Magnetotactic bacteria (MTB) are a diverse group of microorganisms that synthesize intracellular magnetic nanocrystals termed magnetosomes. In this study, a novel marine magnetotactic coccus, designated strain HHB-1, was magnetically enriched from intertidal sediments in Houhai Bay, southern China. Optical microscopy, electron microscopy and elemental analysis revealed that HHB-1 cells are relatively large coccoid-ovoid bacteria (3.9 ± 0.3 μm × 2.8 ± 0.2 μm) containing multiple chains of prismatic magnetite magnetosomes and prominent intracellular Ca/Mg-rich polyphosphate (Ca-Mg-polyP) granules. Whole-genome sequencing and phylogenomic analyses revealed that HHB-1 represents a novel and deeply branching lineage within the order Magnetococcales, exhibiting low average amino acid identity (57.3%-58.7%) with previously reported strains. The magnetosome gene cluster (MGC) of HHB-1 comprises a nearly complete set of mam (magnetosome membrane) genes with conserved gene order and structure, representing the first genomic and MGC characterization of a novel magnetococcus possessing multi-chain magnetosomes. These findings expand our understanding of the diversity, biomineralization strategies and evolutionary history of MTB in marine environments.

The intertidal sediments of Sanya Haitang Bay, a tropical coast, harbor abundant multicellular magnetotactic prokaryotes (MMPs). Using light and electron microscopy, micromanipulation sorting, and whole-genome amplification, we examined their diversity from morphological, phylogenetic, and ecological perspectives. Two types of MMPs were identified: ellipsoidal (eMMPs) and spherical (sMMPs). Their average abundance was 1.37 × 103 ind./dm3 in autumn and 0.27 × 103 ind./dm3 in spring, indicating strong seasonal variation. eMMPs averaged 9.74 × 8.15 µm, consisting of 80–100 cells arranged in layers, whereas sMMPs averaged 5.64 µm in diameter with 40–50 cells organized radially or spirally. Electron microscopy revealed bullet-shaped magnetosomes in both types: those in eMMPs averaged 90.1 × 34.0 nm, while those in sMMPs averaged 97.2 × 36.3 nm. Interestingly, Cu was homogenously detected in the magnetosomes of sMMPs. 16S rRNA gene analysis identified nine OTUs, including three potential new species in the Desulfobacteraceae family within Thermodesulfobacteriota phylum. Of these, two may represent a new genus, and one is affiliated with Candidatus Magnetananas. Global distribution analysis suggests that eMMPs prefer stable, nutrient-rich environments, whereas sMMPs occupy broader ecological niches. Together, these findings expand understanding of tropical MMP diversity and distribution, and the discovery of Cu-containing magnetosomes provides new insight into biomineralization mechanisms.

Synechococcus is abundant and globally widespread in various marine environments. Seasonal and spatial variations in Synechococcus abundance, pigment types, and genetic diversity were investigated based on flow cytometric analysis and high-throughput sequencing of cpcBA operon (encoding phycocyanin) and rpoC1 gene (encoding RNA polymerase) in a temperate semi-enclosed bay. Synechococcus abundance exhibited seasonal variations with the highest value in summer and the lowest value in winter, which was consistent with temperature variation. Three pigment types of Synechococcus type 1, type 2, and type 3 were distinguished based on cpcBA operon, which displayed obvious variations spatially between the inner and the outer bay. Freshwater discharge and water turbidity played important roles in regulating Synechococcus pigment types. Synechococcus assemblages were phylogenetically diverse (12 different lineages) based on rpoC1 gene and dominated by three core lineages S5.1-I, S5.1-IX, and S5.2-CB5 in different seasons. Our study demonstrated that Synechococcus abundance, pigment types, and genetic diversity displayed variations seasonally and spatially by different techniques, which were mainly driven by temperature, salinity, nutrients, and turbidity. The combination of more technical means provides more information for studying Synechococcus distribution. In this study, three pigment types of Synechococcus were discriminated simultaneously by dual lasers flow cytometer for the first time.

