many other chemical agents have been evaluated: specific detergents (sodium cholate and sodium deoxycholate), which interact with bacterial lipopolysaccharides, polyethylene glycol (PEG) and SDS which dissolve hydrophobic material, PVPP which removes gumic acids. However, chemical agent may have adverse side effects. For example, the metabolic state of soil bacteria as measured by cellular adenosinetriphosphate levels was negatively affected when a combined SDS-Chelex chemical treatment was applied. Preservation of bacterial integrity during cell separation seems to be essential in order to prevent released DNA to be degraded by physical, chemical or enzymatic processes.