Abstract: The present invention relates to methods for preparing an isolated biological sample containing at least one of DNA and RNA, such that the DNA and/or RNA is preserved in the sample at ambient temperatures for at least thirty days, the method comprising: contacting the isolated biological sample with a composition comprising a chaotropic agent, and subjecting the contacted sample to microbial cell lysis; and optionally, contacting the lysed biological sample with a slurry of size-selected silicon dioxide to form at least one of DNA-silicon dioxide complexes or RNA-silicon dioxide complexes in the sample; isolating at least one of DNA-silicon dioxide complexes or RNA-silicon dioxide complexes from the sample; and, separating at least one of DNA and RNA from the silicon dioxide and collecting at least one of the DNA and RNA.