Experimentally validated data were obtained from experimental literatures. Bioinformatically predicted data were obtained by performing BLASTp search on 26573 complete bacterial genomes downloaded from NCBI against experimantally validated data in the database. For T6SS gene cluster prediction, we first performed BLASTp search against all experimentally validated T6SS core components archived in our database with identities > 30% and E-value < 0.0001, and identified regions containing more than 5 T6SS components, and the interval between two adjacent genes should not exceed 15000 bp, which resulted in 17183 putative T6SS gene clusters. For the prediction of T6SS-related proteins, we took as input the protein sequences of all bacteria genomes to perform BLASTp search against experimentally validated T6SEs, T6SIs, T6SRs and T6SAs archived in SecReT6. Proteins with Ha-value > 0.64 were considered as putative T6SS-related proteins. As a result, 74712, 37805, 420060 and 44019 putative T6SEs, T6SIs, T6SRs and T6SAs in bacterial genomes were identified, respectively.