Identification of a nth-Like Gene Encoding an Endonuclease III in Campylobacter jejuni

In this study, a BER homolog encoded by cj0595c (named nth) in C. jejuni was analyzed for endonuclease III activity and for its role in maintaining genomic stability. It was found that inactivation of nth resulted in elevated frequencies of spontaneous fluoroquinolone-resistant (FQR) and oxidative stress resistant (OXR) mutants, compared with the wild-type strain in C. jejuni. Sequencing analysis of the FQR and OXR mutants revealed that the elevated mutation rates were associated with C → T or G → A transition in gyrA (FQR mutants) or perR (for OXR mutants). In an in vitro assay, a purified recombinant C. jejuni Nth protein demonstrated endonuclease III activity that recognized and excised the thymine glycol (Tg) base from a double stranded DNA. These findings indicate that Nth functions as a BER repair enzyme in C. jejuni and is important for the repair of DNA damage, protecting the bacteria from stresses encountered within a host and in the environment. Introduction Campylobacter jejuni, a major bacterial foodborne pathogen, is among the most common causes of bacterial diarrhea in humans worldwide (Nachamkin et al., 2000). According to the United States Centers for Disease Control and Prevention (CDC), C. jejuni is estimated to cause 1.3 million infections and 120 deaths each year in the United States (Centers for Disease Control and Prevention [CDC], 2014). The main source of human Campylobacter infections is via contaminated food, water, or milk (Tau...
Source: Frontiers in Microbiology - Category: Microbiology Source Type: research