The bacterial capsule is a gatekeeper for mobile DNA

Evolution of Virulence, Fitness, and Carbapenem Resistance Transmission in ST23 Hypervirulent Klebsiella pneumoniae with the Capsular Polysaccharide Synthesis Gene wcaJ Inserted via Insertion Sequence Elements

“…Consistent with the previous view that the conjugation rate of the resistance plasmid is higher in isolates lacking capsule barriers ( 31 , 32 ), isolates with lower capsule production owing to wcaJ inactivation in this study exhibited greater conjugation efficiency with respect to the bla KPC-2 plasmid. More alarmingly, isolates with wcaJ interrupted by IS elements demonstrated a lower fitness cost than wcaJ -complemented isolates.…”

Interruption of Capsular Polysaccharide Biosynthesis Gene wbaZ by Insertion Sequence IS 903B Mediates Resistance to a Lytic Phage against ST11 K64 Carbapenem-Resistant Klebsiella pneumoniae

“…In addition to interruption of wbaZ and wcaJ , alterations of several other genes within the capsule gene cluster, including mshA ( 16 ), wcaI ( 25 ), wbaP ( 25 – 27 ), wza ( 28 ), and wzc ( 25 , 26 , 29 ) have also been reported to be able to confer resistance to phages in K. pneumoniae . These findings together with previous reports ( 8 , 30 , 31 ) underscore that alterations in capsule genes, especially glycosyltransferases, are important mechanisms to confer phage resistance in bacterial species ( 7 , 32 ). Transposable elements, in particular insertion sequences, appear to be play a vital role to alter capsule genes by interruption or truncation ( 16 , 33 ), highlighting that the plasticity offered by these elements is an important mechanism for bacteria to enhance the chance of survival in response to the selection pressure imposed by phages ( 7 ).…”