Summary: The cellular responses of Borrelia burgdorferiTo reactive oxygen species (ROS) encountered during the different stages of its infective cycle are poorly understood. Few enzymes responsible for protecting proteins, DNA/RNA and lipids from damage by ROS have been identified and characterized. Data presented here suggest that bb0728 encodes an enzyme involved in this process. Biochemical analyses on purified recombinant BB0728 indicated that it functioned as a coenzyme A disulphide reductase (CoADR) (specific activity ≈ 26 units per mg of protein). This enzyme was specific for coenzyme A (CoA) disulphide, required NADH and had no significant activity against other disulphides, such as oxidized glutathione or thioredoxin. The high intracellular concentration of reduced CoA (CoASH) in B. burgdorferi cells (∼1 mM) and absence of glutathione suggest that CoA is the major low‐molecular‐weight thiol in this spirochete. Interestingly, CoASH was able to reduce H₂O₂ and be regenerated by CoADR suggesting one role for the system may be to protect B. burgdorferi from ROS. Further, mobility‐shift assays and transcriptional fusion data indicated that bb0728 was positively regulated by the Borrelia oxidative stress response regulator, BosR. Taken together, these data suggest a role for BB0728 in intracellular redox and the oxidative stress response in B. burgdorferi.

Shewanella algae , S. putrefaciens , and Photobacterium damselae subsp. damselae are indigenous marine bacteria and human pathogens causing cellulitis, necrotizing fasciitis, abscesses, septicemia, and death. Infections are rare and are most often associated with the immunocompromised host. A study was performed on the microbiological flora of oysters and seawater from commercial oyster harvesting sites in the Delaware Bay, New Jersey. From 276 water and shellfish samples tested, 1,421 bacterial isolates were picked for biochemical identification and 170 (12.0%) of the isolates were presumptively identified as S. putrefaciens , 26 (1.8%) were presumptively identified as P. damselae subsp. damselae , and 665 (46.8%) could not be identified using the API 20E identification database. Sequencing of the 16S rRNA genes of 22 S. putrefaciens -like isolates identified them as S. abalonesis , S. algae , S. baltica , S. hafniensis , S. marisflavi , S. putrefaciens , Listonella anguillarum , and P. damselae . Beta-hemolysis was produced by some S. algae and P. damselae isolates, while isolates of S. baltica and L. anguillarum , species perceived as nonpathogenic, also exhibited β-hemolysis and growth at 37°C. To our knowledge, this is the first time these beta-hemolytic strains were reported from shellfish or seawater from the Delaware Bay. Pathogenic Shewanella and Photobacterium species could pose a health threat through the ingestion of contaminated seafood, by cuts or abrasions acquired in the marine environment, or by swimming and other recreational activities.

A wealth of H₂O‐producing NADH oxidase (NOX) homologues have been discovered in the genomes of the hyperthermophilic Archaea, including two homologues in the genome of Pyrococcus furiosus which have been designated as NOX1 and NOX2. In order to investigate the function of NOX1, the structural gene encoding NOX1 was cloned from the genome of P. furiosus and expressed in Escherichia coli, and the resulting recombinant enzyme (rNOX1) was purified to homogeneity. The enzyme is a thermostable flavoprotein that can be reconstituted only with FAD. rNOX1 catalyzes the oxidation of NADH, producing both H₂O₂ and H₂O as reduction products of O₂ (O₂ + 1–2NADH + 1–2H⁺ → 1–2NAD⁺ + H₂O₂ or 2H₂O). To our knowledge, this is the first NADH oxidase found to produce both H₂O₂ and H₂O. The enzyme exhibits a low K_m for NADH (< 4 µm), and shows little or no reaction with NADPH. Transcriptional analyses demonstrated that NOX1 is constitutively expressed regardless of the carbon source and a single promoter was identified 25 bp upstream of the nox1 gene by primer extension. Although P. furiosus is a strict anaerobe, it may tolerate oxygen to some extent and we anticipate NOX1 to be involved in the response to oxygen at high temperatures.