Automated system for bacterial identificationDEEKSHANT KUMAR
[DOWNLOAD IT OPEN IT WITH MICROSOFT POWERPOINT THEN YOU WILL BE ABLE TO UNDERSTAND THE TOPIC COVERED.]
1. WHOLE TEXT IS RELIABLE.
2. TEXT HAS BEEN TAKEN FROM STANDARD TEXT BOOK FOR MEDICAL MICROBIOLOGY.
3. SOME PICTURE HAS BEEN TAKEN FROM JOURNAL.
Susceptibility testing is used to determine which antimicrobials will inhibit the growth of the bacteria or fungi causing a specific infection. The results from this test will help a healthcare practitioner determine which drugs are likely to be most effective in treating a person's infection.
Automated system for bacterial identificationDEEKSHANT KUMAR
[DOWNLOAD IT OPEN IT WITH MICROSOFT POWERPOINT THEN YOU WILL BE ABLE TO UNDERSTAND THE TOPIC COVERED.]
1. WHOLE TEXT IS RELIABLE.
2. TEXT HAS BEEN TAKEN FROM STANDARD TEXT BOOK FOR MEDICAL MICROBIOLOGY.
3. SOME PICTURE HAS BEEN TAKEN FROM JOURNAL.
Susceptibility testing is used to determine which antimicrobials will inhibit the growth of the bacteria or fungi causing a specific infection. The results from this test will help a healthcare practitioner determine which drugs are likely to be most effective in treating a person's infection.
Isolation and identification of salmonella &e.coliNoman Ch
This presentation is made by concerning three books. The data used in this is mainly revolve about poultry point of view.
REFERENCE
Isolation and identification of avian pathogen(AAAP)
Isolation and identification of salmonella &e.coliNoman Ch
This presentation is made by concerning three books. The data used in this is mainly revolve about poultry point of view.
REFERENCE
Isolation and identification of avian pathogen(AAAP)
i have make this slide from different medical books... i hope this slide well be help you and will increased your knowledge.. Just pray for me and to my parents and also to my teachers ,,,. thank you......
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
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
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
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.
Food hygiene is more than cleanliness ......
Protecting food from risk of contamination, including harmful bacteria, poison and other foreign bodies.
Preventing any bacteria present multiplying to an extent which would result in the illness of consumers or the early spoilage of the food.
Destroying any harmful bacteria in the food by thorough cooking
or processing.
Discarding unfit or contaminated food.
T-Cell Activation
• Concept of immune response
• T cell-mediated immune response
• B cell-mediated immune response
I. Concept of immune response
• A collective and coordinated response to the introduction of foreign substances in an individual mediated by the cells and molecules in the immune system.
II. T cell-mediated immune response
• Cell-mediated immunity is the arm of the adaptive immune response whose role is to combat infection of intracellular pathogens, such as intracellular bacteria (mycobacteria, listeria monocytogens), viruses, protozoa, etc.
Major Histocompatibility Complex
MHC:
• Major Histocompatibility Complex
– Cluster of genes found in all mammals
– Its products play role in discriminating self/non-self
– Participant in both humoral and cell-mediated immunity
• MHC Act As Antigen Presenting Structures
• In Human MHC Is Found On Chromosome 6
– Referred to as HLA complex
• In Mice MHC Is Found On Chromosome 17
– Referred to as H-2 complex
• Genes Of MHC Organized In 3 Classes
– Class I MHC genes
• Glycoproteins expressed on all nucleated cells
• Major function to present processed Ags to TC
– Class II MHC genes
• Glycoproteins expressed on macrophages, B-cells, DCs
• Major function to present processed Ags to TH
– Class III MHC genes
• Products that include secreted proteins that have immune functions. Ex. Complement system, inflammatory molecules
Antigen Processing and Presentation MID
Antigens and “foreignness”
• Antigens (or, more properly, immunogens) have a series of features which confer immunogenicity.
• One of these features is “foreignness.”
• So, we can infer that – most often – antigens – ultimately – originate externally.
• (There are exceptions, of course. Some cells become transformed by disease [e. g., cancer] or by aging. In such instances, the antigens have an internal origin.)
Extinction of a particular animal or plant species occurs when there are no more individuals of that species alive anywhere in the world - the species has died out. This is a natural part of evolution. But sometimes extinctions happen at a much faster rate than usual. Natural Causes of Extinction.
Difference between In-Situ and Ex-Situ conservation
Conservation of biodiversity and genetic resources helps protect, maintain and recover endangered animal and plant species. There are mainly two strategies for the conservation of wildlife: In-situ conservation and Ex-situ conservation. Although, both the strategies aim to maintain and recover endangered species, they are different from each other. Let us see how they differ from each other!
Evolution Of Bacteria
Bacteria have existed from very early in the history of life on Earth. Bacteria fossils discovered in rocks date from at least the Devonian Period (419.2 million to 358.9 million years ago), and there are convincing arguments that bacteria have been present since early Precambrian time, about 3.5 billion years ago. Bacteria were widespread on Earth at least since the latter part of the Paleoproterozoic, roughly 1.8 billion years ago, when oxygen appeared in the atmosphere as a result of the action of the cyanobacteria. Bacteria have thus had plenty of time to adapt to their environments and to have given rise to numerous descendant forms.
