Planktonic Microbial Population Profiles Do Not Accurately Represent Same Location Sessile Population Profiles

Abstract Obtaining representative and accurate microbiological samples often proves challenging in the oil and gas industry. It is common to sample and test fluids (containing planktonic/free-floating microbes) for the detection and enumeration of problematic species, despite the fact that biofilms or sessile (attached to pipe or vessel wall) microbes are those which cause the majority of problems. This practice occurs because many field scenarios do not allow for sessile sampling. Collecting a representative sample is imperative in any microbial monitoring program, as they estimate the possible risk to the facilities. Misinformation can lead to microbiologically influenced corrosion (MIC) failures or other costly consequences. These planktonic samples are also often used for kill tests, or biocide selection testing, which may not accurately determine the ideal chemistry for the eradication of the sessile bacteria consortia. In this study, metagenomic population analyses of planktonic and sessile samples taken from three geographically distant locations reveals that the planktonic sample population is not representative of the sessile population. In fact, planktonic and sessile samples from the same location may be as different from each other as they are to samples obtained from other locations. Therefore, planktonic sample analyses should not be inferred to accurately or satisfactorily represent the sessile population and associated risk to the facilities.