TABLE 1

Major sources of variability in microbiome studies

SamplingDNA extraction16s amplification and sequencingBioinformatics
Processing biasesSpecies bias due to different wall compositionSelection of regions to amplifyThresholds for abundance
Constraints associated with type of sampleBatch effect#Polymerase chain reaction and sequencing errorsAlignment of sequences to databases
Adapter additionClassification of sequences
Batch effect
  • #: batch effect refers to the bias introduced if not all samples are processed at the same time, in a single batch; : adapters are oligonucleotides that are ligated to the amplified DNA in order to do the sequencing. The efficiency of the ligation process can influence the sequencing results.