It is critical that you master both serial and simple single dilutions. In other words, if the product is having too much bacterial count which is nearly uncountable, in that case also serial dilution is useful. Be careful to not crash the objective into the hemocytometer at the time of focusing. Mar 29, 2019 calculate the final dilution ratio in a serial dilution. Lab report 1 sample serial dilution of a bacterial culture introduction genetic analysis often requires the measurement of the frequency of events that are. Incubate the 3 agar plates upside down and stacked in the petri plate holder on the shelf of the 37c incubator corresponding to your lab section until the next lab period. Serial dilution lab in this unit we will be discussing measurements of concentration that us e both very big and very small numbers. A serial dilution is the dilution of a sample, in 10fold dilutions. Booker microbiology 2310 lab report 3 serial dilutions october 15, 2017 introduction. Ce 573 lab 2microbial enumeration university of kansas. In this lab, a serial dilution will be made of a sample of bacteria, and then those dilutions will be used to. The very first is mistake propagation across columns or rows. This can be mathematically illustrated with the equation dt d1 x d2 x d3 x x dn where dt is the total dilution factor and dn is the dilution ratio. Sample lab report introduction to the spectrophotometer.
A perfect spread plate technique will results visible and isolated colonies of bacteria that are evenly distributed in the plate and are countable. As seen in lab 2, when you mix the bacteria growing in a liquid medium. Learn vocabulary, terms, and more with flashcards, games, and other study tools. As part of daily routine, the laboratory microbiologist often has to determine the number of bacteria in a given sample as well as having to compare the amount of bacterial growth under various conditions. Here is an example of a lab report that was actually submitted and received a perfect grade along with stepbystep instructions on writing an effective lab report. Therefore, it is important that each person understand how to use the pipette, how to read the pipette accurately, and how to determine what dilution was produced. Avoid repeating information, unless the information is expanded to provide additional insight. For both samples a series of dilutions were performed in a 9ml dilution buffer of 0. Serial dilutionagar plate procedure to quantitate viable. We get the result by using serial dilution, spread plate method and gram staining. Standard obligations in laboratory experiments such as preciseness in calculating and measuring numerous substances, as well as meticulousness are undoubtedly vital. Dilution and concentration theory dilution and concentration theory sounds ominous but you use dilutions and concentrations fairly frequently outside of your scientific life. Your microbiology lab instructor taught you the basics of serial dilution and how to use it to determine the number of cells in an original bacterial culture. The identification of two unknown substances by analyzing protein concentrations through the usage of the bradford assay.
A key property of solutions is the concentration of solute. Culturing and enumerating bacteria from soil samples. Estimation method for serial dilution experiments sciencedirect. They will need to understand dilution in order to be able to do these experiments in any kind of meaningful way. We will begin our discussion of solution concentration with two related and relative terms dilute and concentrated. Mar 30, 2014 serial dilution is a method intended to reduce the numbers of colonies to a range between 30 and 300. For example, when you are making orange juice from a frozen concentrate, you mix 1 can of concentrate with 3 cans of water. Dilutions in the range 101 110 to 108 1100,000,000 are generally used, although with particular types of samples the range of dilutions can be restricted.
Hemocytometer counting of cells sakshat amrita virtual lab. Serial dilution is the stepwise dilution of a substance in solution. These include quantifying the number of bacteria in a sample using plate counts and the development of standard curves for quantitative colorimetric, radiometric, and enzymatic assays. The diluted sample is then used as the base solution to make an additional dilution. Introduction microorganism is an organism that is microscopic or submicroscopic, which is too small to be seen under naked eyes. Hemocytometer counts are, however, subject to the following sources of error. Think through what is happening in each step until it makes. In this short dry lab exercise, students perform serial dilutions using seed beads. Serial dilution simulation lab the american biology teacher. If the sample is not dissolved well, the cells become crowded and will be difficult to count. A simple method is presented to estimate the microbial counts obtained with the serial dilution technique for microorganisms that can grow on bacteriological media and develop into a colony.
