Quorum-Sensing Systems LuxS/Autoinducer 2 and Com Regulate Streptococcus pneumoniae Biofilms in a Bioreactor with Living Cultures of Human Respiratory Cells

Abstract

dStreptococcus pneumoniae forms organized biofilms in the human upper respiratory tract that may play an essential role in both persistence and acute respiratory infection. However, the production and regulation of biofilms on human cells is not yet fully understood. In this work, we developed a bioreactor with living cultures of human respiratory epithelial cells (HREC) and a continuous flow of nutrients, mimicking the microenvironment of the human respiratory epithelium, to study the production and regulation of S. pneumoniae biofilms (SPB). SPB were also produced under static conditions on immobilized HREC. Our experiments demonstrated that the biomass of SPB increased significantly when grown on HREC compared to the amount on abiotic surfaces. Additionally, pneumococcal strains produced more early biofilms on lung cells than on pharyngeal cells. Utilizing the bioreactor or immobilized human cells, the production of early SPB was found to be regulated by two quorum-sensing systems, Com and LuxS/AI-2, since a mutation in either comC or luxS rendered the pneumococcus unable to produce early biofilms on HREC. Interestingly, while LuxS/autoinducer 2 (AI-2) regulated biofilms on both HREC and abiotic surfaces, Com control was specific for those structures produced on HREC. The biofilm phenotypes of strain D39-derivative ⌬comC and ⌬luxS QS mutants were reversed by genetic complementation. Of note, SPB formed on immobilized HREC and incubated under static conditions were completely lysed 24 h postinoculation. Biofilm lysis was also regulated by the Com and LuxS/AI-2 quorum-sensing systems.

The CpAL Quorum Sensing System Regulates Production of Hemolysins CPA and PFO To Build Clostridium perfringens Biofilms

“…Where shown, error bars indicate the standard errors of the mean calculated using data from three independent experiments. the cbp gene, encoding C. perfringens beta toxin (61), is maximally expressed in planktonic cultures during the early-mid-log phase of growth (60). In comparison to planktonic cultures, the population of biofilm bacteria 4 h postinoculation had downregulated transcription of the cbp gene (ϳ4-fold decrease) but mRNA levels of cpa and pfoA remained similarly expressed (Fig.…”

“…perfringens releases eDNA into the culture medium. The biofilm matrix of other pathogens, such as Streptococcus pneumoniae (61,62) or Enterococcus faecalis (63), is partially composed of DNA that has been excreted into the medium (i.e., eDNA). It has been recently reported that eDNA is present in the C. perfringens biofilm matrix (49,50).…”

Research on the biology of the pneumococcus and pneumococcal diseases: the number one cause of death in children worldwide.

“…Controlling pneumococcal colonization may be a way to reduce the burden of disease, and so biofilm research has been a focus of basic science studies in my laboratory. We developed a life-like model that simulates the human upper and lower airways to investigate production of colonizing biofilms 8 . The last few years, we have learned that pneumococcal biofilms are controlled by quorum sensing, small molecules that activates other mechanisms of virulence 9 , including a potent toxin known as pneumolysin or Ply 10 .…”

The Variable Region of Pneumococcal Pathogenicity Island 1 Is Responsible for Unusually High Virulence of a Serotype 1 Isolate

“…Biofilm formation was performed on immobilized A549 cells as previously described (23). Briefly, cells were grown until confluent in 12-well polystyrene plates and immobilized by fixation with 2% paraformaldehyde (Sigma).…”