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Tucson is known for being a trailblazer in voluntary partial publicly financed campaigns. Since 1985, both mayoral and council candidates have been eligible to receive matching public funds from the city. To become eligible, council candidates must receive 200 donations of $10 or more (300 for a mayoral candidate). Can...
Tucson has one daily newspaper, the morning Arizona Daily Star. Wick Communications publishes the daily legal paper The Daily Territorial, while Boulder, Colo.-based 10/13 Communications publishes Tucson Weekly (an "alternative" publication), Inside Tucson Business and the Explorer. TucsonSentinel.com is a nonprofit in...
The Tucson metro area is served by many local television stations and is the 68th largest designated market area (DMA) in the U.S. with 433,310 homes (0.39% of the total U.S.). It is limited to the three counties of southeastern Arizona (Pima, Santa Cruz, and Cochise) The major television networks serving Tucson are: K...
Tucson's primary electrical power source is a coal and natural gas power-plant managed by Tucson Electric Power that is situated within the city limits on the south-western boundary of Davis-Monthan Air-force base adjacent to Interstate-10. The air pollution generated has raised some concerns as the Sundt operating sta...
Perhaps the biggest sustainability problem in Tucson, with its high desert climate, is potable water supply. The state manages all water in Arizona through its Arizona Department of Water Resources (ADWR). The primary consumer of water is Agriculture (including golf courses), which consumes about 69% of all water. Muni...
In an effort to conserve water, Tucson is recharging groundwater supplies by running part of its share of CAP water into various open portions of local rivers to seep into their aquifer. Additional study is scheduled to determine the amount of water that is lost through evaporation from the open areas, especially durin...
To prevent further loss of groundwater, Tucson has been involved in water conservation and groundwater preservation efforts, shifting away from its reliance on a series of Tucson area wells in favor of conservation, consumption-based pricing for residential and commercial water use, and new wells in the more sustainabl...
Tucson's Sun Tran bus system serves greater Tucson with standard, express, regional shuttle, and on-demand shuttle bus service. It was awarded Best Transit System in 1988 and 2005. A 3.9-mile streetcar line, Sun Link, connects the University of Arizona campus with 4th Avenue, downtown, and the Mercado District west of ...
Cycling is popular in Tucson due to its flat terrain and dry climate. Tucson and Pima County maintain an extensive network of marked bike routes, signal crossings, on-street bike lanes, mountain-biking trails, and dedicated shared-use paths. The Loop is a network of seven linear parks comprising over 100 mi (160 km) of...
Armenia is a unitary, multi-party, democratic nation-state with an ancient cultural heritage. Urartu was established in 860 BC and by the 6th century BC it was replaced by the Satrapy of Armenia. In the 1st century BC the Kingdom of Armenia reached its height under Tigranes the Great. Armenia became the first state in ...
Between the 16th century and 19th century, the traditional Armenian homeland composed of Eastern Armenia and Western Armenia came under the rule of the Ottoman and successive Iranian empires, repeatedly ruled by either of the two over the centuries. By the 19th century, Eastern Armenia had been conquered by the Russian...
The exonym Armenia is attested in the Old Persian Behistun Inscription (515 BC) as Armina ( ). The ancient Greek terms Ἀρμενία (Armenía) and Ἀρμένιοι (Arménioi, "Armenians") are first mentioned by Hecataeus of Miletus (c. 550 BC – c. 476 BC). Xenophon, a Greek general serving in some of the Persian expeditions, describ...
Several bronze-era states flourished in the area of Greater Armenia, including the Hittite Empire (at the height of its power), Mitanni (South-Western historical Armenia), and Hayasa-Azzi (1500–1200 BC). The Nairi people (12th to 9th centuries BC) and the Kingdom of Urartu (1000–600 BC) successively established their s...
During the late 6th century BC, the first geographical entity that was called Armenia by neighboring populations was established under the Orontid Dynasty within the Achaemenid Empire, as part of the latters' territories. The kingdom became fully sovereign from the sphere of influence of the Seleucid Empire in 190 BC u...
