The human body is home to trillions of microorganisms - bacteria, viruses, fungi and archaea - which are collectively referred to as the microbiome. An estimated 100 trillion bacteria from several hundred different species live in the gut alone. This complex ecosystem not only influences digestion, but also the immune system, metabolism, brain function and even the effectiveness of cancer therapies.
Microbiome research has developed explosively over the last ten years. This has brought a fundamental challenge into focus: how can sensitive bacterial communities be preserved in such a way that they still reflect the composition and functionality of the original microbiome even after months or years of storage?
As is so often the case in the life sciences, the answer lies in cryopreservation.
A microbiome is not a collection of isolated bacterial species, but a dynamic ecosystem in which the species interact in complex ways. Some bacteria are strictly anaerobic - they die within minutes on contact with oxygen. Others require specific nutrients or pH values. Sample processing must take these sensitivities into account.
Different types of bacteria react differently to the freezing process. Gram-positive bacteria generally survive better than Gram-negative ones, and aerobic species better than anaerobic ones. Uncontrolled cryopreservation can therefore distort the composition of the microbiome - certain species are overrepresented and others underrepresented.
The time between sample collection (e.g. stool sample) and cryopreservation should be minimal. International protocols recommend processing within 30 minutes to a maximum of 2 hours. During this time, the sample should be stored refrigerated (4°C).
Each sample should be divided into several aliquots to avoid repeated thawing and refreezing. Each thawing cycle changes the composition of the microbiome and jeopardizes the scientific validity.
In contrast to cell preservation, microbiome samples are often frozen without CPA or with glycerol as a cryoprotectant. The choice of CPA and its concentration influence the survival rates of different bacterial species differently.
The optimal freezing method for microbiome samples is the subject of active research. Some protocols use controlled freezing in a controlled rate freezer, others rely on rapid shock freezing. The choice depends on the aim of the study: For metagenomic analyses (DNA), the freezing rate is less critical than for cultivation-based studies, where the viability of the bacteria must be maintained.
In FMT, the microbiome of a healthy donor is transferred into the intestine of a diseased recipient. The cryostorage of the donor stool samples enables preliminary testing for pathogens, quality assurance and the temporal decoupling of donation and transplantation. FMT stool banks are basically highly specialized cryobanks.
Large epidemiological studies collect thousands of stool samples over many years. The long-term cryopreservation of these samples enables retrospective analyses: how did the microbiome change before a disease broke out? Such longitudinal data is of inestimable scientific value.
Pharmaceutical companies are developing defined bacterial consortia as therapeutics (Live Biotherapeutic Products, LBPs). Cryopreservation is an integral part of the manufacturing process for these novel drugs.
Consarctic® offers research institutions and stool banks the cryogenic infrastructure for the storage of microbiome samples:
The ability to reliably preserve and analyze the microbiome is one of the key competencies of modern biomedical research. Cryotechnology provides the tools for this.
Are you working in microbiome research and looking for reliable cryo solutions? Contact our experts for an individual consultation.