Biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined together to form macromolecules; this process consists of metabolic pathways. Some of these biosynthetic pathways are located within a single cellular organelle, while others involve enzymes that are located within multiple cellular organelles. Examples of these biosynthetic pathways include the production of lipid membrane components and nucleotides. Biosynthesis is synonymous with anabolism; the prerequisite elements for biosynthesis include: precursor compounds, chemical energy, catalytic enzymes which may require coenzymes. These elements create the building blocks for macromolecules; some important biological macromolecules include: proteins, which are composed of amino acid monomers joined via peptide bonds, DNA molecules, which are composed of nucleotides joined via phosphodiester bonds.
Biosynthesis occurs due to a series of chemical reactions. For these reactions to take place, the following elements are necessary: Precursor compounds: these compounds are the starting molecules or substrates in a reaction; these may be viewed as the reactants in a given chemical process. Chemical energy: chemical energy can be found in the form of high energy molecules; these molecules are required for energetically unfavorable reactions. Furthermore, the hydrolysis of these compounds drives a reaction forward. High energy molecules, such as ATP, have three phosphates; the terminal phosphate is split off during hydrolysis and transferred to another molecule. Catalytic enzymes: these molecules are special proteins that catalyze a reaction by increasing the rate of the reaction and lowering the activation energy. Coenzymes or cofactors: cofactors are molecules that assist in chemical reactions; these may be metal ions, vitamin derivatives such as NADH and acetyl CoA, or non-vitamin derivatives such as ATP.
In the case of NADH, the molecule transfers a hydrogen, whereas acetyl CoA transfers an acetyl group, ATP transfers a phosphate. In the simplest sense, the reactions that occur in biosynthesis have the following format: Reactant → e n z y m e Product Some variations of this basic equation which will be discussed in more detail are: Simple compounds which are converted into other compounds as part of a multiple step reaction pathway. Two examples of this type of reaction occur during the formation of nucleic acids and the charging of tRNA prior to translation. For some of these steps, chemical energy is required: Precursor molecule + ATP ↽ − − ⇀ product AMP + PP i Simple compounds that are converted into other compounds with the assistance of cofactors. For example, the synthesis of phospholipids requires acetyl CoA, while the synthesis of another membrane component, requires NADH and FADH for the formation the sphingosine backbone; the general equation for these examples is: Precursor molecule + Cofactor → e n z y m e macromolecule Simple compounds that join together to create a macromolecule.
For example, fatty acids join together to form phospholipids. In turn and cholesterol interact noncovalently in order to form the lipid bilayer; this reaction may be depicted as follows: Molecule 1 + Molecule 2 ⟶ macromolecule Many intricate macromolecules are synthesized in a pattern of simple, repeated structures. For example, the simplest structures of lipids are fatty acids. Fatty acids are hydrocarbon derivatives; these fatty acids create larger components, which in turn incorporate noncovalent interactions to form the lipid bilayer. Fatty acid chains are found in two major components of membrane lipids: phospholipids and sphingolipids. A third major membrane component, does not contain these fatty acid units; the foundation of all biomembranes consists of a bilayer structure of phospholipids. The phospholipid molecule is amphipathic; the phospholipid heads interact with each other and aqueous media, while the hydrocarbon tails orient themselves in the center, away from water. These latter interactions drive the bilayer structure that acts as a barrier for molecules.
There are various types of phospholipids. However, the first step in phospholipid synthesis involves the formation of phosphatidate or diacylglycerol 3-phosphate at the endoplasmic reticulum and outer mitochondrial membrane; the synthesis pathway is found below: The pathway starts with glycerol 3-phosphate, which gets converted to lysophosphatidate via the addition of a fatty acid chain provided by acyl coenzyme A. Then, lysophosphatidate is converted to phosphatidate via the addition of another fatty acid chain contributed by a second acyl CoA.
