Bio-probes are used to collect samples of bacteria in Oil and gas systems, including refineries, offshore platforms, pipelines, etc. Bacteria may be present in a system as either sessile (attached to the metal surface), or planktonic (present in the process fluid). There can be considerable differences between the types of bacteria present in either of these two forms. From a corrosion perspective, the sessile bacteria are the ones that are of primary importance since these are the ones that affect the corrosion, and the ones that must be controlled with chemical treatment. For this reason fluid samples for testing of bacteria only test for planktonic bacteria and may be of no relevance at all to corrosion.