Expression of internalin A and biofilm formation among Listeria monocytogenes clinical isolates.
Internalin A (InlA), a cell wall-bound protein of Listeria monocytogenes, is among the major components involved in the adhesion to and invasion of host cells expressing specific forms of E-cadherin. Some L. monocytogenes strains secrete truncated non-functional forms of InlA. The purpose of this study is to compare the biofilm-forming abilities of L. monocytogenes strains from clinical sources expressing InlA proteins in the different forms. A total of 70 L. monocytogenes strains were examined using SDS-PAGE, Western blot, DNA sequencing, and microtitre plate biofilm formation assays. We found that 8 of the 70 strains expressed truncated InlA, and that this group of strains exhibited significantly enhanced biofilm-forming ability compared to the group expressing full-length InlA. Further experiments showed that: (i) L. monocytogenes biofilms were detached by treatment with protease K; (ii) protein fragments resulting from proteolysis, rather than intact proteins, are responsible for biofilm enhancement, because biofilm formation was impaired by the protease inhibitor alpha2-macroglobulin; (iii) truncated and/or proteolytically cleaved InlA are likely involved in the biofilm enhancement, based on the effects that anti-InlA monoclonal antibodies produced on the biofilm formation of L. monocytogenes strains expressing either truncated or full-length InlA. These data provide a basis for further investigation of the molecular structure and composition of L. monocytogenes biofilms.
Franciosa
G
G
Department of Food Safety and Veterinary Public Health, Unit of Microorganisms and Food Technologies, Istituto Superiore di Sanità, Rome, Italy. giovanna.franciosa@iss.it
Maugliani
A
A
Scalfaro
C
C
Floridi
F
F
Aureli
P
P
D000911:Antibodies, Monoclonal / Q000276:immunology; D001426:Bacterial Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D018441:Biofilms; D015153:Blotting, Western; D006801:Humans; D008089:Listeria monocytogenes / Q000502:physiology*; D017422:Sequence Analysis, DNA; D000511:alpha-Macroglobulins / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D001426:Bacterial Proteins; D000511:alpha-Macroglobulins; C069761:internalin protein, Bacteria