Abstract
Biofilms are present in all environments and often result in negative effects due to properties of the biofilm lifestyle and especially antibiotics resistance. Biofilms are associated with chronic infections. Controlling bacterial attachment, the first step of biofilm formation, is crucial for fighting against biofilm and subsequently preventing the persistence of infection. Thus deciphering the underlying molecular mechanisms involved in attachment could allow discovering molecular targets from it would be possible to develop inhibitors against bacterial colonization and potentiate antibiotherapy. To identify the key components and pathways that aid the opportunistic pathogen Pseudomonas aeruginosa in attachment we performed for the first time a proteomic analysis as early as after 20 minutes of incubation using glass wool fibers as a surface. We compared the protein contents of the attached and unattached bacteria. Using mass spectrometry, 3043 proteins were identified. Our results showed that, as of 20 minutes of incubation, using stringent quantification criteria 616 proteins presented a modification of their abundance in the attached cells compared to their unattached counterparts. The attached cells presented an overall reduced gene expression and characteristics of slow-growing cells. The over-accumulation of outer membrane proteins, periplasmic folding proteins and O-antigen chain length regulators was also observed, indicating a profound modification of the cell envelope. Consistently the sigma factor AlgU required for cell envelope homeostasis was highly over-accumulated in attached cells. In addition our data suggested a role of alarmone (p)ppGpp and polyphosphate during the early attachment phase. Furthermore, almost 150 proteins of unknown function were differentially accumulated in the attached cells. Our proteomic analysis revealed the existence of distinctive biological features in attached cells as early as 20 minutes of incubation. Analysis of some mutants demonstrated the interest of this proteomic approach in identifying genes involved in the early phase of adhesion to a surface.
Highlights
Bacterial biofilms are a source of recurrent problems in medical fields
Protein synthesis was required for an optimal colonization of the glass wool (GW) surface We previously reported that tetracycline negatively impacts the attachment capacity of PAO1 in both the GW Sponge System and the 96-well plate system [10]
Even if we did not quantify all P. aeruginosa proteins, our analysis provided an overview of what can biologically happen and highlighted some features about mechanisms underlying bacterial attachment
Summary
Bacterial biofilms are a source of recurrent problems in medical fields. Infections caused by biofilms are significant socioeconomic burden that implicates patient diseases, lost employment and hospitalization. In USA, nosocomial infections, mainly related to the presence of biofilms [1,2], cause US$4.5 billion in care surcharge per year and lead to the death of nearly 100,000 inpatients [3] The origin of these problems lies in the particular physiology of the bacteria immobilized within biofilms, called sessile bacteria, which escape the immune system of the host and are characterized by a “resistant” phenotype [4]. New anti-biofilm strategies require a thorough knowledge about the biology of biofilms In this context, many studies have been performed on various bacterial species to understand how a biofilm is formed and to identify the genes involved in its development. Targeted studies (i.e. mutant analysis) have been performed on the early attachment phase and provide piecemeal information into the molecular players involved in the early stages of biofilm formation [8,9]
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