Updated project metadata. Recently the function and cellular importance of small proteins became more and more visible. Whereas many examples of small protein functions have been described in eukarya and bacteria, less is known about small protein functions in archaea. A previous determination of the proteome in the halophilic archaeon Haloferax volcanii by mass spectrometry confirmed the expression of several annotated genes for small proteins. One such protein is encoded by HVO_0582. To identify the biological function of the encoded small protein we attempted to generate a deletion strain. Since we were not successful in generating the deletion we repressed HVO_0582 using CRISPRi. The repression strain showed a severe growth defect as well as strong changes in morphology. ChIPSeq experiments revealed several binding sites for this putative transcription factor. Transcriptome and proteome analyses show a clear effect on RNA and protein expression in the CRISPRi strain. Based on our findings we conclude that the small protein CdrS is involved in regulation of cell division / cell morphology.