Physicochemical Properties of the Soluble Dietary Fiber from Laminaria japonica and Its Role in the Regulation of Type 2 Diabetes Mice

Laminaria japonica is a large marine brown alga that is annually highly productive. However, due to its underutilization, its potential value is substantially wasted. For example, a lot of Laminaria japonica cellulose remains unused during production of algin. The soluble dietary fiber (SDF) was prepared from the byproducts of Laminaria japonica, and its physicochemical properties were explored. SDF exhibits good water-holding, oil-holding, water-absorbing swelling, glucose and cholesterol absorption capacity, and inhibitory activity of α-amylase and α-glucosidase. In addition, the beneficial effects of SDF in diabetic mice include reduced body weight, lower blood glucose, and relieved insulin resistance. Finally, the intestinal flora and metabolomic products were analyzed from feces using 16S amplicon and LC-MS/MS, respectively. SDF not only significantly changed the composition and structure of intestinal flora and intestinal metabolites, but also significantly increased the abundance of beneficial bacteria Akkermansia, Odoribacter and Bacteroides, decreased the abundance of harmful bacteria Staphylococcus, and increased the content of bioactive substances in intestinal tract, such as harmine, magnolol, arachidonic acid, prostaglandin E2, urimorelin and azelaic acid. Taken together, these findings suggest that dietary intake of SDF alleviates type 2 diabetes mellitus disease, and provides an important theoretical basis for SDF to be used as a functional food.

A diguanylate cyclase regulates biofilm formation in Rhodococcus sp. NJ-530 from Antarctica

Biofilms represent a protective survival mode in which bacteria adapt themselves to the natural environment for survival purposes. Biofilm formation is regulated by 3,5-cyclic diguanylic acid (c-di-GMP), which is a universal second messenger molecule in bacteria. Diguanylate cyclase (DGC) catalyses c-di-GMP intracellular synthesis, which plays important roles in bacterial adaptation to the natural environment. In this study, the DGC gene was first cloned from Antarctic Rhodococcus sp. NJ-530. DGC contained 948 nucleotides and encoded 315 amino acids with a molecular weight of 34.6 KDa and an isoelectric point of 5.58. qRT-PCR demonstrated that the DGC expression level was significantly affected by lower salinity and temperature. Consistently, more biofilm formation occurred under the same stress. It has been shown that Rhodococcus sp. NJ-530 can adapt to the extreme environment in Antarctica, which is closely related to biofilm formation. These results provide an important reference for studying the adaptive mechanism of Antarctic microorganisms to this extreme environment.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-03093-z.

External validation of the HCM Risk-Kids model for predicting sudden cardiac death in childhood hypertrophic cardiomyopathy

Background

Sudden cardiac death (SCD) is the most common mode of death in childhood hypertrophic cardiomyopathy (HCM). The newly developed HCM Risk-Kids model provides clinicians with individualised estimates of risk. The aim of this study was to externally validate the model in a large independent, multi-centre patient cohort.

Methods

A retrospective, longitudinal cohort of patients diagnosed with HCM aged 1–16 years independent of the HCM-Risk-Kids development and internal validation cohort was studied. Data on HCM Risk-Kids predictor variables (unexplained syncope, non-sustained ventricular tachycardia, maximal left ventricular wall-thickness, left atrial diameter and left ventricular outflow tract gradient) were collected from the time of baseline clinical evaluation. The performance of the HCM Risk-Kids model in predicting risk at 5 years was assessed.

Results

The cohort consisted of 421 patients with a median age at baseline evaluation of 12.3 years (IQR 7.3, 14.4). Over a median total follow up 3.48 years (IQR 1.83, 6.62, range 1 month – 20.7 years). Fourteen patients (3.3%) died and 10 (2.4%) underwent cardiac transplantation. Twenty-three patients (5.4%) met the SCD end-point within 5-years, with an overall incidence rate of 2.03 per 100 patient years (95% CI 1.48–2.78). Model validation showed a Harrell's C-index of 0.745 (95% CI 0.52–0.97) and Uno's C-index 0.714 (95% 0.58–0.85) with a calibration slope of 1.15 (95% 0.51–1.80). Figure 1a describes the agreement between predicted and observed 5-year cumulative proportion of SCD or equivalent events for each tertile of predicted risk in one imputed data set. One hundred and twenty-five (29.7%) patients had a predicted 5-year risk of ≥6%. SCD events occurred in 6 patients (2.0%) with a predicted risk <6% and 17 (13.6%) with a predicted risk ≥6. A 5-year predicted risk threshold of ≥6% identified 17 (73.9%) SCD-events with a corresponding C-statistic of 0.702 (95% CI 0.60–0.81) (Figure 1b).

