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.