This document describes several methods for enumerating or counting bacteria in a sample, including viable plate count, direct microscopic count, and turbidity count. The viable plate count method involves making serial dilutions of a sample and counting the number of colonies that grow on an agar plate, then multiplying by the dilution factor to determine the concentration in the original sample. The direct microscopic count uses a counting chamber to directly view and count bacteria under a microscope. The turbidity count uses spectrophotometry to measure the turbidity or cloudiness of diluted samples, which correlates to the number of bacteria present based on a generated standard curve. Procedures for each method are provided.
Enumeration is counting of microorganisms present in a sample.
This is done to know the intense of presence of the spoilers in the spoiled food.
To detect which type of organism is responsible for the spoilage.
Mostly this is done two important methods.
Viable count
Total count
VIABLE COUNT:
A viable cell count allows one to identify the number of actively growing or dividing cells in a sample.
The plate count method or spread plate method relies on bacteria growing a colony on a nutrient medium.
Number of colonies can be counted.
Plate count agar is used for general count
MacConkey agar is used for Gram negative organisms.
TOTAL COUNT:
The initial analysis is done by mixing serial dilution of sample in liquid nutrient agar which is then poured into bottles.
The bottles are then sealed and laid on their sides to produce a slopping agar surface.
The colonies are then counted by eye.The total number of colonies are said as Total Viable Count. The initial analysis is done by mixing serial dilution of sample in liquid nutrient agar which is then poured into bottles.
The bottles are then sealed and laid on their sides to produce a slopping agar surface.
The colonies are then counted by eye.The total number of colonies are said as Total Viable Count.
Pour plate method:
The same procedure is done for this till serial dilution.
The serially diluted sample is then mixed with the molten nutrient agar.
Then poured onto the sterile petridish.
Incubated under appropriate temperature amd the colonies where counted.
ConclusionThe enumeration of these spoiled food samples are important to encounter the type of microbe is causing the spoilage.
And hence this is used to prevent the same type of spoilage.
This can be avoided by making the environmental changes which inhibits the organism which is responsible for the spoilage.
Enumeration is counting of microorganisms present in a sample.
This is done to know the intense of presence of the spoilers in the spoiled food.
To detect which type of organism is responsible for the spoilage.
Mostly this is done two important methods.
Viable count
Total count
VIABLE COUNT:
A viable cell count allows one to identify the number of actively growing or dividing cells in a sample.
The plate count method or spread plate method relies on bacteria growing a colony on a nutrient medium.
Number of colonies can be counted.
Plate count agar is used for general count
MacConkey agar is used for Gram negative organisms.
TOTAL COUNT:
The initial analysis is done by mixing serial dilution of sample in liquid nutrient agar which is then poured into bottles.
The bottles are then sealed and laid on their sides to produce a slopping agar surface.
The colonies are then counted by eye.The total number of colonies are said as Total Viable Count. The initial analysis is done by mixing serial dilution of sample in liquid nutrient agar which is then poured into bottles.
The bottles are then sealed and laid on their sides to produce a slopping agar surface.
The colonies are then counted by eye.The total number of colonies are said as Total Viable Count.
Pour plate method:
The same procedure is done for this till serial dilution.
The serially diluted sample is then mixed with the molten nutrient agar.
Then poured onto the sterile petridish.
Incubated under appropriate temperature amd the colonies where counted.
ConclusionThe enumeration of these spoiled food samples are important to encounter the type of microbe is causing the spoilage.
And hence this is used to prevent the same type of spoilage.
This can be avoided by making the environmental changes which inhibits the organism which is responsible for the spoilage.
Methods to detect potability of water samplevimala rodhe
Water is precious and it is the base for living, Several disease causing pathogens are transmitted through water. There are various methods to detect the presence of pathogens in drinking water samples.Some of the methods to detect microbiological quality of water are discussed.