The following formula can easily be used to carry out a simple dilution. Molarity and serial dilutions teacher handout module overview one of the most important skills in science is to calculate dilutions. Use an appropriate dilution of the mixture with regard to the number of cells to be counted. Enumeration counting of microbes in a sample is especially. Understand how stock solutions are used in the laboratory. We will solve this problem by doing a serial dilution. For example, a tenfold serial dilution could result in the following concentrations. This exercise is intended to familiarize us with using scientific notation to express big and small number easily and the process of using serial dilutions to make concentrations of known values. How to write a conclusion or discussion section for a lab report. Lab 9 serial dilution, pour plates, and enumeration of bacteria introduction. Serial dilutions involve diluting a stock or standard solution multiple times in a row. Since the enumeration of microorganisms involves the use of extremely small dilutions and extremely large numbers of cells, scientific notation is routinely used in calculations.
Today you will learn how to use the spectronic 20 spectrophotometer, commonly referred to as the spec 20. This exercise helps students gain skill at performing dilutions without using reagents, bacterial cultures, or viral cultures, while being able to visualize the process. Once organism is diluted out by certain dilution factor, it is allowed to inoculate on suitable nutrient media in petri dished. The organization, accuracy, completeness, interest in topic, results and explanations determine report grade. Typically, a standard curve will have a sigmoidal shape in which the higher concentrations of standard dilutions will.
All fields of chemistry and biology use solutions and their dilutions in the lab and in the field, so knowing how to prefom a dilution is a very important skill. In this lab you will investigate several techniques. In this lesson an attempt has been made to relate dilution to the real world. Explain how concentrations can be changed in the lab. If the technique is done correctly, then the living viable cells will be counted as a colony forming unit cfu that will decrease following the increasing of total dilution and the original sample cell could be calculated based on the result.
A microbe is an organism that is microscopic and submicroscopic, which is too tiny to be viewed under a naked eye. However, the numbers of microbes in a given specimen are required to identify in particular aspect such as diary manufacturing, diseases research and study, and. Usually the dilution factor at each step is constant, resulting in a geometric progression of the concentration in a logarithmic fashion. Because of this, a variety of methods have been developed. Conclusion form this experiment, the bacteria that found in the porridge are bacillus cereus and escherichia coli. Lab reports can also be written for college classes, as well as other professional areas including engineering and computer sciences. Calculating serial dilutions serial dilutions are a way of dividing up a large dilution into a number of successive dilution steps with dilution factors of 100fold or less. The result will be that the highest dilutions will possess the many inaccurate results.
Practical lab reports 18 introduction to microbiology. Serial dilution is often a difficult concept for students to understand. First, the absorption spectrum obtained from methylene blue should peak at an intermediate range approximately equal to 668 nm optical absorption of methylene blue. Lab report overview each student is responsible for 50% of lab work, and for individual, original reports. One way to enumerate the number of bacteria present in a soil sample is to utilize dilution and plating methodology. How would you do a serial dilution based on a factor of 2. Discussion both of the methods utilized in this laboratory experiment provide us with useful. This methodology utilizes agar as a medium for bacterial growth, a process termed, culturable technology. Introduction the aims of the lab session was to familiarize with the principles, operation and application of a light spectrophotometer. Jan 27, 2020 explain how concentrations can be changed in the lab. We are often concerned with how much solute is dissolved in a given amount of solution.
Discussion discussions should do more than sling words around. Since a great deal of experimental lab work in biology involves solutions, the ability to work with and manipulate them is very important. Calculate the mass of sucrose needed to prepare 200 ml of 1. With each sequential serial diiution phase, exchange inaccuracies prospect to less accurate and less accurate dispensing.
In the experiment lab students will be diluting environmental toxins to see their effect on fertilization and development. Genetics lab fall 2000 sample lab report for lab 1 even those of you who just answered the questions no doubt noticed that if you strung those answers together and added the appropriate headings, youd get something very close to a real lab report. In this experiment we learned how light can be used and measured and that all atoms and molecules absorb light of certain wavelengths. Wavelength, absorbance, and concentration in methylene blue. It should be noted that some level of dilution was achieved as demonstrated with colony counts of 175 and 50 on plates 1a and 2a, respectively. This is a one millionfold dilution clearly too big to do at once.
