Prevalence and phylogenetic relationship of two β-carbonic anhydrases in affiliates of Enterobacteriaceae

Abstract

Enterobacteriaceae, one of the major families of microorganisms that inhabit the soil and gut, internally regulate constant fluctuations in soil and gut pH by buffer- ing these changes through the presence of carbonic anhy- drase (CA). In our study, we prove the prevalence of β-CA, derived from the can gene, in members of Enterobacteria- ceae by using a combination of experimental and bioinfor- matics approaches. Enzyme purification and western blot analysis revealed the presence of β-CA in Enterobacter sp. RS1. Genetic studies confirmed the presence of β-CA in both Enterobacter sp. RS1 and Citrobacter freundii SW3. Our analysis of the divergence of cynTand can genes among harboring members indicated that the can gene was more prominent in Enterobacteriaceae than cynT. Sequence anal- ysis of the can gene revealed a >25 % similarity among all sequences and a >50 % similarity among sequences from the Enterobacteriaceae family. The β-CA from C. freundii SW3 and Enterobacter sp. RS1, isolated from soil and used in this study, possessed a high similarity with the can gene. The close association among Enterobacteriaceae genera usu- ally found in the soil and gut and the sequence similarity of β-CA in the different genera of Enterobacteriaceae suggest the importance of the can gene in oscillating environmental conditions.