Some strains of "Escherichia coli" cause bloody diarrhea. Alkaline phosphatase is found in the periplasmic space of "E. coli" bacteria. Common bacterial contaminants include "E. coli", "Salmonella", "Shigella", and "Campylobacter jejuni". Threonine is synthesized from aspartate in bacteria such as "E. coli". Numerous pathogens, including "Escherichia coli", commonly exhibit resistance. It is also under research as an bactericidal agent against "Escherichia coli" and "Staphylococcus aureus". There is a tentative link with "Staphylococcus aureus" and "Escherichia coli". Certain strains of "E. coli" are a major cause of foodborne illness. Three-letter abbreviations are used to describe phenotypes in bacteria including "E. coli". Other studies have linked specific strains of enteroadherent "E. coli" to the disease. Colaspase is the BAN of asparaginase obtained from "Escherichia coli". The typical culprits are enterohemorrhagic "Escherichia coli", of which is the best known. Most heterologous proteins are expressed in the cytoplasm of "E. coli". Small populations of "E. coli" in an antibiotic gradient can become resistant. The biosynthesis of histidine has been widely studied in prokaryotes such as "E. coli".