Use of Diaminobenzidine to Stain for Cytochrome c Oxidase Activity in Caulobacter crescentus and Escherichia coli

Abstract

Caulobacter crescentus is an aerobic Gram negative bacterium found in bacterial biofilms. C. crescentus produces a sessile stalked cell during its life cycle that allows it to attach to surfaces. Due to the oxygen gradient found in the bacterial biofilm, we postulated that C. crescentus would localize the terminal cytochrome to the cell body that remains in the aerobic portion of the biofilm. The terminal electron acceptor in the electron transport system was determined using Kovac's oxidase test to be cytochrome c oxidase. We are able to use diaminobenzidine to locate the oxidase histochemically using transmission electron microscopy. Upon examination of sectioned bacteria, we determined that cytochrome c oxidase of C. crescentus is found only in the cell body.

Key Words:

• Caulobacter crescentus
• cytocrome oxidase
• protein localization