Effect of frozen storage on the composition of bacterial OTUs found in the infant nasopharynx. The composition (mean number of OTUs) per subject against 16S rRNA-based T-RFLP before and after freezing at -70°C dichotomized by sex. Dotted lines represent females, and the bold dotted line shows the mean change. The difference in composition pre and post freezing was significant for female (p = 0.0014) but not for male infants (p = 0.56).
Kwambana et al. BMC Clinical Pathology 2011 11:2 doi:10.1186/1472-6890-11-2