Biostasis

Biostasis refers to the capacity of an organism to endure adverse environmental conditions without the need for active physiological adaptation. Instead of responding dynamically to environmental stressors, the organism enters a suspended or dormant state that enables survival until favourable conditions return. This phenomenon is widespread across biological systems and is observed in insects, microorganisms, and certain extremophile animals inhabiting environments characterised by periodic drought, low temperatures, fluctuations in pH, or other forms of physiological stress.
In insects, biostasis commonly takes the form of diapause, a programmed developmental arrest that may be obligatory for survival. Some insects are able to initiate preparatory physiological changes before the onset of the triggering environmental event, demonstrating an anticipatory dimension to biostasis in these species.

Biostasis in Microorganisms

Among microorganisms, biostasis is frequently discussed in the context of the viable but non-culturable (VBNC) state, a condition in which bacterial cells remain alive but fail to grow on standard culture media. Historically, such cells were assumed to be dead; however, research has shown that many bacteria can enter a reversible state of suspended animation when exposed to stress.
Entry into the VBNC state may be triggered by:

• Starvation
• Exposure to temperatures outside the normal growth range
• High osmotic concentrations or seawater conditions
• Variations in oxygen levels
• Exposure to white light

This capacity offers a survival mechanism in conditions that would otherwise be lethal. Bacteria in the VBNC state display a range of physiological changes, including dwarfing, altered metabolic activity, reduced respiration, diminished nutrient uptake, and reduced macromolecular synthesis. Although macromolecular production slows, biosynthetic activity does not cease entirely, and stress-related proteins continue to be produced.
One notable observation is that ATP levels remain elevated, distinguishing VBNC cells from dying cells, which exhibit a rapid decline in energy generation. Structural changes also occur, such as increased peptidoglycan crosslinking in Escherichia coli, and enhanced autolytic capacity relative to actively growing cells.
A significant challenge in microbial biostasis is the difficulty of reversing the state. Studies on Legionella pneumophila have shown that while VBNC entry can be induced readily through nutrient deprivation, successful resuscitation may require interaction with other organisms, as demonstrated by the restoration of culturability following co-incubation with the amoeba Acanthamoeba castellanii.

Fungistasis and Soil Biostasis

Biostasis also occurs in fungi through a mechanism known as fungistasis or mycostasis. This refers to the phenomenon in which viable fungal propagules—despite not being inherently dormant—fail to germinate under otherwise favourable temperature and moisture conditions. Soil environments impose a variety of stressors, including nutrient availability, oxygen concentrations, or unidentifiable environmental cues, that inhibit fungal growth and maintain fungi in a VBNC-like state.
Soil fungistasis is recognised as a widespread ecological process affecting pathogens and saprophytic fungi alike, contributing to soil health, microbial community interactions, and the suppression of plant diseases.

Contemporary Directions in Biostasis Research

At the frontier of biostasis research is the effort to translate naturally occurring dormancy strategies into biomedical applications. One notable development occurred in March 2018 when the United States Defence Advanced Research Projects Agency (DARPA) launched its Biostasis programme, directed towards extending the critical “golden hour” for trauma patients. The initiative aims to create technologies capable of slowing biological processes at the cellular level, thereby preserving life during catastrophic injuries.
Through a Broad Agency Announcement, DARPA invited research proposals exploring mechanisms to slow or modulate intracellular reactions. The challenge lies in influencing the rate of complex biochemical networks without causing irreversible cellular damage.

Possible Mechanistic Approaches

Several biological systems and molecular processes offer insights into how biostasis might be achieved in higher organisms:

• Protein chaperoningChaperone proteins facilitate the folding, unfolding, and assembly of macromolecules. By reducing conformational flexibility, it may be possible to reduce reaction rates and stabilise cellular structures under stress. Evidence suggests that protein promiscuity—where proteins perform multiple functional roles—plays a part in evolutionary adaptation, and manipulating this promiscuity may offer a means of inducing biostasis.
• Intracellular crowdingCellular environments are naturally crowded with macromolecules. This crowding affects protein behaviour, water interactions, and reaction dynamics. Artificially modifying intracellular crowdedness using engineered polymers or compartmentalisation strategies could regulate the pace of biochemical reactions, offering a potential route for controlled metabolic slowdown.
• Tardigrade-derived intrinsically disordered proteinsTardigrades exhibit extraordinary survival capabilities, including endurance of freezing, desiccation, and extreme pressure. These abilities are partly attributed to intrinsically disordered proteins (IDPs) that stabilise cellular components during extreme conditions. Through peptide engineering, researchers aim to introduce similar protective mechanisms into other organisms, potentially enabling controlled states of stasis.

Significance and Applications

Biostasis offers a compelling model of survival in fluctuating environments. Its implications span multiple scientific and medical fields, including:

• Microbiology, through the understanding of bacterial survival, spoilage, and pathogenesis, particularly where VBNC cells evade detection yet retain viability.
• Soil science and plant pathology, where fungistasis influences nutrient cycling and disease suppression.
• Biomedicine, with potential future applications such as emergency resuscitation, trauma care, organ preservation, and space travel.
• Evolutionary biology, providing insight into resilience adaptations across species.