Lactobacillus casei is a species of genus Lactobacillus found in the human urinary tract and mouth. This particular species of Lactobacillus is documented to have a wide pH and temperature range, complements the growth of L. acidophilus, a producer of the enzyme amylase. The most common application of L. casei is industrial for dairy production. Lactobacillus casei is the dominant species of nonstarter lactic acid bacteria present in ripening cheddar cheese, the complete genome sequence of L. casei ATCC 334 has become available. L. casei is the dominant species in fermented Sicilian green olives. A commercial beverage containing L. casei strain Shirota has been shown to inhibit the in vivo growth of Helicobacter pylori, but when the same beverage was consumed by humans in a small trial, H. pylori colonization decreased only and the trend was not statistically significant. Some L. casei strains are considered to be probiotic, may be effective in alleviation of gastrointestinal pathogenic bacterial diseases.
According to World Health Organization, those properties have to be demonstrated on each specific strain—including human clinical studies—to be valid. L. casei has been combined with other probiotic strains of bacteria in randomized trials studying its effects in preventing antibiotic-associated diarrhea and Clostridium difficile infections, patients in the trials who were not given the placebo had lower rates of AAD or CDI with no adverse effects reported. Additionally, trials have shown shorter recovery times in children suffering from acute diarrhea when given different L. casei treatments when compared to placebo. Studies suggest that Lactobacillus is a safe and effective treatment for acute and infectious diarrhea. In the preparation of food, L. casei bacteria can be used in the natural fermentation of beans to lower levels of the compounds causing flatulence upon digestion. Among the best-documented, probiotic L.casei, L. casei DN-114001, L. casei Shirota have been extensively studied and are available as functional foods.
Another commercially available form of L. casei can be found in Danactive made by Dannon. They registered trademarked L. casei as L. casei Immunita. In the past few years, many studies have been conducted in the decolorization of azo dyes by lactic acid bacteria such as L. casei TISTR 1500, L. paracasei, Oenococcus oeni, etc. With the azoreductase activity, mono- and diazo bonds are degraded and generate other aromatic compounds as intermediates. Amul yoghurt Prebiotic Lactic acid bacteria Type strain of Lactobacillus casei at BacDive - the Bacterial Diversity Metadatabase
Dairy products, milk products or lacticinia are a type of food produced from or containing the milk of mammals cattle, water buffaloes, sheep and humans. Dairy products include food items such as yogurt and butter. A facility that produces dairy products is known as dairy factory. Dairy products are consumed worldwide, with the exception of much of East and Southeast Asia and some parts of central Africa. Milk is produced after optional homogenization or pasteurization, in several grades after standardization of the fat level, possible addition of the bacteria Streptococcus lactis and Leuconostoc citrovorum. Milk can be broken down into several different categories based on type of product produced, including cream, cheese, infant formula, yogurt. Cream and fermented cream Single cream, double cream and whipped cream Clotted cream, spoonable cream made by heating milk Kaymak Sour cream Smetana and Eastern European variety of sour cream Crème fraîche fermented cream Soured milk obtained by fermentation with mesophilic bacteria Lactococcus lactis and other bacterial cultures and yeasts Cultured buttermilk resembling buttermilk, but uses different yeast and bacterial cultures Clabber, milk fermented to a yogurt-like state Filmjölk Ymer Viili Kefir, fermented milk drink from the Northern Caucasus Kumis, fermented mares' milk popular in Central Asia Amasi Mursik Yogurt, milk fermented by thermophilic bacteria, mainlyStreptococcus salivarius ssp. thermophilus and Lactobacillus delbrueckii ssp. bulgaricus sometimes with additional bacteria, such as Lactobacillus acidophilus Acidophiline Matzoon Skyr Strained yogurt Qatyq Ryazhenka Varenets Ayran Doogh Lassi, Indian subcontinent LebenBaked milk, milk simmered on low heat for long time which results in mild caramelization.