Direct methods of measurement of microbial growth includes various methods of enumeration of both viable and non viable cell also includes growth curve. Helpful for UG and PG programs of microbiology
Preservation of industrially important microorganisms, methods of preservation, periodic transfer, storage in saline suspension, storage in sterile soil, cryopreservation
Methods to detect potability of water samplevimala rodhe
Water is precious and it is the base for living, Several disease causing pathogens are transmitted through water. There are various methods to detect the presence of pathogens in drinking water samples.Some of the methods to detect microbiological quality of water are discussed.
Direct methods of measurement of microbial growth includes various methods of enumeration of both viable and non viable cell also includes growth curve. Helpful for UG and PG programs of microbiology
Preservation of industrially important microorganisms, methods of preservation, periodic transfer, storage in saline suspension, storage in sterile soil, cryopreservation
This presentation gives an overview of : Validation of microbiological methods , Considering some of the limitations and
Key criteria that may be applicable for assessment.
Random micro-confinement of bacteria into picolitre emulsion droplets for rap...Pierre R. Marcoux
May 27th 2010
BIOSENSORS 2010: 20th Anniversary World Congress on Biosensors
Pierre R. Marcoux (1,2), Mathieu Dupoy (1,2), Raphael Mathey (1,3), Armelle Novelli Rousseau (1,3), Pierre Joly (1,2), Florence Rivera (1,2), Sophie Le Vot (1,2), Jean-Pierre Moy (1,2), Frédéric Mallard (1,3)
1 bioMérieux – CEA joint team, 17 rue des Martyrs, 38054 Grenoble cedex9, France.
2 Commissariat à l'Energie Atomique (CEA), LETI, MINATEC, Grenoble, France.
3 bioMérieux, Grenoble, France
Today, rapid detection and identification of bacteria in microbiological diagnosis is a major issue. Methods relying on the observation of few or single bacteria will allow much faster delivery of clinical information. We report here a method for rapid detection of single bacteria and real-time monitoring of one of their metabolic activities.
We have used reverse emulsions (water in perfluorinated oil) as a way of encapsulating Escherichia coli into microreactors using MMFD (dire par quelle technologie). Every aqueous homodisperse droplet (200 pL) is either empty or includes a single bacterium, provided that the concentration of bacteria in aqueous phase is low enough. Moreover, this phase contains a fluorogenic substrate (MUG), so that we can monitor the glucuronidase activity through fluorescence microscopy. Such a confinement provides us with two major advantages: we can monitor the enzymatic activities of single bacteria and the concentration of fluorescent bacterial metabolites is strongly increased. We have also discovered a perfluorinated formulation that is non toxic for bacteria.
Working on a 2.105 cfu/mL sample and using phenotypic characteristic of the bacteria (glucuronidase activity) , we demonstrated it is possible to detect bacteria in less than 2 hours. We also showed that metabolic detection enables rapid and reliable enumeration in less than 10 hours. Our innovative enumeration technique has been validated by reference methods (growth on agar dish plates CPS3). Furthermore, thanks to confinement of single bacteria, we studied the heterogeneity of a clonal population of bacteria: over ~200 single bacteria on a 24h-period, we monitored glucuronidase enzymatic activity and growth for every confined cell.
Microbiological analysis of food products is the use of biological, biochemical, molecular or chemical methods for the detection, identification or enumeration of microorganisms in a material. Here some of the common methods have been described.
GROWTH OF BACTERIA CANNOT BE MEASURED DIRECTLY BY SEEING THEM AS THEY ARE MICROSCOPIC STRUCTURES THEREFORE WE HAVE TO USE SEVERAL METHODS WHICH ARE DESCRIBED IN THIS PRESENTATION
Evaluation of Bactericidal and BacteriostaticRajsingh467604
What are disinfectants?
As per the definition given by WHO ( World health organization ) : a disinfectant is a chemical agent, which destroys or inhibits growth of pathogenic microorganisms in the non-sporing or vegetative state.
Why Evaluation?
Evaluation of disinfectants is used to check the ability or efficacy of any disinfectant against specific microorganisms to establish its effectiveness.
Evaluation tests of bactericide.
