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Imbibition: Definition, Mechanism, and Examples
Continue ReadingImbibition Definition
Imbibition refers to the movement of water molecules absorbed by any living or dead material of plant by joint action of capillary and electrostatic force. Imbibition is a passive process without conversion of metabolic products or energy utilized.
Features of Imbibition
Seed germination completely depends on radicle formation and imbibition of seeds by water; Cellulose, hemicellulose, pecten and other proteinaceous hydrophilic substance of the dry seed swells when subjected to water. Significant adaptation of plant to produce dry seed is to protect from the harsh condition germination where it causes death to their progeny.
Apart from seed germination; imbibition plays a small role in transfer of water and nutrition in plants; by its ability to move the water over a very small distance. Transport over large distance is dependable on the species of plants and are explored less.
Imbibition along with other passive forces also contributes to water transport in root hairs. The phenomenon is easily understood; as a dead tree trunk in water swells voluminously is the exact mechanism of uptake of water by imbibition. The volume of the imbibant (i.e.) cellulose or hemicellulose, pecten increases the whole volume of the plant or the trunk does not increase because of the rearrangement and reorientation of the water molecules attachment to the imbibant makes water to obtain less volume.
Main difference between a diffusion and imbibition is that it involves a solid as an absorbing substance (i.e.) the solid substance is the imbibant ; developing higher pressure after absorption. Imbibition is more specific to Hydrophilic colloids to absorb or transport water; is irreversibly dependent on matric pressure which was once termed as imbibition pressure. The pressure is similar to osmotic pressure which is really high to even break a rock and removes the external hard seed coat facilitating germination of seed. Imbibition takes place in both living and dead parts of plant.
History of Imbibition
Imbibition is a regular process of water uptake in plants especially in trunk is derived from Latin word – imbibere which means to drink in. In Ancient times during pyramid construction in Egypt; Egyptians used to break stones using the technique of imbibition. The small trunk pieces are inserted in rock cervices and trunks are soaked with water. The trunks expand absorbing the water produces high pressure induces a force up to 1000 kPa to break open a rock.
Similarly, the imbibition is used to break skull sutures to operate surgery in brain in ancient days by “Witch Doctors”. Witch Doctors opens the skull by prior treatment of skull by soaked seeds which on germination opens the seed coat produces force to open the skull allowing to perform the surgery. Imbibition examples are well present in our day today life; where the wooden doors, windows or other wooden articles exposed to sun rain absorb water and swells; which disables the ability of wood to function properly.
Imbibition in Water Transport
Passive forces constitute movement of water from the soil to roots hairs of plants and constitutes short distance transport of water. Water from soil due to the difference in concentration gradient move from higher concentration to lower concentration.
Short distance transport is easily achieved by either of the physical forces or in combination. Later, the transpiration pull created use to the evaporation and active transport in intracellular protein structures also constitutes transport of materials and water throughout the length of the plant.
Imbibition in Seed Germination
Water becomes essential for a seed to germinate at favorable environmental condition. Seeds undergo dehydration and rehydration process for germination. Once the seed is matured the water content of the seeds are given out by dehydration where the storage and genetic material are intact enough to survive for few days. On favorable condition with water the seed imbibes water and swells because of absorption of water. This causes a pressure to build up which breaks the seed coat for the seed to germinate. Following imbibition, a heat is generated; which is essential to drive the metabolic activities for seed development; caused by the liberation of heat because of water absorption.
The developmental changes in seeds are:
• Releasing hydrolytic enzymes to digest and mobilize the reserves
• Cell division and cell enlargement is started again
• Respiratory pathways start
• Development proceeds to produce new plant.
Imbibition Condition
Process of Imbibition depends on the chemical and electrostatic forces and the colloidal substance available to take up water. These are the 2 main contains for imbibition to occur:
Water potential is necessary between the imbibant and the water. Generally, imbibition takes place when the potential difference between the substance is high like in plants; the cellulose and pecten are colloid which absorbs water and transfer the water content from the lower potential region to higher potential region. Water potential on a colloid must be lower for a water to be absorbed.