Conclusions

This study reports the first external validation of the HCM Risk-Kids model in a large and geographically diverse patient population. A 5-year predicted risk of ≥6% identified over 70% of events, confirming that HCM Risk-Kids provides a method for individualised risk predictions and shared decision making in children with HCM. Incorporation of the model into routine clinical care will enable independent prospective model validation and assessment of the effect of its use in clinical practice.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): British Heart FoundationMedical Research Council Observed vs predicted risk by tertilesObserved vs predicted by threshold

[Advances in indocyanine green fluorescence imaging during hepatectomy]

While surgical operation is the preferred treatment for liver malignancies,the postoperative recurrence rate remains high. In the early 21^st century,Japanese scientists first reported the use of indocyanine green(ICG) in liver resection. Follow-up studies also found its potential applications such as identifying tumors,determining surgical margins,delineating segmental boundaries,and preventing bile leakage. At present,ICG fluorescence imaging is applied to some types of hepatectomy with excellent effect and is expected to assist in generating surgical strategies for liver malignancies. However,its safety and efficacy still need further studies to evaluate.

[The comparison of prognosis and risk factors after radical resection for pancreatic ductal adenocarcinoma between China Pancreas Data Center and SEER]

Objectives: To compare the prognosis of patients underwent radical resection for pancreatic ductal adenocarcinoma(PDAC) in Surveillance, Epidemiology, and End Results(SEER) and China Pancreas Data Center(CPDC), and to compare the prognostic factors for PDAC in both databases. Methods: The data of patients underwent radical resection for PDAC in CPDC database from January 2016 to December 2017 and SEER database from January 2014 to December 2015 were retrospectively analyzed. The prognosis of patients in both databases was analyzed by the Kaplan-Meier method, Log-rank method, and propensity score matching, and the Cox proportional hazard regression was used to analyze the independent prognosis factors for PDAC. Results: There were 1 977 cases and 2 220 cases of pancreatic cancer that underwent radical resection from CPDC and SEER, respectively. There were more male patients(60.90%,1 204/1 977) than female patients(39.10%,773/1 977) in CPDC, while nearly 1∶1 ratio(male:1 112 cases,female:1108)was observed between male and female in SEER(χ²=48.977,P<0.01). The proportion of patients under 45 years old was the smallest in both databases, and the age group with the most significant proportion was 60 to 74 years old. The ratio of patients over 75 years old in the SEER(24.28%,539/2 220) was higher than that of CPDC(7.89%,156/1 977)(χ²=202.090,P<0.01), while the proportion of patients between 45 and 59 years old in CPDC(33.69%,666/1 977) was higher than that in SEER(19.77%,439/2 220)(χ²=103.640,P<0.01). There were more pancreatic head cancers than body and tail cancers in both databases, and no statistical difference was found in tumor size between the two databases (W=2 181 502,P=0.740). More positive and examined lymph nodes were found in SEER patients (W=3 265 131,W=2 954 363,all P<0.01); and the proportion of patients who had at least 15 lymph nodes dissected was higher in SEER(63.24%,1 404/2 220)(χ²=532.130,P<0.01). There were more patients without neoadjuvant or adjuvant therapy in CPDC(57.16%,1 130/1 977) than that in SEER(24.91%,553/2 220)(χ²=451.390,P<0.01). After propensity score matching, the overall survival for CPDC was better than that for SEER(Log-rank test:χ²=4.500,P=0.034), and the median overall survival was 24 months and 23 months respectively. Cox regressional analysis showed the common independent prognosis factors in both databases were ≥75 years old, pancreatic head cancer, poorly differentiated and undifferentiated tumors, T stage, N stage(All P<0.05). Neoadjuvant or adjuvant therapy was a protective factor in both databases(CPDC:Wald=27.082;SEER:Wald=212.285, all P<0.01) and 45 to 59 years old was protective factor in the SEER database(Wald=5.212,P=0.020). Conclusions: The data in both databases have a good consistency. However, in terms of data quality, examined lymph nodes count, and neoadjuvant/adjuvant therapy rate, the CPDC differs greatly from the SEER.

