The accumulation of ammonia in poultry houses is of concern to bird and human health. Acidification of the litter by application of acidifying amendments such as sodium bisulfate ( SBS ) retains ammonia generated by microbial degradation of uric acid as harmless ammonium in the litter. Although some studies on the effects of litter amendments on specific bacteria and groups of bacteria have been carried out previously, wide gaps in knowledge remain. In the present study, 2 types of samples were prepared and either left unamended or amended with 2.5 or 10% SBS. One set of samples consisted of a 1:1 mixture of built-up litter and fresh poultry manure ( L/M ); the other of fresh wood shavings and fresh poultry manure ( S/M ). The samples were kept in the laboratory at room temperature for 35 d. The pH of unamended mixtures increased to 7.3 and 6.9 for L/M and S/M, respectively. A pH of 6.7 and 3.9 on day 35 was observed for L/M and SM with 2.5% SBS, respectively. The corresponding values for LM and SM amended with 10% SBS were 3.5 and 2.5, respectively. Plating data indicated that coliforms became less numerous in the unamended samples than the SBS-amended samples. This difference was also seen in data obtained by high-throughput sequencing of 16S rDNA. The sequencing data also indicated that sequences from the genus Oceanisphaera accounted for as much as 80% of the sequences from L/M and about 40% of those from S/M samples early on. Sequences from members of the order Clostridiales were enriched in L/M and S/M amended with 10% SBS as were sequences from the genus Turicibacter. Weisella species sequences were more prevalent in SBS-amended samples than in unamended ones. Sequences from the genus Corynebacterium, Brachybacterium, and Arthrobacter were more common in L/M samples than in S/M samples regardless of the SBS content. The data indicate that litter amendments affect some bacteria populations and not others. Further studies are required to determine if the observed population changes such as increased survival of coliforms warrant actions to improve the microbial quality of litter to be reused.