Popular in Eastern Europe. Scalded milk Skim milk Whole milk products Condensed milk, milk, concentrated by evaporation, with sugar added for reduced process time and longer life in an opened can Dulce de leche Evaporated milk, milk without added sugar Malai Khoa, milk, concentrated by evaporation, used in Indian cuisine Powdered milk, produced by removing the water from milk Whey, the liquid drained from curds and used for further processing or as a livestock feed Buttermilk, the liquid left over after producing butter from cream dried as livestock feedInfant formula, dried milk powder with specific additives for feeding human infants High milk-fat and nutritional products Confectionery products Milk chocolateButter milk fat, produced by churning cream Ghee, clarified butter, by gentle heating of butter and removal of the solid matter Smen, a fermented, clarified butter used in Moroccan cooking Anhydrous milkfat Cheese, produced by coagulating milk, separating from whey and letting it ripen with bacteria and sometimes with certain molds Fresh cheeses and curds, the soft, curdled part of milk used to make cheese Cottage cheese Quark Fromage frais Faisselle Farmer cheese Queso fresco Chhena, soft solids from curdled milk, used in Indian cuisine.
This is dried and compacted to make paneer Paneer Junket, milk solidified with rennet Cream cheese, produced by the addition of cream to milk and curdled to form a rich curd or cheese Ricotta, acidified whey cheese Casein are Caseinates, sodium or calcium salts of casein Milk protein concentrates and isolates Whey protein concentrates and isolates, reduced lactose whey Hydrolysates, milk treated with proteolytic enzymes to alter functionality Mineral concentrates, byproduct of demineralizing whey Ice cream frozen cream, milk and emulsifying additives Gelato frozen milk and water, lesser fat than ice cream Ice milk, low-fat version of ice cream Frozen custard Frozen yogurt, yogurt with emulsifiers Custard Vla Dairy products can cause problems for individuals who have lactose intolerance or a milk allergy. Excessive consumption of dairy products can contribute significant amounts of cholesterol and saturated fat to the diet, which can increase the risk of heart disease, cause other serious health problems.
There is no excess cardiovascular risk with dietary calcium intake, but calcium supplements are associated with a higher risk of coronary artery calcification. Consumption of dairy products does not cause mucus production, will not make cold or asthma symptoms worse; this held belief stems from some people mistaking the thin coat of residue left behind after consuming milk or ice cream for mucus. Rates of dairy consumption vary worldwide. High-consumption countries consume more than 150 kg per capita per year; these countries are: Argentina, Australia, Costa Rica, most European counties, Kyrgyzstan, North America and Pakistan. Medium-consumption countries consume 30 to 150 kg per capita per year; these countries are: India, Japan, Mexico, New Zealand and Southern Africa, most of the Middle East, most of Latin America and the Caribbean. Low-consumption countries consume under 30 kg per capita per year; these countries are: Senegal, most of Central Africa, most of East and Southeast Asia. Some groups avoid dairy products for non-health related reasons: Religious – Some religions restrict or do not allow for the consumption of dairy products.
For example, some scholars of Jainism advocate not consuming any dairy products because dairy is perceived to involve violence against cows. Orthodox Judaism requires that meat and dairy products not be served at the same meal, served or cooked in the same utensils, or stored together, as prescribed in Deu
In the fields of molecular biology and genetics, a genome is the genetic material of an organism. It consists of DNA; the genome includes both the genes and the noncoding DNA, as well as mitochondrial DNA and chloroplast DNA. The study of the genome is called genomics; the term genome was created in 1920 by Hans Winkler, professor of botany at the University of Hamburg, Germany. The Oxford Dictionary suggests the name is a blend of the words chromosome. However, see omics for a more thorough discussion. A few related -ome words existed, such as biome and rhizome, forming a vocabulary into which genome fits systematically. A genome sequence is the complete list of the nucleotides that make up all the chromosomes of an individual or a species. Within a species, the vast majority of nucleotides are identical between individuals, but sequencing multiple individuals is necessary to understand the genetic diversity. In 1976, Walter Fiers at the University of Ghent was the first to establish the complete nucleotide sequence of a viral RNA-genome.