Impact of Environment on Loss of Genetic Diversity and Speciation
Genetic variation describes naturally occurring genetic differences among individuals of the same species. This variation permits flexibility and survival of a population in the face of changing environmental circumstances. Consequently, genetic variation is often considered an advantage, as it is a form of preparation for the unexpected. But how does genetic variation increase or decrease? And what effect do fluctuations in genetic variation have on populations over time?
GENE ENVIRONMENT INTERACTION
Subtle differences in one person’s genes can cause them to respond differently to the same environmental exposure as another person. As a result, some people may develop a disease after being exposed to something in the environment while others may not.
As scientists learn more about the connection between genes and the environment, they pursue new approaches for preventing and treating disease that consider individual genetic codes.
How to store food in hot
The Good News
To maximize benefit of preservation, keep your food as fresh as possible for as long as possible. You can do this, even in the heat, by creating a “cooler” made from two basic terra cotta pots, one larger than the other. Put the smaller pot in the larger one, fill the gap with sand, and saturate the sand with water. Then cover it with a cloth. To add additional insulation from the heat, bury the pot up to its rim. The evaporation of moisture from the wet sand will cool the air around the food and help keep it fresh.
What is IUPAC naming?
In order to give compounds a name, certain rules must be followed. When naming organic compounds, the IUPAC (International Union of Pure and Applied Chemistry) nomenclature (naming scheme) is used. This is to give consistency to the names. It also enables every compound to have a unique name, which is not possible with the common names used (for example in industry). We will first look at some of the steps that need to be followed when naming a compound, and then try to apply these rules to some specific examples.
IUPAC Nomenclature
IUPAC nomenclature uses the longest continuous chain of carbon atoms to determine the basic root name of the compound. The root name is then modified due to the presence of different functional groups which replace hydrogen or carbon atoms in the parent structure.
Hybridization describes the bonding atoms from an atom's point of view. For a tetrahedral coordinated carbon (e.g. methane CH4), the carbon should have 4 orbitals with the correct symmetry to bond to the 4 hydrogen atoms.
INTRODUCTION:
Hybrid Orbitals
Developed by Linus Pauling, the concept of hybrid orbitals was a theory created to explain the structures of molecules in space. The theory consists of combining atomic orbitals (ex: s,p,d,f) into new hybrid orbitals (ex: sp, sp2, sp3).
1. Why Firefly give light during night?
2. Why atomic mass and Atomic numbers are given to elements ?
3. Why elements have been characterized and classified into different groups?
4. What is the transition of elements and what they play their role in elements stability?
Climate Change All over the World .pptxsairaanwer024
Climate change refers to significant and lasting changes in the average weather patterns over periods ranging from decades to millions of years. It encompasses both global warming driven by human emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. While climate change is a natural phenomenon, human activities, particularly since the Industrial Revolution, have accelerated its pace and intensity
Epcon is One of the World's leading Manufacturing Companies.EpconLP
Epcon is One of the World's leading Manufacturing Companies. With over 4000 installations worldwide, EPCON has been pioneering new techniques since 1977 that have become industry standards now. Founded in 1977, Epcon has grown from a one-man operation to a global leader in developing and manufacturing innovative air pollution control technology and industrial heating equipment.
UNDERSTANDING WHAT GREEN WASHING IS!.pdfJulietMogola
Many companies today use green washing to lure the public into thinking they are conserving the environment but in real sense they are doing more harm. There have been such several cases from very big companies here in Kenya and also globally. This ranges from various sectors from manufacturing and goes to consumer products. Educating people on greenwashing will enable people to make better choices based on their analysis and not on what they see on marketing sites.
Willie Nelson Net Worth: A Journey Through Music, Movies, and Business Venturesgreendigital
Willie Nelson is a name that resonates within the world of music and entertainment. Known for his unique voice, and masterful guitar skills. and an extraordinary career spanning several decades. Nelson has become a legend in the country music scene. But, his influence extends far beyond the realm of music. with ventures in acting, writing, activism, and business. This comprehensive article delves into Willie Nelson net worth. exploring the various facets of his career that have contributed to his large fortune.
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Introduction
Willie Nelson net worth is a testament to his enduring influence and success in many fields. Born on April 29, 1933, in Abbott, Texas. Nelson's journey from a humble beginning to becoming one of the most iconic figures in American music is nothing short of inspirational. His net worth, which estimated to be around $25 million as of 2024. reflects a career that is as diverse as it is prolific.
Early Life and Musical Beginnings
Humble Origins
Willie Hugh Nelson was born during the Great Depression. a time of significant economic hardship in the United States. Raised by his grandparents. Nelson found solace and inspiration in music from an early age. His grandmother taught him to play the guitar. setting the stage for what would become an illustrious career.
