Current Articles

Review
Proteases from the marine bacteria in the genus Pseudoalteromonas: diversity, characteristics, ecological roles, and application potentials
Xiu-Lan Chen, Yan Wang, Peng Wang, Yu-Zhong Zhang
2020, 2(4): 309-323. doi: 10.1007/s42995-020-00058-8
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Abstract:
Bacterial strains of the genus Pseudoalteromonas, which includes 48 species, are widely distributed in various ocean environments. Many strains are often abundant and the highest protease producer among marine culturable protease-secreting bacteria, suggesting their important role in marine organic nitrogen degradation and cycling. The extracellular proteases of Pseudoalteromonas are diverse, including serine proteases, metalloproteases, and cystine proteases. Pseudoalteromonas proteases have unique properties, such as cold adaptation, salt tolerance, distinct substrate specificity, and catalytic mechanism. They play important ecological roles in marine organic nitrogen degradation and in the interactions of Pseudoalteromonas with other organisms. Some Pseudoalteromonas proteases have shown promising application potentials in bioactive peptide preparation and meat processing. In this review, advances in our knowledge of Pseudoalteromonas proteases are introduced, with a focus on diversity, characters, ecological significance, and application potentials.
Roles of dietary taurine in fish nutrition
W. W. H. A. Sampath, R. M. D. S. Rathnayake, Mengxi Yang, Wenbing Zhang, Kangsen Mai
2020, 2(4): 360-375. doi: 10.1007/s42995-020-00051-1
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Taurine is a conditionally essential amino acid in fish nutrition. The present study addressed the practical application of examining published data on fish nutrition over the past 20 years, emphasizing the topic of taurine by using computational tools and their applications. According to the published articles, an increased linear growth of research occurred, with Japanese flounder being the most examined fish species. Dietary taurine supplementation has several beneficial effects in fish nutrition, such as survival, growth, feed utilization, protein and energy retention, intermediate metabolism, anti-oxidation, anti-stress, disease resistance, muscle texture and reproductive performance. Also, there are negative effects in some species. Dietary taurine exerted effects on several gene expressions and enzyme activities; these are important in taurine metabolism in fish. These genes and enzymes included taurine transporter (TauT), cysteine dioxygenase (CDO), cysteamine dioxygenase (ADO), cysteine sulfonate decarboxylase (CSD) and pretrypsinogen (Ptry). Plant protein-based diets with taurine supplementation are recommended because of the absence of taurine in plant protein.
Applications of chitosan-based biomaterials: a focus on dependent antimicrobial properties
Zhenwei Deng, Ting Wang, Xiguang Chen, Ya Liu
2020, 2(4): 398-413. doi: 10.1007/s42995-020-00044-0
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Marine-derived chitosan has been widely examined for its use in developing biomedical materials. Not only is it non-toxic, biocompatible, and degradable, it has also shown unique antimicrobial properties. The antimicrobial properties of chitosan are restricted by neutral and physiological conditions because it is insoluble in water and its pKa values is 6.5. One solution to this problem is to graft chemically modified groups onto the backbone of chitosan. The aim of this paper is to review the mode of antimicrobial action of chitosan and chitosan derivatives. Using chitosan alone may not meet the demands of various applications. However, the introduction of additional polymers and antimicrobial agents is commonly used to enhance the antimicrobial potential of chitosan-based biomaterials. Chitosan-based composite biomaterials have been developed that allow diversified formulations to broaden applications, including nanoparticles, hydrogels, films, sponges, fibers, or even microspheres. These along with recent advances on chitosan-based composite biomaterials used for wound healing, food packaging, textile sector, 3D printing and dental materials, were reviewed in detail.
