Taxonomic identification and temperature stress tolerance mechanisms of Aequorivita marisscotiae sp. nov.

The deep sea harbours microorganisms with unique life characteristics and activities due to adaptation to particular environmental conditions, but the limited sample collection and pure culture techniques available constrain the study of deep-sea microorganisms. In this study, strain Ant34-E75 was isolated from Antarctic deep-sea sediment samples and showed the highest 16 S rRNA gene sequence similarity (97.18%) with the strain Aequorivita viscosa 8-1bT. Strain Ant34-E75 is psychrotrophic and can effectively increase the cold tolerance of Chlamydomonas reinhardtii (a model organism). Subsequent transcriptome analysis revealed multiple mechanisms involved in the Ant34-E75 response to temperature stress, and weighted gene co-expression network analysis (WGCNA) showed that the peptidoglycan synthesis pathway was the key component. Overall, this study provides insights into the characteristics of a deep-sea microorganism and elucidates mechanisms of temperature adaptation at the molecular level.

Taxonomic Identification of the Arctic Strain Nocardioides Arcticus Sp. Nov. and Global Transcriptomic Analysis in Response to Hydrogen Peroxide Stress.

Microorganisms living in polar regions rely on specialized mechanisms to adapt to extreme environments. The study of their stress adaptation mechanisms is a hot topic in international microbiology research. In this study, a bacterial strain (Arc9.136) isolated from Arctic marine sediments was selected to implement polyphasic taxonomic identification based on factors such as genetic characteristics, physiological and biochemical properties, and chemical composition. The results showed that strain Arc9.136 is classified to the genus Nocardioides, for which the name Nocardioides arcticus sp. nov. is proposed. The ozone hole over the Arctic leads to increased ultraviolet (UV-B) radiation, and low temperatures lead to increased dissolved content in seawater. These extreme environmental conditions result in oxidative stress, inducing a strong response in microorganisms. Based on the functional classification of significantly differentially expressed genes under 1 mM H2O2 stress, we suspect that Arc9.136 may respond to oxidative stress through the following strategies: (1) efficient utilization of various carbon sources to improve carbohydrate transport and metabolism; (2) altering ion transport and metabolism by decreasing the uptake of divalent iron (to avoid the Fenton reaction) and increasing the utilization of trivalent iron (to maintain intracellular iron homeostasis); (3) increasing the level of cell replication, DNA repair, and defense functions, repairing DNA damage caused by H2O2; (4) and changing the composition of lipids in the cell membrane and reducing the sensitivity of lipid peroxidation. This study provides insights into the stress resistance mechanisms of microorganisms in extreme environments and highlights the potential for developing low-temperature active microbial resources.

Diversity of Cultivable Microbes From Soil of the Fildes Peninsula, Antarctica, and Their Potential Application.

To explore the diversity and application potential of Antarctic microorganisms, 1208 strains bacteria and fungi were isolated from 5 samples collected from the Fildes Peninsula during China's 27th and 31st Antarctic expeditions. By using 16S and ITS sequence similarity alignment, 83 strains bacteria belonging to 20 genera and 30 strains fungi belonging to 7 genera were identified. Among them, 1 strains bacteria and 6 strains fungi showed low sequence similarity to the database, suggesting that they might be novel species. Physiological-biochemical characteristics showed that the identified bacteria could utilize many kinds of carbohydrates and that the identified fungi could produce several kinds of extracellular enzymes. The fungal strain MS-19, identified as Aspergillus sydowii, possesses the potential to produce antifungal activity agents based on an activity-guided approach. Further isolation yielded four polyketones: versicone A (1), versicone B (2), 4-methyl-5,6-dihydro-2H-pyran-2-one (3), and (R)-(+)-sydowic acid (4). It should be noted that 1 displayed strong activity against Candida albicans, with an MIC value of 3.91 µg/mL.

Hepcidin Gene Cloning and Expression Pattern in Turbot (Scophthalmus maximus) after Vibrio. anguillarum Infection.

BACKGROUND: Antimicrobial peptides play crucial roles in organisms as the first line of defense against invading pathogens. OBJECTIVE: To isolate the hepcidin (hepc1) gene from the liver of turbot (Scophthalmus maximus) challenged with Vibrio anguillarum (GenBank accession number: AM113708), characterize it, and assess its expression level in various tissues. MATERIALS AND METHODS: The DNA sequence of hepcidin from S. maximus was determined from the total RNA extracted and reverse transcribed from this fish. The expression levels of tissue-specific hepcidin transcripts were determined using reverse-transcriptase polymerase chain reactions. RESULTS: Hepcidin levels increased in the livers, head kidneys and spleens of the fish. The transcriptional increase was especially noticeable in the liver after bacterial infection commencement. The presence of hepcidin and interleukin-beta (IL-1ß) in blood leukocytes was compared at the transcription level and hepcidin transcripts were detected earlier than IL-1ß transcripts after infection, indicating that hepcidin might serve as the first line of defense to kill bacteria and may also play a more direct and effective role than that of IL-1ß during the initial stage of the innate immune response when turbot are exposed to bacteria invasion. CONCLUSIONS: Hepcidin might serve as the first line of defense to kill bacteria and may also play a more direct and effective role than that of IL-1ß during the initial stage of the innate immune response when turbot are exposed to bacteria invasion.

