Cyanobacteria plays a significant role in the global carbon cycle.As the place for carbon dioxide fixation，carboxysome is a proteinaceous compartment that encapsulates the carbonfixing enzyme ribulose1,5 -bisphosphate carboxylase (RuBisCO) and carbonic anhydrase.In this study,the effects of chloramphenicol on carboxysome number and cellular abundance of CcmK2 in Synechocystis sp. PCC 6803 were analyzed.A batch of test were performed to study the inhibited effect of chloramphenicol on the growth of -Synechocystis- sp. PCC 6803 and its derivatives.Results showed that 5.0 μg/mL of chloramphenicol inhibited bacterial multiply completely.From heterotrophic status to photoautotrophic growth,the number of carboxysome rapidly increased in 12 h,but the addition of 5.0 μg/mL chloramphenicol inhibited effectively the increase of cellular carboxysome number.Result of Western blot analysis showed that the abundance of the most abundant carboxysome shell protein CcmK2 was inhibited by this antibiotics.It is indicated that chloramphenicol could inhibit novel carboxysome shell protein and disturb the carboxysome formation under different carbonenvironment.Further studies on carboxysome assembly are needed.