Environmental perspectives of microplastic pollution in the aquatic environment: a review
Manzoor Ahmad, Jia-Ling Li, Pan-Deng Wang, Wael N. Hozzein, Wen-Jun Li
2020, 2(4): 414-430. doi: 10.1007/s42995-020-00056-w
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Abstract:
Microplastics are a highly concerning pollutant that have gained attention from the scientific community and other regulatory authorities due to their potential risks to organisms and ecosystems. Microplastics are widespread in both terrestrial and aquatic ecosystems and can be found even in Antarctica and deep-sea sediments. The ability to survive for long periods in the environment and their aptitude of inter- and intra-environmental translocation can prompt poor environmental outcomes. The adsorption of heavy metals and other toxic persistent organic pollutants is a further cause for concern. Furthermore,microplastics enable the development of a distinct microbial niche within an ecosystem,which could potentially impair ecosystem function by promoting the growth of selective microbial communities. The acquisition of metal-resistant,antibiotic-resistant genes,and the enrichment of antibiotic-resistant bacteria on microplastic surfaces have recently been reported. Moreover,some studies have also reported the colonization of pathogenic bacterial strains such as Vibrio spp. on microplastic surfaces. This review aims to address the sources of microplastic pollution in the freshwater and marine environments and to discuss their potential functions in the environment.
Research Paper
High abundance and reproductive output of an intertidal limpet (Siphonaria japonica) in environments with high thermal predictability
Jie Wang, Xin Peng, Yunwei Dong
2020, 2(4): 324-333. doi: 10.1007/s42995-020-00059-7
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Abstract:
The predictability of high temperatures is important for intertidal species for coping with thermal stress. To investigate the roles of high temperature and its predictability on the population abundance and reproductive output of an intertidal rocky shore limpet, Siphonaria japonica, we monitored the operative temperature, recorded the population abundance of egg ribbons and adults, and quantified the expression of heat shock protein 70 (hsp70) mRNA on two warm-temperate rocky shores with different thermal environments. Abundances of limpets and egg ribbons in the hotter but more predictable (HP) habitats were higher than those in the relatively benign and unpredictable (BU) habitats. In the HP habitats, there was a strong positive correlation between habitat temperature and population abundance. For limpets living in the HP habitats, the expression of hsp70 exhibited a smaller increase with rising body temperature than for BU limpets, indicating the existence in HP limpets of a preparatory strategy in cellular stress response against thermal stress. Our results demonstrate that the predictability of operative temperature can affect physiological responses and population dynamics. The importance of predictability should be considered in analyses of the ecological consequences of climate warming.
Morphology, taxonomy and molecular phylogeny of three marine peritrich ciliates, including two new species: Zoothamnium apoarbuscula n. sp. and Z. apohentscheli n. sp. (Protozoa, Ciliophora, Peritrichia)
Tong Wu, Yuqing Li, Borong Lu, Zhuo Shen, Weibo Song, Alan Warren
2020, 2(4): 334-348. doi: 10.1007/s42995-020-00046-y
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Zoothamnium is a speciose genus, most species of which have incomplete morphological data based on modern criteria. In the present study, the morphology of three species of Zoothamnium, i.e., Z. apoarbuscula n. sp., Z. apohentscheli n. sp., and Z. alternans, collected in Qingdao, China, was revealed using living observation and silver staining. In addition, the SSU rDNA of each species was sequenced for phylogenetic analyses. Zoothamnium apoarbuscula n. sp. is characterized by its umbellate colony which is up to 900 μm high, dichotomously branched stalk, differentiation of zooids, and infundibular polykinety 3 comprising three equal-length ciliary rows. Zoothamnium apohentscheli n. sp is characterized by its large colony up to 1700 μm high, alternately branched stalk, and infundibular polykinety 3 comprising three equal-length ciliary rows. A population of Z. alternans is described in detail. Phylogenetic analyses based on SSU rDNA sequence data revealed that species with an alternately branched stalk cluster together in gene trees and probably represent an independent lineage within the genus Zoothamnium.