Affinity between imbibant and liquid is essential. Colloids such as cellulose, pecten have higher affinity to water than to ether
Factor Affecting Imbibition
Imbibition depends on both internal environment of plants and external factors of the environment.
Temperature: Imbibition increase with an increase in temperature. Higher temperature increases the rate of imbibition by the movement produced by the kinetic energy of the colloids or the imbibing molecules. This the main external environmental factor influencing imbibition. At lower temperature; the surface becomes stiffer for absorption and enter a dormant stage or die due to unfavorable conditions.
Osmotic Potential: Osmotic potential between the imbibant and the medium must be steeper for imbibition to occur consistently and effectively. Increase in solute concentration in water leads to less absorption of water which does not support the movement of water or the germination.
Imbibition Citations
- Measurement and Modeling of Spontaneous Capillary Imbibition in Coal. ACS Omega . 2020 Jun 12;5(24):14461-14472.
- Experimental Investigation on the Imbibition Capacity and Its Influencing Factors in Hydrate Sediments. ACS Omega . 2020 Jun 9;5(24):14564-14574.
- Studies on the molecular mechanisms of seed germination. Proteomics . 2015 May;15(10):1671-9.
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Facilitated Diffusion: Definition, Mechanism, and Examples
Continue ReadingWhat is Facilitated Diffusion?
Active and passive transport are the 2 main transport mechanisms mediating commination between an environment and a plant in which organizing tissues are directly interconnected and respond to environmental changes directly. Lack of central organizing unit and control mechanism in lower organisms such as plants directly interact with the environment at cellular or tissue level massively depends on Active and Passive transports. In plants water is a main element of circulation and in assimilation of CO2 to sucrose; absorbed in root hairs Passive uptake of water – Diffusion and facilitated diffusion.
Facilitated diffusion – a modified mechanism of diffusion; involves membrane transporters to allow water and other molecules on difference between concentration and electrochemical gradient. In 1930, passive transport of water in cells were experimented by artificially creating a cell to understand the better transport mechanism; resulted in efficient flow of water and minerals through membrane transporters in facilitated diffusion rather than through lipid bilayers as in simple diffusion. Facilitated diffusion is bi – directional depending upon either concentration gradient and electrochemical gradient. At equilibrium, the rate of transport of net molecules of water or other elements is minimal or null.
Schematic Representation of Facilitated Diffusion
Facilitated Diffusion Characteristic
1. Specificity: Transmembrane proteins are frequent in between sets of lipid bilayer. Molecules of transport are permitted in specific transporter molecules depending upon the molecule that enters a cell.
2. Passive Nature: Transport through the channels does not require the conversion of ATP into ADP or AMP to power the movement of molecules from higher concentration to lower concentration.
3. Saturation Kinetics: Apart from the specificity and passive transport; driving force of the net movement of molecules depends on the concentration or the net number of molecules present between external and internal environment of cell.
Facilitated Diffusion Citations
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Diffusion: Definition, Formula and Examples
Continue ReadingWhat is Diffusion?
Diffusion is a process of passive transport predominant in root transferring water, minerals, and nutrients from soil to root by the difference between concentration gradient between root hairs and the soil. Diffusion is passive without powered by energy molecules – ATP; takes place in the absence of barriers (i.e.) cell wall specifically in plants and other living tissues and becomes effective in free space over a short distance.
Diffusion is a random motion of molecules in a free space without barriers of the molecules. Molecules above absolute zero in motion has a kinetic energy with heat and diffusion is a random motion in system to attain an equilibrium and hence the diffusion is governed by thermal agitation. Moles, atoms, or any particles in random motion is a medium collide with each other changing their course of motion in other random direction is diffusion.
Diffusion Formula
Diffusion was quantitatively measured by Adolf Fick in 1880’s determining the rate of diffusion to be the difference in the concentration gradient. The law formulated from Fick’s derivation is the “Fick’s first law” from the given equation
Js = -Ds ΔCs / Δ x
Js is the density of the diffusion at a unit area per time known as Density Flux
D is the diffusion coefficient of a substance over a medium, a proportionality constant depends on the medium in which the substance diffuses.
– negative sign indicates the rate of diffusion moves down a concentration gradient.