The next year, Fred Sanger completed the first DNA-genome sequence: Phage Φ-X174, of 5386 base pairs. The first complete genome sequences among all three domains of life were released within a short period during the mid-1990s: The first bacterial genome to be sequenced was that of Haemophilus influenzae, completed by a team at The Institute for Genomic Research in 1995. A few months the first eukaryotic genome was completed, with sequences of the 16 chromosomes of budding yeast Saccharomyces cerevisiae published as the result of a European-led effort begun in the mid-1980s; the first genome sequence for an archaeon, Methanococcus jannaschii, was completed in 1996, again by The Institute for Genomic Research. The development of new technologies has made genome sequencing cheaper and easier, the number of complete genome sequences is growing rapidly; the US National Institutes of Health maintains one of several comprehensive databases of genomic information. Among the thousands of completed genome sequencing projects include those for rice, a mouse, the plant Arabidopsis thaliana, the puffer fish, the bacteria E. coli.
In December 2013, scientists first sequenced the entire genome of a Neanderthal, an extinct species of humans. The genome was extracted from the toe bone of a 130,000-year-old Neanderthal found in a Siberian cave. New sequencing technologies, such as massive parallel sequencing have opened up the prospect of personal genome sequencing as a diagnostic tool, as pioneered by Manteia Predictive Medicine. A major step toward that goal was the completion in 2007 of the full genome of James D. Watson, one of the co-discoverers of the structure of DNA. Whereas a genome sequence lists the order of every DNA base in a genome, a genome map identifies the landmarks. A genome map is less detailed than aids in navigating around the genome; the Human Genome Project was organized to sequence the human genome. A fundamental step in the project was the release of a detailed genomic map by Jean Weissenbach and his team at the Genoscope in Paris. Reference genome sequences and maps continue to be updated, removing errors and clarifying regions of high allelic complexity.
The decreasing cost of genomic mapping has permitted genealogical sites to offer it as a service, to the extent that one may submit one's genome to crowdsourced scientific endeavours such as DNA. LAND at the New York Genome Center, an example both of the economies of scale and of citizen science. Viral genomes can be composed of either RNA or DNA; the genomes of RNA viruses can be either single-stranded or double-stranded RNA, may contain one or more separate RNA molecules. DNA viruses can have either double-stranded genomes. Most DNA virus genomes are composed of a single, linear molecule of DNA, but some are made up of a circular DNA molecule. Prokaryotes and eukaryotes have DNA genomes. Archaea have a single circular chromosome. Most bacteria have a single circular chromosome. If the DNA is replicated faster than the bacterial cells divide, multiple copies of the chromosome can be present in a single cell, if the cells divide faster than the DNA can be replicated, multiple replication of the chromosome is initiated before the division occurs, allowing daughter cells to inherit complete genomes and partially replicated chromosomes.
Most prokaryotes have little repetitive DNA in their genomes. However, some symbiotic bacteria have reduced genomes and a high fraction of pseudogenes: only ~40% of their DNA encodes proteins; some bacteria have auxiliary genetic material part of their genome, carried in plasmids. For this, the word genome should not be used as a synonym of chromosome. Eukaryotic genomes are composed of one or more linear DNA chromosomes; the number of chromosomes varies from Jack jumper ants and an asexual nemotode, which each have only one pair, to a fern species that has 720 pairs. A typical human cell has two copies of each of 22 autosomes, one inherited from each parent, plus two sex chromosomes, making it diploid. Gametes, such as ova, sperm and pollen, are haploid, meaning they carry only one copy of each chromosome. In addition to the chromosomes in the nucleus, organelles such as the chloroplasts and mitochondria have their own DNA. Mitochondria are sometimes said to have their own genome referred to as the "mitochondrial genome".
