Chemotaxis, a kind of taxis, is the phenomenon in which bodily cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. A taxis (plural taxes, ˈtæksiːz is an Innate behavioural response by an Organism to a directional stimulus. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Multicellular organisms are Organisms consisting of more than one cell, and having Differentiated cells that perform specialized functions This is important for bacteria to find food (for example, glucose) by swimming towards the highest concentration of food molecules, or to flee from poisons (for example, phenol). Glucose (Glc a Monosaccharide (or simple Sugar) also known as grape sugar, is an important Carbohydrate in Biology. In the context of Biology, poisons are substances that can cause damage, Illness, or Death to Organisms usually by Phenol, is a toxic colourless Crystalline Solid with a sweet tarry odor commonly referred to as a "hospital smell" In multicellular organisms, chemotaxis is critical to early (e. g. movement of sperm towards the egg during fertilization) and subsequent phases of development (e. The term sperm is derived from the Greek word (σπέρμα sperma (meaning "seed" and refers to the male reproductive cells. For soil improvement see Fertilization (soil. g. migration of neurons or lymphocytes) as well as in normal function. Neurons (ˈnjuːɹɒn also known as neurones and nerve cells) are responsive cells in the Nervous system that process and transmit information A lymphocyte is a type of White blood cell in the Vertebrate Immune system. In addition, it has been recognized that mechanisms that allow chemotaxis in animals can be subverted during cancer metastasis. Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled Metastasis ( Greek: displacement μετά=next + στάσις=placement, plural metastases) sometimes abbreviated mets,
Chemotaxis is called positive if movement is in the direction of a higher concentration of the chemical in question, and negative if the direction is opposite.
Although migration of cells was detected from the early days of the development of microscopy (Leeuwenhoek), erudite description of chemotaxis was first made by T. Antonie Philips van Leeuwenhoek (October 24 1632 &ndash August 30 1723 was a Dutch tradesman and Scientist from Delft, the Netherlands W. Engelmann (1881) and W.F. Pfeffer (1884) in bacteria and H.S. Jennings (1906) in ciliates. Wilhelm Friedrich Philipp Pfeffer (9 March 1845 - 31 January 1920 was a German Botanist and plant physiologist who was born in Grebenstein. Herbert Spencer Jennings (born in Tonica, Illinois, April 8, 1868; died in Santa Monica, California, April 14 The ciliates are one of the most important groups of Protists common almost everywhere there is water — lakes ponds oceans rivers and soils with many ectosymbiotic The Nobel Prize Laureate E. Metchnikoff also contributed to the study of the field with investigations of the process as an initial step of phagocytosis. Ilya Ilyich Mechnikov (Илья Ильич Мечников ( May 16 1845 – July 15 1916) was a Russian microbiologist Phagocytosis is the cellular process of engulfing solid particles by the Cell membrane to form an internal Phagosome, or "food vacuole The significance of chemotaxis in biology and clinical pathology was widely accepted in the 1930s. The most fundamental definitions belonging to the phenomenon were also drafted by this time. The most important aspects in quality control of chemotaxis assays were described by H. Harris in the 1950s. Chemotaxis assays are experimental tools for evaluation of Chemotactic ability of Prokaryotic or Eukaryotic cells Sir Henry Harris, FRS, (born January 28 1925) is an Australian-born professor of Medicine at Oxford University In the 1960s and 1970s, the revolution of modern cell biology and biochemistry provided a series of novel techniques which became available to investigate the migratory responder cells and subcellular fractions responsible for chemotactic activity. The pioneering works of J. Adler represented a significant turning point in understanding the whole process of intracellular signal transduction of bacteria. Julius Adler PhD is an Emeritus Professor of Biochemistry and Genetics at the University of Wisconsin-Madison. 
