Characterization of a new Klebsiella pneumoniae amyloid in biofilm formation
Translated title
Karakterisering af et nyt Klebsiella pneumoniae amyloid i biofilm formation
Author
Moussa, Fatema Ali
Term
4. term
Publication year
2022
Pages
28
Abstract
Klebsiella pneumoniae is a Gram-negative bacterium that can cause serious infections in older adults, people with diabetes, and those with weakened immune systems, including urinary tract infections, pneumonia, and sepsis. Many urinary tract infections are linked to indwelling catheters because K. pneumoniae can colonize medical devices by forming biofilms—slimy communities of bacteria embedded in a self-made matrix. In other bacteria such as Escherichia coli, amyloid fibers (sturdy protein filaments) are a major component of biofilms. Although amyloids have been identified in several bacteria, they had not been characterized in K. pneumoniae. This study aimed to characterize a new K. pneumoniae amyloid involved in biofilm formation. Bacteria were grown with the dye Congo red, which binds amyloid and highlights biofilm material. Biofilms were examined by brightfield and fluorescence microscopy, and the fibers were imaged by electron microscopy. To identify the proteins, samples were analyzed by gel electrophoresis and mass spectrometry. Among seven K. pneumoniae isolates, strain CA402 showed the strongest biofilm formation and Congo red binding, with microscopic features typical of amyloid; it was therefore used for further experiments. Electron microscopy revealed abundant fibers with amyloid-like properties. After formic acid treatment, gel electrophoresis showed a prominent band at about 20 kDa. Mass spectrometry detected peptides, including a distinctive one that matched the MrkA subunit of type 3 fimbriae in the CA402 protein database. Together, these results indicate that the amyloid fiber in the CA402 biofilm is MrkA. Identifying MrkA as an amyloid component of K. pneumoniae biofilms improves our understanding of how this pathogen attaches to surfaces and forms device-associated infections, since type 3 fimbriae are known to promote biofilm formation and MrkA is part of these structures.
Klebsiella pneumoniae er en gramnegativ bakterie, der kan give alvorlige infektioner hos ældre, personer med diabetes og mennesker med svækket immunforsvar, blandt andet urinvejsinfektioner, lungebetændelse og sepsis. Mange urinvejsinfektioner hænger sammen med permanente urinvejskatetre, fordi K. pneumoniae kan kolonisere medicinsk udstyr ved at danne biofilm – slimede bakteriesamfund indlejret i et selvproduceret materiale. Hos andre bakterier som Escherichia coli er amyloide fibre (stærke proteintråde) en vigtig del af biofilmen. Selvom amyloider er fundet i flere bakterier, var de ikke karakteriseret i K. pneumoniae. Formålet med dette studie var at karakterisere et nyt amyloid fra K. pneumoniae, som er involveret i biofilmdannelse. Bakterierne blev dyrket i nærvær af farvestoffet Congo red, som binder amyloider og fremhæver biofilm. Biofilmen blev undersøgt med lys- og fluorescensmikroskopi, og fibrene blev afbildet med elektronmikroskopi. For at identificere proteinerne blev der efterfølgende anvendt gelelektroforese og massespektrometri. Blandt syv K. pneumoniae-isolater viste stamme CA402 den tydeligste biofilmdannelse og Congo red-binding med mikroskopiske træk, der er typiske for amyloider; derfor blev den valgt til de videre forsøg. Elektronmikroskopi viste mange fibre med amyloid-lignende egenskaber. Efter behandling med myresyre gav gelelektroforese et markant bånd ved cirka 20 kDa. Massespektrometri identificerede peptider, herunder et særligt karakteristisk, som matchede MrkA-underenheden af type 3-fimbriae i CA402’s proteindatabase. Samlet peger resultaterne på, at amyloidfiberen i CA402-biofilmen er MrkA. Disse fund forbedrer forståelsen af bakteriens sygdomsmekanismer, fordi type 3-fimbriae er kendt for at fremme biofilmdannelse, og MrkA er en del af disse strukturer.
[This apstract has been rewritten with the help of AI based on the project's original abstract]
Keywords