The DNA found within the chloroplast may be referred to as the "plastome". Like the bacteria they originated from and chloroplasts have a circular chromosome
In biology, a strain is a low-level taxonomic rank used at the intraspecific level. Strains are seen as inherently artificial concepts, characterized by a specific intent for genetic isolation; this is most observed in microbiology where strains are derived from a single cell colony and are quarantined by the physical constraints of a Petri dish. Strains are commonly referred to within virology and with rodents used in experimental studies. A strain is a genetic subtype of a microorganism. For example, a "flu strain" is a certain biological form of "flu" virus; these flu strains are characterized by their differing isoforms of surface proteins. New viral strains can be created due to mutation or swapping of genetic components when two or more viruses infect the same cell in nature; these phenomena are known as antigenic drift and antigenic shift. Microbial strains can be differentiated by their genetic makeup using metagenomic methods to maximize resolution within species; this has become a valuable tool to analyze the microbiome.
Scientists have engineered flu virus strains pandemic in humans. Funding for this research has been controversial as a result of safety concerns, has been halted at times. However, this research continues today. In biotechnology, microbial strains have been engineered to establish metabolic pathways suitable for treating a variety of applications. A major effort of metabolic research has been devoted to the field of biofuel production. Optimized strains of E. coli are are used for this application. E. coli are often used as a chassis for the expression of simple proteins. These strains, such as BL21, are engineered to minimize protease activity, hence enabling potential for high efficiency industrial scale protein expression. In the case of complex proteins including biologics, mammalian strains are used for expression. See Chinese hamster ovary cell. Yeasts are the most common subjects of eukaryotic strain engineering with respect to industrial fermentation. E. coli is most common species for prokaryotic strain engineering.
Scientists have succeeded in establishing viable minimal genomes from which new strains can be developed. These minimal strains provide a near guarantee that experiments on genes outside the minimal framework will not be effected by non-essential pathways; the term has no official ranking status in botany. A strain is a designated group of offspring that are either descended from a modified plant, or which result from genetic mutation; as an example, some rice strains are made by inserting new genetic material into a rice plant, all the descendants of the genetically modified rice plant are a strain with unique genetic information, passed on to generations. The rice plants in the strain can be bred to other rice strains or cultivars, if desirable plants are produced, these are further bred to stabilize the desirable traits. A laboratory mouse or rat strain is a group of animals, genetically uniform. Strains are used in laboratory experiments. Mouse strains can be inbred, mutated, or genetically engineered, while rat strains are inbred.
A given inbred rodent population is considered genetically identical after 20 generations of sibling-mating. Many rodent strains have been developed for a variety of disease models, they are often used to test drug toxicity; the common fruit fly was among the first organisms used for genetic analysis, has a simple genome, is well understood. It has remained a popular model organism for many other reasons, like the ease of its breeding and maintenance, the speed and volume of its reproduction. Various specific strains have been developed, including a flightless version with stunted wings. Genetic isolate Race Coli Genetic Stock Center EcoliWiki E. coli strain index International Mouse Strain Resource Rat strain index
Gram-positive bacteria are bacteria that give a positive result in the Gram stain test, traditionally used to classify bacteria into two broad categories according to their cell wall. Gram-positive bacteria take up the crystal violet stain used in the test, appear to be purple-coloured when seen through a microscope; this is because the thick peptidoglycan layer in the bacterial cell wall retains the stain after it is washed away from the rest of the sample, in the decolorization stage of the test. Gram-negative bacteria cannot retain the violet stain after the decolorization step, their peptidoglycan layer is much thinner and sandwiched between an inner cell membrane and a bacterial outer membrane, causing them to take up the counterstain and appear red or pink. Despite their thicker peptidoglycan layer, gram-positive bacteria are more receptive to certain cell wall targeting antibiotics than gram-negative bacteria, due to the absence of the outer membrane. In general, the following characteristics are present in gram-positive bacteria: Cytoplasmic lipid membrane Thick peptidoglycan layer Teichoic acids and lipoids are present, forming lipoteichoic acids, which serve as chelating agents, for certain types of adherence.