On November 3, 2006, Dr. Events 644 - Umar ibn al-Khattab, the second Muslim Caliph, is killed by a Persian slave in Medina. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Dennis Bray of University of Cambridge was awarded the Microsoft European Science Award for his work on chemotaxis on E. coli. Dr Dennis Bray is an active Emeritus professor at University of Cambridge. The University of Cambridge (often Cambridge University) located in Cambridge, England, is the second-oldest university in the The Microsoft European Science Award is an annual award given by the Royal Society and the Académie des Sciences to scientists working in Europe who have made a major 
Chemotaxis is one of the most basic cell physiological responses. Development of receptor systems for the detection of harmful and favorable substances in the environment was most essential to unicellular organisms from the very early stages of phylogeny. Comprehensive analysis of chemotactic activity of the eukaryotic protozoon Tetrahymena pyriformis and consensus sequences of appearance of amino acids in the primordial soup suggest that there was a good correlation between the chemotactic character of these relative simple organic molecules and their development on the Earth. Tetrahymena are free-living Ciliate Protozoa that can also switch from commensalistic to Pathogenic modes of survival In Molecular biology and Bioinformatics, a consensus sequence is a way of representing the results of a multiple Sequence alignment, where related sequences In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this In the Natural sciences, Abiogenesis, or origin of life, is the study of how Life on Earth emerged from Inanimate Organic In this way the earliest molecules are suggested to be highly chemoattractant (e. Inorganic or organic substances possessing Chemotaxis inducer effect in motile cells g. Gly, Glu, Pro), while latter ones are thought to be strongly chemorepellent (e. Glycine (abbreviated as Gly or G) is the Organic compound with the formula NH2CH2COOH Glutamic acid (abbreviated as Glu or E) is one of the 20 Alpha Amino acids It is not among the human Essential amino acids Its Proline (abbreviated as Pro or P) is an α- Amino acid, one of the twenty DNA -encoded amino acids Etymology chêmeia (gr = chemistry repellent (lat = inspiring aversion resistant or impervious to something Inorganic or organic substances possessing Chemotaxis g. Tyr, Trp, Phe) amino acids. Tyrosine (abbreviated as Tyr or Y) or 4-hydroxyphenylalanine, is one of the 20 Amino acids that are used by cells to synthesize Tryptophan (abbreviated as Trp or W) is one of the 20 standard amino acids, as well as an Essential amino acid in the Human diet Phe redirects here For the BitTorrent feature see PHE. For the constellation see Phoenix (constellation. 
Some bacteria, such as E. coli, have several flagella per cell (4–10 typically). The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have A flagellum ( plural flagella) is a tail-like structure that projects from the Cell body of certain Prokaryotic and Eukaryotic cells and it These can rotate in two ways :
The directions of rotation are given for an observer outside the cell looking down the flagella toward the cell.
The overall movement of a bacterium is the result of alternating tumble and swim phases. If one watches a bacterium swimming in a uniform environment, its movement will look like a random walk with relatively straight swims interrupted by random tumbles that reorient the bacterium. A random walk, sometimes denoted RW, is a Mathematical formalization of a trajectory that consists of taking successive Random steps Bacteria such as E. coli are unable to choose the direction in which they swim, and are unable to swim in a straight line for more than a few seconds due to rotational diffusion. Diffusion is the net movement of particles (typically molecules from an area of high concentration to an area of low concentration by uncoordinated random movement In other words, bacteria "forget" the direction in which they are going. Given these limitations, it is remarkable that bacteria can direct their motion to find favorable locations with high concentrations of attractants (usually food) and avoid repellents (usually poisons).
In the presence of a chemical gradient bacteria will chemotax, or direct their overall motion based on the gradient. In Vector calculus, the gradient of a Scalar field is a Vector field which points in the direction of the greatest rate of increase of the scalar If the bacterium senses that it is moving in the correct direction (toward attractant/away from repellent), it will keep swimming in a straight line for a longer time before tumbling. If it is moving in the wrong direction, it will tumble sooner and try a new direction at random. In other words, bacteria like E. coli use temporal sensing to decide whether life is getting better or worse. In this way, it finds the location with the highest concentration of attractant (usually the source) quite well. Even under very high concentrations, it can still distinguish very small differences in concentration. Fleeing from a repellent works with the same efficiency.
