Characteristics of a Novel Manganese Superoxide Dismutase of a Hadal Sea Cucumber (Paelopatides sp.) from the Mariana Trench

Characterization of a Novel Superoxide Dismutase from a Deep-sea Sea Cucumber (Psychoropotes verruciaudatus)

At present, deep-sea enzymes are a research hotspot. In this study, a novel copper-zinc superoxide dismutase (CuZnSOD) was successfully cloned and characterized from a new species of sea cucumber Psychropotes verruciaudatus (PVCuZnSOD). The relative molecular weight of the PVCuZnSOD monomer is 15 kDa. The optimum temperature of PVCuZnSOD is 20 °C, and it maintains high activity in the range of 0-60 °C. It also has high thermal stability when incubated at 37 °C. PVCuZnSOD has a maximum activity of more than 50% in the pH range of 4-11 and a high activity at pH 11. In addition, PVCuZnSOD has strong tolerance to Ni²⁺, Mg²⁺, Ba²⁺, and Ca²⁺, and it can withstand chemical reagents, such as Tween20, TritonX-100, ethanol, glycerol, isopropanol, DMSO, urea, and GuHCl. PVCuZnSOD also shows great stability to gastrointestinal fluid compared with bovine SOD. These characteristics show that PVCuZnSOD has great application potential in medicine, food, and other products.

The Keap1-Nrf2 signaling pathway regulates antioxidant defenses of Ctenopharyngodon idella induced by bacterial infection

Respiratory burst is a process involving rapid production of reactive oxygen species (ROS) for eliminating invading pathogens. However, excessive ROS production can be fatal to the host organism. The Keap1-Nrf2-ARE (Kelch-like ECH-associated protein 1 [Keap1]; Nuclear factor erythroid-derived 2-like 2 [Nrf2]; Antioxidant responsive element [ARE]) signaling pathway plays an important role in alleviating oxidative stress and preserving cellular homeostasis. However, the role of Keap1 during bacterial infection in fish remains unclear. In this study, we cloned and characterized the Keap1 gene of grass carp (CiKeap1) for the first time. CiKeap1 encodes a 593-amino acid protein of the Keap1b type. The tissue distribution analysis data revealed that the brain contains the highest transcription level of Keap1, followed by the heart and liver. The infection of Aeromonas hydrophila and Staphylococcus aureus obviously modulated the gene transcription and protein expression levels of Keap1, which suggested that the CiKeap1 participates in antibacterial immune responses. Furthermore, in vitro overexpression assays clarified the defensive and regular roles of CiKeap1 in maintaining host redox homeostasis in response to bacterial infection through the Keap1-Nrf2-ARE signaling pathway. In conclusion, the present results provide an expanded perspective on the role of Keap1 in teleost immunology that can guide healthy farming cultivation of grass carp.

Advances in cold-adapted enzymes derived from microorganisms

Cold-adapted enzymes, produced in cold-adapted organisms, are a class of enzyme with catalytic activity at low temperatures, high temperature sensitivity, and the ability to adapt to cold stimulation. These enzymes are largely derived from animals, plants, and microorganisms in polar areas, mountains, and the deep sea. With the rapid development of modern biotechnology, cold-adapted enzymes have been implemented in human and other animal food production, the protection and restoration of environments, and fundamental biological research, among other areas. Cold-adapted enzymes derived from microorganisms have attracted much attention because of their short production cycles, high yield, and simple separation and purification, compared with cold-adapted enzymes derived from plants and animals. In this review we discuss various types of cold-adapted enzyme from cold-adapted microorganisms, along with associated applications, catalytic mechanisms, and molecular modification methods, to establish foundation for the theoretical research and application of cold-adapted enzymes.

Effects of microbial community and disease resistance against Vibrio splendidus of Yesso scallop (Patinopecten yessoensis) fed supplementary diets of tussah immunoreactive substances and antimicrobial peptides

This study was conducted to investigate the effects of dietary supplementation of tussah immunoreactive substances (TIS) and antimicrobial peptides (AMPs) on microbial community and resistance against Vibrio splendidus of Yesso scallop Patinopecten yessoensis. Scallops were fed with the basal diets supplemented with TIS (T group), AMPs (A group), or both of the two (TA group). After the feeding trial, the microbial community changes were evaluated, and the challenge test with V. splendidus was conducted, as well as the immune parameters and digestive enzyme activities were determined. The results revealed that the TA group was more capable of modulating the bacterial community composition of scallops by increasing the potentially beneficial bacteria and suppressing the pathogenic microorganism during the feeding trial. After injection, the cumulative mortality rate in TA group was notably lower than others. In addition, the TA group showed better digestive and immune parameters involved in digestive capacity, phagocyte function, phosphatase-responsiveness, and oxidation resistance. These results collectively confirmed that dietary TIS and AMPs in diet could effectively modulate the microflora structure and improve disease resistance against V. splendidus of scallop, and the positive effects were more obvious when dietary supplementation of them in combination.

