Expression of Vha100-4^{dsRNA.shRNA.Scer\UAS} under the control of Scer\GAL4^Tsp42Ec leads to reduced acidity in the acidic region of the larval midgut, but no significant differences in cross-sectional area in each gut region, as compared with controls. Under optimal rearing conditions, the survival rate and development of these larvae is not significantly different from controls, but there is a small but significant increase in adult lifespan. When mutant first instar larvae are orally infected with Pseudomonas aeruginosa, survival rate is significantly decreased and developmental time is significantly increased, as compared with controls. When mutant third instar larvae are fed Pseudomonas entomophila, the number of CFUs in the midgut per larva is significantly increased, as compared to controls. Mutant larvae exposed to high dietary KCl or NaCl exhibit decreased survival. Mutant larvae exhibit differences in the relative abundance of various bacterial genera typically found in lab-reared Drosophila as compared with controls, with significantly increased Acetobacter in gut regions distal to the acidic region, and Lactobacillus significantly elevated in the acidic and neutral regions.