ABSTRACTConcrete contains low microbial biomass, but some bacteria can grow in this highly alkaline environment. We used silica-based DNA extraction and 16S rRNA sequence analysis to identify the bacteria in a corroded concrete bridge sample from Bethlehem, Pennsylvania.Staphylococcus,Streptococcus,Corynebacterium,Leifsonia,Vicinamibacterales, andActinophytocolawere the most abundant genera.