Q1. Discuss the four phases of the bacterial growth curve.
The first phase of bacterial growth is known as the 'lag phase.' The 'lag phase' is when the population is "temporarily unchanged" (Todar, 2012, Growth: 3). However, the phrase 'lag phase' may be something of a misnomer. "Although there is no apparent cell division occurring, the cells may be growing in volume or mass, synthesizing enzymes, proteins, RNA, etc., and increasing in metabolic activity" (Todar, 2012, Growth: 3). The environment is apparently dormant, but the conditions for growth are bubbling beneath the surface.
The second phase of the bacterial growth curve is known as the exponential or log phase and features the most dynamic growth. "The exponential phase of growth is a pattern of balanced growth wherein all the cells are dividing regularly by binary fission, and are growing by geometric progression" (Todar, 2012, Growth: 3). During this phase, the bacteria are multiplying rapidly, as much as can be accommodated by the environs in which they are located.
However, the exponential phase of rapid expansion cannot continue indefinitely. The third phase is the stationary phase, whereby "population growth is limited by one of three factors: 1. exhaustion of available nutrients; 2. accumulation of inhibitory metabolites or end products; 3. exhaustion of space, in this case called a lack of biological space" (Todar, 2012, Growth: 3). The bacteria are now in a new state of homeostasis with their
The conditions needed for the growth of micro-organisms are: Micro - organisms need food to survive. They like high protein food to survive, eg. Poultry & fish. Most micro - organisms need warmth & grow best at 20-40c. They need moisture to multiply. They need air to multiply, though some can without. A single Micro-organism becomes two every twenty minutes.
All bacteria need time to be able to multiply and it has been observed that generally bacteria divide into two every twenty minutes.
Background information: In this lab you will be looking at the growth of bacteria under different conditions to see the how populations of bacteria grow. Read about cells in the text or e-text. For everyone, in your e-text read chapter 13, sections 13.3 and 13.4 to learn more about bacteria. Then answer the questions below.
The purpose of this report is to analyse the growth of the bacteria known as Citrobacter Freundii as well as distinguishing what antibiotics effect its growth. This will be done so by answering the following question after completing its associated experiments. This question includes: what antibiotics are most effective in denaturing the bacteria? It has been predicted that chloramphenicol will be the most effective due to the fact that its medical uses are treating meningitis which is an infection caused by Citrobacter freundii. After conducting the experiments it was found that the chloramphenicol antibiotic was the most effective in denaturing the bacteria, although streptomycin was also affective. However, none of the other antibiotics were able to halt the growth of the bacteria.
this means that is the optimal temperature, but in bacterial occur in less time than in fungal
Bacteria are small, unicellular prokaryotic microbes. They have many morphologies, which include rod-shaped, spherical, spirals, helices, stars, cubes, and clubs. Classification of bacteria begins with either aerobic (requiring diatomic oxygen for growth) or anaerobic (not requiring O2 for growth). Bacteria can simply be narrowed down to gram positive (organism that stains purple or blue by Gram stain) or gram negative (organism that stains red or pink by Gram stain). Many physical and nutritional factors influence bacterial growth. Physical factors include temperature (psychrophiles, thermophiles, and mesophiles), pH (neutrophiles, acidophiles, and alkalinophiles), O2 concentration (aerobic
Since E.coli is found in mammals, studying this subject is important because the factors of E. Coli have risks such as food poisoning. Escherichia Coli is found everywhere! Knowing this, they studied the rapid growth measurements of E.Coli in the lab study. After studying the E. Coli, it was hypothesized that it had a logistic growth overtime. Meaning the growth rapidly grew continuously in size ending with a resting point.
