Possible antimicrobial compounds from the pouch of the koala, Phascolarctos cinereus

The antimicrobial activity of secretions of the pouch of the koala, Phascolarctos cinereus has been documented in the presence and absence of young. These secretions have been analysed by polyacrylamide gel electrophoresis, high performance liquid chromatography and mass spectrometry (MS) including time of flight (TOF), MS-MS and Edman sequencing. Gel electrophoresis of reduced samples revealed the presence of a four polypeptides in active and inactive secretions. The sequence data obtained from all four do not appear to be either defensin or cathelicidin-like peptides and show little homology with known antimicrobial protein/peptide sequence available on public access databases. It is proposed that marsupials regulate microbial populations in the pouch via cleavage of large, inactive molecules to produce small active peptides.