ΔCs is the concentration of the diffusing molecule Diffusion is slow over longer distances. This can be determined from the first law where the average time taken for a particle to diffuse over a distance id determined by the square of the distance L by the Diffusion coefficient. t= L2/Ds,
Diffusion Citations
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Cell, Electrochemical Cell, Diagram, and Structure
Continue ReadingWhat is Cells?
The device which convert electrical energy into chemical energy or chemical energy into electrical energy is called cell.
Types of Cells
Cells are of two types;
1. Electrochemical Cell
The cell which convert chemical energy into electrical energy is called electrochemical cell.
Eg: Daniell cell
Daniell Electrochemical Cell Diagram
2. Electrolytic Cell
The cell which convert electrical energy into chemical energy is called electrolytic cell.
Ex- electrolysis of NaCl.
o In electrolytic cell redox reaction takes place.
o In electrolytic cell non-spontaneous (ΔG = positive) reaction type is proceed.
o For this cell, the value ΔG is positive.
The Electrolysis of Molten NaCl
If H Cl solution is take place in electrolytic cell then the following reaction takes place at cathode and at anode
H CL ⇔ H+ Cl–
At cathode: H+ + e- → ½ H2(g)
At anode: Cl– → ½ Cl2(g) + e-
Electrochemical Cell Citations
- An electrochemical cell for in operando studies of lithium/sodium batteries using a conventional x-ray powder diffractometer. Rev Sci Instrum . 2014 Oct;85(10):104103.
- Electrochemical cell-based chip for the detection of toxic effects of bisphenol-A on neuroblastoma cells. Biosens Bioelectron . 2011 Mar 15;26(7):3371-5.
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Electrolytes: Definition, Type, and Functions
Continue ReadingWhat are Electrolytes?
An electrolyte is a substance that produces an electrically conducting solution when dissolved in a polar solvent, such as water. The dissolved electrolyte separates into cations and anions, which disperse uniformly through the solvent. Electrolytes are essential minerals such as sodium, calcium, and potassium. Electrolytes play an important role in many key functions in the body.
Classification of Electrolytes
All electrolytes do not dissociate in same amount at all the given dilution. on the basis, electrolytes are divided mainly in two parts strong electrolytes and weak electrolytes.
i. Strong Electrolytes
Strong electrolytes are those substance which are completely ionized in their aqueous solution. Generally, this class contains strong acids , strong bases and salt of acid-base (strong), salts of strong acid-weak base and weak acid-strong base.
Eg: HCl , NaOH , NaCl , CH3COONa , NH4Cl etc.
These salts are completely dissociated at normal dilution.
ii. Weak Electrolytes
Weak electrolytes are those substances which are not completely dissociated in their aqueous solution and degree of dissociation increase with increase in solution.
Ionic part of weak electrolytes is called “degree of dissociation” or “degree of ionization”. It is denoted by α. This class contains weak acids, weak bases and salt of weak acid and weak base.
Eg: CH3COOH, H2CO3, H3BO3, NH4OH, Al(OH)3, CH3COONH4
Factors Affecting Electrolyte Conductance
The conductance depends upon the following factors;
a) Inter-ionic Attraction
If strong ionic attraction is present between the ions of solute then they do not dissociate easily, when they dissolve in solvent, due to this the value of conductivity become less. The energy released in ion-solvent reaction is called “salvation-energy” and if water is solvent then it is called ‘hydration energy’. So, if the amount of ion -ion attraction energy is more than ion-solvent attraction then electrolytes are taken in class of weak electrolytes.
b) Salvation of Ions
It depends on attractive forces present between ions and solvents, which are called “ ion-solvent interactions”. If this attractive force is very strong then ion becomes solvate in which the layers of solvent molecules are attached to ions and decrease its size. In this condition, the movement of ions towards electrode decreases, so the conductivity decreases.
c) Viscosity of Solvent
Viscosity of solvent depends on solvent-solvent interactions. Greater the attraction, greater is the viscosity of solvent, which decreases the conductivity .
d) Concentration of Solution
Concentration of solution is greater than concentration of electrolyte solution, lesser is the value of its conductivity. The amount of dissociation increases with the increase in dilution due to which, the conductivity of solution of electrolyte increases.
e) Effect of Temperature
The average kinetic energy of ions of electrolyte increases with increase in temperature, which increases the degree of dissociation of electrolyte. Hence, the amount of conductivity increases with increase in temperature.
