Using genomics to track the dissemination of Yersinia pestis strains. Transmission cycle of plague. A useful diagram illustrating the transmission cycle of the plague by Neil Chamberlain “Transmission Cycles of Plague” is available for educational use from microbelibrary.org.
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Using genomics to track the dissemination of Yersinia pestis strains
A useful diagram illustrating the transmission cycle of the plague by Neil Chamberlain “Transmission Cycles of Plague” is available for educational use from microbelibrary.org
Information from Neil Chamberlain “Transmission Cycles of Plague” www.microbelibrary.org
Historic 3 pandemics of plague
-Pandemic is defined as an epidemic that spreads throughout the human population across a large region such as a continent or worldwide
-1st pandemic ~550 A.D. Confined mainly to Africa and some parts of the Middle east
-2nd pandemic originated in Central Asia and spread via trading routes into Europe (Killed ~30-60% of European population)
-3rd pandemic started in 1850’s in China’s Yunnan province and was confined mainly to Asia
-French researcher Paul-Louis Simond postulated a connection between human and rodent plague and identified the flea as a possible vector
-In 1894, in Hong Kong, bacteriologist Alexandre Yersin isolated the responsible bacterium (Yersinia pestis) and determined the common mode of transmission
-A short time later, Japanese physician and researcher Shibasaburo Kitasato independently identified the plague bacillus (after mis-identifying the bacterium at an earlier point).
As of 2010 there are 7 complete and 14 draft Y. pestis genomes
Traditionally the strains are classified as biovars (Antiqua, Mediaevalis, Orientalis, and other) based on the following phenotypic characteristics:
-Antiqua = East Africa: (glycerol positive, arabinose positive, and nitrate positive)
-Mediaevalis = Central Asia: (glycerol positive, arabinose positive, and nitrate negative)
-Orientalis = Central Asia (glycerol negative, arabinose positive, and nitrate positive)
-other (ie Microtus, Pestoides) = not consistent for above phenotypes
-The prefix paleo comes from the Greek work palaios, meaning “ancient”
-Bacterial colonization of dental pulp can occur during bacteremia
-Bacteremia (also known as plague septicaemia with Y. pestis) is the presence of bacteria in the blood
Extraction of bacterial DNA from dental pulp
-Some historians believed that a flu-like virus and not Y. pestis was responsible for the 1st and 2nd pandemics
-DNA detected in dental pulp confirm that Y. pestis was the cause
-Which biovar(s) are most similar to the Y. pestis strain(s) from the dental pulp from the corpses?
-Up regulated in human plasma
Known or putative virulence factors for Y. pestis separated into categories (n=148 genes)
Concepts in this module that you will address:
#1) Mutations that affect the production of a fully functional gene product that has phenotypic consequences (insertions, deletions, single nucleotide polymorphisms [SNP’s]) to study the genes glpD, napA, and araC
#2) Paleomicrobiology investigation: Determine which biovar(s) have the most similar genes to the amplified sequences from the dental pulp of 3 corpses.
#3) Use of genome alignments: Determine an island that is unique to the four genomes for strains that infect humans and is absent in Y. pestis strain 91001.
#4) Determine the conservation of a virulence factor in the five strains in the genome alignment. Determine if it is a fully functional product in strain 91001.