Our main research focus is directed to study of a regularly structured surface (S) layer and the biotechnology applications that derive from our understanding of this structure. The Caulobacter S-layer is a two-dimensional crystalline array on the cell’s surface composed of a single secreted protein. The S-layer probably helps Caulobacters fend off pathogenic bacteria, viruses and lytic enzymes. It appears to be important to cover the entire cell at all times and so this is the most abundant protein of the cell. We analyze the S-layer genetically and biochemically to understand the high level secretion apparatus, as well as to learn how the S-layer self-assembles and remains surface attached.