Organism contamination and false positive
Plant particles such as leaf fragments, pollen grains and spores can be carried away by wind and contaminations to experimental samples are very likely to arise while collecting and processing samples. Although higher plants cannot move, spores and pollen grains can move for a long distance (Rousseau et al., 2006). Such particles accumulate on surfaces on experimental benches, apparatuses and even clothes (Thomsen & Willerslev, 2015). Despite the amount of contaminants are very very small, they are detectable when amplified by PCR and sequenced on NGS platforms. A biological contaminant free laboratory is ideal for this purpose. To lower the risk of contaminants, only organisms specific to unique environments can be considered, for example, diatoms in wet environment, forage herbs in prairies, crops in crop fields. Diatoms are of high species diversity and ubiquitous in wet environments. In this study, we barcoded diatoms in the soil because the accident happened in a canal and diatoms are very good indicators.