It seems remarkable that this purposeful random walk is a result of simply choosing between two methods of random movement; namely tumbling and straight swimming. In Cell biology, a biased random walk enables Bacteria to search for food and flee from harm In fact, chemotactic responses such as forgetting direction and choosing movements resemble the decision-making abilities of higher lifeforms with brains that process sensory data.
The helical nature of the individual flagellar filament is critical for this movement to occur. As such, the protein that makes up the flagellar filament, flagellin, is quite similar among all flagellated bacteria. Flagellin is a Protein that arranges itself in a hollow cylinder to form the filament in Bacterial Flagellum. Vertebrates seem to have taken advantage of this fact by possessing an immune receptor (TLR5) designed to recognize this conserved protein.
As in many instances in biology, there are bacteria that do not follow this rule. Many bacteria, such as Vibrio, are monoflagellated and have a single flagellum at one pole of the cell. Their method of chemotaxis is different. Others possess a single flagellum that is kept inside the cell wall. These bacteria move by spinning the whole cell, which is shaped like a corkscrew. 
Chemical gradients are sensed through multiple transmembrane receptors, called methyl accepting chemotaxis proteins (MCPs), which vary in the molecules that they detect. Transmembrane receptors are Integral membrane proteins which reside and operate typically within a cell's Plasma membrane, but also in the membranes of These receptors may bind attractants or repellents directly or indirectly through interaction with proteins of periplasmatic space. The periplasmic space or periplasm is a space between the inner Cytoplasmic membrane and external Outer membrane of Gram-negative bacteria The signals from these receptors are transmitted across the plasma membrane into the cytosol, where Che proteins are activated. The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer The cytosol or intracellular fluid (or cytoplasmic matrix) is the liquid found inside cells. The Che proteins alter the tumbling frequency, and alter the receptors.
The proteins CheW and CheA bind to the receptor. The activation of the receptor by an external stimulus causes autophosphorylation in the histidine kinase, CheA, at a single highly conserved histidine residue. Phosphorylation is the addition of a Phosphate (PO4 group to a Protein molecule or a small molecule CheA in turn transfers phosphoryl groups to conserved aspartate residues in the response regulators CheB and CheY [ note: CheA is a histidine kinase and it does not actively transfer the phosphoryl group. The response regulator CheB takes the phosphoryl group from CheA]. This mechanism of signal transduction is called a 'Two Component System' and is a common form of signal transduction in bacteria. CheY induces tumbling by interacting with the flagellar switch protein FliM, inducing a change from counter-clockwise to clockwise rotation of the flagellum. Change in the rotation state of a single flagellum can disrupt the entire flagella bundle and cause a tumble.
CheB, when activated by CheA, acts as a methylesterase, removing methyl groups from glutamate residues on the cytosolic side of the receptor. An esterase is a Hydrolase Enzyme that splits Esters into an Acid and an Alcohol in a Chemical reaction with water Glutamic acid (abbreviated as Glu or E) is one of the 20 Alpha Amino acids It is not among the human Essential amino acids Its The cytosol or intracellular fluid (or cytoplasmic matrix) is the liquid found inside cells. It works antagonistically with CheR, a methyltransferase, which adds methyl residues to the same glutamate residues. In Biochemistry, a transferase is an Enzyme that catalyzes the transfer of a Functional group (e The more methyl residues are attached to the receptor, the more sensitive the receptor. As the signal from the receptor induces demethylation of the receptor in a feedback loop, the system is continuously adjusted to environmental chemical levels, remaining sensitive for small changes even under extreme chemical concentrations. Feedback is a circular causal Process whereby some proportion of a system's output is returned (fed back to the Input. This regulation allows the bacterium to 'remember' chemical concentrations from the recent past and compare them to those it is currently experiencing, thus 'know' whether it is traveling up or down a gradient. However, the methylation system alone cannot account for the wide range of sensitivity that bacteria have to chemical gradients. Additional regulatory mechanisms such as receptor clustering and receptor-receptor interactions also modulate the signalling pathway.
