The bacteria Streptococcus pneumoniae is the leading cause of community-acquired pneumonia in all ages worldwide. The pneumococcus can spread from person to person via contact with nasal and oral secretions of colonised individuals during commonplace activities such as talking, sneezing and coughing. Droplets of these secretions have been shown to allow for the pneumococcus survival and growth, dictated by specific physiological and metabolical changes. A previous genome-wide screening has identified potential bacterial factors that are involved in this process. One such factors is a protein, designated Ptp which shows homology to the low molecular weight protein tyrosine phosphatases (LMWPTP). LMWPTPs are widely found in eukaryotes and prokaryotes and play diverse roles including cell signalling and proliferation. LMWPTPs are also recognised as major virulence factors in a range of bacterial pathogens. Purification of the Ptp from E. coli, enabled us to show that Ptp is indeed a phosphatase, with specificity against tyrosine. Our preliminary data suggest that human saliva can support the survival and growth of the wild type pneumococcal strain but not the mutant strain that carries a chromosomal deletion in ptp. Additionally, the mutant strain also appears to be more susceptible to lysozyme, an antimicrobial enzyme found abundantly in saliva. This suggests that Ptp may assist in the bacterial survival and spread via human saliva by conferring resistance to lysozyme. The exact role of Ptp in modifying the cell wall of the bacteria, which is the substrate of lysozyme is currently under investigation. Overall, this study hopes to further our understanding of the bacterial transmission that precedes disease and outbreaks.