A prokaryote is a unicellular organism that lacks a membrane-bound nucleus, mitochondria, or any other membrane-bound organelle. The word prokaryote comes from the Greek πρό and κάρυον. Prokaryotes are divided into two domains and Bacteria. Species with nuclei and organelles are placed in Eukaryota. Prokaryotes are asexual; the first living organisms are thought to have been prokaryotes. The term prokaryote however is now used informally to refer to bacteria and archaea as in the late 1970s Carl Woese determined that bacteria and archaea were less related than thought. In the prokaryotes, all the intracellular water-soluble components are located together in the cytoplasm enclosed by the cell membrane, rather than in separate cellular compartments. Bacteria, however, do possess protein-based bacterial microcompartments, which are thought to act as primitive organelles enclosed in protein shells; some prokaryotes, such as cyanobacteria, may form large colonies. Others, such as myxobacteria, have multicellular stages in their life cycles.
Molecular studies have provided insight into the evolution and interrelationships of the three domains of biological species. Eukaryotes are organisms, including humans, whose cells have a well defined membrane-bound nucleus and organelles; the division between prokaryotes and eukaryotes reflects the existence of two different levels of cellular organization. Distinctive types of prokaryotes include methanogens; the division between prokaryotes and eukaryotes was established by the microbiologists Roger Stanier and C. B. van Niel in their 1962 paper The concept of a bacterium. That paper cites Édouard Chatton's 1937 book Titres et Travaux Scientifiques for using those terms and recognizing the distinction. One reason for this classification was so that what was often called blue-green algae would not be classified as plants but grouped with bacteria. Prokaryotes have a prokaryotic cytoskeleton, more primitive than that of the eukaryotes. Besides homologues of actin and tubulin, the helically arranged building-block of the flagellum, flagellin, is one of the most significant cytoskeletal proteins of bacteria, as it provides structural backgrounds of chemotaxis, the basic cell physiological response of bacteria.
At least some prokaryotes contain intracellular structures that can be seen as primitive organelles. Membranous organelles are known in some groups of prokaryotes, such as vacuoles or membrane systems devoted to special metabolic properties, such as photosynthesis or chemolithotrophy. In addition, some species contain carbohydrate-enclosed microcompartments, which have distinct physiological roles. Most prokaryotes are between 1 µm and 10 µm. Prokaryotic cells have various shapes. E.g. Streptococcus, Staphylococcus. Bacilli – A bacterium with cylindrical shape called rod or a bacillus. Spiral bacteria – Some rods twist into spiral shapes and are called spirilla. Vibrio – comma-shapedThe archaeon Haloquadratum has flat square-shaped cells. Bacteria and archaea reproduce through asexual reproduction by binary fission. Genetic exchange and recombination still occur, but this is a form of horizontal gene transfer and is not a replicative process involving the transference of DNA between two cells, as in bacterial conjugation.
DNA transfer between prokaryotic cells occurs in bacteria and archaea, although it has been studied in bacteria. In bacteria, gene transfer occurs by three processes; these are bacterial virus -mediated transduction, plasmid-mediated conjugation, natural transformation. Transduction of bacterial genes by bacteriophage appears to reflect an occasional error during intracellular assembly of virus particles, rather than an adaptation of the host bacteria; the transfer of bacterial DNA is under the control of the bacteriophage's genes rather than bacterial genes. Conjugation in the well-studied E. coli system is controlled by plasmid genes, is an adaptation for distributing copies of a plasmid from one bacterial host to another. Infrequently during this process, a plasmid may integrate into the host bacterial chromosome, subsequently transfer part of the host bacterial DNA to another bacterium. Plasmid mediated transfer of host bacterial DNA appears to be an accidental process rather than a bacterial adaptation.
Natural bacterial transformation involves the transfer of DNA from one bacterium to another through the intervening medium. Unlike transduction and conjugation, transformation is a bacterial adaptation for DNA transfer, because it depends on numerous bacterial gene products that interact to perform this complex process. For a bacterium to bind, take up and recombine donor DNA into its own chromosome, it must first enter a special physiological state called competence. About 40 genes are required in Bacillus subtilis for the development of competence; the length of DNA transferred during B. subtilis transformation can be as much as a third to the whole chromosome. Transformation is a common mode of DNA transfer, 67 prokaryotic species are thus far known to be competent for transformation. Among archaea, Halobacteri
The Ministry of Aviation, abbreviated RLM, was a government department during the period of Nazi Germany. It is the original name of the Detlev-Rohwedder-Haus building on the Wilhelmstrasse in central Berlin, which today houses the German Finance Ministry; the Ministry was in charge of development and production of all aircraft developed and built in Germany during the existence of the Third Reich, overseeing all matters concerning both military and civilian designs — it handled military aviation matters as its top priority for the Luftwaffe. As was characteristic of government departments in the Nazi era, the Ministry was personality-driven and formal procedures were ignored in favour of the whims of the Minister, Reichsmarschall Hermann Göring; as a result, early successes in aircraft development progressed only and erratically during World War II. The Ministry was formed in April 1933 from the Reich Commissariat for Aviation, established two months earlier with Göring at its head. In this early phase the Ministry was little more than Göring's personal staff.