1. RIDEAL WALKER TEST
This test is also known as the phenol coefficient test,in which any chemical is compared with phenol for its antimicrobial activity.
The result is shown in the form of phenol coefficient.
▪ If a phenol coefficient of a given test disinfectant is less than 1, it means that disinfectant is less effective than phenol.
▪ If a phenol coefficient of a given test disinfectant is more than 1, it means that disinfectant is more effective than phenol.
Procedure
1.1 Different dilutions of the test disinfectant and phenol are prepared and 5 ml of each dilution is inoculated with 0.5ml of the 24 hour growth culture of the organisms.
1.2 All tubes(Disinfectant + organisms & phenol + organisms) are placed in a water bath ( at 17.5° C)
1.3 Subcultures of each reaction mixture are taken and transferred to 5ml sterile broth at an interval of 2.5 minutes from zero to 10 mintues.
1.4 Broth tubes are incubated at 37° C for 2 to 3 days & examined for the presence or absence of the growth.
1.5 Then the Rideal Walker coefficient is calculated :
2. CHICK MARTIN TEST.
CHICK MARTIN test is performed in the much similar way as the RIDEAL Walker test but with a little variation.
Principle : This test is carried out in the presence of organic matter like 3% human feces or dried yeast.
Procedure
2.1 Serial dilutions of test solution and phenol is prepared in distilled water.
2.2 To this 3% yeast suspension is also added.
2.3 To this solution the S. typhi is added
2.4 After contact time of 30 mins the above mixture is transferred to the freshly prepared 10 ml of broth.
2.5 The test tubes are incubated at 37°C for 48 hours.
2.6 Presence or absence of the growth is calculated.
Evaluation tests of Bacteriostatic.
1. Tube dilution & Agar plate Method
1.1 The chemical agent is incorporated into nutrient broth or agar medium and inoculated with test micro-organisms.
1.2 These tubes are incubated at 30° TO 35°C for 2 to 3 days and then the results in the form of turbidity or colonies are observed.
1.3 The results are recorded and the activity of the given disinfectant is compared.
2. Cup plate method
2.1 Agar is melted and cooled at 45° Celsius.
2.2 Then inoculated with test micro-organisms and poured into a sterile petri plate.
2.3 In the cup plate method, when the inoculated agar has solidified, holes around 8mm in diameter are cut in the medium with a steel cork borer.
2.4 Now the antimicrobial agents are directly placed in the holes.
Bacteria are microscopic, single-celled organisms that thrive in diverse environments. These organisms can live in soil, the ocean and inside the human gut. Humans' relationship with bacteria is complex. Sometimes bacteria lend us a helping hand, such as by curdling milk into yogurt or helping with our digestion
Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
Welcome to TechSoup New Member Orientation and Q&A (May 2024).pdfTechSoup
In this webinar you will learn how your organization can access TechSoup's wide variety of product discount and donation programs. From hardware to software, we'll give you a tour of the tools available to help your nonprofit with productivity, collaboration, financial management, donor tracking, security, and more.
Embracing GenAI - A Strategic ImperativePeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
Francesca Gottschalk - How can education support child empowerment.pptxEduSkills OECD
Francesca Gottschalk from the OECD’s Centre for Educational Research and Innovation presents at the Ask an Expert Webinar: How can education support child empowerment?
Introduction to AI for Nonprofits with Tapp NetworkTechSoup
Dive into the world of AI! Experts Jon Hill and Tareq Monaur will guide you through AI's role in enhancing nonprofit websites and basic marketing strategies, making it easy to understand and apply.
Biological screening of herbal drugs: Introduction and Need for
Phyto-Pharmacological Screening, New Strategies for evaluating
Natural Products, In vitro evaluation techniques for Antioxidants, Antimicrobial and Anticancer drugs. In vivo evaluation techniques
for Anti-inflammatory, Antiulcer, Anticancer, Wound healing, Antidiabetic, Hepatoprotective, Cardio protective, Diuretics and
Antifertility, Toxicity studies as per OECD guidelines
2. INTRODUCTION
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.