Brain uptake of a non-radioactive pseudo-carrier and its effect on the biodistribution of [(18)F]AV-133 in mouse brain.

INTRODUCTION: 9-[(18)F]Fluoropropyl-(+)-dihydrotetrabenazine ([(18)F]AV-133) is a new PET imaging agent targeting vesicular monoamine transporter type II (VMAT2). To shorten the preparation of [(18)F]AV-133 and to make it more widely available, a simple and rapid purification method using solid-phase extraction (SPE) instead of high-pressure liquid chromatography (HPLC) was developed. The SPE method produced doses containing the non-radioactive pseudo-carrier 9-hydroxypropyl-(+)-dihydrotetrabenazine (AV-149). The objectives of this study were to evaluate the brain uptake of AV-149 by UPLC-MS/MS and its effect on the biodistribution of [(18)F]AV-133 in the brains of mice. METHODS: The mice were injected with a bolus including [(18)F]AV-133 and different doses of AV-149. Brain tissue and blood samples were harvested. The effect of different amounts of AV-149 on [(18)F]AV-133 was evaluated by quantifying the brain distribution of radiolabelled tracer [(18)F]AV-133. The concentrations of AV-149 in the brain and plasma were analyzed using a UPLC-MS/MS method. RESULTS: The concentrations of AV-149 in the brain and plasma exhibited a good linear relationship with the doses. The receptor occupancy curve was fit, and the calculated ED50 value was 8.165mg/kg. The brain biodistribution and regional selectivity of [(18)F]AV-133 had no obvious differences at AV-149 doses lower than 0.1mg/kg. With increasing doses of AV-149, the brain biodistribution of [(18)F]AV-133 changed significantly. CONCLUSION: The results are important to further support that the improved radiolabelling procedure of [(18)F]AV-133 using an SPE method may be suitable for routine clinical application.

Mapping the target localization and biodistribution of non-radiolabeled VMAT2 ligands in rat brain.

Imaging targeting vesicular monoamine transporter (VMAT2) alterations is a sensitive tool for early diagnosis of Parkinson's disease. Our group has reported several novel 2-amino-DTBZ derivatives as potential VMAT2 imaging agents. The objective of this paper is to develop a non-radiolabeled methodology to screen the candidate compounds for accelerating the drug discovery process. 9-[(18)F]fluoropropyl-(+)-dihydrotetrabenazine ([(18)F]AV-133) is a PET imaging agent targeting VMAT2 binding sites in the brain. Nonradioactive AV-133 was injected (iv) into rats, at the end of the allotted time, the animals were killed and six regions of brain and plasma from each animal were processed for quantitative measurement of AV-133 by LC-MS/MS. These data were converted to the percentage injected dose per gram tissue weight (%ID/g tissue) and the brain target tissue to background ratios to allow direct comparison with data obtained by gamma counting of the injected radioactive [(18)F]AV-133. The %ID/g and the brain target tissue to background ratios calculated using the LC-MS/MS method were highly correlated to the values obtained by standard radioactivity measurements of [(18)F]AV-133. The pattern of AV-133 in rat brain was consistent with the known distribution of VMAT2. The concordance indicated that high-sensitivity LC-MS/MS is an indispensable tool in evaluating the quantity of administered chemical in tissue as part of the development of new molecular imaging probes. Furthermore, several novel 2-amino-DTBZ derivatives were detected using this methodology, and their biodistribution data in rat brain were obtained. The information about target engagements of candidates was provided.

Dose-response relationships of FMISO between trace dose and various macro-doses in rat by ultra-performance liquid chromatography with mass spectrometry and radioactivity analysis.

Screening the pharmacokinetics of candidates using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) may be efficacious and safe for the research and development of new PET imaging agents. However, the PET imaging agent is administered as trace dose and the sensitivity of LC-MS/MS is often insufficient. If the dose was increased to be quantifiable, it should be necessary to prove whether the pharmacokinetics between trace and macro-doses is consistent or not. In this paper, fluoromisonidazole (FMISO), a tumor PET imaging agent, was chosen to evaluate the dose-response pharmacokinetics by administering various single intravenous doses (0.1, 0.4, 1.6 and 6.4 mg/kg) in male Sprague-Dawley rats. The plasma concentration of FMISO was determined by an ultra-performance liquid chromatography-tandem mass spectrometric (UPLC-MS/MS) method, and the blood radioactivity of [(18)F]FMISO was detected by a gamma counter. By calculating and comparing the pharmacokinetic parameters, the total area under the plasma concentration-time curve from time zero to infinity (AUC(0-∞)) and peak plasma concentration (C(max)) values increased with the selected FMISO doses, and showing linear dose-dependent. On the other hand, some parameters related to time, such as the elimination half-lives (t(1/2)) and elimination rate constant (K(e)) were dose-independent, and there is no significant deference between trace dose and various macro-doses. The data should be useful to evaluate the novel 2-nitroimidazole derivatives as potential PET tumor imaging agents.