Identification, expression analysis, and functional characterization of ghrelin and its receptors in spotted sea bass (Lateolabrax maculatus)
Peng Yu, Yangyang Zhou, Xin Qi, Hongying Fan, Kaiqiang Zhang, Xiaoyan Zhang, Yun Li, Haishen Wen
2020, 2(4): 349-359. doi: 10.1007/s42995-020-00055-x
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Abstract:
Ghrelin (Ghrl), an appetite-inducing peptide hormone secreted by the stomach, is the endogenous ligand for the growth hormone secretagogue receptor (Ghs-r). In this study, we identified the preproghrelin gene and its receptors in spotted sea bass (Lateolabrax maculatus). The ghrl gene consisted of an open reading frame (ORF) of 324 nucleotides encoding 107 amino acids, and the premature protein contained a 20-amino-acid mature peptide. Through a syntenic analysis, we also validated the annotation of growth hormone secretagogue receptor 1a (ghs-r1a) and growth hormone secretagogue receptor 1a-like (ghs-r1a-like), which contained seven-transmembrane structures, in spotted sea bass. The ORF of ghs-r1a consisted of 1152 bp that encoded a 383-amino-acid protein, and ghs-r1a-like contained an ORF of 2631 bp and produced a protein with 876 amino acids. A phylogenetic analysis showed that spotted sea bass ghrl and its receptors clustered with those of other fishes and were more distantly related to those of other vertebrates. In situ hybridization revealed that ghrl was highly expressed in the stomach and localized in the mucosa and submucosa. The expression of these genes varied during short-term starvation in a time-dependent manner. In vitro studies showed that after incubation with Ghrl for 3 h enhanced the expression of motilin (mln), gastrin (gas) and cholecystokinin (cck), but this effect vanished after 6 h of incubation. In summary, Ghrl and its receptors might play important roles in the regulation of food intake in spotted sea bass.
Optimal amounts of coconut oil in diets improve the growth, antioxidant capacity and lipid metabolism of large yellow croaker (Larimichthys crocea)
Tao Ding, Ning Xu, Yongtao Liu, Xueshan Li, Xiaojun Xiang, Dan Xu, Chuanwei Yao, Qiangde Liu, Zhaoyang Yin, Kangsen Mai, Qinghui Ai
2020, 2(4): 376-385. doi: 10.1007/s42995-020-00045-z
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Abstract:
The purpose of this study was to investigate the effect of different dietary coconut oil (CO) levels on growth, antioxidant capacity and lipid metabolism of juvenile large yellow croaker (Larimichthys crocea). Five iso-nitrogen (45% crude protein) and iso-lipid (13% crude lipid) experimental diets were prepared by replacing 0% (the control), 25%, 50%, 75% and 100% fish oil with coconut oil. The results showed that dietary CO had no significant effect on survival rate (SR, P > 0.05). However, the specific growth rate was increased significantly when compared with the control group when fish were fed the diet with 50% CO (P < 0.05). The saturated fatty acids were increased significantly with increasing dietary CO in the liver and muscle, whereas the content of n-3 PUFA was decreased significantly (P < 0.05). The highest activities of glutathione peroxidase and superoxide dismutase in the liver were recorded in fish-fed diet with 50% CO; conversely, the content of malondialdehyde was significantly decreased (P < 0.05). The mRNA expression of peroxisome proliferator-activated receptor α, carnitine palmitoyl transferase 1 and acyl-CoA oxidase reached the highest levels in fish-fed diet with 50% CO. To some extent, this indicated that the rapid oxidation reaction of fatty acids to provide energy may be the reason for the rapid growth of large yellow croaker. In conclusion, fish-fed diet with 50% CO increased the growth rate and antioxidant capacity. Therefore, the optimal replacement level of CO to FO in the diet should be 50%.
Acetylcholinesterase inhibitors and antioxidants mining from marine fungi: bioassays, bioactivity coupled LC–MS/MS analyses and molecular networking
Yingying Nie, Wencong Yang, Yayue Liu, Jingming Yang, Xiaoling Lei, William H. Gerwick, Yi Zhang
2020, 2(4): 386-12. doi: 10.1007/s42995-020-00065-9
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Marine fungi are potentially important resources for bioactive lead compounds for discovering new drugs for diseases such as Alzheimer's disease. In this paper, the combined bioassay model of acetylcholinesterase (AChE) inhibition, 1, 1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging, and Artemia larval lethality was used to evaluate the activity and toxicity of 35 marine fungal strains from seas around China. Their bioactive constituents were revealed by thin layer chromatography (TLC) autography, bioactivity coupled LC–MS/MS and Global Natural Products Social Molecular Networking (GNPS). The results show that the extracts of five strains exhibited higher AChE inhibition ratios than the positive control compound, 'tacrine', for which the ratio was 89.8% at 200 μg/ml. Six strains displayed both AChE inhibition (inhibition ratios>20% at 200 μg/ml) and DPPH scavenging activity (scavenging ratios>30% at 200 μg/ml) together with low Artemia larval toxicity (lethal rates<12%). TLC autography showed that the fractioned extracts of four strains contained highly diverse and different bioactive constituents, including strains Talaromyces sp. C21-1, Aspergillus terreus C23-3, Trichoderma harzianum DLEN2008005, and Penicillium corylophilum TBG1-17. From the most potent sample F-11-1-b (derived from Aspergillus terreus C23-3), five AChE inhibitors and seven antioxidants were recognized as bioactive molecules by AChE coupled ultrafiltration followed by LC–MS/MS, and LC–MS/MS coupled with DPPH incubation. Furthermore, with the aid of GNPS, the AChE inhibitors were plausibly annotated as territrem analogues including territrems A–C/D, arisugacin A and an unknown compound 4, and the seven antioxidants were assigned as butyrolactone Ι, aspernolide E, a phenolic derivative and possibly unknown compounds 810 and 12.