Scientific and technological progress in the microbial exploration of the hadal zone

The hadal zone is the deepest point in the ocean with a depth that exceeds 6000 m. Exploration of the biological communities in hadal zone began in the 1950s (the first wave of hadal exploration) and substantial advances have been made since the turn of the twenty-first century (the second wave of hadal exploration), resulting in a focus on the hadal sphere as a research hotspot because of its unique physical and chemical conditions. A variety of prokaryotes are found in the hadal zone. The mechanisms used by these prokaryotes to manage the high hydrostatic pressures and acquire energy from the environment are of substantial interest. Moreover, the symbioses between microbes and hadal animals have barely been studied. In addition, equipment has been developed that can now mimic hadal environments in the laboratory and allow cultivation of microbes under simulated in situ pressure. This review provides a brief summary of recent progress in the mechanisms by which microbes adapt to high hydrostatic pressures, manage limited energy resources and coexist with animals in the hadal zone, as well as technical developments in the exploration of hadal microbial life.

Molecular and functional characterization of mitochondrial manganese superoxide dismutase from Macrobrachium rosenbergii during bacterial infection

Superoxide dismutases (SODs) are the main antioxidant enzymes involved in alleviating oxidative stress. Although mitochondrial manganese SOD (mMnSOD) has been reported to be correlated with the immune response in crustaceans, its biological properties and role in the immune response remain unclear. Here, we cloned the Macrobrachium rosenbergii mMnSOD (MrmMnSOD), analyzed its activity and expression pattern under Staphylococcus aureus and Vibrio parahaemolyticus infection, and further explored its possible mechanism during antibacterial immune response. The results showed that both enzyme activity and the expression of MrmMnSOD were significantly up-regulated by bacterial infection. MrmMnSOD knockdown made the prawn susceptible to Vibrio infection, which increased the mortality rate and the number of bacteria in haemocytes. The bacterial agglutination assay confirmed that MrmMnSOD decreases bacterial abundance via agglutination. Overall, this work identified antibacterial function of MrmMnSOD in the immune response. In addition to contributing to immunological theory, these findings aid disease prevention and control in crustacean aquaculture.

A thermostable Fe/Mn SOD of Geobacillus sp. PCH100 isolated from glacial soil of Indian trans-Himalaya exhibits activity in the presence of common inhibitors

Superoxide dismutases are the enzymes involved in dismutation of superoxide radicals into oxygen and hydrogen peroxide. The present work reports a thermostable Fe/Mn SOD of Geobacillus sp. strain PCH100 (GsSOD) isolated from glacial soil. Purified recombinant GsSOD is a dimeric protein of ~57 kDa that exhibited highest activity at a temperature of 10 °C and pH of 7.8. Maximum enzyme velocity and Michaelis constant of the GsSOD were 1098.90 units/mg and 0.62 μM, respectively. At 80 °C, thermal inactivation rate constant and half-life of GsSOD were 3.33 × 10^-3 min^-1 and 208 min, respectively. Interestingly, GsSOD tolerated a temperature of 100 °C and 130 °C up to 15 min and 5 min, respectively. Circular dichroism and differential scanning calorimetry confirmed thermostable nature of GsSOD. Apoenzyme of GsSOD regained enzymatic activity in the presence of Fe²⁺ and Mn²⁺ as metal ion cofactors. GsSOD was stable under varying concentrations of chemicals, namely ethylenediaminetetraacetic acid, potassium cyanide, hydrogen peroxide, chloroform-ethanol, 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate, Tween-20, Triton X-100, urea, and guanidine hydrochloride. The enzyme exhibited >70% activity in presence of 10 mM metal ions. Owing to its thermostable nature and resistance to chemical inhibitors, GsSOD is a potential enzyme for industrial applications.