One of its first actions was to requisition control of all patents and companies of Hugo Junkers and Richard Wolfgang the German aeronautical engineer. These included all rights to the Junkers Ju 52 aircraft. Defence Minister General Werner von Blomberg decided that the importance of aviation was such that it should no longer be subordinate to the German Army. In May 1933 he transferred the army's Department of Military Aviation, to the Ministry; this is considered the birth of the Luftwaffe. The Ministry was now much larger, consisting of two large departments: the military Luftschutzamt and the civilian Allgemeines Luftamt. Erhard Milch, the former head of Deutsche Luft Hansa, was placed in direct control of the LA, in his function as Secretary of State for Aviation. In September 1933, a reorganization was undertaken to reduce duplication of effort between departments; the primary changes were to move the staffing and technical development organizations out of the LB, make them full departments on their own.
The result was a collection of six: Luftkommandoamt, Allgemeines Luftamt, Technisches Amt in charge of all research and development, but having no clear way of receiving and acting on requests from front-line combat personnel of the Luftwaffe during the war years, to improve their aviation and weapons technology as a "technical-tactical" department would do in other nations' military aviation bureaus, the Luftwaffenverwaltungsamt for construction, Luftwaffenpersonalamt for training and staffing, the Zentralabteilung, central command. In 1934, an additional department was added, the Luftzeugmeister in charge of logistics. With the rapid growth of the Luftwaffe following the outbreak of World War II in 1939, the Ministry grew so large that Göring was no longer able to maintain control; this period was marked by an increasing inability to deliver the new aircraft designs that were needed, as well as continued shortages of aircraft and engines. In 1943 Albert Speer took over from Milch, things improved.
Production reached their highest levels in 1943 and 1944, though Speer introduced the same measures of self-regulation that he had introduced in other areas of industry, tried to take credit for the so-called Armaments Miracle, contemporary German statistics show that the real reason for increased production were measures and investments made by Milch and his staff in 1941 and 1942. Though German aircraft production had caught up with that of the Soviet Union in 1944, it collapsed in 1945; the RLM never overcame the shortage of raw materials and fuel supply, lack of experienced pilots and deficits in technology and know-how that had handicapped it since the beginning of the war. The Ministry building was one of the few public edifices in central Berlin to survive the severe Allied bombings in 1944–45. On 5 May 1933 the German Air Ministry, with Hermann Göring as Reich Minister for Aviation was founded; this event came along with the introduction of a command flag, produced in different sizes, ranging from 200 to 30 cm.
The flag consisted of bright red material on, placed in the centre of the obverse a wreath of silver coloured laurel leaves. In the centre of the leaves was a black eagle. Suspended from the base of the wreath was a true-coloured representation of the "Pour le Mérite". Extending from the left and right side of the wreath were a pair of stylised wings each consisting of four ascending "feathers". Extending from the wreath towards the four corners of the flag were four black-edged white inactive wedges, a feature, to be incorporated in the design of the future unit Colours of the new Luftwaffe. In each of the four corners was set a black swastika; the reverse looked the same as the obverse but a black swastika replaced the eagle and eagles replaced the four swastikas. The flag was in use until the end of 1935. On 26 February 1935 Hitler created the Luftwaffe with Hermann Göring as its Commander-in-Chief. Late in 1935 a flag was instituted; the flag was similar to some extent to that used before. The differences of the obverse were that now there was placed in the centre a gold swastika and instead of the four black swastikas four golden Luftwaffe eagles were added.
The wings were left out. Moreover, the flag was edged on all four sides with a gold-braided border, which incorporated a row of 76 small
Dora Valesca Becker was an American violinist. In 1898, she became the first female violinist to play on a musical recording. Dora Valesca Becker was born in Galveston and raised in New York, the daughter of Francis Louis Becker and Maria Antonia Tekla Langhammer, her father was conductor of the Galveston Singing Society, her mother had musical ambitions. She studied violin from an early age with Sam Franko and made her first appearance at Steinway Hall in 1880, aged 10 years, she studied with Joseph Joachim in Berlin on a Felix Mendelssohn scholarship. Her brother Gustav Louis Becker was a pianist and arranger. Becker returned to the United States after making her debut with the Berlin Philharmonic in 1890, began the New York Ladies' Trio with pianist Mabel Phipps and cellist Flavie Van den Hende, she became the first woman violinist to play on a musical recording in 1898, when she performed Henryk Wieniawski's "Mazurka Kujawiak" for a Bettini Phonograph Laboratory wax cylinder recording. She left the concert stage in 1899, except for occasional accompaniment appearances and recitals.
She traveled and played in Europe in 1908. After marriage, she lectured and taught music in New York and New Jersey, was a member of the New York State Teachers' Association, the Newark Musicians' Club, the Newark Contemporary Club. In 1899, Becker married organist Charles Grant Schaffer, she died in 1958, aged 88 years, in Pennsylvania. Dora Valesca Becker at Find a Grave