Enumeration of microorganisms is especially
important in dairy microbiology, food microbiology,
and water microbiology. Knowing the bacterial count
in drinking water, fresh milk, buttermilk, yogurt, can be
useful in many aspects of industrial microbiology.
Bacteria are so small and numerous, counting them
directly can be very difficult. Some of the methods
used involve diluting the sample to a point at which
the number of bacteria has been reduced to very
small numbers. This enables an estimate to be
established for quantifying the bacteria. Direct counts
of bacteria require a dye to be introduced to the
populations of bacteria to allow the observer to view
the bacteria.
3. VIABLE (STANDARD) PLATE COUNT
• Viable Plate Count (also called a Standard Plate Count) is one of the most common
methods, for enumeration of bacteria. Serial dilutions of bacteria are plated onto
an agar plate. Dilution procedure influences overall counting process. The
suspension is spread over the surface of growth medium. The plates are incubated
so that colonies are formed. Multiplication of a bacterium on solid media results in
the formation of a macroscopic colony visible to naked eye. It is assumed that each
colony arises from an individual viable cell. Total number of colonies is counted
and this number multiplied by the dilution factor to find out concentration of cells
in the original sample. Counting plates should have 30-300 colonies at least. 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.
• A major limitation in this method is selectivity. The nature of the growth medium
and the incubation conditions determine which bacteria can grow and thus be
counted. Viable counting measures only those cells that are capable of growth on
the given medium under the set of conditions used for incubation. Sometimes
cells are viable but non-culturable.
4. VIABLE (STANDARD) PLATE
COUNT
• The number of bacteria in a given sample is usually too great to be counted directly. However, if the sample
is serially diluted and then plated out on an agar surface in such a manner that single isolated bacteria form
visible isolated colonies, the number of colonies can be used as a measure of the number of viable (living)
cells in that known dilution. The viable plate count method is an indirect measurement of cell density and
reveals information related only to live bacteria.
• Normally, the bacterial sample is diluted by factors of 10 and plated on agar. After incubation, the number
of colonies on a dilution plate showing between 30 and 300 colonies is determined. A plate having 30-300
colonies is chosen because this range is considered statistically significant. If there are less than 30 colonies
on the plate, small errors in dilution technique or the presence of a few contaminants will have a drastic
effect on the final count. Likewise, if there are more than 300 colonies on the plate, there will be poor
isolation and colonies will have grown together.
5. VIABLE (STANDARD) PLATE COUNT
• Generally, one wants to determine the number of
(colony forming units) CFUs per milliliter (ml) of
sample. To find this, the number of colonies (on a
plate having 30-300 colonies) is multiplied by the
number of times the original ml of bacteria was
diluted (the dilution factor of the plate counted).
For example, if a plate containing a 1/1,000,000
dilution of the original ml of sample shows 150
colonies, then 150 represents 1/1,000,000 the
number of CFUs present in the original ml.
Therefore the number of CFUs per ml in the
original sample is found by multiplying 150 x
1,000,000 as shown in the formula below:
CFUs per ml of sample = The number of colonies
counted X The dilution factor of the plate counted
At the end of the incubation period, select all of the
agar plates containing between 30 and 300 colonies.
Plates with more than 300 colonies cannot be
counted and are designated "too numerous to
count" (TNTC). Plates with fewer than 30 colonies are
designated "too few to count" (TFTC).
6. PROCEDURE
VIABLE PLATE COUNT
• We will be testing four samples of water for the Viable Count. The samples
include:
• 1) water from a drinking fountain
2) boiled water from a drinking fountain
3) water from the local river
4) boiled water from the local river
• You will need DATA TABLE 1 to input your data and calculate the number of CFU
per ml.
7. PROCEDURE
VIABLE PLATE COUNT
1) Take 6 dilution tubes, each containing 9 ml of sterile saline.
2) Dilute 1 ml of a sample by withdrawing 1 ml of the sample and
dispensing this 1 ml into the first dilution tube.
