Nanoscale Structural and Mechanical Properties of Nontypeable Haemophilus influenzae Biofilms

Abstract

Nontypeable Haemophilus influenzae (NTHI) bacteria are commensals in the human nasopharynx, as well as pathogens associated with a spectrum of acute and chronic infections. Two important factors that influence NTHI pathogenicity are their ability to adhere to human tissue and their ability to form biofilms. Extracellular polymeric substances (EPS) and bacterial appendages such as pili critically influence cell adhesion and intercellular cohesion during biofilm formation. Structural components in the outer cell membrane, such as lipopolysaccharides, also play a fundamental role in infection of the host organism. In spite of their importance, these pathogenic factors are not yet well characterized at the nanoscale. Here, atomic force microscopy (AFM) was used in aqueous environments to visualize structural details, including probable Hif-type pili, of live NTHI bacteria at the early stages of biofilm formation. Using single-molecule AFM-based spectroscopy, the molecular elasticities of lipooligosaccharides present on NTHI cell surfaces were analyzed and compared between two strains (PittEE and PittGG) with very different pathogenicity profiles. Furthermore, the stiffness of single cells of both strains was measured and subsequently their turgor pressure was estimated.

Nanoscale characterization of effect of l-arginine on Streptococcus mutans biofilm adhesion by atomic force microscopy

“…One early study used AFM to measure the adhesive forces between the cantilever tip and E. coli mutants (Razatos et al, 1998). Various efforts subsequently were made to measure adhesive forces of bacteria (Arce et al, 2009;Dufrene, 2003;Dupres et al, 2005;Harimawan et al, 2011) and adhesion forces of S. mutans were measured to reveal its role in dental caries (Busscher et al, 2007;Liu et al, 2013;Loskill et al, 2013;Mei et al, 2011). In this study, we used AFM to characterize the adhesive properties of S. mutans biofilms by probing the adhesive forces between the biofilm and the AFM tip as well as measuring the lengths of the rupture events that occur at varying distances from the biofilm surface as the AFM tip is pulled away from the surface.…”

Contour and persistence length of Corynebacterium diphtheriae pili by atomic force microscopy

“…Atomic force microscopy (AFM) can image the topography of unstained samples and has already been intensively applied to the study of bacteria (Anselmetti et al 2007;Dupres et al 2009;Wright et al 2010) and to bacterial pili (Touhami et al 2006;Miller et al 2006;Fälker et al 2008;Arce et al 2009). The contour length of the pili can vary by one order of magnitude within a single cell (Yanagawa and Honda 1976;Touhami et al 2006).…”

Nitric oxide in primary ciliary dyskinesia

“…P. aeruginosa is the best characterised bacteria to undergo the genetic adaptations from motile planktonic bacteria to a noncytotoxic, nonmotile, mucoid phenotype caused by overproduction of a surface polysaccharide known as alginate. Biofilm formation also occurs with Haemophilus influenzae and S. aureus, common pathogens in the PCD population [104][105][106]. Bacteria embedded within biofilms can be 1,000-fold more resistant to antibiotic treatments [107].…”