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Bacillus anthracis

Bacillus anthracis is the agent of anthrax—a common disease of livestock and of humans—and the only obligate pathogen within the genus Bacillus. This disease can be classified as a zoonosis, causing infected animals to transmit the disease to humans. B. anthracis is a Gram-positive, endospore-forming, rod-shaped bacterium, with a width of 1.0–1.2 µm and a length of 3–5 µm. It can be grown in an ordinary nutrient medium under anaerobic conditions, it is one of few bacteria known to synthesize a protein capsule. Like Bordetella pertussis, it forms a calmodulin-dependent adenylate cyclase exotoxin known as anthrax edema factor, along with anthrax lethal factor, it bears close genotypical and phenotypical resemblance to Bacillus cereus and Bacillus thuringiensis. All three species share morphology. All form oval spores located centrally in an unswollen sporangium. B. anthracis endospores, in particular, are resilient, surviving extremes of temperature, low-nutrient environments, harsh chemical treatment over decades or centuries.

The endospore is a dehydrated cell with thick walls and additional layers that form inside the cell membrane. It can remain inactive for many years, but if it comes into a favorable environment, it begins to grow again, it develops inside the rod-shaped form. Features such as the location within the rod, the size and shape of the endospore, whether or not it causes the wall of the rod to bulge out are characteristic of particular species of Bacillus. Depending upon the species, the endospores are round, oval, or cylindrical, they are refractile and contain dipicolinic acid. Electron micrograph sections show they have a thin outer endospore coat, a thick spore cortex, an inner spore membrane surrounding the endospore contents; the endospores resist heat and many disinfectants. Because of these attributes, B. anthracis endospores are extraordinarily well-suited to use as biological weapons. Such weaponization has been accomplished in the past by at least five state bioweapons programs—those of the United Kingdom, the United States and Iraq—and has been attempted by several others.

B. anthracis are rod-shaped bacteria 3 to 5 micrometers long and 1 to 1.2 micrometers wide. When grown in culture, they tend to form long chains of bacteria. On agar plates, they form large colonies several millimeters across that are white or cream colored. Most B. anthracis strains produce a capsule. B. anthracis has a single chromosome, a circular, 5,227,293-bp DNA molecule. It has two circular, double-stranded DNA plasmids, pXO1 and pXO2. Both the pXO1 and pXO2 plasmids are required for full virulence and represent two distinct plasmid families; the pXO1 plasmid contains the genes that encode for the anthrax toxin components: pag and cya. These factors are contained within a 44.8-kb pathogenicity island. The lethal toxin is a combination of PA with LF and the edema toxin is a combination of PA with EF; the PAI contains genes which encode a transcriptional activator AtxA and the repressor PagR, both of which regulate the expression of the anthrax toxin genes. PXO2 encodes a five-gene operon; this capsule allows B. anthracis to evade the host immune system by protecting itself from phagocytosis.

Expression of the capsule operon is activated by the transcriptional regulators AcpA and AcpB, located in the pXO2 pathogenicity island. AcpA and AcpB expression are under the control of AtxA from pXO1; the 89 known strains of B. anthracis include: Sterne strain, used by Max Sterne in his 1930s vaccines Vollum strain weaponized by the US, UK, Iraq. A contributing factor to the reconstruction is B. anthracis being monomorphic, meaning it has low genetic diversity, including the absence of any measurable lateral DNA transfer since its derivation as a species. The lack of diversity is due to a short evolutionary history that has precluded mutational saturation in single nucleotide polymorphisms. A short evolutionary time does not mean a short chronological time; when DNA is replicated, mistakes occur. The buildup of these mutations over time leads to the evolution of a species. During the B. anthracis lifecycle, it spends a significant amount of time in the soil spore reservoir stage, in which DNA replication does not occur.

These prolonged periods of dormancy have reduced the evolutionary rate of the organism. B. anthracis belongs to the B. cereus group consisting of the strains: B. cereus, B. anthracis, B. thuringiensis, B. weihenstephanensis, B. mycoides, B. pseudomycoides. The first three strains are pathogenic or opportunistic to insects or mammals, while the last three

Weston Hills Tunnel

The Weston Hills Tunnel is a 230m twin road tunnel under the Weston Hills near Baldock in Hertfordshire. It was constructed as part of the A505 Baldock bypass. A public inquiry was held in 1995, in 2002 the government granted permission to build the road. Construction started in April 2004 and the bypass and tunnels opened on 16 March 2006 The bypass as a whole, including the tunnel, cost £43 million; the tunnel itself was constructed using a cut and cover method, during which the hill was cut away and the concrete tunnel structure put in place. The hillside was re-filled in over the top - see Bypass Construction Gallery; the purpose of the tunnel at this position is to reduce the gradient of the road, to preserve the visual line of the hills and provide crossing points for wildlife such as deer. The chalk cuttings for the tunnel have become a haven for butterflies which are native to the area

Taekwondo at the 2016 Summer Olympics – Men's 68 kg

The men's 68 kg competition at the 2016 Summer Olympics was held on 18 August, at the Carioca Arena 3. The main bracket consisted of a single elimination tournament; the top eight athletes in each event were seeded so as not to face each other in the preliminary round. The remainder of the qualified athletes were drawn randomly on 15 August 2016. Two bronze medals were awarded at the Taekwondo competitions. A repechage was used to determine the bronze medal winners; every competitor who lost to one of the two finalists competed in the repechage, another single-elimination competition. Each semifinal loser faced the last remaining repechage competitor from the opposite half of the bracket in a bronze medal match. All times are in local time; every practitioner was seeded at the event. LegendPTG – Won by points gap SUD – Won by sudden death WD – Withdrew from contest