3) Using the same procedure, withdraw 1 ml from the first dilution tube
and dispense into the second dilution tube. Subsequently withdraw 1 ml
from the second dilution tube and dispense into the third dilution tube.
Continue doing this from tube to tube until the dilution is completed.
8. PROCEDURE
VIABLE PLATE COUNT
4) Transfer 1 ml from each of only the last three dilution
tubes onto the surface of the corresponding agar plates.
5) Incubate the agar plates at 37°C for 48 hours.
6) Choose a plate that appears to have between 30 and
300 colonies.
9. PROCEDURE
VIABLE PLATE COUNT
7) Count the exact number of colonies on that plate
8) Calculate the number of CFUs per ml of original sample as
follows:
CFUs per ml of sample = The number of colonies X The dilution
factor of the plate counted
10. DIRECT MICROSCOPIC CELL COUNT
• In the direct microscopic count, a counting chamber with a ruled slide is employed. It is
constructed in such a manner that the ruled lines define a known volume. The number of
bacteria in a small known volume is directly counted microscopically and the number of
bacteria in the larger original sample is determined by extrapolation.
• The Petroff-Hausser counting chamber for example, has small etched squares 1/20 of a
millimeter (mm) by 1/20 of a mm and is 1/50 of a mm deep. The volume of one small
square therefore is 1/20,000 of a cubic mm or 1/20,000,000 of a cubic centimeter (cc).
There are 16 small squares in the large double-lined squares that are actually counted,
making the volume of a large double-lined square 1/1,250,000 cc. The normal procedure
is to count the number of bacteria in five large double-lined squares and divide by five to
get the average number of bacteria per large square. This number is then multiplied by
1,250,000 since the square holds a volume of 1/1,250,000 cc, to find the total number of
organisms per ml in the original sample.
12. DIRECT MICROSCOPIC CELL COUNT
• If the bacteria are diluted, such as by mixing the
bacteria with dye before being placed in the counting
chamber, then this dilution must also be considered in
the final calculations.
• The formula used for the direct microscopic count is:
# bacteria per cc (ml)
=
The # of bacteria per large double-lined square
X
The dilution factor of the large square (1,250,000)
X
The dilution factor (dye)
14. PROCEDURE
DIRECT MICROSCOPIC COUNT
1) Add 1 ml of the sample into a tube containing 1
ml of the dye methylene blue. This gives a 1/2
dilution of the sample.
2) Fill the chamber of a Petroff-Hausser counting
chamber with this 1/2 dilution.
3) Place the chamber on a microscope and focus on
the squares using 400X.
4) Count the number of bacteria in one of the large
double-lined squares. Count all organisms that are
on or within the lines.
15. PROCEDURE
DIRECT MICROSCOPIC COUNT
5) Calculate the number of bacteria per cc (ml) as follows:
The number of bacteria per cc (ml)
=
The number of bacteria per large square
X
The dilution factor of the large square (1,250,000)
X
The dilution factor of any dilutions made prior to placing the sample
in the counting chamber, such as mixing it with dye (2 in this case)
16. PROCEDURE
DIRECT MICROSCOPIC COUNT
The large, double-lined square holds a volume
of 1/1,250,000 of a cubic centimeter. Using a
microscope, the bacteria in the large square are
counted. Count all organisms that are on or
within the darker double lines.
17. TURBIDITY COUNT
• When you mix the bacteria growing in a liquid medium, the culture appears
turbid. This is because a bacterial culture acts as a colloidal suspension that
blocks and reflects light passing through the culture. Within limits, the light
absorbed by the bacterial suspension will be directly proportional to the
concentration of cells in the culture. By measuring the amount of light
absorbed by a bacterial suspension, one can estimate and compare the
number of bacteria present. Spectrophotometric analysis is based on turbidity
and indirectly measures all bacteria (cell biomass), dead and alive.
