Transposon mutagenesis enables determination of pathways involved in biofilm formation

Transposon mutagenesis is still considered to be an excellent tool for probing the genomics of bacterial species to create gene-silencing mutations. This approach can help elucidate the genetic markers responsible for various bioactivities.

A report by Garavaglia et al. explores the pathway of biosynthetic genes responsible for biofilm formation in the bacterium E. coli MG1655. Using the EZ-Tn5™ <R6Kγori/KAN-2> Transposome, insertional mutants were characterized that allowed the researchers to determine that blocking transcription of the csgDEFG operon in the uridine monophosphate (UMP) biosynthesis pathway inhibits biofilm formation. The transposon mutation was found to be in the carB gene, encoding a subunit of carbamoyl phosphate synthetase, which catalyzes the first step in the de novo pyrimidine nucleotide biosynthetic pathway.

A requirement of biofilm formation is the production of cellulose by E. coli, and this biosynthesis is modulated by the UMP pathway. Mutations in the carB gene also shut down cellulose production, as shown by lack of biofilm formation. Adding back exogenous uracil (which can be converted to UMP through the pyrimidine nucleotide salvage pathway) restored cellulose production and biofilm formation. Thus, the authors conclude that there exist tight links between pyrimidine metabolism and cellulose production/biofilm formation.

Garavaglia, M. et al. (2012). The Pyrimidine Nucleotide Biosynthetic Pathway Modulates Production of Biofilm Determinants in Escherichia coli PLoS ONE, 7 (2) DOI: 10.1371/journal.pone.0031252