In the next centuries, Armenia was in the Persian Empire's sphere of influence during the reign of Tiridates I, the founder of the Arsacid dynasty of Armenia, which itself was a branch of the eponymous Arsacid dynasty of Parthia. Throughout its history, the kingdom of Armenia enjoyed both periods of independence and pe...
After the Marzpanate period (428–636), Armenia emerged as the Emirate of Armenia, an autonomous principality within the Arabic Empire, reuniting Armenian lands previously taken by the Byzantine Empire as well. The principality was ruled by the Prince of Armenia, and recognized by the Caliph and the Byzantine Emperor. I...
In 1045, the Byzantine Empire conquered Bagratid Armenia. Soon, the other Armenian states fell under Byzantine control as well. The Byzantine rule was short lived, as in 1071 Seljuk Turks defeated the Byzantines and conquered Armenia at the Battle of Manzikert, establishing the Seljuk Empire. To escape death or servitu...
The Seljuk Empire soon started to collapse. In the early 12th century, Armenian princes of the Zakarid noble family drove out the Seljuk Turks and established a semi-independent Armenian principality in Northern and Eastern Armenia, known as Zakarid Armenia, which lasted under the patronage of the Georgian Kingdom. The...
In the 16th century, the Ottoman Empire and Safavid Empire divided Armenia. From the early 16th century, both Western Armenia and Eastern Armenia fell under Iranian Safavid rule. Owing to the century long Turco-Iranian geo-political rivalry that would last in Western Asia, significant parts of the region were frequentl...
While Western Armenia still remained under Ottoman rule, the Armenians were granted considerable autonomy within their own enclaves and lived in relative harmony with other groups in the empire (including the ruling Turks). However, as Christians under a strict Muslim social system, Armenians faced pervasive discrimina...
During the 1890s, the Armenian Revolutionary Federation, commonly known as Dashnaktsutyun, became active within the Ottoman Empire with the aim of unifying the various small groups in the empire that were advocating for reform and defending Armenian villages from massacres that were widespread in some of the Armenian-p...
The Ottoman Empire began to collapse, and in 1908, the Young Turk Revolution overthrew the government of Sultan Hamid. In April 1909, the Adana massacre occurred in the Adana Vilayet of the Ottoman Empire resulting in the deaths of as many as 20,000–30,000 Armenians. The Armenians living in the empire hoped that the Co...
When World War I broke out leading to confrontation between the Ottoman Empire and the Russian Empire in the Caucasus and Persian Campaigns, the new government in Istanbul began to look on the Armenians with distrust and suspicion. This was because the Imperial Russian Army contained a contingent of Armenian volunteers...
The genocide was implemented in two phases: the wholesale killing of the able-bodied male population through massacre and subjection of army conscripts to forced labour, followed by the deportation of women, children, the elderly and infirm on death marches leading to the Syrian desert. Driven forward by military escor...
Turkish authorities deny the genocide took place to this day. The Armenian Genocide is acknowledged to have been one of the first modern genocides. According to the research conducted by Arnold J. Toynbee, an estimated 600,000 Armenians died during deportation from 1915–16). This figure, however, accounts for solely th...
Although the Russian Caucasus Army of Imperial forces commanded by Nikolai Yudenich and Armenians in volunteer units and Armenian militia led by Andranik Ozanian and Tovmas Nazarbekian succeeded in gaining most of Ottoman Armenia during World War I, their gains were lost with the Bolshevik Revolution of 1917.[citation ...
At the end of the war, the victorious powers sought to divide up the Ottoman Empire. Signed between the Allied and Associated Powers and Ottoman Empire at Sèvres on 10 August 1920, the Treaty of Sèvres promised to maintain the existence of the Armenian republic and to attach the former territories of Ottoman Armenia to...
