Mycoplasmas are obligate parasites with minimal genomes. As a consequence of their extended history of reductive evolution they have lost much biosynthetic capacity and are dependent on exogenous sources of most complex nutrients. However, the mechanisms that they use to acquire these biosynthetic substrates are poorly understood. Among these complex molecules that they must scavenge from their environment are nucleotides, and it is likely that efficient derivation and transport of these nucleic acid precursors into their cytoplasm is essential for virulence. We have used a variety of approaches to identify and characterise genes that are likely to be involved in this process and to establish the activity of their products in several pathogenic mycoplasma species of animals, including Mycoplasma gallisepticum, Mycoplasma hyopneumoniae and Mycoplasma bovis. In earlier studies cloning and site directed mutagenesis in E. coli allowed us to identify a lipoprotein nuclease in M. hyopneumoniae (Mhp379)1, while in recent transposon mutagenesis we have identified a distinct, major lipoprotein nuclease of M. bovis (MBOVPG45_0215). Gene synthesis and expression in E. coli have enabled us to demonstrate that the function of the product of a gene (mslA) shown to be required for virulence in M. gallisepticum binds oligonucleotides. In many mycoplasmas this gene is located in an operon that contains both the orthologue of the lipoprotein nuclease of M. hyopneumoniae and also genes predicted to encode an ABC transporter. Our findings suggest that the oligonucleotide binding protein and the nuclease act in concert to facilitate degradation of host nucleic acids to nucleotides for transport into these pathogenic mycoplasmas, thus enhancing their pathogenicity.