Magnetotactic bacteria (MTB) are a unique group of microorganisms that sense and navigate through the geomagnetic field by biomineralizing magnetic nanoparticles. MTB from the phylum Nitrospirota (previously known as Nitrospirae) thrive in diverse aquatic ecosystems. They are of great interest due to their production of hundreds of magnetite (Fe3O4) magnetosome nanoparticles per cell, which far exceeds that of other MTB. The morphological, phylogenetic, and genomic diversity of Nitrospirota MTB have been extensively studied. However, the metabolism and ecophysiology of Nitrospirota MTB are largely unknown due to the lack of cultivation techniques. Here, we established a method to link the morphological, genomic, and metabolic investigations of an uncultured Nitrospirota MTB population (named LHC-1) at the single-cell level using nanoscale secondary-ion mass spectrometry (NanoSIMS) in combination with rRNA-based in situ hybridization and target-specific mini-metagenomics. We magnetically separated LHC-1 from a freshwater lake and reconstructed the draft genome of LHC-1 using genome-resolved mini-metagenomics. We found that 10 LHC-1 cells were sufficient as a template to obtain a high-quality draft genome. Genomic analysis revealed that LHC-1 has the potential for CO2 fixation and NO3− reduction, which was further characterized at the single-cell level by combining stable-isotope incubations and NanoSIMS analyses over time. Additionally, the NanoSIMS results revealed specific element distributions in LHC-1, and that the heterogeneity of CO2 and NO3− metabolisms among different LHC-1 cells increased with incubation time. To our knowledge, this study provides the first metabolic measurements of individual Nitrospirota MTB cells to decipher their ecophysiological traits. The procedure constructed in this study provides a promising strategy to simultaneously investigate the morphology, genome, and ecophysiology of uncultured microbes in natural environments.

The Clarion-Clipperton Fracture Zone (CCFZ) in the eastern central Pacific Ocean is the world's largest area for potential deep-sea polymetallic nodule mining and is attracting increased scientific and commercial interest. Recent studies indicate that biogenic magnetite, generated intracellularly by magnetotactic bacteria (MTB), can carry a biogeochemical remanent magnetization in polymetallic nodules, although whether biogenic or physical-chemical processes are responsible for nodule formation remain poorly constrained. Here, we report a combination of magnetic, electron microscope and geochemical analyses on seafloor surface sediments from the eastern CCFZ to understand the spatial distribution of biogenic magnetite and possible relationships between MTB and polymetallic nodules. Experimental results indicate that sedimentary magnetic minerals from the northern and southern regions are dominated by detrital (eolian loess and volcanic material) and biogenic magnetic minerals (magnetosomes), respectively. Sediments from the intermediate region contain both detrital and biogenic magnetic minerals. Quantitative first-order reversal curve-principal component analysis indicates that biogenic magnetite has the highest concentration in the intermediate CCFZ region, coincident with the highest polymetallic nodule density. Combined with previous research, we speculate that MTB growth on the CCFZ seafloor is driven mainly by local redox conditions. Manganese nodule surfaces are rich in organic biofilms, which results in a relatively thick oxic-anoxic transition zone in high-abundance manganese nodule regions, which generates an optimal microenvironment for both MTB growth and magnetite biomineralization. This study provides new clues for understanding the ecological distribution of MTB and the biogeochemical remanent magnetization recorded by biogenic magnetite in deep-sea sediments. Polymetallic nodules are an important seafloor resource because they contain economically important minerals (e.g., Ni, Co, and Mn) that are not common on land. Hence, there is increased economic and scientific interest in understanding the formation mechanisms of these materials. Several studies indicate that biogenic magnetite crystals produced by magnetotactic bacteria (MTB) occur within polymetallic nodules. Testing the relationship between MTB abundance and polymetallic nodule distribution can help to better understand how these materials formed. Here, we study seafloor sediments from the Clarion-Clipperton Fracture Zone (CCFZ) and find that they mainly contain biogenic and detrital magnetic minerals. Detrital magnetic minerals come from volcanic chains and eolian dust, while biogenic magnetite forms within bacterial cells. We find that increased biogenic magnetite abundance coincides with higher polymetallic nodule occurrences in the CCFZ. This implies that MTB activity may play a significant role in the formation and growth of polymetallic nodules. Biogenic and detrital magnetic minerals are quantified in seafloor surface sediments from the Clarion-Clipperton Fracture Zone Biogenic magnetite concentrations and polymetallic nodule density are increased in the central Clarion-Clipperton Fracture Zone Polymetallic nodule growth likely produced reducing, organic-rich microenvironments suitable for magnetotactic bacteria

