Erwinia is a genus of Enterobacteriaceae bacteria containing mostly plant pathogenic species which was named for the famous phytobacteriologist, Erwin Frink Smith.
The hisB gene, found in the enterobacteria (such as E. coli), in Campylobacter jejuni and in Xylella/Xanthomonas encodes a protein involved in catalysis of two step in histidine biosynthesis (the sixth and eight step), namely the bifunctional Imidazoleglycerol-phosphate dehydratase/histidinol-phosphatase.