Using proteomics to study the Listeria monocytogenes secretome

Bacteria modify their environment through the secretion of protein. During infection, these secreted proteins carry out functions critical for a bacterium’s ability to cause disease. Interestingly, not all bacteria are equal in their ability to cause disease, even among siblings of the same type of bacteria. By studying the collection of proteins secreted by related bacteria, we can better understand why they differ in their ability to cause disease. Here we show that different types of one bacterium, Listeria monocytogenes, vary in the proteins they secrete in conditions relevant to infection. We observe differences mainly in proteins relating to metabolism, such as proteins involved in the acquisition and utilization of important nutrients like iron and heme. Additionally, significant differences exist in the amount of protein they secrete to carry out functions such as infecting cells and spreading to neighboring cells. These results indicate that the bacteria behave differently during infection and may help explain why we see different clinical outcomes during Listeria monocytogenes infection.