Electrolytes Citations
- Investigation of the role of electrolytes and non-electrolytes on the cloud point and dye solubilization in antidepressant drug imipramine hydrochloride solutions. Colloids Surf B Biointerfaces . 2008 Aug 1;65(1):74-9.
- Electrolytes. Isha Shrimanker; Sandeep Bhattarai.
- Selection of an electrolyte to enhance the electrochemical decolourisation of indigo. Optimisation and scale-up. Chemosphere . 2005 Aug;60(8):1080-6.
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Conductors: Definition, Types, and Examples
Continue ReadingWhat are Conductors?
Conductors are those substance from which electric current can pass through are called conductors. Metals are good conductor of electricity.
eg: copper, silver, tin.
Types of Conductors
Conductors can be classified into two types:-
I. Metallic Conductors
Metallic conductors are those conductors in which electricity is flow due to the presence of free e- are called metallic conductors.
Factors Affecting Metallic Conductor
The nature and structure of the matter.
The no valence electrons per atom.
The density of matter.
Temperature: if we increase the temperature then the conductivity of metallic conductor decreases.
II. Electrolytic Conductors
Electrolytic conductors are those conductors which do not flow electricity in solid state but in molten state.
This type conductor, conduct electricity due to the presence of free ions, are called electrolyte conductor.
Metallic Conductors vs Electrolytic Conductors
Metallic Conductors Electrolytic Conductors In these conductors, conductivity is produced due to movement of e-. In these conductor conductivity is produced due to movement of free ions. In metallic conductors, no chemical change take place during the conduction of electricity. In these conductors chemical change take place. In metallic conductor flow of substance does not take place. In these conductors flow of substance take place. The conductivity of these conductor decrease with increase in temperature. The conductivity of electrolyte increase with increase in temperature. Electrochemistry
o The branch of chemistry which deals with the study of relationship between electrical and chemical energy and their interconversion is called electrochemistry.
o The basis of such processes is redox-reactions.
o The redox reactions take place in various chemical and biological reactions.
o Redox reactions are used in – burning of fuels, industrial processes, digestion of food by organism, photosynthesis for getting energy from sun, metal extraction, preparation of important chemicals, preparation of dry and moist batteries, fuel cell etc.
o The chemical reactions which are take place by electrochemical processes are energy rich and produce less pollution.
o Hence, the study of electrochemistry is very important to develop new eco-friendly techniques.
o Biological system like transfer of sense actions from brain to cells to opposite to opposite to this is also coordinated by electrochemistry.
Conductors Citations
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Ketone Bodies: Definition, Synthesis, and Physiology
Continue ReadingWhat are Ketone Bodies?
Ketone bodies can also be generally called as ketones. These are the substances that is produced by the liver while performing the process of gluconeogenesis.
Gluconeogenesis, is one of the vital process that runs in our body, during fasting or when the body starves. At these times our body creates glucose by its own.
Generally, there are about three ketone bodies that is being produced by the liver, namely acetoacetate, Beta-hydroxybutyrate and the acetone.
These are the compounds that are usually present in a healthy individual and supplements energy to the cells of the body when the amount of glucose is absent or it may be low in cases of dieting.
Generally, fatty acids undergo the process of Beta-oxidation in the liver, which makes the mitochondria to Generate high amount of energy for the body by using the three compounds which are known as Ketone bodies.
These bodies are basically water soluble and they do not require a lipoprotein for transporting them across the membrane.
Ketone bodies are one of the lipid molecules which contains carbonyl groups being attached to the two -R groups.
Ketone Body Synthesis
Usually when we over take the foods that is rich in carbohydrates, our body starts storing excess of glucose in our body in the form of fats and other building proteins, which are the things that especially makes us to grow. This state of our cells is known as absorptive state.
In case, when we fast or starve ourselves, the glucose levels in our blood starts decreasing suddenly. This makes our body to enter into the postabsorptive state. In postabsorptive state our body again converts the stored fat into fatty acids and glycogen, which are further converted into glucose and are used by our body cells for breaking up the amino acids and synthesing energy molecules.
