The universal stress protein (USP) domain is a superfamily of conserved genes which can be found in bacteria, archaea, fungi, protozoa and plants.

[2] Proteins containing the domain are induced by many environmental stressors such as nutrient starvation, drought, extreme temperatures, high salinity, and the presence of uncouplers, antibiotics and metals.

[2] During bacterial starvation the USP genes upregulated will often arrest cell growth and promote its metabolism to adapt to sparse nutrients.

Additionally, in Halmonas elongate, there is a USP called TeaD has been described as a key regulator in the transport of Ectoine across the cell membrane.

UspA is especially implicated in the resistance of a huge number of stressors most notably tetracycline exposure and high temperatures, with the exception of not forming a response to cold shock.

[12] The induction of USP proteins have also been implicated in transitions not only in metabolism or growth but in changes in the colonies' entire phenotype.

[12] With findings such as these, it's beginning to be accepted that USPs are acting using an extremely wide range of mechanisms to ensure cell survival.

This includes sigma factor σ70 which through binding to a single promoter region, upregulates the transcription of UspA in bacteria.

[15] Whatever the mechanism exhibited by the proteins, one thing which can be concluded is that USP domains are crucial for survival of many bacterial species.

[16] USP domain genes are regulated by a number of proteins involved with growth, DNA repair and cell division.

Notable positive regulation occurs via the action of ppGpp, RecA and FtsZ dependent regulatory pathways.

Water limiting conditions are a common environmental pressure which plants will need to cope with on a regular basis, depending on their habitat.

These resistant phenotypes will have an increased survival as they allow the plant to conserve energy in times of restricted water which is key to glucose production through photosynthesis.

TB is known for its ability to transition into a latent state whereby there is slow growth but high persistence within the mammalian host in structures known as granulomas.

Specifically, Rv2623, a type of USP in M. tuberculosis, is induced by the presence of nitric oxide, reactive oxygen species and a downshift in pH.

All of these conditions are suggested to be produced by the actions of macrophages which are particularly prevalent within the granuloma structures that are characteristic of TB latent infections.

Therefore, these USP genes could be crucial for the long-term survival of the bacteria, meaning that there may be potential therapeutic avenues of research to explore in treating latent TB.

As a result, UspA aids Salmonella to resist stressors produced by the mammalian immune system assisting in survival and hence, pathogenicity.

[24] When UspA is inactivated in Salmonella, the mutants die prematurely, demonstrating how crucial these proteins are to survival and persistence.