The mechanism by which eukaryotic cells chemotax is quite different from that in bacteria; however, sensing of chemical gradients is still a crucial step in the process. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex Due to their size, prokaryotes cannot detect effective concentration gradients, therefore these cells scan and evaluate their environment by a constant swimming (consecutive steps of straight swims and tumbles). In contrast to prokaryotes, the size of eukaryotic cells allows for the possibility of detecting gradients, which results in a dynamic and polarized distribution of receptors. Induction of these receptors by chemoattractants or chemorepellents results in migration towards or away from the chemotactic substance.
Levels of receptors, intracellular signalling pathways and the effector mechanisms all represent diverse, eukaryotic type components. In eukaryotic unicellular cells, ameboid movement and cilium or the eukaryotic flagellum are the main effectors (e. g. Amoeba or Tetrahymena). Amoeba (sometimes amœba or ameba, plural amoebae) is a Genus of Protozoa that moves Tetrahymena are free-living Ciliate Protozoa that can also switch from commensalistic to Pathogenic modes of survival Some eukaryotic cells of higher vertebrate origin, such as immune cells also move to where they need to be. An immune system is a collection of mechanisms within an Organism that protects against Disease by identifying and killing Pathogens and Tumor Besides immune competent cells (granulocyte, monocyte, lymphocyte) a large group of cells - considered previously to be fixed into tissues - are also motile in special physiological (e. Granulocytes are a category of White blood cells characterised by Monocyte is a type of Leukocyte, part of the Human body 's Immune system. A lymphocyte is a type of White blood cell in the Vertebrate Immune system. g. mast cell, fibroblast, endothelial cells)or pathological conditions (e. A mast cell (or mastocyte) is a resident cell of several types of tissues and contains many granules rich in Histamine and Heparin A fibroblast is a type of cell that synthesizes and maintains the Extracellular matrix of many Animal tissues The endothelium is the thin layer of cells that line the interior surface of Blood vessels forming an interface between circulating Blood in the g. metastases). Metastasis ( Greek: displacement μετά=next + στάσις=placement, plural metastases) sometimes abbreviated mets, Chemotaxis has high significance in the early phases of embryogenesis as development of germ layers is guided by gradients of signal molecules. Embryogenesis is the process by which the Embryo is formed and develops A germ layer is a collection of cells formed during animal Embryogenesis.
Unlike motility in bacterial chemotaxis, the mechanism by which eukaryotic cells physically move is unclear. There appear to be mechanisms by which an external chemotactic gradient is sensed and turned into an intracellular PIP3 gradient, which results in a gradient in the activation of signaling pathway culminating in the polymerisation of actin filaments. Phosphatidylinositol (345-trisphosphate (PtdIns(345 P 3 commonly abbreviated to PIP3 is the product of the class I Phosphoinositide In Polymer chemistry, polymerization is a process of reacting Monomer Molecules together in a Chemical reaction to form three-dimensional networks Actin is a globular roughly 42-kDa Protein found in all eukaryotic cells (except for Nematode sperm where it may be present at concentrations of The growing distal end of actin filaments develops connections with the internal surface of the plasma membrane via different sets of peptides and results in the formation of pseudopods. Pseudopods or pseudopodia (from the Greek word ψευδοπόδια, ψευδός "fake false" Cilium of eukaryotic cells can also result in chemotaxis, while in this case it is mainly a Ca2+ dependent induction of the microtubular system of the basal body and the 9x2+2 microtubules stroke of cilia. A cilium (plural cilia) is an Organelle found in eukaryotic cells Cilia are tail-like projections extending approximately A basal body (sometimes basal granule or kinetosome) is an Organelle formed from a Centriole, a short Cylindrical array Microtubules are one of the components of the Cytoskeleton. They have a diameter of 25 nm and length varying from 200 nanometers to 25 micrometers The orchestered beating of hundreds of cilia is synchronized by a submembranous system built between basal bodies. The details of the signaling pathways are still not totally clear.
Although chemotaxis is the most frequently studied form of migration there are several other forms of locomotion on the cellular level.