When glucose is stored in the form of glycogen and converted back into the same form as vice versa, liver plays a major role in storing it. Once these storages are depleted, our body cells take up the other form for getting out the energy that is needed by the body.
We all must know that brain losses its function without the adequate amount of energy that is being supplied to it. So, the liver always ensures, whether the brain is getting enough energy, thus the process of converting the glycerol, pyruvate and the lactase into glucose by the liver is known as glucogenesis, during this process, two ketone bodies are formed namely acetoacetate and beta-hydroxybutyrate.
These ketone bodies are released into the blood stream along with the glucose to feed the brain. While performing this process, all the other organs and muscles gets shifted to the fatty acids for getting their energy thus conserving the glucose for the brain. As brain needs energy only from the glucose. This process is known as glucose sparing, which is also considered as very important for all the animals that undergoes long duration of fasting or those which starves.
Though we say that brain opts for glucose for the source of energy, but not for so long days. After 4 days of full starvation, and absence of glucose in the body, the brain swifts for energy source from the ketones. This situation greatly increases the time taken by the organism to starve without food which results in many side effects.
At this time if food is not taken by an organism to replenish the supply of glucose, Ketone bodies build up. These ketone bodies are usually the one which is being removed by the kidney during filtrations.
If they are over built due to these starvations then it leads to severe damage of the kidney. Further ketone bodies break into its units and it results in the formation of the acetones.
Acetone is considered as one of the volatile and a highly reactive substance. When this acetone builds up in the blood it lowers the pH of the blood and this condition is known as acidosis.
Acidosis makes all over body tissues to get irrespective of its function and it also makes the cells and tissues to mess up with all the enzymes of the body, depending of the pH balance.
Ketoacidosis or acidosis is caused by excess ketone bodies. This condition if left untreated it leads to coma and even death.
Ketone Bodies vs Keto Diet
Keto diet is becoming a lifestyle adaptation by many of the people who choose it as their platform for losing weight. But actually, keto diet is not usually recommended by the researches, as this diet involves the reduced amount of glucose to be supplied to the body which results in many of the effects as listed above.
Even if keto diet is considered as an effective way to lose weight, it should be done under the supervision of the physician as in many of the cases, it leads to formation of kidney stones, brain issues etc.
Ketone Bodies Citations
- Ketone bodies mimic the life span extending properties of caloric restriction. IUBMB Life . 2017 May;69(5):305-314.
- Ketone bodies as epigenetic modifiers. Curr Opin Clin Nutr Metab Care . 2018 Jul;21(4):260-266.
- Metabolism of ketone bodies during exercise and training: physiological basis for exogenous supplementation. J Physiol . 2017 May 1;595(9):2857-2871.
- Multi-dimensional Roles of Ketone Bodies in Fuel Metabolism, Signaling, and Therapeutics. Cell Metab . 2017 Feb 7;25(2):262-284.
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Nitrate Reduction Test: Result, Principle, Procedure, and...
Continue ReadingNitrate Reduction Test Introduction
Biochemical tests are generally used to determine the ability of the microorganism to be stable in the enzymatic field. One such test is Nitrate reduction test, which helps us to differentiate between the species of the bacteria based on the ability or their inability to reduce nitrate into nitrite using an anaerobic respiration.
This anaerobic metabolism usually required an electron acceptor other than the atmospheric oxygen.
Many of the gram-negative bacteria use of the nitrate as the final electron acceptor.
Nitrate reduction test is one of vital test which helps us to determine the production of an enzyme known nitrate reductase, which helps us to reduce the nitrate.
Bacterial species is generally used to differentiate bacteria on the basis of their ability to reduce nitrate into nitrite or nitrogenous gases.
Nitrate Reduction Test Objective
• The main aim of the Nitrate Reduction Test is to determine the ability of an organism to reduce nitrate to nitrite.
• Nitrate Reduction Test also helps us to identify the different ways in which the nitrate is reduced in the bacteria.
Nitrate Reduction Test Principle
A heavy inoculum of the test organism is incubated into a broth, that contains nitrate. The organism which are all capable of producing a nitrate reductase enzyme has the capability to reduce nitrate to nitrite that is present in the broth which is further reduced in nitric oxide or nitrogen or nitrous oxide.