In 1920, Turkish nationalist forces invaded the fledgling Armenian republic from the east. Turkish forces under the command of Kazım Karabekir captured Armenian territories that Russia had annexed in the aftermath of the 1877–1878 Russo-Turkish War and occupied the old city of Alexandropol (present-day Gyumri). The vio...
Armenia was annexed by Bolshevist Russia and along with Georgia and Azerbaijan, it was incorporated into the Soviet Union as part of the Transcaucasian SFSR (TSFSR) on 4 March 1922. With this annexation, the Treaty of Alexandropol was superseded by the Turkish-Soviet Treaty of Kars. In the agreement, Turkey allowed the...
The TSFSR existed from 1922 to 1936, when it was divided up into three separate entities (Armenian SSR, Azerbaijan SSR, and Georgian SSR). Armenians enjoyed a period of relative stability under Soviet rule. They received medicine, food, and other provisions from Moscow, and communist rule proved to be a soothing balm i...
Fears decreased when Stalin died in 1953 and Nikita Khruschev emerged as the Soviet Union's new leader. Soon, life in Soviet Armenia began to see rapid improvement. The church, which suffered greatly under Stalin, was revived when Catholicos Vazgen I assumed the duties of his office in 1955. In 1967, a memorial to the ...
During the Gorbachev era of the 1980s, with the reforms of Glasnost and Perestroika, Armenians began to demand better environmental care for their country, opposing the pollution that Soviet-built factories brought. Tensions also developed between Soviet Azerbaijan and its autonomous district of Nagorno-Karabakh, a maj...
Gorbachev's inability to alleviate any of Armenia's problems created disillusionment among the Armenians and fed a growing hunger for independence. In May 1990, the New Armenian Army (NAA) was established, serving as a defence force separate from the Soviet Red Army. Clashes soon broke out between the NAA and Soviet In...
Further firefights between Armenian militiamen and Soviet troops occurred in Sovetashen, near the capital and resulted in the deaths of over 26 people, mostly Armenians. The pogrom of Armenians in Baku in January 1990 forced almost all of the 200,000 Armenians in the Azerbaijani capital Baku to flee to Armenia. On 17 M...
Ter-Petrosyan led Armenia alongside Defense Minister Vazgen Sargsyan through the Nagorno-Karabakh War with neighboring Azerbaijan. The initial post-Soviet years were marred by economic difficulties, which had their roots early in the Karabakh conflict when the Azerbaijani Popular Front managed to pressure the Azerbaija...
The Karabakh war ended after a Russian-brokered cease-fire was put in place in 1994. The war was a success for the Karabakh Armenian forces who managed to capture 16% of Azerbaijan's internationally recognised territory including Nagorno-Karabakh itself. Since then, Armenia and Azerbaijan have held peace talks, mediate...
International observers of Council of Europe and US Department of State have questioned the fairness of Armenia's parliamentary and presidential elections and constitutional referendum since 1995, citing polling deficiencies, lack of cooperation by the Electoral Commission, and poor maintenance of electoral lists and p...
Armenia presently maintains good relations with almost every country in the world, with two major exceptions being its immediate neighbours, Turkey and Azerbaijan. Tensions were running high between Armenians and Azerbaijanis during the final years of the Soviet Union. The Nagorno-Karabakh War dominated the region's po...
Turkey also has a long history of poor relations with Armenia over its refusal to acknowledge the Armenian Genocide. Turkey was one of the first countries to recognize the Republic of Armenia (the 3rd republic) after its independence from the USSR in 1991. Despite this, for most of the 20th century and early 21st centu...
On 10 October 2009, Armenia and Turkey signed protocols on normalisation of relationships, which set a timetable for restoring diplomatic ties and reopening their joint border. The ratification of those had to be made in the national parliaments. In Armenia it passed through the required by legislation approval of the ...
Due to its position between two unfriendly neighbours, Armenia has close security ties with Russia. At the request of the Armenian government, Russia maintains a military base in the northwestern Armenian city of Gyumri as a deterrent against Turkey.[citation needed] Despite this, Armenia has also been looking toward E...
