Among the transcripts up-regulated in the whole gut and down-regulated in bacteriocytes (supplementary 2, Supplementary Material online), the antimicrobial peptide attacin (–3.3 FC) and two lysozymes (–550.9 FC and –17.6 FC) are very likely responsible for controlling bacterial infections in the gut and not targeting obligate symbionts A. melophagi (fig. 4). Here, LYZ is linked to bacterial infectious disease.