The nitrate reduction test is completely based on how the nitrate is reduced by the organism and its ability to form a red compound on it reacts with a sulfonic acid to form a complex known as nitrite-sulfanilic acid which then reacts with the alpha-napthylamine and produces a red precipitate known as Prontonisil which has an ability to soluble in water.
However, when the nitrate is alone present in the medium, there will be production of red color. If there is no formation of red color in the media in which the sulfamic acid and the alpha-naphthylamine is added and nitrite will not be present.
There are generally two explanations for the observation;
1. The nitrate should not be reduced, the strain is considered as nitrate-negative.
2. The nitrative can be reduced into nitrite that have been completely reduced into the nitric oxide or nitrous oxide or in the form of nitrogen which on reacting with nitrogen produces a nitrate-positive strain.
In case, when nitrate is not detected it is significant for the test that the organism is reduced into nitrate beyond the nitrite. This can be done my indirect means by adding a small amount of zinc powder into the culture.
Zinc powder helps in catalyzing the reduction of nitrate into nitrite. The development of red color can be seen on addition of the zinc which indicated that the nitrate has not been reduced by the particular organism as it does not have its capability to reduce nitrate.
In case if there is no change in color after adding zinc powder, it shows that the organisms reduced the nitrate present in the medium into nitrite or other compounds of nitrogen, and shows that it is a nitrate reducer.
Nitrate Reduction Test Reagents
Media:
Ingredients Gram per liter Peptone 5.0 Meat extract 3.0 Potassium nitrate 1.0 Nitrate Reduction Test Procedure
• Here the determination of nitrate reduction involves two steps of processes as follows
• Initially, the reduction of nitrate into nitrite is usually determined by addition of reagents of the nitrate A and B, if it is necessary, the reduction of nitrate beyond the nitrite is usually determined by adding the nitrogen reagent as zinc powder.
• First, the nitrate broths are inoculated in a bacterial suspension.
• The tubes are usually inoculated at a temperature of 30 to 37ºC for about 24 hours.
• After completing the process of incubation, the release of nitrogen gas is noted before addition of the reagents.
• Then about 6 to 8 drops of nitrogen reagents A and B are adding into the medium.
• After addition of the ingredients a medium is observed for any color change.
• In case, if there is no color change is noted, then zinc powder is added into the medium.
• Then the medium is being observed for at least 3 minutes for a change or formation of red color.
Nitrate Reduction Test Results
Positive Nitrate Reduction Test:
• In case of positive results, there will be a formation of a cherry red color while adding the reagents A and B.
• There will be no change in color or production of red color after adding the zinc powder.
Negative Nitrate Reduction Test:
• In case of negative result, there will a formation of red color only after adding the zinc powder into the medium containing the reagents
Nitrate Reduction Test Citations
- Nitrate reduction: new method for testing the antibiotic susceptibility of Haemophilus influenzae. Antimicrob Agents Chemother . 1978 May;13(5):791-5.
- Simple and rapid method for detection of nitrate reductase activity of Mycobacterium tuberculosis and Mycobacterium canettii grown in the Bactec MGIT960 system. J Microbiol Methods . 2010 May;81(2):208-10.
- The Use of the Nitrate Reduction Test in Characterizing Bacteria. J Bacteriol. 1919 May; 4(3): 267–290.
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Motility Test: Result, Principle, Procedure, and Reagents
Continue ReadingMotility Test
Generally, Motility is the ability of the organism to move itself by using a flagella or some other propellers which are unique for each of the organism and helps in its locomotion.
Where as bacteria confines a unique form of locomotion by using its specific fibrils which looks like a gliding sort of motion.
The motile bacteria move either by using a flagellum, a thread like locomotor which extends outward from the cell membranes.
Motility is too long to be recognized as it has it own important characteristic feature in the world of taxonomy.
Usually, the flagella are present primarily in all kind of basic bacilli’s, but few of them are flagellated cocci, which have their motility varying manner depending upon the different genera.
However, identification of motility is very important for categorizing the family of Enterobacteriaceae.