Armenia is also a member of the Council of Europe, maintaining friendly relations with the European Union, especially with its member states such as France and Greece. A 2005 survey reported that 64% of Armenia's population would be in favor of joining the EU. Several Armenian officials have also expressed the desire f...
The Armenian Army, Air Force, Air Defence, and Border Guard comprise the four branches of the Armed Forces of the Republic of Armenia. The Armenian military was formed after the collapse of the Soviet Union in 1991 and with the establishment of the Ministry of Defence in 1992. The Commander-in-Chief of the military is ...
Armenia is member of Collective Security Treaty Organisation (CSTO) along with Belarus, Kazakhstan, Kyrgyzstan, Russia, Tajikistan and Uzbekistan. It participates in NATO's Partnership for Peace (PiP) program and is in a NATO organisation called Euro-Atlantic Partnership Council (EAPC). Armenia has engaged in a peaceke...
Within each province are communities (hamaynkner, singular hamaynk). Each community is self-governing and consists of one or more settlements (bnakavayrer, singular bnakavayr). Settlements are classified as either towns (kaghakner, singular kaghak) or villages (gyugher, singular gyugh). As of 2007[update], Armenia incl...
The economy relies heavily on investment and support from Armenians abroad. Before independence, Armenia's economy was largely industry-based – chemicals, electronics, machinery, processed food, synthetic rubber, and textile – and highly dependent on outside resources. The republic had developed a modern industrial sec...
Agriculture accounted for less than 20% of both net material product and total employment before the dissolution of the Soviet Union in 1991. After independence, the importance of agriculture in the economy increased markedly, its share at the end of the 1990s rising to more than 30% of GDP and more than 40% of total e...
Like other newly independent states of the former Soviet Union, Armenia's economy suffers from the breakdown of former Soviet trading patterns. Soviet investment in and support of Armenian industry has virtually disappeared, so that few major enterprises are still able to function. In addition, the effects of the 1988 ...
Nevertheless, the government was able to make wide-ranging economic reforms that paid off in dramatically lower inflation and steady growth. The 1994 cease-fire in the Nagorno-Karabakh conflict has also helped the economy. Armenia has had strong economic growth since 1995, building on the turnaround that began the prev...
This steady economic progress has earned Armenia increasing support from international institutions. The International Monetary Fund (IMF), World Bank, European Bank for Reconstruction and Development (EBRD), and other international financial institutions (IFIs) and foreign countries are extending considerable grants a...
A liberal foreign investment law was approved in June 1994, and a law on privatisation was adopted in 1997, as well as a program of state property privatisation. Continued progress will depend on the ability of the government to strengthen its macroeconomic management, including increasing revenue collection, improving...
In the 1988–89 school year, 301 students per 10,000 population were in specialized secondary or higher education, a figure slightly lower than the Soviet average. In 1989 some 58% of Armenians over age fifteen had completed their secondary education, and 14% had a higher education. In the 1990–91 school year, the estim...
On the basis of the expansion and development of Yerevan State University a number of higher educational independent Institutions were formed including Medical Institute separated in 1930 which was set up on the basis of medical faculty. In 1980 Yerevan State Medical University was awarded one of the main rewards of th...
Foreign students' department for Armenian diaspora established in 1957 later was enlarged and the enrollment of foreign students began. Nowadays the YSMU is a Medical Institution corresponding to international requirements, trains medical staff for not only Armenia and neighbor countries, i.e. Iran, Syria, Lebanon, Geo...
Other educational institutions in Armenia include the American University of Armenia and the QSI International School of Yerevan. The American University of Armenia has graduate programs in Business and Law, among others. The institution owes its existence to the combined efforts of the Government of Armenia, the Armen...
Instruments like the duduk, the dhol, the zurna, and the kanun are commonly found in Armenian folk music. Artists such as Sayat Nova are famous due to their influence in the development of Armenian folk music. One of the oldest types of Armenian music is the Armenian chant which is the most common kind of religious mus...
