A Proteomic Analysis of the Bacterially Infected Midgut of the Silkworm Bombyx mori L.

The midgut is a crucial organ for the digestion and absorption of nutrients in silkworms. It also serves as a barrier to the entry of various diseases. The primary objective of this study was to investigate the midgut proteins expressed after the inoculation of bacteria, specifically Staphylococcus aureus and Bacillus subtilis. These two pathogens cause the bacterial flacherie in silkworms. We focused on the midgut proteins of 5th instar larvae and analysed them using SDS gel electrophoresis and matrix-assisted laser desorption time-of-flight mass spectrometry. The midgut samples were collected from both infected and uninfected larvae on the second to sixth day post-infection (DPI). The protein content was determined using the nano-drop spectrophotometric method to gain insights into the variations in protein expression in bacterially infected silkworms. The outcome revealed that total protein concentration increased on day 2 and decreased on days 3 and 4. On days 5 and 6, the Bacillus subtilis post-infection gradually increased. In contrast, protein content increases in samples with Staphylococcus aureus infection on days 2 and 3, decreases on days 4, and then gradually increases on days 5 and 6. The expressed 43 kDa protein was analysed by MALDI-TOF/MS following electrophoresis. The expressed protein is a member of the actin A3 protein family. This member of the actin family includes Actin A3.