First Steps in Music
Nelson's initial foray into the music industry was fraught with challenges. He moved to Nashville, Tennessee, to pursue his dreams, but success did not come . Working as a songwriter, Nelson penned hits for other artists. which helped him gain a foothold in the competitive music scene. His songwriting skills contributed to his early earnings. laying the foundation for his net worth.
Rise to Stardom
Breakthrough Albums
The 1970s marked a turning point in Willie Nelson's career. His albums "Shotgun Willie" (1973), "Red Headed Stranger" (1975). and "Stardust" (1978) received critical acclaim and commercial success. These albums not only solidified his position in the country music genre. but also introduced his music to a broader audience. The success of these albums played a crucial role in boosting Willie Nelson net worth.
Iconic Songs
Willie Nelson net worth is also attributed to his extensive catalog of hit songs. Tracks like "Blue Eyes Crying in the Rain," "On the Road Again," and "Always on My Mind" have become timeless classics. These songs have not only earned Nelson large royalties but have also ensured his continued relevance in the music industry.
Acting and Film Career
Hollywood Ventures
In addition to his music career, Willie Nelson has also made a mark in Hollywood. His distinctive personality and on-screen presence have landed him roles in several films and television shows. Notable appearances include roles in "The Electric Horseman" (1979), "Honeysuckle Rose" (1980), and "Barbarosa" (1982). These acting gigs have added a significant amount to Willie Nelson net worth.
Television Appearances
Nelson's char
"Understanding the Carbon Cycle: Processes, Human Impacts, and Strategies for...MMariSelvam4
The carbon cycle is a critical component of Earth's environmental system, governing the movement and transformation of carbon through various reservoirs, including the atmosphere, oceans, soil, and living organisms. This complex cycle involves several key processes such as photosynthesis, respiration, decomposition, and carbon sequestration, each contributing to the regulation of carbon levels on the planet.
Human activities, particularly fossil fuel combustion and deforestation, have significantly altered the natural carbon cycle, leading to increased atmospheric carbon dioxide concentrations and driving climate change. Understanding the intricacies of the carbon cycle is essential for assessing the impacts of these changes and developing effective mitigation strategies.
By studying the carbon cycle, scientists can identify carbon sources and sinks, measure carbon fluxes, and predict future trends. This knowledge is crucial for crafting policies aimed at reducing carbon emissions, enhancing carbon storage, and promoting sustainable practices. The carbon cycle's interplay with climate systems, ecosystems, and human activities underscores its importance in maintaining a stable and healthy planet.
In-depth exploration of the carbon cycle reveals the delicate balance required to sustain life and the urgent need to address anthropogenic influences. Through research, education, and policy, we can work towards restoring equilibrium in the carbon cycle and ensuring a sustainable future for generations to come.
Artificial Reefs by Kuddle Life Foundation - May 2024punit537210
Situated in Pondicherry, India, Kuddle Life Foundation is a charitable, non-profit and non-governmental organization (NGO) dedicated to improving the living standards of coastal communities and simultaneously placing a strong emphasis on the protection of marine ecosystems.
One of the key areas we work in is Artificial Reefs. This presentation captures our journey so far and our learnings. We hope you get as excited about marine conservation and artificial reefs as we are.
Please visit our website: https://kuddlelife.org
Our Instagram channel:
@kuddlelifefoundation
Our Linkedin Page:
https://www.linkedin.com/company/kuddlelifefoundation/
and write to us if you have any questions:
info@kuddlelife.org
WRI’s brand new “Food Service Playbook for Promoting Sustainable Food Choices” gives food service operators the very latest strategies for creating dining environments that empower consumers to choose sustainable, plant-rich dishes. This research builds off our first guide for food service, now with industry experience and insights from nearly 350 academic trials.
Characterization and the Kinetics of drying at the drying oven and with micro...Open Access Research Paper
The objective of this work is to contribute to valorization de Nephelium lappaceum by the characterization of kinetics of drying of seeds of Nephelium lappaceum. The seeds were dehydrated until a constant mass respectively in a drying oven and a microwawe oven. The temperatures and the powers of drying are respectively: 50, 60 and 70°C and 140, 280 and 420 W. The results show that the curves of drying of seeds of Nephelium lappaceum do not present a phase of constant kinetics. The coefficients of diffusion vary between 2.09.10-8 to 2.98. 10-8m-2/s in the interval of 50°C at 70°C and between 4.83×10-07 at 9.04×10-07 m-8/s for the powers going of 140 W with 420 W the relation between Arrhenius and a value of energy of activation of 16.49 kJ. mol-1 expressed the effect of the temperature on effective diffusivity.
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 (estimation).
• 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 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.
13. 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)
15. 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.
16. 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)
17. 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.
18. 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.
19. 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.
20. 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.
•ABSORBANCE VS TRANSMITTANCE
21. 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.
22. 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.
23.
24. 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.
25. 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.
26. 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.
27. 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.
28. The End
Big thanks to
http://biologyonline.us/Microbiology/Fall
%2008%20White%20Earth/Micro%20Lab
%20Manual/Lab%206/12.htm