The Armenian Genocide caused widespread emigration that led to the settlement of Armenians in various countries in the world. Armenians kept to their traditions and certain diasporans rose to fame with their music. In the post-Genocide Armenian community of the United States, the so-called "kef" style Armenian dance mu...
Richard Hagopian is perhaps the most famous artist of the traditional "kef" style and the Vosbikian Band was notable in the 1940s and 1950s for developing their own style of "kef music" heavily influenced by the popular American Big Band Jazz of the time. Later, stemming from the Middle Eastern Armenian diaspora and in...
Other Armenian diasporans that rose to fame in classical or international music circles are world-renowned French-Armenian singer and composer Charles Aznavour, pianist Sahan Arzruni, prominent opera sopranos such as Hasmik Papian and more recently Isabel Bayrakdarian and Anna Kasyan. Certain Armenians settled to sing ...
Yerevan Vernissage (arts and crafts market), close to Republic Square, bustles with hundreds of vendors selling a variety of crafts on weekends and Wednesdays (though the selection is much reduced mid-week). The market offers woodcarving, antiques, fine lace, and the hand-knotted wool carpets and kilims that are a Cauc...
The National Art Gallery in Yerevan has more than 16,000 works that date back to the Middle Ages, which indicate Armenia's rich tales and stories of the times. It houses paintings by many European masters as well. The Modern Art Museum, the Children’s Picture Gallery, and the Martiros Saryan Museum are only a few of th...
A wide array of sports are played in Armenia, the most popular among them being wrestling, weightlifting, judo, association football, chess, and boxing. Armenia's mountainous terrain provides great opportunities for the practice of sports like skiing and climbing. Being a landlocked country, water sports can only be pr...
Prior to 1992, Armenians would participate in the Olympics representing the USSR. As part of the Soviet Union, Armenia was very successful, winning plenty of medals and helping the USSR win the medal standings at the Olympics on numerous occasions. The first medal won by an Armenian in modern Olympic history was by Hra...
Football is also popular in Armenia. The most successful team was the FC Ararat Yerevan team of the 1970s who won the Soviet Cup in 1973 and 1975 and the Soviet Top League in 1973. The latter achievement saw FC Ararat gain entry to the European Cup where – despite a home victory in the second leg – they lost on aggrega...
Due to the lack of success lately on the international level, in recent years, Armenia has rebuilt 16 Soviet-era sports schools and furnished them with new equipment for a total cost of $1.9 million. The rebuilding of the regional schools was financed by the Armenian government. $9.3 million has been invested in the re...
Armenian cuisine is as ancient as the history of Armenia, a combination of different tastes and aromas. The food often has quite a distinct aroma. Closely related to eastern and Mediterranean cuisine, various spices, vegetables, fish, and fruits combine to present unique dishes. The main characteristics of Armenian cui...
Bacteria (i/bækˈtɪəriə/; singular: bacterium) constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. ...
There are typically 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water. There are approximately 5×1030 bacteria on Earth, forming a biomass which exceeds that of all plants and animals. Bacteria are vital in recycling nutrients, with many of the stages in nutrient ...
There are approximately ten times as many bacterial cells in the human flora as there are human cells in the body, with the largest number of the human flora being in the gut flora, and a large number on the skin. The vast majority of the bacteria in the body are rendered harmless by the protective effects of the immun...
Once regarded as plants constituting the class Schizomycetes, bacteria are now classified as prokaryotes. Unlike cells of animals and other eukaryotes, bacterial cells do not contain a nucleus and rarely harbour membrane-bound organelles. Although the term bacteria traditionally included all prokaryotes, the scientific...
The ancestors of modern bacteria were unicellular microorganisms that were the first forms of life to appear on Earth, about 4 billion years ago. For about 3 billion years, most organisms were microscopic, and bacteria and archaea were the dominant forms of life. In 2008, fossils of macroorganisms were discovered and n...
