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The most well-characterized are enterotoxin (Clostridium difficile toxin A) and cytotoxin (Clostridium difficile toxin B), both of which may produce diarrhea and inflammation in infected people, although their relative contributions have been debated. [20] Toxins A and B are glucosyltransferases that target and inactivate the Rho family of GTPases.
Bezlotoxumab is a human monoclonal antibody designed for the prevention of recurrence of Clostridium difficile infections. By x-ray crystallized structure of N-terminal of TcdB, the toxin is identified to consist of three domains: a glucosyltransferase domain (GTD), a cysteine protease and a combined repetitive oligopeptide (CROP) domain.
Clostridioides difficile infects pigs, calves, and humans, and inhabits a natural reservoir of soil, faeces of domestic animals and humans, sewage, the human intestinal tract, and retail meat. [36] A 2015 CDC study estimated that C. diff afflicted almost half a million Americans and caused 29,000 deaths in 2011. The study estimated that 40% of ...
Clostridioides difficile toxin A (TcdA) is a toxin produced by the bacteria Clostridioides difficile, formerly known as Clostridium difficile. [1] It is similar to Clostridioides difficile Toxin B . The toxins are the main virulence factors produced by the gram positive , anaerobic, [ 2 ] Clostridioides difficile bacteria.
The incidental purging of non-deleterious alleles due to such spatial proximity to deleterious alleles is called background selection. [4] This effect increases with lower mutation rate but decreases with higher recombination rate. [5] Purifying selection can be split into purging by non-random mating (assortative mating) and purging by genetic ...
Natural selection is inherently involved in the process of speciation, whereby, "under ecological speciation, populations in different environments, or populations exploiting different resources, experience contrasting natural selection pressures on the traits that directly or indirectly bring about the evolution of reproductive isolation". [54]
Natural selection can act on specific alleles both directly or indirectly. [ 29 ] [ 22 ] [ 34 ] In direct selection, the frequency of the selected allele is favored to the extreme. In cases where an allele is indirectly selected, its frequency increases due to a different linked allele experiencing selection ( linkage disequilibrium ).
Macroevolution is guided by sorting of interspecific variation ("species selection" [2]), as opposed to sorting of intraspecific variation in microevolution. [3] Species selection may occur as (a) effect-macroevolution, where organism-level traits (aggregate traits) affect speciation and extinction rates, and (b) strict-sense species selection, where species-level traits (e.g. geographical ...