddin School, in terms of teaching and learning vocabulary? , what are the long term benefits of the award? and would this award help to bridge the gap between year seven and year eight when the students start their secondary schooling? – are taken as consideration. 1. 6 The significance of the study This research will help not only to learn about the ways in which they conduct the award, but also it will give the opportunity to gain a broader knowledge about teaching and learning vocabulary. Furthermore, this case study can be helpful for the education system as a whole and it can be used as an instrument for improvement of teaching and learning vocabulary in schools.Most importantly, it can also be a useful guide for the management of Jamaaluddin School to identify current situation in Shakespeare Award and can be used as a constructive guide for improving the outcome of the Award. We will write a custom essay sample on The Effectiveness of the Young Shakespeare Award or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page 2. 0 Methodology 2. 1 Setting This research is conducted in the Jamadudhdin School – one of the primary schools in male – aiming to identify the effectiveness of the Young Shakespeare Award in Jamaaluddin School, long term benefits the award and how it help to bridge the gap between year seven and eight. In order to get the information, observations and interviews were carried out inside and outside of the school campus, to study the case. 2. 2 Research Participants Participants for this research include teachers, parents and students who undertake the award now and the previous students. Programme in charge, five teachers, three parents, three students who are in Jamaaluddin now and three Shakespeare Award winners who are in year eight, nine and eleven were chosen for the project. 2. 3 Data CollectionIn this case study, small scale research was carried out in school where observations and interviews were conducted inside and outside the school. Observations were carried out for a period of one week to study the behavior, practices and routines of the award in the school. An interview was also carried with the programme in charge; five teachers, six students and three parents.