Bacteria display a wide diversity of shapes and sizes, called morphologies. Bacterial cells are about one-tenth the size of eukaryotic cells and are typically 0.5–5.0 micrometres in length. However, a few species are visible to the unaided eye — for example, Thiomargarita namibiensis is up to half a millimetre long and...
Most bacterial species are either spherical, called cocci (sing. coccus, from Greek kókkos, grain, seed), or rod-shaped, called bacilli (sing. bacillus, from Latin baculus, stick). Elongation is associated with swimming. Some bacteria, called vibrio, are shaped like slightly curved rods or comma-shaped; others can be s...
Many bacterial species exist simply as single cells, others associate in characteristic patterns: Neisseria form diploids (pairs), Streptococcus form chains, and Staphylococcus group together in "bunch of grapes" clusters. Bacteria can also be elongated to form filaments, for example the Actinobacteria. Filamentous bac...
Bacteria often attach to surfaces and form dense aggregations called biofilms or bacterial mats. These films can range from a few micrometers in thickness to up to half a meter in depth, and may contain multiple species of bacteria, protists and archaea. Bacteria living in biofilms display a complex arrangement of cell...
Even more complex morphological changes are sometimes possible. For example, when starved of amino acids, Myxobacteria detect surrounding cells in a process known as quorum sensing, migrate toward each other, and aggregate to form fruiting bodies up to 500 micrometres long and containing approximately 100,000 bacterial...
The bacterial cell is surrounded by a cell membrane (also known as a lipid, cytoplasmic or plasma membrane). This membrane encloses the contents of the cell and acts as a barrier to hold nutrients, proteins and other essential components of the cytoplasm within the cell. As they are prokaryotes, bacteria do not usually...
Many important biochemical reactions, such as energy generation, use concentration gradients across membranes. The general lack of internal membranes in bacteria means reactions such as electron transport occur across the cell membrane between the cytoplasm and the periplasmic space. However, in many photosynthetic bac...
Bacteria do not have a membrane-bound nucleus, and their genetic material is typically a single circular DNA chromosome located in the cytoplasm in an irregularly shaped body called the nucleoid. The nucleoid contains the chromosome with its associated proteins and RNA. The phylum Planctomycetes and candidate phylum Po...
Some bacteria produce intracellular nutrient storage granules for later use, such as glycogen, polyphosphate, sulfur or polyhydroxyalkanoates. Certain bacterial species, such as the photosynthetic Cyanobacteria, produce internal gas vesicles, which they use to regulate their buoyancy – allowing them to move up or down ...
In most bacteria, a cell wall is present on the outside of the cell membrane. The cell membrane and cell wall comprise the cell envelope. A common bacterial cell wall material is peptidoglycan (called "murein" in older sources), which is made from polysaccharide chains cross-linked by peptides containing D-amino acids....
Gram-positive bacteria possess a thick cell wall containing many layers of peptidoglycan and teichoic acids. In contrast, gram-negative bacteria have a relatively thin cell wall consisting of a few layers of peptidoglycan surrounded by a second lipid membrane containing lipopolysaccharides and lipoproteins. Lipopolysac...
Acid-fast bacteria, such as Mycobacteria, are resistant to decolorization by acids during staining procedures. The high mycolic acid content of Mycobacteria, is responsible for the staining pattern of poor absorption followed by high retention. The most common staining technique used to identify acid-fast bacteria is t...
Fimbriae (sometimes called "attachment pili") are fine filaments of protein, usually 2–10 nanometres in diameter and up to several micrometers in length. They are distributed over the surface of the cell, and resemble fine hairs when seen under the electron microscope. Fimbriae are believed to be involved in attachment...
Certain genera of Gram-positive bacteria, such as Bacillus, Clostridium, Sporohalobacter, Anaerobacter, and Heliobacterium, can form highly resistant, dormant structures called endospores. In almost all cases, one endospore is formed and this is not a reproductive process, although Anaerobacter can make up to seven end...
