  Protein synthesis is an important determinant of microbial growth and
response that demands a high amount of metabolic and biosynthetic resources.
Despite these costs, microbial species from different taxa and habitats
massively synthesize proteins that are not utilized in the conditions they
currently experience. Based on resource allocation models, recent studies have
begun to reconcile the costs and benefits of these conditionally unutilized
proteins (CUPs) in the context of varying environmental conditions. Such
massive synthesis of CUPs is crucial to consider in different areas of modern
microbiology, from the systematic investigation of cell physiology, via the
prediction of evolution in laboratory and natural environments, to the rational
design of strains in biotechnology applications.