Study on Catalytic Oxidation, Flocculation and Sedimentation of Acidizing and Fracturing Wastewater

The acidizing and fracturing waste fluid in a wellsite in northern Shaanxi was treated by catalytic oxidation and flocculation precipitation. It investigated the effect of different coagulants and their dosage and the wastewater pH on coagulation precipitation. As for chemical oxidation experiment, it investigated the effect of oxidant dosage and reaction time on its treatment effect. The results showed that when 30% hydrogen peroxide (volume percentage) was added at the dosage of 0.3% and oxidized for 50 min, the pH was adjusted to 7.5 and 350 mg/L polyaluminum chloride (PAC) and 4 mg/L polyacrylamide were added (PAM); after processing the waste liquid, total iron, chemical oxygen demand (COD), chromaticity, and average corrosion rate were reduced from 252.75 mg/L, 3427.50 mg/L, 624.15°, and 0.1226 mm/a to 0.12 mg/L, 275.18 mg/L, 125° and 0.0217 mm/a, respectively; effective removal of iron and color, reduced COD, and controlled corrosion was achieved.

Two class II CPD photolyases, PiPhr1 and PiPhr2, with CPD repair activity from the Antarctic diatom Phaeodactylum tricornutum ICE-H

Two gene of class II photolyases, PiPhr1 (1833 bp) and PiPhr2 (1809 bp), from the Antarctic diatom Phaeodactylum tricornutum ICE-H were cloned, the recombinant proteins expressed and purified. The molecular weight of the recombinant photolyases were determined to be 68 kDa with a pI of 9.04 and 68.82 with a pI of 7.31, respectively. Activity studies showed that both the recombinant enzymes were involved in the repair DNA damaged by UV light, that is they were most likely photolyases involved in photorepair of DNA. Further confirmation of this function was demonstrated by the increased expression of PiPhr1 and PiPhr2 after exposure to UV radiation, blue light and dark conditions by qRT-PCR. In summary, PiPhr1 and PiPhr2 were up regulated by UVB irradiation and blue light at 0.5 h and 3 h. Longtime (3 h) exposure to dark also increased the expression of PiPhr1 and PiPhr2. In vitro photoreactivation assays showed that PiPhr1 and PiPhr2 could repair CPDs utilizing blue light. This is the first time CPD Class II photolyase has been reported from Antarctic diatom. These results will add to the knowledge of the diatom CPF family and assist in understanding the functional role of these genes in Antarctic diatoms.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02927-0.

The complete chloroplast genome of Ishige okamurae

Ishige okamurae plays an important role in marine ecosystem and biological resource utilization. The total length of chloroplast genome was 129,988 bp, containing a large single-copy region (LSC, 77,531 bp), a small single-copy region (SSC, 41,795 bp) and a pair of inverted repeat regions (IRs, 10,662 bp). The circular genome consisted of 101 protein-coding genes, 29 tRNA genes, and six rRNA genes, with a total of 136. Phylogenetic analysis confirmed the position of I. okamurae within the Phaeophyta.

Effects of Dietary Supplementation with κ-Selenocarrageenan on the Selenium Accumulation and Intestinal Microbiota of the Sea Cucumbers Apostichopus japonicus

