Yersinia pestis genome sequenced

Scientists have extracted Yersinia pestis dna sequences from black death victims from a cementary in the city of london.
The yersinia pestis chromosone is over 4 megabases long.
Yersinia pestis is related to yersinia pseudotuberculosis, an soil living bacteria from which it differs by 2 additional plasmids.
The black death strain of yersinia pestis appears to be the ancestor  of all modern strains infecting humans emerging perhaps around 1340(black death was spreading in europe 1346-1353,spreading from india /china direction )
The black death may have originated from marmots in whom plague bacteria  has been discovered that is similiar to yersinia pestis in humans(indeed yersinia pestis has been called marmot plague in the past).