In microbiology, from early days, differentiation and classification of Enterobacteriaceae is identified by means of performing the kinds of motility test.
Motility Test Objective
• The main aim of the test is to detect the motility of the bacterium.
• To differentiate between the motile and a non-motile species of bacteria.
Motility Test Principle
Usually, the motility of the bacterium is demonstrated by using a semi solid medium of agar. As in the semi solid medium, motile bacteria swarm and it gives a diffused spread of growth which can be recognized in a naked eye.
The agar medium is usually used in the Sulphide Indole motility medium which is a combination of the differential medium where the test is performed using three different parameters such as reduction of Sulphur, Indole production, and motility.
This media has a very soft consistency which allows the bacterium to migrate along with and causing cloudiness in the medium, the inoculum is stabbed to the center of the semi solid medium deeply.
Bacterial motility is identified by a diffuse zone of growth which extends from the line of the inoculation. Whereas some organisms which grow along the entire medium shows very small areas of growth or there will be formation of nodules in a particular area.
On the other hand, non-motile bacteria grow only in the soft agar tube and only in areas where they are inoculated.
Motility Test Reagents
Here SIM medium is generally used. It consists of the following ingredients.
Ingredients Gram per liter Pancreatic digest of casein 20.0 Peptic digest of animal tissue 6.1 Fe (NH4)2(SO4)2.6H2O 0.2 Na2S2O3.5H2O 0.2 Motility Test Procedure
Initially, a straight needle is used to touch a young colony which has been kept for about 18-to-24-hour culture in a medium of agar.
Then the medium is stabbed once in the middle of the tube up to half an inch of the tube.
It should also be made sure that the needle should be removed from the tube as the same way it entered.
Then the medium is incubated at a temperature of 35 to 37ºC and it is observed frequently up to 7 days.
Within seven days, the diffused zone of growth which is flaring out from the line of inoculation can be seen.
Motility Test Results
Positive Motility Test Result: If the medium gives a positive result, then it gives a diffuse, hazy growth that spreads across the medium which is renders as slightly opaque one.
Negative Motility Test Result: In case of negative results, the growth is confined to the stab line, which has sharp defined margins and leaves the surrounding area of the medium opaque.
Motility Test Uses
• Motility Test is significantly used for differentiating the microorganisms on the basis of their motility performed in a laboratory setting
• Motility Test is also useful for assigning a taxonomic classification of the organisms.
• Motility Tests also plays an important role in characterizing the pathogens.
• Motility Test are usually employed for identifying the protocols which belongs to the family of Enterobacteriaceae.
• Motility Test is used for the specific species which helps to differentiate the gram-positive cocci, Enterococci, Faecalis, E. casseliflacus, Enterococcus faecium.
Motility Test Limitations
Some kind of organisms will not show the sufficient growth in the medium, which makes an accurate determination and the additional follow-up testing is needed.
It is also recommended that the biochemical, molecular, mass, spectrometry testing; are all performed in the colonies that are taken from the pure culture for complete identification of the species.
If the flagella of the bacteria are damaged due to heating, shaking or any other trauma it results in false-negative results. On the other hand, if the organisms are found to have a weak and unstable mode of motility, it leads to false-negative reactions.
While inoculating in a semi-solid media, it is important to note that the inoculating medium is removed along the straight line in the same way it is inserted. A fanning motion of removing a needle may result in false-positive results.
Motility Test Citations
- Evaluation of 15 motility media and a direct microscopic method for detection of motility in enterococci. J Clin Microbiol . 2002 Jul;40(7):2476-9.
- Use of Two Selective Media and a Broth Motility Test Can Aid in Identification or Exclusion of Bacillus anthracis. J Clin Microbiol. 2005 Sep; 43(9): 4336–4341.
- Bacterial Motility .J Bacteriol. 1934 Feb; 27(2): 165–174.
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MUG Test: Result, Principle, Procedure, and Reagents
Continue ReadingMUG Test
It has been reported that the enzyme beta-glucuronidase is generally present in many strains o the E. coli and also in other organisms like Salmonella, Shigella, Staphylococcus, Streptococcus along with E. coli which contains the enzyme Beta-glucuronidase.