A 30-day feeding trial was conducted to investigate the effect of κ-selenocarrageenan on the growth performance, selenium accumulation, antioxidant capacity, and intestinal microbiota of sea cucumbers Apostichopus japonicus, with different sizes (70 g ± 10 g and 100 g ± 10 g). Sea cucumbers of each size were randomly assigned into two groups; a diet without supplemented κ-selenocarrageenan was referred to as a control diet, or supplemented with κ-selenocarrageenan at selenium (Se) levels of 2.0 μg/g. Selenium accumulation in the body wall and intestine was determined on days 0, 10, 20, and 30. The survival rate (SR) was significantly higher in the κ-selenocarrageenan-treated group (Se group) than in the control group. After 30 days of feeding, κ-selenocarrageenan supplementation increased the activities of glutathione peroxidase (GSH-Px) and total antioxidant capacity (T-AOC), and decreased malondialdehyde (MDA) levels in A. japonicus. Furthermore, the intestinal microbiota diversity of sea cucumbers was increased by dietary supplementation with κ-selenocarrageenan and the relative abundances of some probiotics (such as Sulfitobacter and Rhodobacteraceae) were also increased. It is suggested that κ-selenocarrageenan could increase the antioxidant capacity and modulate the intestinal microbiota of sea cucumbers A. japonicus. Further researches will be conducted for its optimal administration concentrations in vivo.

A Class II CPD Photolyase and a 6-4 Photolyase with Photorepair Activity from the Antarctic Moss Pohlia nutans M211

Antarctic mosses are the dominant vegetation in the Antarctic continent. Because of stratospheric ozone depletion, they can withstand physiological extreme UV. The formation of CPD and 6-4PP is one of the most harmful damages of UV to DNA. DNA damage can interfere with replication and transcription, resulting in mutation and death. Two types of photolyase, CPD photolyase and 6-4 photolyase, are capable of specific binding CPD or 6-4PP and repairing these lesions. However, there is little research on photolyase in Antarctic moss. Here, we isolated a gene encoding class II CPD photolyase (PnCPDPhr) and a gene encoding 6-4 photolyase (Pn6-4Phr) from Antarctic moss P. nutans M211. When exposed to UVB, CPDs accumulated in gametophytes and the gene expressions of PnCPDPhr and Pn6-4Phr were both up-regulated. In addition, the in vitro expression and photoreactivation assays of PnCPDPhr and Pn6-4Phr were performed. Our results demonstrated that PnCPDPhr and Pn6-4Phr have an effective activity of DNA repair. This is the first study to determine the CPD accumulation in Antarctic moss as well as the first report isolating CPD photolyase and 6-4 photolyase from Antarctic moss. These results will enrich the knowledge of photolyase family and benefit the exploitation of functioning gene in Antarctic moss.

The complete mitochondrial genome of Sporobolus alterniflorus (loisel.) P.M. Peterson & Saarela (Poaceae) and phylogenetic analysis

The complete mitochondrial genome of Sporobolus alterniflorus was a circular molecule of 566,328 bp in length and encoded 64 genes, including 35 protein-coding genes, 24 tRNA genes, and 5 rRNA genes. The most common initiated codon was ATG and the most common termination codon was CAT. The overall A + T content was 55.96%. The phylogenomic analysis revealed that Sporobolus alterniflorus have a closest phylogenetic relationship with Sorghum bicolor.

[A comparative study on the construction methods of animal models of aortic arch dissection]