Seamounts are ubiquitous features in the world ocean with potential for increasing plankton biodiversity and abundance, and providing important habitats for aquatic predators. Although ecological importance of seamount is well known, the mechanisms for supporting seamount-associated microzooplankton (e.g., pelagic ciliates) communities remains to be substantiated. In this study, pelagic ciliate community structure variations and their relationship with environmental variables were investigated in the Caroline seamount in late (2017) and early summer (2019). Above the seamount in 2019, ciliates exhibited higher abundance and biomass than off the seamount, which supported the classic hypothesis of seamount effect. Aloricate ciliate small size-fraction (10-20 mu m) was dominant in bathypelagic (>1000 m) zone. Although relative abundance of small size-fraction was similar in both 2017 and 2019, the absolute abundance in 2019 seamount-effect stations were obviously higher than that in 2017. All abundant tintinnids were classified into surface-and DCM (deep Chl a maximum layer)-peak groups. Among them, four abundant tintinnids (Acanthostomella conicoides, Eutintinnus hasleae, Salpingella curta and S. minutissima) had higher abundance at DCM and might uplifted to shallower waters by upwelling at 2019 seamount-effect stations. The multivariate biota-environment analysis showed that environmental variables have significant impacts on the ciliate community structures in 2017 and 2019. Higher Chl a and nutrient concentrations, and sustained upwelling might be two potential mechanisms for microzooplankton seamount effect. Our study constitutes a rather solid foundation for quantitative and functional study of microzooplankton populations over oligotrophic tropical seamounts.

Magnetotactic bacteria (MTB) within the Nitrospirota phylum play important roles in biogeochemical cycles due to their outstanding ability to biomineralize large amounts of magnetite magnetosomes and intracellular sulfur globules. For several decades, Nitrospirota MTB were believed to only live in freshwater or low-salinity environments. While this group have recently been found in marine sediments, their physiological features and ecological roles have remained unclear. In this study, we combine electron microscopy with genomics to characterize a novel population of Nitrospirota MTB in a coral reef area of the South China Sea. Both phylogenetic and genomic analyses revealed it as representative of a novel genus, named as Candidatus Magnetocorallium paracelense XS-1. The cells of XS-1 are small and vibrioid-shaped, and have bundled chains of bullet-shaped magnetite magnetosomes, sulfur globules, and cytoplasmic vacuole-like structures. Genomic analysis revealed that XS-1 has the potential to respire sulfate and nitrate, and utilize the Wood-Ljungdahl pathway for carbon fixation. XS-1 has versatile metabolic traits that make it different from freshwater Nitrospirota MTB, including Pta-ackA pathway, anaerobic sulfite reduction, and thiosulfate disproportionation. XS-1 also encodes both the cbb3-type and the aa3-type cytochrome c oxidases, which may function as respiratory energy-transducing enzymes under high oxygen conditions and anaerobic or microaerophilic conditions, respectively. XS-1 has multiple copies of circadian related genes in response to variability in coral reef habitat. Our results implied that XS-1 has a remarkable plasticity to adapt the environment and can play a beneficial role in coral reef ecosystems.

Though diel variations are geographically widespread phenomena among phytoplankton and zooplankton, knowledge is limited regarding diel variations in planktonic ciliate (microzooplankton) community structure. In this study, we analyzed diel variations in community structure of planktonic ciliates in the northern South China Sea (nSCS) and tropical Western Pacific (tWP). Hydrological characteristics during day and night were slightly different over both the nSCS and tWP, while ciliate average abundance at night was clearly higher than in the day in the upper 200 m. In both the nSCS and tWP, abundance proportions of large size-fraction (> 30 μm) aloricate ciliates at night were higher than in the day. While for tintinnids, abundance proportion of large lorica oral diameter at night were lower than in the day. The relationship between environmental factors and ciliate abundance pointed out that depth and temperature were main factors influencing aloricate ciliate and tintinnid in both day and night. For some dominant tintinnid species, chlorophyll a was another important factor influencing their diel vertical distribution. Our results provide fundamental data for better understanding the mechanisms of planktonic ciliate community diel variation in the tropical Western Pacific Ocean.

