Proteomic analysis of the interaction Fusarium solani - Staphylococcus epidermidis isolated from human corneal ulcers

Abstract

Purpose: To study the proteomic profile of co-culture of Fusarium solani and Staphylococcus epidermidis in comparison with mono-cultures.

Methods: Fusarium solani and Staphylococcus epidermidis were isolated from human corneal ulcers. The microorganisms were characterized by microbiological and molecular technics. Mono-cultures and co-cultures were established in Müller-Hinton Agar. Plates containing 72-h biomass were processed to obtain the cellular extract; proteins were quantified and purified before two-dymensional electrophoresis (2D) was performed. The proteomic profiles were analyzed by the software Dymension 2 to determine the differential expression of the co-culture compared with the mono-cultures. The spots that showed differential expression were identified by mass spectrometry using MALDI-TOF 4800 (ABsciex).

Results: The fungi growth was lower in the co-cultures than in monocultures (p <0.0001). Proteomic profiles from the mono-cultures and co-cultures showed 40 proteins with differential expression; 21 of these were identified and classified as: metabolism (13), defense mechanisms (4) and pathogenic/antagonism traits (4). The majority of the identified proteins corresponding to metabolic proteins and also the majority of them were down-regulated. These down-regulated proteins suggest that the metabolism of both microorganisms is in “stand-by”, while they are adapting to share the same space, because the defense mechanisms proteins are up-regulated. As it is known, the bacteria grew faster and it propitiated the acid conditions that the fungi needed to grow. While this was happening, the fungi had a low metabolism that it is reflected in the proteins involved in energy metabolic pathways.

Conclusions: The proteomic profile of the co-culture Fusarium solani-Staphylococcus epidermidis showed differential expression compared with the mono-cultures proteomic profiles. The majority of the proteins with differential expression were identified as enzymes that participate in important metabolic pathways, suggesting that the co-culture is a cooperative interaction instead of competitive. Two proteins, FBA and enolase, could be possible biomarkers.

Keywords: 480 cornea: basic science • 530 fungal disease • 663 proteomics