Objective: To compare the effectiveness and safety of different methods to construct animal models of aortic arch dissection (AAD), and explore safe and effective methods for constructing AAD animal models. Methods: Twenty-four healthy mongrel dogs were divided into 4 groups by random number table (n=6). Group A: Venous incision needle high pressure water flow impact method; Group B: Venous incision needle non-high pressure water flow impact method; Group C: Transarterial sheath non-high pressure water flow impact method; Group D: Two-way balloon expansion combined with elastase perfusion method. Imaging examinations were performed immediately and 7 days after operation, aortic tissue biopsy and pathological staining were performed 15 days after operation to observe the formation of AAD. The operation time, aortic blood flow block time, model construction success rate, dissection tear length, postoperative survival rate and survival time of four groups of experimental dogs were collected to compare the effectiveness and safety of different construction methods. Results: There were no significant difference of the gender, age and weight between four groups of experimental dogs (all P>0.05). The operation time of four groups of experimental dogs were (111.6±8.0), (168.0±17.4), (164.4±13.9), (202.8±21.5)min, and the difference was statistically significant (F=39.973, P<0.001). The operation time of group A was significantly lower than group B, C and D (all P<0.001). The aortic blood flow block time of four groups of experimental dogs were (5.2±1.8), (19.6±3.8), (20.6±3.9), and (18.6±3.0) min, and the difference was statistically significant (all P<0.001). The aortic blood flow block time of group A was significantly lower than group B, C and D (F=27.598, P<0.001). The four groups of experimental dogs had 5, 5, 4, and 1 model were successfully constructed, respectively, and the difference was statistically significant (P=0.008). The successful rate of model construction in group A was significantly higher than that in group D (P=0.040). The dissection tear length of four groups were (14.4±3.0), (11.3±4.2), (7.0±2.3), (4.7±0.6) cm,and the difference was statistically significant (F=8.103, P=0.003). The dissection tear length of group A was significantly longer than group C, D (all P<0.05). The postoperative survival time were 15.0(10.0, 15.0), 5.0(3.0, 10.0), 3.5(1.5, 4.8), 10.0(2.8, 15.0) days, and the difference was statistically significant (χ²=7.825,P=0.036). The postoperative survival time of group A was significantly higher than group B, C (all P<0.05). There was no significant difference in the survival rate of the four groups (P=1.000). The pathological staining results showed that the elastic fiber at the tearing point of AAD was destroyed, and the elastic fiber on the outer wall of the false cavity was over-stretched, which was consistent with the pathological changes of aortic dissection. Conclusion: Transvenous incision needle high-pressure water flow impact modeling method is easy to operate. The aortic blood flow block time is short, the dissection tear length is wide, and the postoperative survival time is long, can be used as the preferred method of animal AAD model construction.

Adaptation to Extreme Antarctic Environments Revealed by the Genome of a Sea Ice Green Alga

The unicellular green alga Chlamydomonas sp. ICE-L thrives in polar sea ice, where it tolerates extreme low temperatures, high salinity, and broad seasonal fluctuations in light conditions. Despite the high interest in biotechnological uses of this species, little is known about the adaptations that allow it to thrive in this harsh and complex environment. Here, we assembled a high-quality genome sequence of ∼542 Mb and found that retrotransposon proliferation contributed to the relatively large genome size of ICE-L when compared to other chlorophytes. Genomic features that may support the extremophilic lifestyle of this sea ice alga include massively expanded gene families involved in unsaturated fatty acid biosynthesis, DNA repair, photoprotection, ionic homeostasis, osmotic homeostasis, and reactive oxygen species detoxification. The acquisition of multiple ice binding proteins through putative horizontal gene transfer likely contributed to the origin of the psychrophilic lifestyle in ICE-L. Additional innovations include the significant upregulation under abiotic stress of several expanded ICE-L gene families, likely reflecting adaptive changes among diverse metabolic processes. Our analyses of the genome, transcriptome, and functional assays advance general understanding of the Antarctic green algae and offer potential explanations for how green plants adapt to extreme environments.

[Manual suture or stapler closure: management of pancreatic stump during distal pancreatectomy]

Postoperative pancreatic fistula is the most common complication after distal pancreatectomy.With the update of the domestic and international guidelines or consensuses, the definition of pancreatic fistula has become more standardized.And the classification of pancreatic fistula is able to represent the severity of clinical outcomes more accurately.Currently, the determination of risk factors of pancreatic fistula after distal pancreatectomy, the establishment of prediction model, and the surgical closure mode of pancreatic stump still remain the major topics.With the rapid development of laparoscopic and robotic surgery in pancreatectomy, there are more and more selectionsin transection and managing the pancreatic stump after distal pancreatectomy for prevention of pancreatic fistula.However, there has not been a uniform fashion in terms of manual suture or stapler use to close the pancreatic stump.Herein the current status and development of pancreatic fistula after distal pancreatectomy are reviewed.The strategy of managing the pancreatic stump after distal pancreatectomy should be adopted individually according to the texture and thickness of pancreatic parenchyma.

Resveratrol protects against oxidative damage of retinal pigment epithelium cells by modulating SOD/MDA activity and activating Bcl-2 expression

OBJECTIVE

Age-related macular degeneration (AMD) is mainly characterized by dysfunction of retinal pigment epithelium (RPE) cells. This study aimed to investigate the protective effects of resveratrol on oxidative damaged RPE cells.