For the most part, eukaryotic cells sense the presence of chemotactic stimuli though the use of 7-transmembrane (or serpentine) heterotrimeric G-protein coupled receptors. GTP chemical structurepng|thumb|180px| Guanosine triphosphate]] G proteins short for guanine nucleotide-binding proteins, are a family of Proteins involved This class of receptors is huge, representing a significant portion of the genome. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby Some members of this gene superfamily are used in eyesight (rhodopsins) as well as in olfaction (smelling). The main classes of professional chemotaxis receptors are triggered by formyl peptides - formyl peptide receptors (FPR), chemokines - chemokine receptors (CCR or CXCR) and leukotrienes - leukotriene receptors (BLT); however, induction of a wide set of membrane receptors (e. The formyl peptide receptor s ( FPR) are a members of a class of G protein-coupled receptors involved in Chemotaxis. Chemokines are a family of small Cytokines, or Proteins secreted by cells Proteins are classified as chemokines according to shared structural characteristics Chemokine receptors are Cytokine receptors found on the surface of certain cells which interact with a type of Cytokine called a Chemokine. Leukotrienes are naturally produced Eicosanoid lipid mediators, which may be responsible for the effects of an inflammatory response g. amino acids, insulin, vasoactive peptides) also elicit migration of the cell. In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this Insulin is a Hormone with intensive effects on both metabolism and several other body systems (eg vascular compliance
While some chemotaxis receptors are expressed in the surface membrane with long-term characteristics as they are determined genetically, others have short-term dynamics as they are assembled ad hoc in the presence of the ligand. The diverse features of the chemotaxis receptors and ligands allows for the possibility of selecting chemotactic responder cells with a simple chemotaxis assay. By chemotactic selection we can determine whether a still uncharacterized molecule acts via the long- or the short-term receptor pathway. Chemotaxis receptors are expressed in the surface membrane with diverse dynamics some of them have long-term characteristics as they are determined genetically others have The term chemotactic selection is also used to designate a technique which separates eukaryotic or prokaryotic cells according to their chemotactic responsiveness to selector ligands. 
The number of molecules capable of eliciting chemotactic responses is relatively high, and we can distinguish primary and secondary chemotactic molecules. The main groups of the primary ligands are as follows:
Investigations of the three-dimensional structures of chemokines proved that a characteristic composition of beta-sheets and an alpha helix provides expression of sequences required for interaction with the chemokine receptors. Formation of dimers and their increased biological acitvity was demonstrated by crystallography of several chemokines e. g. IL-8.
Chemotactic responses elicited by the ligand-receptor interactions are distinguished generally upon the optimal effective concentration(s) of the ligand. Nevertheless, correlation of the amplitude elicited and ratio of the responder cells compared to the total number are also characteristic features of the chemotactic signaling. Investigations of ligand families (e. g. amino acids or oligo peptides) proved that there is a fitting of ranges (amplitudes; number of responder cells) and chemotactic activities: chemoattractant moiety is accompanied by wide ranges, while chemorepellent character by narrow ranges.
A changed migratory potential of cells has relatively high importance in the development of several clinical symptoms and syndromes. Altered chemotactic activity of extracellular (e. g. Escherichia coli) or intracellular (e. g. Listeria monocytogenes) pathogens itself represents a significant clinical target. Listeria monocytogenes is a Gram-positive Bacterium, in the division Firmicutes, named for Joseph Lister. Modification of endogenous chemotactic ability of these microorganisms by pharmaceutical agents can decrease or inhibit the ratio of infections or spreading of infectious diseases. Apart from infections, there are some other diseases where impaired chemotaxis is the primary etiological factor, as in Chediak-Higashi syndrome where giant intracellular vesicles inhibit normal migration of cells.