Endospores show no detectable metabolism and can survive extreme physical and chemical stresses, such as high levels of UV light, gamma radiation, detergents, disinfectants, heat, freezing, pressure, and desiccation. In this dormant state, these organisms may remain viable for millions of years, and endospores even all...
Bacteria exhibit an extremely wide variety of metabolic types. The distribution of metabolic traits within a group of bacteria has traditionally been used to define their taxonomy, but these traits often do not correspond with modern genetic classifications. Bacterial metabolism is classified into nutritional groups on...
Carbon metabolism in bacteria is either heterotrophic, where organic carbon compounds are used as carbon sources, or autotrophic, meaning that cellular carbon is obtained by fixing carbon dioxide. Heterotrophic bacteria include parasitic types. Typical autotrophic bacteria are phototrophic cyanobacteria, green sulfur-b...
Bacteria are further divided into lithotrophs that use inorganic electron donors and organotrophs that use organic compounds as electron donors. Chemotrophic organisms use the respective electron donors for energy conservation (by aerobic/anaerobic respiration or fermentation) and biosynthetic reactions (e.g., carbon d...
These processes are also important in biological responses to pollution; for example, sulfate-reducing bacteria are largely responsible for the production of the highly toxic forms of mercury (methyl- and dimethylmercury) in the environment. Non-respiratory anaerobes use fermentation to generate energy and reducing pow...
Lithotrophic bacteria can use inorganic compounds as a source of energy. Common inorganic electron donors are hydrogen, carbon monoxide, ammonia (leading to nitrification), ferrous iron and other reduced metal ions, and several reduced sulfur compounds. In unusual circumstances, the gas methane can be used by methanotr...
Regardless of the type of metabolic process they employ, the majority of bacteria are able to take in raw materials only in the form of relatively small molecules, which enter the cell by diffusion or through molecular channels in cell membranes. The Planctomycetes are the exception (as they are in possessing membranes...
Unlike in multicellular organisms, increases in cell size (cell growth) and reproduction by cell division are tightly linked in unicellular organisms. Bacteria grow to a fixed size and then reproduce through binary fission, a form of asexual reproduction. Under optimal conditions, bacteria can grow and divide extremely...
In the laboratory, bacteria are usually grown using solid or liquid media. Solid growth media, such as agar plates, are used to isolate pure cultures of a bacterial strain. However, liquid growth media are used when measurement of growth or large volumes of cells are required. Growth in stirred liquid media occurs as a...
Most laboratory techniques for growing bacteria use high levels of nutrients to produce large amounts of cells cheaply and quickly. However, in natural environments, nutrients are limited, meaning that bacteria cannot continue to reproduce indefinitely. This nutrient limitation has led the evolution of different growth...
Bacterial growth follows four phases. When a population of bacteria first enter a high-nutrient environment that allows growth, the cells need to adapt to their new environment. The first phase of growth is the lag phase, a period of slow growth when the cells are adapting to the high-nutrient environment and preparing...
Most bacteria have a single circular chromosome that can range in size from only 160,000 base pairs in the endosymbiotic bacteria Candidatus Carsonella ruddii, to 12,200,000 base pairs in the soil-dwelling bacteria Sorangium cellulosum. Spirochaetes of the genus Borrelia are a notable exception to this arrangement, wit...
Bacteria, as asexual organisms, inherit identical copies of their parent's genes (i.e., they are clonal). However, all bacteria can evolve by selection on changes to their genetic material DNA caused by genetic recombination or mutations. Mutations come from errors made during the replication of DNA or from exposure to...
Transduction of bacterial genes by bacteriophage appears to be a consequence of infrequent errors during intracellular assembly of virus particles, rather than a bacterial adaptation. Conjugation, in the much-studied E. coli system is determined by plasmid genes, and is an adaptation for transferring copies of the plas...
Transformation, unlike transduction or conjugation, depends on numerous bacterial gene products that specifically interact to perform this complex process, and thus transformation is clearly a bacterial adaptation for DNA transfer. In order for a bacterium to bind, take up and recombine donor DNA into its own chromosom...

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