• The instrument used to measure turbidity is a spectrophotometer. It consists
of a light source, a filter which allows only a single wavelength of light to pass
through, the sample tube containing the bacterial suspension, and a photocell
that compares the amount of light coming through the tube with the total
light entering the tube.
18. TURBIDITY COUNT
• The ability of the culture to block the light can be
expressed as the amount of light absorbed in the
tube. The absorbance (or optical density) is directly
proportional to the cell concentration. (The greater
the absorbance, the greater the number of
bacteria.) Light entering a cloudy solution will be
absorbed. A clear solution will allow almost all of
the light through.
• The amount of absorbance measures what fraction
of the light passes through a given solution and
indicates on the absorbance display the amount of
light absorbed compared to that absorbed by a
clear solution.
19. TURBIDITY COUNT
• Inside, a light shines through a filter
(which can be adjusted by controlling
the wavelength of light), then through
the sample and onto a light-sensitive
phototube. This produces an electrical
current. The absorbance meter
measures how much light has been
blocked by the sample and thereby
prevented from striking the phototube.
A clear tube of water or other clear
solution is the BLANK and has zero
absorbance. The amount of substance in
the solution is directly proportional to
the absorbance reading. A graph of
absorbance vs. concentration will
produce a straight line. As the number
of bacteria in a broth culture increases,
the absorbance increases.
20. TURBIDITY COUNT
• A standard curve comparing
absorbance to the number of
bacteria can be made by plotting
absorbance versus the number of
bacteria per ml. Once the
standard curve is completed, any
dilution tube of that organism can
be placed in a spectrophotometer
and its absorbance read. Once
the absorbance is determined,
the standard curve can be used to
determine the corresponding
number of bacteria per ml.
21. PROCEDURE
TURBIDITY COUNT
• We will be testing only two samples of water for the
turbidity enumeration test. One of the samples has been
drawn from a drinking water faucet while the other was
taken from the local river. You will need DATA TABLE 3 and
a printable version of the STANDARD CURVE CHART to
enumerate your samples bacteria.
22.
23. PROCEDURE
TURBIDITY COUNT
1) Place the ORIGINAL tube of the sample and
four tubes of the sterile broth in a test-tube
rack. Each tube of broth contains 5 ml of sterile
broth.
2) Use four of these tubes (tubes 2 to 5) of
broth to make four serial dilutions of the
culture.
3) Transfer 5ml of the ORIGINAL sample to the
first broth tube. Transfer 5ml from that tube to
the next tube, and so on until the last of the
four tubes has 5ml added to it. These tubes will
be 1/2, 1/4, 1/8, and 1/16 dilutions.
24. PROCEDURE
TURBIDITY COUNT
4) Set the display mode on the Spectrophotometer to ABSORBANCE
by pressing the MODE control key until the appropriate red LED is lit.
5) Set the wavelength to 520 nm by using the WAVELENGTH dial.
6) Standardize the spectrophotometer by using a BLANK. The BLANK
used to standardize the machine is sterile nutrient broth: it is called
the BLANK because it has a sample concentration equal to zero (# of
bacteria = 0).
7) Place the original bacterial specimen into the spectrophotometer.
8) Next insert the 1/2 dilution and read it. Repeat this with the 1/4,
1/8, and 1/16 dilutions. Read to the nearest thousandth (0.001) on the
absorbance digital display.
25. PROCEDURE
TURBIDITY COUNT
9) Record your values in TABLE 3 for each of the
individual samples, along with the dilutions that
they came from.
10) Using the standard curve table given below,
calculate the number of bacteria per milliliter for
each dilution.
26. PROCEDURE
TURBIDITY COUNT
**Review the example of absorbance counts acquired
and the determinations of # of bacteria for the dilutions
using the STANDARD CURVE CHART given below. Be sure
to keep track of all of the zeros in your calculations of the
subsequent calculations for average bacteria per ml.
27. The End
Big thanks to
http://biologyonline.us/Microbiology/Fall%2008
%20White%20Earth/Micro%20Lab%20Manual/L
ab%206/12.htm