Thus, the detection of this enzyme, Beta-glucuronidase is determined in the biochemical laboratories by using this method which helps us to identify and differentiate the certain organisms.
The substance known as MUG (4-methylumbellferyl-Beta-D-glucuronide is considered as a sensitive and a selective substrate for detecting the activity of Beta-glucuronidase.
Thus, MUG test is considered as a conjunction with the substrate like oxidase, indole and the fermentation of lactose, which is generally performed in an effective manner in order to identify the species of E. coli and the other such related organisms.
MUG is an acronym of 4-methylumberlliferyl Beta-D-glucuronide. Shortly, MUG test is used for rapid identification of the E. coli which has the capability to produce Verodoxin from the strain that do not produce it.
MUG Test Objective
The main aim of the test is to identify the activity of glucuronidase in the organisms by fluorescence, when it is observed under the UV light source having a long wave of about 365nm.
MUG Test Principle
E. coli and the other species of Enterobacteriaceae produces an enzyme known as Beta-D-glucuronidase, that hydrolyses the Beta-D-glucopyranoside-uronic derivatives into the aglycons and the d-glucuronic acid.
Here, the substrate 4-methylumbelliferyl-β-d-glucuronide which is impregnated into the disk and it is further hydrolyzed by the enzyme in order to yield methyl umbelliferyl moiety, that fluoresces blue under a long wavelength in the UV light.
Hence, if the test organism produces the enzyme known as glucuronidase which helps in breaking the substrate thus resulting in the formation of a fluorescence, which is noted as the positive test.
On the other hand, if there is no desired enzymatic activity, then the substrate will not be broken down into fluorescence on test, which is notes as a result for negative test.
MUG Test Reagents
Media: MUG disks are generally prepared by using the impregnating the MUG i.e., 4-mrthylumbelliferyl Beta-glucuronide onto a high-quality filter paper disk.
MUG test
2 to 3 isolated colonies of organisms
Inoculating loops
Petri dishes
Test tubes
Incubator
Long wave UV light
MUG Test Procedure
Generally, two methods are used for performing the MUG test;
i. Direct Disk MUG Test
Initially, the petri dish is made wet using a drop of water. It should not be saturated.
With the help of a wooden applicator small portion of a colony is rubbed from an 18 to 24-hour culture.
Then the culture is incubated in a closed container for about 35 to 37º C for about 2 hours.
After incubating, the disk is observed under a ultra violet light, a long wave of about 360nm in a darkened room, fluorescence can be observed.
ii. Tube MUG Test
Initially 0.25 ml of deionized water is taken in a clean glass tube.
Then a heavy suspension is created using up to 3 to 4 colonies of the isolated test in the glass tube.
With the help of the force, a MUG disk is placed in the tube and it is shaken strenuously to make sure that the adequate elution of the substrate in the surrounding medium.
Further the medium is incubated aerobically for about one hour at a temperature of 35 to 37ºC.
After incubation, the tubes are taken out and they are detected for the presence of fluorescence by using a longwave of ultra violet for about 360nm in a darkened room.
MUG Test Results
Positive MUG Test Results: In case of positive result, there will be fluorescence, which resembles an electric blue.
Negative MUG Test Results: Whereas in case of negative results there will be absence of blue fluorescence.
MUG Test Uses
This test is widely used for identifying the different genera which belongs to the family of Enterobacteriaceae in a presumptive manner.
This test also helps us to characterize the Verotoxin producing E. coli. As the Verotoxin producing strains of E. coli does not have the capability to produce a MUG, and a negative test indicates the presence of a clinically important strain.
This test also aids in detecting the Escherichia coli in the water and in food samples.
MUG Test Limitations
In MUG test, the colonies that are isolated from the media containing dyes, are not suggested for test as it makes the interpretation difficult.
This test is reliable only for oxidase-positive organisms as some of the oxidative negative organisms has its fluorescence naturally.
It is also suggested that the tests such as biochemical, immunological, molecular or a mass spectrometry are generally performed in the colonies that is present in the pure culture for the complete identification.
Where as some strains of the Shigella results as MUG positive. Serological testing is usually required to differentiate the species of Shigella and E. coli.
MUG Test Citations
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