MATERIALS AND METHODS

Human D407 cells were divided into normal control (NC), H2O2 treated (H2O2, treating with H2O2 at a final concentration of 200 mol/l) and resveratrol treatment groups (treating with resveratrol at a concentration of 12.5, 25, 50 and 100 mg/l). Malondialdehyde (MDA) and superoxide dismutase (SOD) activities were examined using enzyme-linked immunosorbent assay (ELISA). 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) and cell count kit-8 (CCK-8) were used to examine cell viability. Cell cycle phase distribution and apoptosis of D407 cells were evaluated using flow cytometry assay. B-cell lymphoma-2 (Bcl-2) and cleaved caspase 3 expression were detected using quantitative real-time PCR (qRT-PCR) and Western blot assay, respectively.

RESULTS

Resveratrol significantly decreased inhibitive ratios of D407 cell growth compared to that of H2O2 group (p<0.05). Resveratrol significantly increased SOD activity compared to that of H2O2 group (p<0.05). Resveratrol significantly reduced MDA activity compared to that of H2O2 group (p<0.05). Resveratrol affected cell cycle phase distribution of D407 cells compared to that of H2O2 group (p<0.05). Resveratrol significantly decreased the early stage and late stage apoptosis rates compared to that of H2O2 group (p<0.05). Resveratrol significantly enhanced Bcl-2 levels and decreased cleaved caspase 3 levels compared to that of H2O2 group (p<0.05).

CONCLUSIONS

Resveratrol protected against the oxidative damage of RPE cells by modulating SOD/MDA activity and activating Bcl-2 expression.

Characterization of the complete mitochondrial genome of the Pohlia nutans M211 from Antarctica

The complete mitochondrial genome of Pohlia nutans M211, sequenced using Illumina NovaSeq PE150, was 99864 bp in length. It encoded 65 genes, comprising 38 protein-coding genes, 24 tRNA genes and 3 ribosomal RNA genes. For these 38 PCGs, the most common start codon was ATG and the most common termination codon was TAA. The total GC content was 36.91% while the composition of A + T was 60.39%. Phylogenomic analysis indicated that P. nutans M211 was closely related to Mielichhoferia elongate.

The complete chloroplast genome of Spartina alterniflora

Spartina alterniflora (also named as Sporobolus alterniflorus) grows in coastal salt marshes area, which has important economic value in coastal natural wetlands. In the process of this research, the whole chloroplast genome sequence of Spartina alterniflora was recovered by Illumina sequencing. The complete genome was 135,560 bp in length with 38.45% GC content which was a circular genome containing a large single-copy region (LSC, 80,828 bp), a small single-copy region (SSC, 12,714 bp) and a pair of inverted repeat regions (IRs, 42,018 bp). Totally, it encodes 130 genes, including 84 protein-coding genes, 38 tRNAs, and 8 rRNAs. Phylogenetic analysis indicated that Spartina alterniflora was closely related to Sporobolus maritimus.

Molecular Cloning and Expression of a Cryptochrome Gene CiCRY-DASH1 from the Antarctic microalga Chlamydomonas sp. ICE-L

Cryptochromes (CRYs) are flavin-binding proteins that sense blue and near-ultraviolet light and participate in the photoreactions of organisms and the regulation of biological clocks. In this study, the complete open reading frame (ORF) of CiCRY-DASH1 (GenBank ID MK392361), encoding one kind of cryptochrome, was cloned from the Antarctic microalga Chlamydomonas sp. ICE-L. The quantitative real-time PCR study showed that the CiCRY-DASH1 had the highest expression at 5 °C and salinity of 32‰. The CiCRY-DASH1 was positively regulated by blue, yellow, or red light. Moreover, the CiCRY-DASH1 can positively respond to extreme polar day and night treatment and exhibit a certain circadian rhythm, which indicated that CiCRY-DASH1 participated in the circadian clock and its expression was regulated by circadian rhythms. And the CiCRY-DASH1 was more noticeably affected by ultraviolet-B radiation than ultraviolet-A radiation, indicating ultraviolet-B light does obvious damage to Antarctic microalgae.

