Staphylococcus aureus and Pseudomonas aeruginosa Express and Secrete Human Surfactant Proteins

Abstract

Surfactant proteins (SP), originally known from human lung surfactant, are essential to proper respiratory function in that they lower the surface tension of the alveoli. They are also important components of the innate immune system. The functional significance of these proteins is currently reflected by a very large and growing number of publications. The objective goal of this study was to elucidate whether Staphylococcus aureus and Pseudomonas aeruginosa is able to express surfactant proteins. 10 different strains of S. aureus and P. aeruginosa were analyzed by means of RT-PCR, Western blot analysis, ELISA, immunofluorescence microscopy and immunoelectron microscopy. The unexpected and surprising finding revealed in this study is that different strains of S. aureus and P. aeruginosa express and secrete proteins that react with currently commercially available antibodies to known human surfactant proteins. Our results strongly suggest that the bacteria are either able to express ‘human-like’ surfactant proteins on their own or that commercially available primers and antibodies to human surfactant proteins detect identical bacterial proteins and genes. The results may reflect the existence of a new group of bacterial surfactant proteins and DNA currently lacking in the relevant sequence and structure databases. At any rate, our knowledge of human surfactant proteins obtained from immunological and molecular biological studies may have been falsified by the presence of bacterial proteins and DNA and therefore requires critical reassessment.

Immunolocalization of Surfactant Proteins SP-A, SP-B, SP-C, and SP-D in Infantile Labial Glands and Mucosa

“…6,9,10 Along with the lung, glandular tissues are one of the most studied in this field. 17,20,28 We provide the first investigation on SPs in infantile labial glands and broaden the spectrum of occurrence.…”

Structure, genetics and function of the pulmonary associated surfactant proteins A and D: The extra-pulmonary role of these C type lectins

“…In 2013, Bräuer and colleagues made the first known determination of expression of all four SP's by bacteria (Brauer et al, 2013) in the bacterial strains Staphylococcus aureus and Pseudomonas aeruginosa . For all four SP's, genomic DNA was identified by PCR, mRNA transcripts identified by RT-PCR, protein expression was detected by western blotting and quantified by ELISA.…”

Surfactants: Pharmaceutical and Medicinal Aspects

“…Surfactant proteins are an important part of the human immune system for fighting bacterial pathogens. It has now shown that the surfactant proteins also exist in pathogenic bacteria (Bräuer et al, 2013). Researchers have now shown these proteins to exist in two pathogenic types of bacteria, staphylococcus aureus and pseudomonas aeruginosa, which are both germs that can cause severe infections of the lungs and other organs.…”