As shown in the figure above, it is evident that V.natriegens grew faster when the Brain Heart Infusion (BHI) broth contained 250mM NaCl. The # of bacterial cells at each time point was measured following the equation given in the “How to generate a bacterial growth curve” supplemental material posted on D2L. (2) The data was then recorded in the table listed above. A growth curve graph was constructed using the data above which illustrated the differences between each of the different BHI mixtures. The graph was then used to determine the generation time of V.natriegens for each different environmental condition. In order to calculate the generation time (g) the mean growth rate (k) must be calculated. The formula to do this is posted in the supplemental material “How to generate a bacterial growth curve” on D2L. The k value calculated for each condition goes as follows:
The lag phase is when the organisms are first place into a new medium and will take time to get used the their new environment. During this phase, organisms will grow in size but cannot replicate. The next phase is the log phase. In this phase cells are dividing and growing at a very fast rate. DNA replication begins in this phase as well as their metabolic rate starts to increase rapidly. (Bacterial Growth Curve) Cells divide by binary fission. The organisms will eventually reach maximum growth and start to level off beginning the next phase, the stationary phase. In this phase, the bacterial population will start to slow down and stop dividing because the nutrients needed for them to grow are being used up. The pH and temperatures start to shift making the environment and unfavorable one and the accumulation of waste and toxic metabolites the growth starts to die off, transitioning into the last and final stage. (Bacterial Growth Curve) The death phase is when there is longer any nutrients to grow and to much waste has built up along with toxic materials, killing the cells. However, some organisms can withstand this environment and begin to produce endospores. (Bacterial Growth Curve)
During the lag phase there is no increase in cell numbers, although the bacteria are synthesizing enzymes present in their environment in preparation for the exponential phase. During the exponential or logarithmic phase, the bacterial population grows at a rate that doubles the population during the generation time. The stationary phase incurs neither an increase nor a decrease in the cell population. The population growth cannot continue at the exponential rate since the nutrient supplies have been depleted and waste products have accumulated. The final phase of the bacterial population growth curve is the death phase, during which more cells die than are replaced by new cells.
Being able to control bacterial growth is something that is important in our everyday lives. As shown in the previous labs, bacteria can grow and create colonies extremely quickly especially in the right environments. By acknowledging this, it is then important to get an understanding of how bacterial growth can be controlled by humans. To control microorganisms it means to inhibit their growth (static) and or kill them (cidal) (Kenneth Todar, 2015); therefore since focusing on bacteria the terms bactericidal and bacteriostatic are both extremely important for this lab. One broad method we will use to control bacterial growth is heat. The amount of heat needed to control bacterial growth is different for different species of bacteria (Kenneth Todar, 2015). Bacteria can also respond differently depending if moist heating method such as an autoclave with steam is used, or a dry heating method such as inoculating a loop over a fire is used (Kenneth Todar, 2015). UV works by damaging the cells DNA, without proper DNA, the cells will die and the object
A bacterial growth curve illustrates a lag phase, a log phase, a stationary phase, and a death phase. The lag phase of the growth curve depicts no growth of the population. There is no growth because the bacteria cells are not undergoing division because the bacteria is still adjusting to the environment. The log phase depicts the period of time
These ranges are classed as cardinal temperatures and consist of minimum, optimum and maximum. The optimum is the temperature at which the bacteria will grow most rapidly, whilst temperatures below the minimum and above the maximum no growth will occur. (Prescott et al. 2008..) Growth rate decreases rapidly once temperatures exceed the optimal rate placing the maximum rate very close to it, whilst the minimum temperature is much further away from the optimum. (Ingraham et al..1990) The cardinal temperatures vary between each species of bacteria which places them into subcategories relevant to these experiments as shown below:-
This experiment was performed to test the hypothesis if LB nutrient broth, +pGLO and -pGLO Ampicillin, and Arabinose was placed in the E. coli plates, then there will be a significant growth in the newly transformed bacteria and it will possess the ability to glow under UV light. The measurements were recorded from the bent glass tube in each glass test tube. The transformation protocol tested for the newly possessed traits in E.coli bacteria. Throughout the experiment there were many probable reasons for failure. If the pipettes and sterile loop were not thrown out in between each use, a cross contamination could cause a miscalculation in the experiment causing the data results to fail. The hypothesis that was tested was validated due to the positive results with each experiment stating that newly transformed organisms due in fact pass on traits.
Six experiments were carried in this report concerning the effect that different environmental factors have on microbial growth. The results were recorded into tables where (+) symbolises growth and (–) symbolises no growth.