Effect of Host Human Products on Natural Transformation in Acinetobacter baumannii

Abstract

Our previous data show that serum albumin can trigger natural transformation in Acinetobacter baumannii. However, extracellular matrix/basal membrane components, norepinephrine, and mucin did not have a significant effect on this process. Therefore, the effect of human products appears to be albumin specific, as both BSA and HSA have been shown to increase of natural transformation.

Human fluids alter DNA-acquisition in Acinetobacter baumannii

“…Accordingly, any interaction between A. baumannii and free roaming DNA from its environment would be disrupted as well [19]. Therefore, both the previous results and those obtained here with mucin, where we observed a decrease in transformation frequency, are in correlation with each other [9].…”

“…Previous findings from our group identified both bovine and human serum albumin as inducers of natural transformation in A. baumannii, evidence supported by the induction of two competence genes, comEA (a small DNAbinding periplasmic protein important for DNA uptake) and pilQ (the outer secretin protein found in type IV pili that allows double-stranded DNA to enter into the periplasm) [7,9]. Notably, casein, extracellular matrix/basal membrane components, as well as norepinephrine and mucin did not significantly enhance the transformation rate of this bacterium, showing that albumin effect is specific A C C E P T E D M A N U S C R I P T [9]. These observations support the idea that HSA is a host component that enhances acquisition of foreign genetic material, thus increasing the ability of the bacterium to adapt to environmental conditions.…”

“…Subsequently, our group has studied this mechanism in the naturally competent clinical strain A. baumannii A118 [4,5], showing that a) this clinical isolate can acquire different DNA sources [4,6,7],; b) albumin is a specific inducer of natural competence; and c) sub-inhibitory concentrations of meropenem, one of the last resources of antibiotics, increases transformation frequency in all strains tested [7][8][9].…”

Cerebrospinal fluid (CSF) boosts metabolism and virulence expression factors in Acinetobacter baumannii

“…baumannii genes when the bacterial cells are in contact with HSA-containing fluids, PF or CSF. Furthermore, our previous studies showed that HSA also enhances DNA acquisition through modulation of natural competence-related gene expression and affects the expression of genes related to motility, efflux pumps, pathogenicity and antibiotic resistance, among others (19,22). These characteristics are not unique to A.…”

“…This genetic plasticity, a consequence of its ability to acquire and integrate foreign DNA, gives A. baumannii's a tremendous metabolic versatility that permits the bacterium to adapt and persist in harsh conditions (2,(13)(14)(15)(16)(17). A. baumannii's success in causing numerous infections, where it gets in contact with different body components and fluids, must be the result of its capabilities to not only capture adequate genetic determinants but also regulate expression of the proper cell components (2,(13)(14)(15)(18)(19)(20). We have also previously documented that human serum albumin (HSA) and pleural fluid (HSA-containing fluid), affected A. baumannii behavior, triggering an adaptive response that modulates DNA uptake, cytotoxicity, immune evasion, stress responses and metabolism (18,(20)(21)(22).…”