Peptidoglycan chains are cross-linked to form rigid cell walls by a bacterial enzyme DD-transpeptidase. A much smaller volume of periplasm than that in gram-negative bacteria. Only some species have a capsule consisting of polysaccharides. Only some species are flagellates, when they do have flagella, have only two basal body rings to support them, whereas gram-negative have four. Both gram-positive and gram-negative bacteria have a surface layer called an S-layer. In gram-positive bacteria, the S-layer is attached to the peptidoglycan layer. Gram-negative bacteria's S-layer is attached directly to the outer membrane. Specific to gram-positive bacteria is the presence of teichoic acids in the cell wall; some of these are lipoteichoic acids, which have a lipid component in the cell membrane that can assist in anchoring the peptidoglycan. Along with cell shape, Gram staining is a rapid method used to differentiate bacterial species; such staining, together with growth requirement and antibiotic susceptibility testing, other macroscopic and physiologic tests, forms the full basis for classification and subdivision of the bacteria.
The kingdom Monera was divided into four divisions based on Gram staining: Firmicutes, Gracilicutes and Mendocutes. Based on 16S ribosomal RNA phylogenetic studies of the late microbiologist Carl Woese and collaborators and colleagues at the University of Illinois, the monophyly of the gram-positive bacteria was challenged, with major implications for the therapeutic and general study of these organisms. Based on molecular studies of the 16S sequences, Woese recognised twelve bacterial phyla. Two of these were both gram-positive and were divided on the proportion of the guanine and cytosine content in their DNA; the high G + C phylum was made up of the Actinobacteria and the low G + C phylum contained the Firmicutes. The Actinobacteria include the Corynebacterium, Mycobacterium and Streptomyces genera; the Firmicutes, have a 45 -- 60 % GC content. Although bacteria are traditionally divided into two main groups, gram-positive and gram-negative, based on their Gram stain retention property, this classification system is ambiguous as it refers to three distinct aspects, which do not coalesce for some bacterial species.
The gram-positive and gram-negative staining response is not a reliable characteristic as these two kinds of bacteria do not form phylogenetic coherent groups. However, although Gram staining response is an empirical criterion, its basis lies in the marked differences in the ultrastructure and chemical composition of the bacterial cell wall, marked by the absence or presence of an outer lipid membrane. All gram-positive bacteria are bounded by a single-unit lipid membrane, and, in general, they contain a thick layer of peptidoglycan responsible for retaining the Gram stain. A number of other bacteria—that are bounded by a single membrane, but stain gram-negative due to either lack of the peptidoglycan layer, as in the Mycoplasmas, or their inability to retain the Gram stain because of their cell wall composition—also show close relationship to the Gram-positive bacteria. For the bacterial cells bounded by a single cell membrane, the term "monoderm bacteria" or "monoderm prokaryotes" has been proposed.
In contrast to gram-positive bacteria, all archetypical gram-negative bacteria are bounded by a cytoplasmic membrane and an outer cell membrane. The presence of inner and outer cell membranes defines a new compartment in these cells: the periplasmic space or the periplasmic compartment; these bacteria have been designated as "diderm bacteria." The distinction between the monoderm and diderm bacteria is supported by conserved signature indels in a number of important proteins. Of these two structurally distinct groups of bacteria, monoderms are indicated to be ancestral. Based upon a number of observations including that the gram-positive bacteria are the major producers of antibiotics and that, in general, gram-negative bacteria are resistant to them, it h
A bacteriophage known informally as a phage, is a virus that infects and replicates within bacteria and archaea. The term was derived from "bacteria" and the Greek φαγεῖν, "to devour". Bacteriophages are composed of proteins that encapsulate a DNA or RNA genome, may have simple or elaborate structures, their genomes may encode as many as hundreds of genes. Phages replicate within the bacterium following the injection of their genome into its cytoplasm. Bacteriophages are among the most diverse entities in the biosphere. Bacteriophages are ubiquitous viruses, found, it is estimated there are more than 1031 bacteriophages on the planet, more than every other organism on Earth, including bacteria, combined. One of the densest natural sources for phages and other viruses is seawater, where up to 9x108 virions per millilitre have been found in microbial mats at the surface, up to 70% of marine bacteria may be infected by phages, they have been used for over 90 years as an alternative to antibiotics in the former Soviet Union and Central Europe as well as in France.