How to write a conclusion or discussion section for a lab. Intro to the spectrophotometer a commonly used instrument in the analysis of cellular extracts is the spectrophotometer. Note that serial dilution is a special case of series of dilutions. Upon completion of this lab, the student should be able to proficiently calculate molarities for solutions. Prelab questions show work and include in your lab report 1. Doing this several times results in a range of concentrations. Typically, the dilution factor remains constant for each dilution, resulting in an exponential decrease in concentration. Serial dilution is a series of dilutions used to determine the concentration or titer of a substance 6. For the solutions to be usable in the lab for a titration, for instance, they must be accurately diluted to a known, lesser concentration. Titration of microorganisms in infectious or environmental samples is a corner stone of quantitative microbiology. A series of five dilutions is made of this first dilution by diluting it 110, rediluting 110, and then three times more, each resulting solution then being a 110 dilution of the previous one in the series. The concentration of solute molecules in both solutions is the same. Even on this basic laboratory experiment requires of those standard obligations. This report discusses an experiment to study the relationship of absorbance and concentration, the interaction of electromagnetic radiant energyere and matter which is an important aspect of the beerlamberts law.
The discussion should cover all of the objectives specified in the report in depth. For example, for water that is not turbid, the maximal dilution needed is 106 because we know that if there were 107 or more. Lab math solutions, dilutions, concentrations and molarity. Genetics lab fall 2000 sample lab report for lab 1. Below is a diagram of a serial dilution scheme that should yield countable plates from a starting culture with 10 8 cellsml. Spectrophotometry page 7 of 10 single dilutions background stock solutions are constantly diluted in biological lab settings. Two hypotheses may be made prior to performing this experiment. Pdf lab report of microbiology akbar haqi academia.
Serial dilutions are used to accurately create highly diluted solutions as well as solutions for experiments resulting in concentration. In the lab, correct dilutions of solutions are critical to performing accurate science. Lab 9 serial dilution, pour plates, and enumeration of bacteria introduction the number of bacteria in a small sample can be startling. The format of the report is that of a journal submission. Scientists perform serial dilution to create these sets of. Many procedures performed in modern biology and chemistry laboratories require sets of solutions that cover a range of concentrations. Bio101 lab 3 bacteria enumeration pre lab exercise. Serial dilutions and quantification of bacterial viable counts. This will not be a valid assumption unless the suspension is monodispersable and free of cell clumps. Sample chem217 laboratory reports formal report format. A series of five dilutions is made of this first dilution by diluting it 110, rediluting 110, and then three times more, each resulting solution then. For serial dilution method, increase dilution of sample will decrease the colony count on the agar plate.
The total dilution ratio can be determined by multiplying the dilution factor of each step leading up to the final step. Spread plate technique is a method employed to plate a liquid sample for the purpose of isolating or counting the bacteria present in that sample. A serial dilution is a series of stepwise dilutions, where the dilution factor is held constant at each step. Bio101 lab 3 bacteria enumeration north central college. It is assumed that the volume of cell suspension placed in the chamber represents a truly random sample. Hypothesis predict how the serial dilution of your drink solution will affect the colour, flavor, and other properties of the solution. A lab report should not include any conflicting information that might cause confusion and trigger questions about the credibility of the report. A 25 ml volumetric pipette was used to transfer a 25. However, the numbers of microorganisms in a given sample are required to know in certain aspect such as dairy industries, diseases investigation, and so on. Place the used dilution tubes in the disposal baskets in the hood. In this lab, enzyme kinetics are examined utilizing various experimental techniques, including measurements of absorbance and temperature, to determine the effects on reaction rate dependent on enzyme and substrate concentration, temperature, and substrate specificity, as well as calculate the concentration of enzymes and substrates, v o. Growth can be measured by serial dilution, in which successive 1. In addition, the absorptions of serial dilutions of methylene.
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