Extracellular Proteins of Mycoplasma synoviae

Mycoplasma synoviae is a Gram positive bacteria lacking of cell wall that affects chickens and turkeys causing infection in the upper respiratory tract and in some cases arthritis, with economical impact to broiler breeders. Treatment and prevention of avian synovitis depend on knowledge of the infectious process. Secreted or surface-exposed proteins play a critical role in disease because they often mediate interactions between host and pathogen. In the present work, we sought to identify possible M. synoviae secreted proteins by cultivating the bacteria in a modified protein-free Frey medium. Using this approach, we were able to detect in the cell-free fraction a number of proteins that have been shown in other organisms to be secreted, suggesting that they may also be secreted by M. synoviae. 1. Introduction The growth of poultry industry is often limited by infectious diseases that affect birds. Mycoplasma synoviae is a major avian extracellular pathogen associated with synovitis in chickens and turkeys [1, 2]. Disease can occur as chronical subclinical to severe upper respiratory infection and, under unknown conditions, become systemic and cause arthritis [3]. The disease causes economic losses by retarding growth and downgrading at slaughter [3]. Strategies to control this pathogen rely mainly in better management practices, improvement in housing conditions and antibiotic usage, whereas an effective vaccine is still not available [4]. Secreted proteins of pathogenic bacteria are key factors in host colonization. The analysis of these proteins, called secretome, can therefore permit the identification of new putative virulence factors that are fundamental for host invasion and survival in the environment within the host [5]. In this context, two-dimensional electrophoresis (2DE) along with peptide fingerprinting by mass spectrometry (MS) and subsequent protein identification have become a powerful method to unravel pathogenicity factors in microorganisms [6, 7]. We have recently reported a proteomic analysis of M. synoviae cell extracts in conventional Frey medium [8]. In the present work, we have grown M. synoviae in the same typical culture medium and then incubated the cells in a protein-free modified Frey medium as a strategy to indicate proteins that can be secreted to the medium by the bacteria. 2. Methods 2.1. Mycoplasma synoviae Cultures M. synoviae strain 53 isolated from a broiler breeder was grown in the Laboratory of Genetics and Animal Health from EMBRAPA Swine and Poultry (Concórdia, C, Brazil) as described by Frey and coworkers