They are seen as a possible therapy against multi-drug-resistant strains of many bacteria. Phages of Inoviridae have been shown to complicate biofilms involved in pneumonia and cystic fibrosis and shelter the bacteria from drugs meant to eradicate disease, thus promoting persistent infection. Additionally, Inoviridae leave the host cell intact meaning that they can not be used medically anyway. Bacteriophages occur abundantly in the biosphere, with different genomes, lifestyles. Phages are classified by the International Committee on Taxonomy of Viruses according to morphology and nucleic acid. Nineteen families are recognized by the ICTV that infect bacteria and archaea. Of these, only two families have RNA genomes, only five families are surrounded by an envelope. Of the viral families with DNA genomes, only two have single-stranded genomes. Eight of the viral families with DNA genomes have circular genomes. Nine families infect bacteria only, nine infect archaea only, one infects both bacteria and archaea.
It has been suggested that members of Picobirnaviridae infect bacteria, not mammals. In 1896, Ernest Hanbury Hankin reported that something in the waters of the Ganges and Yamuna rivers in India had marked antibacterial action against cholera and could pass through a fine porcelain filter. In 1915, British bacteriologist Frederick Twort, superintendent of the Brown Institution of London, discovered a small agent that infected and killed bacteria, he believed. Twort's work was interrupted by shortage of funding. Independently, French-Canadian microbiologist Félix d'Hérelle, working at the Pasteur Institute in Paris, announced on 3 September 1917, that he had discovered "an invisible, antagonistic microbe of the dysentery bacillus". For d’Hérelle, there was no question as to the nature of his discovery: "In a flash I had understood: what caused my clear spots was in fact an invisible microbe … a virus parasitic on bacteria." D'Hérelle called the virus a bacteria-eater. He recorded a dramatic account of a man suffering from dysentery, restored to good health by the bacteriophages.
It was D'Herelle who conducted much research into bacteriophages and introduced the concept of phage therapy. In 1969, Max Delbrück, Alfred Hershey and Salvador Luria were awarded the Nobel Prize in Physiology or Medicine for their discoveries of the replication of viruses and their genetic structure. Phages were discovered to be antibacterial agents and were used in the former Soviet Republic of Georgia during the 1920s and 1930s for treating bacterial infections, they had widespread use, including treatment of soldiers in the Red Army. However, they were abandoned for general use in the West for several reasons: Antibiotics were discovered and marketed widely, they were easier to store and to prescribe. Medical trials of phages were carried out, but a basic lack of understanding raised questions about the validity of these trials. Publication of research in the Soviet Union was in the Russian or Georgian languages and were not followed internationally for many years; the use of phages has continued since the end of the Cold War in Georgia and elsewhere in Central and Eastern Europe.
The first regulated, double-blind clinical trial was reported in the Journal of Wound Care in June 2009, which evaluated the safety and efficacy of a bacteriophage cocktail to treat infected venous ulcers of the leg in human patients. The FDA approved the study as a Phase I clinical trial; the study's results demonstrated the safety of therapeutic application of bacteriophages but did not show efficacy. The authors explain that the use of certain chemicals that are part of standard wound care may have interfered with bacteriophage viability. Another controlled clinical trial in Western Europe was reported shortly after this in the journal Clinical Otolaryngology in August 2009; the study concludes that bacteriophage preparations were safe and effective for treatment of chronic ear infections in humans. Additionally, there have been numerous animal and other experimental clinical trials evaluating the efficacy of bacteriophages for