Furthermore, autofluorescence may be due to the nature of the tissue or the fixation method. This requires proper tissue collection, fixation and sectioning. Potassium acetate is used in mixtures applied for tissue preservation, fixation, and mummification. Heterocyst cells are terminally specialized for nitrogen fixation. Cyanobacteria provide soluble nitrates via nitrogen fixation. All biological nitrogen fixation is effected by enzymes called nitrogenases. Others include agriculturally important bacteria capable of inducing nitrogen fixation in symbiosis with plants. Some cyanobacteria are also capable of nitrogen fixation. These bacteria are responsible for nitrogen fixation. Algae are also capable of performing nitrogen fixation. I contains most of the nitrogen fixation genes. In photosynthetic prokaryotes the mechanisms of carbon fixation are more diverse. Nitrogen fixation and petrochemicals were invented by Westerners. This leads to joint fixation and reduced fetal movement. Another popular aldehyde for fixation is glutaraldehyde.