Metabolic diversification of anaerobic methanotrophic archaea in a deep-sea cold seep
Wen-Li Li, Yu-Zhi Wu, Guo-wei Zhou, Hui Huang, Yong Wang
2020, 2(4): 431-441. doi: 10.1007/s42995-020-00057-9
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Anaerobic methanotrophic archaea (ANME) can assimilate methane and govern the greenhouse effect of deep-sea cold seeps. In this study, a total of 13 ANME draft genomes representing five ANME types (ANME-1a, ANME-1b, ANME-2a, ANME-2b and ANME-2c), in size between 0.8 and 1.8 Mbp, were obtained from the Jiaolong cold seep in the South China Sea. The small metagenome-assembled genomes (MAGs) contained all the essential pathways for methane oxidization and carbon dioxide fixation. All genes related to nitrate and sulfate reduction were absent from the MAGs, indicating their syntrophic dependence on partner organisms. Aside from acetate secretion and sugar storage, propanoate synthesis pathway, as an alternative novel carbon flow, was identified in all the MAGs and transcriptionally active. Regarding type-specific features of the MAGs, the genes encoding archaellum and bacteria-derived chemotaxis were specific to ANME-2, perhaps for fitness under fluctuation of methane and sulfate concentration flux. Our genomic and transcriptomic results strongly suggested that ANME could carry out simple carbon metabolism from C1 assimilation to C3 biosynthesis in the SCS cold seep, which casts light on a novel approach for synthetic biology.
Grazing by microzooplankton and copepods on the microbial food web in spring in the southern Yellow Sea, China
Yuan Zhao, Yi Dong, Haibo Li, Shiquan Lin, Lingfeng Huang, Tian Xiao, Gerald Gregori, Li Zhao, Wuchang Zhang
2020, 2(4): 442-455. doi: 10.1007/s42995-020-00047-x
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Assessment of microzooplankton and copepods grazing pressure on picoplankton is a key requirement for resolving the microbial food web efficiency. Although microzooplankton grazing on picoplankton has been extensively studied, the impact of microzooplankton on different groups of picoplankton, i.e., heterotrophic bacteria, Synechococcus and picoeukaryotes have rarely been compared. Furthermore, in the very few existing studies there is no consistent evidence of an enhancing or restraining effect of copepods on picoplankton. More studies are needed to improve our understanding of the influence of microzooplankton and copepod on picoplankton. Dilution incubations and copepod addition incubations were performed during a cruise to the southern Yellow Sea on May 16–29, 2007. The bulk grazing of microzooplankton and the calanoid copepod Calanus sinicus on phytoplankton, flagellates and picoplankton was estimated. Stations were divided into either eutrophic or oligotrophic according to the nutrient and biological parameters. Picoplankton comprised a large part of the diet of microzooplankton in the central oligotrophic area, while phytoplankton was the main food of microzooplankton in the coastal eutrophic area. In the central oligotrophic area, microzooplankton preferred grazing on Synechococcus. After copepod addition, ciliate abundance decreased while Synechococcus abundance increased (382%, 64% and 64% at three experimental stations, respectively), indicating strong grazing pressure of microzooplankton on Synechococcus. Our results suggest that Synechococcus might be an essential carbon source the planktonic food web in the oligotrophic waters of southern Yellow Sea.