Influence of Aae Autotransporter Protein on Adhesion and Biofilm Formation by Aggregatibacter actinomycetemcomitans

Abstract

The periodontopathogen Aggregatibacter actinomycetemcomitans colonizes oral cavity by binding to and invading epithelial cells as well as by participating in biofilms formed on hard surfaces. Aae, an autotransporter protein, is implicated in bacterial adhesion to epithelial cells. Due to the multiple functions of bacterial autotransporter proteins, this study aimed to evaluate the role of aae in A. actinomycetemcomitans ability to adhere to both saliva-coated hydroxyapatite (SHA) and biofilm. An aae null mutant was constructed. Its hydrophobic properties as well as its ability to adhere to epithelial cells, SHA and to form biofilm were evaluated and compared with the parental strain, A. actinomycetemcomitans VT1169. The aae null mutant showed reduced hydrophobicity, as well as decreased binding to SHA and biofilm formation compared to the parental strain. These data suggest that aae mediates A. actinomycetemcomitans adhesion to epithelial cells and may be involved in biofilm formation and interaction with adsorbed salivary proteins. Influence of Aae Autotransporter Protein on Adhesion and Biofilm F o r m a t i o n b y A g g r e g a t i b a c t e r a c t i n o m y c e t e m c o m i t a n s

Contribution of adhesion proteins to Aggregatibacter actinomycetemcomitans biofilm formation

“…Our previously published data suggest a role for EmaA in biofilm formation (Danforth et al., 2019). However, there are contradicting reports in the literature of the involvement of Aae in biofilm development (Fine et al., 2005; Nunes et al., 2016), while little information is available about the role of ApiA/Omp100 in this process. Some data indicate that ApiA/Omp100 contributes to biofilm formation when expressed in an E. coli background (Cugini et al., 2018), but no information is available about the role of this adhesin when expressed in A. actinomycetemcomitans .…”

“…The biofilm formed by the oral bacterium Aggregatibacter actinomycetemcomitans is considered to be exclusively directed by the bundle forming fimbriae produced by the bacterium (Figurski, 2013; Inoue et al., 2003; Kachlany, Planet, Desalle, Fine, Figurski, et al., 2001; Schreiner et al., 2003). However, the nonfimbrial adhesins of A. actinomycetemcomitans (EmaA, Aae, and ApiA/Omp100) have also been implicated in biofilm biogenesis (Cugini et al., 2018; Danforth et al., 2019; Nunes et al., 2016). All three of these characterized adhesins are classified as autotransporters, which encode all the information necessary to catalyze the transport of the protein(s) across the outer membrane (Sauri et al., 2009).…”

“…The significance of the number of these repeats is unknown. The role of Aae in biofilm formation is disputed (Fine et al., 2005; Nunes et al., 2016).…”

Himar1 Transposon for Efficient Random Mutagenesis in Aggregatibacter actinomycetemcomitans

“…Even though substantial progress has been made in understanding the virulence of A. actinomycetemcomitans , it remains a challenge to study the genetics of the organism’s colonization and persistence in the oral cavity, and identify novel virulence factors due to limited genetic tools available to manipulate A. actinomycetemcomitans . So far, the recipient strains of A. actinomycetemcomitans used in transposon mutagenesis studies are limited to nalidixic acid or rifampin resistant isolates of A. actinomycetemcomitans ( Kolodrubetz and Kraig, 1994 ; Thomson et al, 1999 ; Kachlany et al, 2000a ; Isaza et al, 2008 ; Nunes et al, 2016 ). These strains are employed as these antibiotics are used for counter-selection during conjugation experiments with E. coli .…”

“…Forward genetics is a powerful tool to identify novel genes critical for virulence. Tn 916 , Tn 5 , Tn 10 , and IS 903 based gene delivery systems have been used to generate mutant libraries in A. actinomycetemcomitans which led to discovery of genes essential in virulence and survival of A. actinomycetemcomitans ( Kolodrubetz and Kraig, 1994 ; Thomson et al, 1999 ; Kachlany et al, 2000a ; Isaza et al, 2008 ; Nunes et al, 2016 ). However, these systems suffer from several drawbacks.…”