Controlling production of brominated cyclic depsipeptides by Pseudoalteromonas maricaloris KMM 636T.AIMS:  This study aims at evaluating the impact of the nutrient medium components on the in vitro production of the cytotoxic alterochromides. METHODS AND RESULTS:  The employment matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) facilitated the identification of a range of brominated cyclic depsipeptides with molecular masses of 843/845, 857/859 and 922/924/926 Da, and 936/938/940 Da produced by the marine bacterium Pseudoalteromonas maricaloris KMM 636T. The fractions of cytotoxic yellow pigments yielded after methanol extraction of P. maricaloris KMM 636T cells grown on five nutrient media were solely composed of brominated cyclic depsipeptides. Bromo-alterochromides A and B were obtained after cultivation on low nutrient media, while dibrominated derivatives were the principal components of the biosynthesis during cultivation on nutrient rich media. CONCLUSIONS:  The quantity of bromo-alterochromides and their dibromo- derivates varied depending on the media composition. SIGNIFICANCE AND IMPACT OF THE STUDY:  MALDI-TOF mass spectrometry enables to generate accurate mass analysis for the identification of peptide and its derivates which is important in controlling the production of biologically active compounds in vitro.