Variation of Burkholderia cenocepacia cell wall morphology and mechanical properties during cystic fibrosis lung infection, assessed by atomic force microscopy

Abstract

The influence that Burkholderia cenocepacia adaptive evolution during long-term infection in cystic fibrosis (CF) patients has on cell wall morphology and mechanical properties is poorly understood despite their crucial role in cell physiology, persistent infection and pathogenesis. Cell wall morphology and physical properties of three B. cenocepacia isolates collected from a CF patient over a period of 3.5 years were compared using atomic force microscopy (AFM). These serial clonal variants include the first isolate retrieved from the patient and two late isolates obtained after three years of infection and before the patient’s death with cepacia syndrome. A consistent and progressive decrease of cell height and a cell shape evolution during infection, from the typical rods to morphology closer to cocci, were observed. The images of cells grown in biofilms showed an identical cell size reduction pattern. Additionally, the apparent elasticity modulus significantly decreases from the early isolate to the last clonal variant retrieved from the patient but the intermediary highly antibiotic resistant clonal isolate showed the highest elasticity values. Concerning the adhesion of bacteria surface to the AFM tip, the first isolate was found to adhere better than the late isolates whose lipopolysaccharide (LPS) structure loss the O-antigen (OAg) during CF infection. The OAg is known to influence Gram-negative bacteria adhesion and be an important factor in B. cenocepacia adaptation to chronic infection. Results reinforce the concept of the occurrence of phenotypic heterogeneity and adaptive evolution, also at the level of cell size, form, envelope topography and physical properties during long-term infection.

Mechanical Properties of Human Bronchial Epithelial Cells Expressing Wt- and Mutant CFTR

“…Cell stiffness has been described to be strongly affected by the actin filamentous structures under the cell membrane [21]. In recent years, force microscopy has unveiled the relevance of these nanomechanical properties in important cellular mechanisms, such as migration/locomotion [22], differentiation [23] or as a marker for disease progression [24,25]. It has become evident that these properties are fundamental to explain cell's structure, evolution, and response to different stimuli, making AFM a potential tool for biomedical diagnosis and prognosis, with very promising results already obtained in the areas of cancer [26] or cardiovascular diseases [27].…”

Comparative Evolutionary Patterns of Burkholderia cenocepacia and B. multivorans During Chronic Co-infection of a Cystic Fibrosis Patient Lung

“…It is also known that the OAg absence leads to increased internalization of B. cenocepacia into macrophages upon phagocytosis Kotrange et al, 2011) and to facilitate B. multivorans growth inside macrophages (Schmerk and Valvano, 2013). Moreover, the OAg presence was found to interfere with the adhesion of B. cenocepacia to bronchial epithelial cells although it was reported to increase the ability of B. cenocepacia to adhere to atomic force microscope Si 3 N 4 tip (Hassan et al, 2019b). Collectively, the loss of the OAg seems advantageous for disease development associated with B. cenocepacia or B. multivorans infections.…”

Adaptation and Survival of Burkholderia cepacia and B. contaminans During Long-Term Incubation in Saline Solutions Containing Benzalkonium Chloride

“…A model proposed for Escherichia coli suggests that the flux of nutrients into the cell controls the synthesis of fatty acids which, in turn, controls cell size through modeling of the cell membrane surface area and cytoplasmic volume (Yao et al, 2012 ). A recent study performed in our lab also demonstrated a clear length and height decrease of B. cenocepacia cells during more than 3 years of chronic infection, suggesting that the population converged evolutionarily toward the minimization of bacterial size (Hassan et al, 2019 ). Small microbial cell size might allow evasion from important host defenses and cell shape itself has been suggested as a virulence trait (Vadia et al, 2017 ).…”