Microbial food webs (MFW) play an indispensable role in marine pelagic ecosystem, yet their composition and response to abiotic variables were poorly documented in the oligotrophic tropical Western Pacific. During winter of 2015, we conducted a survey to examine key components of MFW, including Synechococcus, Prochlorococcus, picoeukaryotes, heterotrophic prokaryotes (HP), heterotrophic/pigmented nanoflagellates and ciliates, across water column from surface to 2000 m. Each MFW component exhibited unique vertical distribution pattern, with abundance ratio varying over six and three orders of magnitude across Pico/Microplankton (1.6 ± 1.0 × 106) and Nano/Microplankton (3.2 ± 2.8 × 103), respectively. Furthermore, HP was main component for MFW in the bathypelagic (>1000 m) zone. Multivariate biota-environment analysis demonstrated that environmental variables, particularly temperature, significantly impacted MFW composition, suggesting that bottom-up control (resource availability) dominated the water column. Our study provides benchmark information for future environmental dynamics forcing on MFW in the oligotrophic tropical seas.

Marine plankton have different biogeographical distribution patterns. However, it is not clear how the entire plankton assemblage is composed of these species with distinct biogeographical patterns. Tintinnina (tintinnids) is single-celled planktonic protozoa commonly used as model organisms in planktonic studies. In this research, we investigated the organization of Tintinnina assemblages along the Atlantic Meridional Transect (AMT) spanning over 90 degrees of latitude during the 29th AMT cruise (2019). Tintinnina with high frequency of occurrence was classified into four biogeographic distribution patterns (equatorial, gyre, frontal, and deep Chl a maximum) according to their vertical and horizontal distribution. All species falling within each distribution pattern formed a sub-assemblage. Equatorial sub-assemblage dominated in upper waters of the equatorial zone and gyre centres. Equatorial and frontal sub-assemblages co-dominated in upper waters of the frontal zones. Deep Chlorophyll a maximum Layer (DCM) sub-assemblage dominated in the DCM waters. Some Tintinnina species with high abundance could be used as indicator species of sub-assemblages. The Tintinnina assemblages in the northern and southern hemispheres exhibited asymmetry in terms of species composition. The latitudinal gradient of Tintinnina species richness was bimodal, which was shaped by the superposition of the species number of the four sub-assemblages with latitude. The result of this study contributes to the understanding of Tintinnina assemblage in the equatorial zone and subtropical gyres of the Pacific and Indian Ocean. It is also valuable for predicting the influence of global warming on changes in Tintinnina distribution and species richness.

Tintinnids play an important role in the microbial food web and consist of neritic and oceanic ones biogeographically. Neritic tintinnid species are mainly present in continental shelf areas. Knowing their community structure is thus critical to better understand the ecological function of microzooplankton in the Pacific Arctic Region. During the summer of 2019, neritic tintinnid diversity, vertical distribution, and mixing with oceanic tintinnids were investigated from the Bering Sea to the Chukchi Sea. A total of 19 neritic tintinnid species belonging to 5 genera were identified. All of the neritic species were reported in waters south of the Pacific Arctic Region. No endemic Arctic neritic tintinnid was found. The distributions of nine abundant neritic species exhibited no difference between the Bering Sea and Chukchi Sea. Abundant neritic species were divided into surface- and bottom-dwellers according to their vertical distributions. Bering Shelf Water was dominated by neritic bottom-dwellers, while Anadyr Water was inhabited by neritic surface-dwellers. Neritic and oceanic tintinnids from the Pacific were mainly advected into the Chukchi Sea by Bering Shelf Water. Neritic bottomdwellers could be mixed into surface waters possibly due to upwelling caused by Pacific Inflow Water flow over shelves. In surface waters, the neritic tintinnid community represented <50% of the total tintinnid abundance. Our results will help to predict future changes in the microzooplankton community under the influence of global warming and increasing Pacific Inflow Water on the Pacific Arctic Region shelf as well as in the Arctic basin.

