Metaproteomics has been used to highlight changes in protein synthesis in specific bacteria resistant to antibiotics, i. a. to carbapenems . While carbapenem resistance is genetically encoded in all the studied bacteria by genes encoding for the production of carbapenemase enzymes, more intricate proteome changes have been observed in the different genotypes (e.g. "New Delhi metallo-beta-lactamase", "Klebsiella pneumoniae carbapenemase", and "Imipenem-Hydrolyzing β-Lactamase"), showing that bacterial resistance can include more complex cellular responses than expected from the known enzymatic mechanisms of resistance. For example, an increase in the production of outer membrane proteins (ompA) under meropenem exposure was found mainly for E. coli of the "Imipenem-Hydrolyzing β-Lactamase" genotype. In contrast, the "New Delhi metallo-beta-lactamase" genotype rather showed an increase in the synthesis of DNA HU binding proteins and of the chaperonin protein complex GroEL/GroES alongside a higher increase in differential proteome abundance overall. A new application of proteomics addresses persister cells, i.e., subpopulations of cells in which antibiotics act at a slower rate.