Applied Cell Biology

Comparative spatio-temporal evolving histology of staphylococcus aureus and staphylococcus epidermidis colony/biofilm

María L uisa Gómez-L us¹, Fernando Gómez-Aguado²*, César Gar cía-R ey¹, María Teresa Corcuera², Carmen Ramos¹, José Pr ieto¹

¹Department ofMedicine,Area ofMicrobiology, School ofMedicine,ComplutenseUniversity,Madrid, (SPAIN)
²Department ofPathology,Carlos IIIHospital,Madrid, (SPAIN)

Abstract

Microbial colonies are a special type of biofilmand as such should have a defined internal structure. The aim of this study was to assess the evolving architecture of Staphylococcus aureus and Staphylococcus epidermidis colonies. Isolated colonies from 16 hours up to 15 days were processed using histological techniques to visualize their internal structure by light and electron microscopy. A morphometric analysis of the biofilm components was performed by image analysis. Both species followed

the same structural evolution at short andmediumincubation times (up to 96 h), consisting of a sequential stratification in up to 4 layers with different compositions and staining properties. At 15 days, clear cut different architectural patterns were evident. S. aureus showed a multilayered pattern with additional lenticular-shaped invasions of the culture medium. S. epidermidis showed only three strata, with subpopulations regrowing from specific points on the surface and in the base of the colonies, but never invading the agar. Our results demonstrate that evolving architectural pattern of Staphylococcus colony/biofilmpresents as a  complex and time-dependant process that might be considered as a genus phenotypic characteristic in the short and mediumterm, while it would be species or even strain specific in the long run.

Keywords:

Staphylococcus; Biofilm; Histology; Image analysis; Light microscopy; Electronmicroscopy.