为全面了解黄海典型海区微微型浮游植物的季节变化特征,于2009年7月至2010年6月在北黄海獐子岛海域和2010年1～12月在南黄海胶州湾进行逐月调查采样,利用流式细胞仪检测了表层海水中微微型浮游植物(picophytoplankton)的丰度,包括聚球藻(Synechococcus,SYN)和微微型真核浮游植物(picoeukaryotes,PEUK),并分析了其与环境因子的关系.獐子岛海域和胶州湾SYN和PEUK全年广泛分布,獐子岛海域SYN丰度范围在0.05×103～120.00×103 cells/mL之间,丰度在秋季最高;胶州湾SYN丰度范围在0.02×103～61.80×103 cells/mL之间,丰度在夏季最高.獐子岛海域PEUK丰度范围在0.01×103～18.76×103 cells/mL之间,丰度在秋季最高;胶州湾PEUK丰度范围在0.25×103～95.57×103 cells/mL之间,丰度在春季最高.獐子岛海域微微型浮游植物丰度组成以SYN为主;而胶州湾以PEUK为主.PEUK是两海区微微型浮游植物生物量的主要贡献者.相关性分析结果表明,温度是影响两海区SYN丰度季节变化的最主要因素;影响PEUK季节分布的因素不完全一致,獐子岛海域PEUK丰度主要受温度调控;胶州湾PEUK丰度主要受温度和营养盐浓度影响.与已有研究比较,这两个海区的微微型浮游植物生物量对浮游植物生物量的贡献明显高于其他温带沿岸海域,预示微微型浮游植物在獐子岛海域和胶州湾生态系统中的重要作用,值得进一步深入研究.

Multicellular magnetotactic prokaryotes (MMPs) are a unique group of magnetotactic bacteria that are composed of 10–100 individual cells and show coordinated swimming along magnetic field lines. MMPs produce nanometer-sized magnetite (Fe3O4) and/or greigite (Fe3S4) crystals—termed magnetosomes. Two types of magnetosome gene cluster (MGC) that regulate biomineralization of magnetite and greigite have been found. Here, we describe a dominant spherical MMP (sMMP) species collected from the intertidal sediments of Jinsha Bay, in the South China Sea. The sMMPs were 4.78 ± 0.67 μm in diameter, comprised 14–40 cells helical symmetrically, and contained bullet-shaped magnetite and irregularly shaped greigite magnetosomes. Two sets of MGCs, one putatively related to magnetite biomineralization and the other to greigite biomineralization, were identified in the genome of the sMMP, and two sets of paralogous proteins (Mam and Mad) that may function separately and independently in magnetosome biomineralization were found. Phylogenetic analysis indicated that the sMMPs were affiliated with Deltaproteobacteria. This is the first direct report of two types of magnetosomes and two sets of MGCs being detected in the same sMMP. The study provides new insights into the mechanism of biomineralization of magnetosomes in MMPs, and the evolutionary origin of MGCs.

Planktonic ciliates are important components of microzooplankton in marine pelagic ecosystems. However, the study of planktonic ciliate distribution in different water masses of the Southern Ocean was scarce. We investigated planktonic ciliate distribution in different water masses of the Cosmonaut and Cooperation Seas during December 6, 2019 to January 6, 2020. Tintinnids contributed 5.97% and 3.65% to total planktonic ciliate abundance and biomass, respectively. Both total planktonic ciliate and aloricate ciliate abundances were highest in the Winter Water (WW), while tintinnid abundance was highest in the Summer Surface Water (SSW). The biomasses of total planktonic ciliates and aloricate ciliates were highest in SSW, while that of tintinnids was highest in WW. The lowest values were all observed in the Circumpolar Deep Water (CDW). Fourteen tintinnid species were grouped into three types based on their distribution characteristics: Type I (Amphorellopsis quinquealata, Codonellopsis gaussi, Cymatocylis antarctica, Cymatocylis cf. calyciformis, Cymatocylis cf. convallaria, Salpingella faurei, and Salpingella sp.) species distributed in all the water masses; Type II species (Cymatocylis cf. cristallina, Cymatocylis cf. drygalskii, and Laackmanniella naviculaefera) were found in SSW and WW; and Type III species (Amphorides laackmanni, S. costata, S. laackmanni, and one undefined species) were restricted to WW and CDW. Our results characterize the distribution patterns and influencing factors of planktonic ciliates in different water masses in the Cosmonaut and Cooperation Seas, which will be helpful to understand the pelagic assemblage variation and constitute a baseline for studying the marine food web variation in the Antarctic Zone of the Southern Ocean.

