Clash of the Kingdoms: How the quest for nutrients leads to pathogenicity

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Streptomyces is a harmless soil bacterium that is often found around the roots of plants, interacting with them but without causing disease. Streptomyces also interacts with other soil organisms such as amoeba, single celled organisms that behave like the phagocytic cells in the human body, eating bacterial cells. Currently we know very little about how these different species interact at the molecular level. Recently we were able to identify that a group of genes (the mce genes, which stands for Mammalian Cell Entry genes)that are found in Streptomyces and are very closely related to genes in its distant cousin Mycobacterium tuberculosis, the bacterium that causes TB. We showed that these genes encode a transport system and are important for Streptomyces to gather nutrients from plant roots and also to interact with the amoebae. Yet in M. tuberculosis they are required for them to colonise human lung cells and grow within those cells. In this proposal we will fully characterise this transport system and study the molecular details of what the proteins encoded by these genes do, what substrates they bind and take up, and what effect they have on plant and amoeba both physically and also genetically. The findings of this study will have implications for our understanding of how human and animal pathogens have evolved from non-pathogenic bacteria and how bacteria can colonise plants and out-compete plant pathogens to stop them from causing disease. There are also possibilities that these genes can be used in the biotechnology industry to help make useful drugs, such as steroids from plant waste products.