The Helicobacter pylori UvrC Nuclease Is Essential for Chromosomal Microimports after Natural Transformation

Riemerella anatipestifer UvrC is required for iron utilization, biofilm formation and virulence

UvrC is a subunit of excinuclease ABC, which mediates nucleotide excision repair (NER) in bacteria. Our previous studies showed that transposon Tn4531 insertion in the UvrC encoding gene Riean_1413 results in reduced biofilm formation by Riemerella anatipestifer strain CH3 and attenuates virulence of strain YZb1. In this study, whether R. anatipestifer UvrC has some biological functions other than NER was investigated. Firstly, the uvrC of R. anatipestifer strain Yb2 was in-frame deleted by homologous recombination, generating deletion mutant ΔuvrC, and its complemented strain cΔuvrC was constructed based on Escherichia coli - R. anatipestifer shuttle plasmid pRES. Compared to the wild-type (WT) R. anatipestifer strain Yb2, uvrC deleted mutant ΔuvrC significantly reduced biofilm formation, tolerance to H2O2- and HOCl-induced oxidative stress, iron utilization, and adhesion to and invasion of duck embryonic hepatocytes, but not its growth curve and proteolytic activity. In addition, animal experiments showed that the LD50 value of ΔuvrC in ducklings was about 13-fold higher than that of the WT, and the bacterial loads in ΔuvrC infected ducklings were significantly lower than those in Yb2-infected ducklings, indicating uvrC deletion in R. anatipestifer attenuated virulence. Taken together, the results of this study indicate that R. anatipestifer UvrC is required for iron utilization, biofilm formation, oxidative stress tolerance and virulence of strain Yb2, demonstrating multiple functions of UvrC.RESEARCH HIGHLIGHTSDeletion of uvrC in R. anatipestfer Yb2 significantly reduced its biofilm formation.uvrC deletion led to reduced tolerance to H2O2- and HOCl-induced oxidative stress.The iron utilization of uvrC deleted mutant was significantly reduced.The uvrC deletion in R. anatipestifer Yb2 attenuated its virulence.

Genome and population dynamics during chronic infection with Helicobacter pylori

Helicobacter pylori is responsible for one of the most prevalent bacterial infections worldwide. Chronic infection typically leads to chronic active gastritis. Clinical sequelae, including peptic ulcers, mucosa-associated lymphoid tissue lymphoma or, most importantly, gastric adenocarcinoma develop in 10-15% of cases. H. pylori is characterized by extensive inter-strain diversity which is the result of a high mutation rate, recombination, and a large repertoire of restriction-modification systems. This diversity is thought to be a major contributor to H. pylori's persistence and exceptional aptitude to adapt to the gastric environment and evade the immune system. This review covers efforts in the last decade to characterize and understand the multiple layers of H. pylori's diversity in different biological contexts.

The Remarkable Genetics of Helicobacter pylori

The Helicobacter pylori genome is more thoroughly mixed by homologous recombination than by any other organism that has been investigated, leading to apparent "free recombination" within populations. A recent mBio article by F. Ailloud, I. Estibariz, G. Pfaffinger, and S. Suerbaum (mBio 13:e01811-22, 2022, https://doi.org/10.1128/mbio.01811-22) helps to elucidate the cellular machinery that is used to achieve these unusual rates of genetic exchange. Specifically, they show that the UvrC gene, which is part of the repair machinery for DNA damage caused by ultraviolet light, has evolved an additional function in H. pylori, allowing very short tracts of DNA-with a mean length of only 28 bp-to be imported into the genome during natural transformation.