Magnetotactic bacteria (MTB) have been found in a wide variety of marine habitats, ranging from intertidal sediments to deep-sea seamounts. Deep-sea hydrothermal fields are rich in metal sulfides, which are suitable areas for the growth of MTB. However, MTB in hydrothermal fields have never been reported. Here, the presence of MTB in sediments from the Tangyin hydrothermal field was analyzed by 16S rRNA gene amplicon analysis, metagenomics, and transmission electron microscopy. Sequencing 16S rRNA gene yielded a total of 709 MTB sequences belonging to 20 OTUs, affiliated with Desulfobacterota, Alphaproteobacteria, and Nitrospirae. Three shapes of magnetofossil were identified by transmission electron microscopy: elongated-prismatic, bullet-shaped, and cuboctahedron. All of these structures were composed of Fe3O4. A total of 121 sequences were found to be homologous to the published MTB magnetosome-function-related genes, and relevant domains were identified. Further analysis revealed that diverse MTB are present in the Tangyin hydrothermal field, and that multicellular magnetotactic prokaryote (MMPs) might be the dominant MTB.

Planktonic ciliates are an important component of microzooplankton, but there is limited understanding of their responses to changing environmental conditions in the Pacific Arctic Region. We investigated the variations of ciliate community structure and their relationships with environmental features in the Pacific Arctic Region in the summer of 2016 and 2019. The Pacific water was warmer and more saline in 2019 than in 2016. The abundance and biomass of total ciliate and aloricate ciliate were significantly higher in 2019 than those in 2016, while those of tintinnid were significantly lower. The dominant aloricate ciliate changed from large size-fraction (> 30 μm) in 2016 to small size-fraction (10–20 μm) in 2019. More tintinnid species belonging to cosmopolitan genera were found in 2019 than in 2016, and the distribution of tintinnid species (Codonellopsis frigida, Ptychocylis obtusa, and Salpingella sp.1) in 2019 expanded by 5.9, 5.2, and 8.8 degrees further north of where they occurred in 2016. The environmental variables that best-matched tintinnid distributions were temperature and salinity, while the best match for aloricate ciliate distributions was temperature. Therefore, the temperature might play a key role in ciliate distribution. These results provide basic data on the response of the planktonic ciliate community to hydrographic variations and implicate the potential response of microzooplankton to Pacification as rapid warming progresses in the Pacific Arctic Region.

Viruses are far more abundant than cellular microorganisms in the marine ecosystem. However, very few viruses have so far been isolated from marine sediments, especially hydrothermal vent sediments, hindering the understanding of the biology and ecological functions of these tiny organisms. Here, we report the isolation and characterization of a temperate bacteriophage, named PVJ1, which infects Psychrobacillus from a hydrothermal vent field in Okinawa Trough. PVJ1 belongs to the Myoviridae family of the order Caudovirales. The tailed phage possesses a 53,187 bp linear dsDNA genome, with 84 ORFs encoding structural proteins, genome replication, host lysis, etc. in a modular pattern. The phage genome is integrated into the host chromosome near the 3′-end of deoD, a gene encoding purine nucleoside phosphorylase (PNP). The phage integration does not appear to disrupt the function of PNP. The phage DNA is packaged by the headful mechanism. Release of PVJ1 from the host cell was drastically enhanced by treatment with mitomycin C. Phages encoding an MCP sharing significant similarity (≥70% identical amino acids) with that of PVJ1 are widespread in diverse environments, including marine and freshwater sediments, soils, artificial ecosystems, and animal intestines, and primarily infect Firmicutes. These results are valuable to the understanding of the lifestyle and host interactions of bacterial viruses at the bottom of the ocean.