|Type of disease||Chtx. increased||Chtx. decreased|
|Chtx. Inflammation ( Latin, inflamatio, to set on fire is the complex biological response of vascular tissues to harmful stimuli such as Pathogens Brucellosis, also called undulant fever, or Malta fever, is a highly contagious Zoonosis caused by ingestion of unsterilized Milk results the disease||-||Chediak-Higashi syndrome, Kartagener syndrome|
|Chtx. Primary ciliary dyskinesia ( PCD) also known as immotile ciliary syndrome or Kartagener Syndrome (KS, is a rare Autosomal recessive is affected||atherosclerosis, arthritis, periodontitis, psoriasis, reperfusion injury, metastatic tumors||multiple sclerosis, Hodgkin disease, male infertility|
|Intoxications||asbestos, benzpyrene||salts of Hg and Cr, ozone (O3)|
Research of cell migration – as it was shown in the chapter ’History of chemotaxis research’ – requires complementary application of classic and modern techniques. Atherosclerosis is a Disease affecting arterial Blood vessels It is a chronic inflammatory response in the walls of arteries in large part due to the accumulation Arthritis (from Greek arthro-, joint + -itis, inflammation plural arthritides is a group of conditions involving damage to the Joints of the body Psoriasis (səˈraɪəsɪs ( suh-RI-uh-sus) is a non-contagious disorder which affects the Skin and Joints It commonly causes red scaly Reperfusion injury refers to damage to tissue caused when Blood supply returns to the tissue after a period of Ischemia. Metastasis ( Greek: displacement μετά=next + στάσις=placement, plural metastases) sometimes abbreviated mets, Multiple sclerosis (abbreviated MS also known as disseminated sclerosis or encephalomyelitis disseminata) is an autoimmune condition in which the Hodgkin's lymphoma, also known as Hodgkin's disease is a type of Lymphoma first described by Thomas Hodgkin in 1832 Male infertility is a term that refers to Infertility in male humans Asbestos is a group of Minerals with long thin fibrous Crystals The word "asbestos" (῾ἀσβεστος is derived from a Greek adjective Benzopyrene, C20H12 is a five-ring Polycyclic aromatic hydrocarbon that is Mutagenic and highly Carcinogenic It is a crystalline Mercury (ˈmɜrkjʊri also called quicksilver or hydrargyrum, is a Chemical element with the symbol Hg ( Latinized hydrargyrum Chromium (ˈkroʊmiəm is a Chemical element which has the symbol Cr and Atomic number 24 OZONE is an object oriented Operating system written in the C programming language. The filed provides the possibility to present novel and valuable data in the basic research as well as in applied sciences. In the last 20-25 years, due to the factors mentioned above, there was an increase in number of publications dealing with itslef the phenomenon chemotaxis. To publish is to make content Publicly known. The term is most frequently applied to the distribution of text or images on paper or to the placing of content Nevertheless, other publications written in genetics, biochemistry, cell-physiology, pathology and clinical sciences could also incorporate data about migration or especially the chemotaxis of cells. Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is Biochemistry is the study of the chemical processes in living Organisms It deals with the Structure and function of cellular components such as Pathology (from Greek grc πάθος pathos, "fate harm" and grc -λογία -logia) is the study and A curiosity of migration research is that among several works investigating taxes (e. g. thermotaxis, geotaxis, phototaxis) chemotaxis research shows a significantly high ratio, which point to the underlined importance of chemotaxis research both in biology and medicine. Thermotaxis is the phenomenon in which a cell directs its movement according to temperature A taxis (plural taxes, ˈtæksiːz is an Innate behavioural response by an Organism to a directional stimulus. Phototaxis is a kind of Taxis that occurs when a whole organism moves in response to the stimulus Light. Foundations of modern biology There are five unifying principles Medicine is the art and science of healing It encompasses a range of Health care practices evolved to maintain and restore Human Health by the
A wide range of techniques is available to evaluate chemotactic activity of cells or the chemoattractant and chemorepellent character of ligands. The basic requirements of the measurement are as follows:
Despite the fact that an ideal chemotaxis assay is still not available, there are several protocols and pieces of equipment which offer good correspondence with the conditions described above. Chemotaxis assays are experimental tools for evaluation of Chemotactic ability of Prokaryotic or Eukaryotic cells The most commonly used are:
E. g. PP-chamber
E. g. Boyden-chamber - Zigmond chamber - Dunn chambers - Multi-well chambers - Capillary techniques
E. g. T-maze technique - Opalescence technique - Orientation assays
(A more detailed chapter you can find under Chemotaxis assay)