Identifying mutants of Haemophilus parainfluenzae that contribute to biofilm formation 

Kiana Cabana


Haemophilus parainfluenzae is an opportunistic pathogenic, Gram-negative bacterium commonly found in the human oral cavity. Along with other members of the oral microbiome, H. parainfluenzae can form a biofilm, a complex polymicrobial structure attached to the tooth surface. Biofilms provide resistance for the microorganisms against physical and chemical perturbation. Moreover, biofilms are recognized as important virulence factors in many oral diseases. Outside the oral cavity, H. parainfluenzae can colonize heart tissue causing endocarditis. Thus, it is important to understand the mechanisms associated with biofilm formation in H. parainfluenzae. In this research we are using a transposon mutant library to investigate which genes are essential to biofilm formation in H. parainfluenzae. 4,608 H. parainfluenzae mutants were individually assayed in a high-throughput screen for biofilm formation that relies upon crystal violet staining of attached cells. Mutants that consistently displayed little or an excess of staining  were subcultured and subjected to targeted genome sequencing to identify which gene was interrupted to cause the biofilm phenotypes. Using this approach, we have discovered that under aerobic conditions, H. parainfluenzae has at least 23 genes that are essential for high biofilm formation and no genes that are associated with low biofilm formation.