Identification of a functional dddD-Rh for dimethyl sulfide production in the Antarctic Rhodococcus sp. NJ-530

Dimethylsulfoniopropionate (DMSP) is widespread in the oceans, and its biological metabolite, dimethyl sulfide (DMS), plays an important role in the atmosphere. The Antarctic region has become a hotspot in DMS studies due to the high spatial and temporal variability in DMS(P) concentration, but the level of bacterial DMS production remains unclear. In this study, a bacterium isolated from Antarctic floating ice, Rhodococcus sp. NJ-530, was found to metabolize DMSP into DMS, and the rate of DMS production was measured as 3.96 pmol·mg protein^-1 ·h^-1 . Rhodococcus sp. NJ-530 had a DddD-Rh enzyme containing two CaiB domains, which belonged to the CoA-transferase III superfamily. However, the DddD-Rh had a molecular weight of 73.21 kDa, which was very different from previously characterized DddD enzymes in sequence and evolution. In vitro assays showed that DddD-Rh was functional in the presence of acetyl-CoA. This was the first functional DddD from Gram-positive Actinobacteria. Moreover, a quantitative real-time polymerase chain reaction revealed that high temperature facilitated the expression of dddD-Rh, and changes of salinity had little effect on it. This study adds new evidence to the bacterial DMS production in the Southern Ocean and provides a basis for investigating the metabolic mechanism of DMSP in extreme environments.

Complete genome sequence of Bacillus sp. N1-1, a κ-selenocarrageenan degrading bacterium isolated from the cold seep in the South China Sea

κ-Selenocarrageenan is made from natural κ-carrageenan, in which Se partially replaces Sulfur (S). The underlying mechanism of κ-selenocarrageenan degradation remain unreported so far. Here, we describe the complete genome of a cold seep bacterium, Bacillus sp. N1-1, which can degrade κ-selenocarrageenan. The strain has a circular genome of 4,497,340 bp and 40.48 mol% G + C content, consisting of 4272 protein-coding sequences (CDSs), 87 tRNAs, as well as 28 rRNA operons as 5S-16S-23S rRNA. N1-1 genome contains several protein-coding genes relating to polysaccharide degradation and the potential of this bacterium to produce enzymes for the hydrolysis of κ-selenocarrageenan on the basis of complete genome analysis could be discovered.

Characterization of the complete chloroplast genome of the Pohlia nutans M211 from Antarctica

The Antarctic Pohlia nutans M211 complete chloroplast (cp) genome, sequenced using Illumina NovaSeq PE150, was 125,199 bp in length. It contained 19,836 bp of inverted repeat (IR) regions that separated a large single-copy region (LSC) of 86,738 bp and a small single-copy region (SSC) of 18,580 bp. The whole-genome encodes 132 genes (80 protein-coding genes, 36 tRNA genes, and 8 rRNA genes) and had 29.5% GC content. The M211 was congruent with Sanionia uncinata (KM111545.1) according to the Phylogenetic tree analyses.

The Parallel Molecular Adaptations to the Antarctic Cold Environment in Two Psychrophilic Green Algae

Psychrophilic green algae from independent phylogenetic lines thrive in the polar extreme environments, but the hypothesis that their psychrophilic characteristics appeared through parallel routes of molecular evolution remains untested. The recent surge of transcriptome data enables large-scale evolutionary analyses to investigate the genetic basis for the adaptations to the Antarctic extreme environment, and the identification of the selective forces that drive molecular evolution is the foundation to understand the strategies of cold adaptation. Here, we conducted transcriptome sequencing of two Antarctic psychrophilic green algae (Chlamydomonas sp. ICE-L and Tetrabaena socialis) and performed positive selection and convergent substitution analyses to investigate their molecular convergence and adaptive strategies against extreme cold conditions. Our results revealed considerable shared positively selected genes and significant evidence of molecular convergence in two Antarctic psychrophilic algae. Significant evidence of positive selection and convergent substitution were detected in genes associated with photosynthetic machinery, multiple antioxidant systems, and several crucial translation elements in Antarctic psychrophilic algae. Our study reveals that the psychrophilic algae possess more stable photosynthetic apparatus and multiple protective mechanisms and provides new clues of parallel adaptive evolution in Antarctic psychrophilic green algae.