Information on tintinnid community structure variations in different water masses in the Arctic Basin is scarce. During the summer of 2020, tintinnid diversity and vertical distribution were investigated in the Arctic Ocean. A total of 21 tintinnid species were found in five water masses and each water mass had a unique tintinnid community structure. In the Pacific Summer Water (PSW), Salpingella sp.1 occupied the top abundance proportion (61.8%) and originated from the North Pacific. In the Remnant Winter Water (RWW), Acanthostomella norvegica occupied the top abundance proportion (85.9%) and decreased northward. In the Mixed Layer Water, Pacific Winter Water, and Atlantic-origin Water, Ptychocylis urnula had the highest abundance proportion (67.1, 54.9, and 52.2%, respectively). The high abundance distribution area of Salpingella sp.1 and A. norvegica were separated by the boundary of the Beaufort Gyre and Transpolar Drift. The above species could be indicator species of each water masses. The highest abundance proportion of Salpingella sp.1 contributes 81.9% to the dominance of 12–16 μm lorica oral diameter in the PSW, which indicated that the preferred food items of tintinnid were also getting smaller. The occurrence of North Pacific tintinnid in the PSW might be due to the increasing Pacific Inflow Water. Further studies are needed to explore the lasting period of this species and whether it can establish a local population under rapid Arctic warming progress.

与太平洋和大西洋相比,印度洋有独特的季风和洋流系统和由此驱动的浮游生物分布及生产规律.在全球变暖的背景下,印度洋的变暖趋势比太平洋和大西洋更为显著,是研究变暖对海洋浮游生态系统影响的热点海区之一.文章结合国内外文献,评述印度洋浮游生态系统的现状、特点及对全球变暖的响应,包括印度洋的浮游生物地理分布、南北印度洋浮游生态系统的特点、印度洋特殊气候现象的生态学效应等内容.我国的印度洋浮游生态学研究正处于发展阶段,建议将跨越10°S不同生物地理分布区中浮游生物的交汇格局、低盐水覆盖的孟加拉湾独特最小含氧带浮游生态研究和东印度洋暖池区漂浮生物对海洋变暖的响应作为切入点.

Endosomal sorting complex required transport (ESCRT) III proteins are essential for membrane remodeling and repair across all domains of life. Eukaryotic ESCRT-III and the cyanobacterial homologs PspA and Vipp1/Imm30 remodel membrane into vesicles, rings, filaments and tubular rods structures. Here our microscopy analysis showed that multicellular bacteria, referred to as magnetoglobules, possess multiple compartments including magnetosome organelles, polyphosphate granules, vesicles, rings, tubular rods, filaments and MVB-like structures. Therefore, membrane remodeling protein PspA might be required for the formation of these compartments, and contribute to the morphogenesis and evolution of multicellularity. To assess these hypotheses, we sequenced nine genomes of magnetoglobules and found a significant genome expansion compared to unicellular magnetotactic bacteria. Moreover, PspA was ubiquitous in magnetoglobules and formed a distinct clade on the tree of eubacterial and archaeal ESCRT-III. The phylogenetic feature suggested the evolution of magnetoglobules from a unicellular ancestor of deltaproteobacterium. Hetero-expression of ellipsoidal magnetoglobule pspA2 gene alone in Escherichia coli resulted in intracellular membrane aggregation. GFP fusion labeling revealed polar location of PspA2 in rod-shaped unicells and regular interval location in filamentous cells. Cryo-electron tomography analysis showed filament bundle, membrane sacculus, vesicles and MVB-like structure in the cells expressing PspA2. Moreover, electron-dense area with a similar distribution as GFP-PspA2 foci in filamentous cells changed the inward orientation of the septum, which might interfere with the cell division. Collectively, these results show the membrane remodeling function of magnetoglobule PspA proteins, which may contribute to morphogenesis and the evolution of multicellularity of magnetotactic bacteria.