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In order to rapidly screen microalgae species as feedstocks for antioxidants, extracts were obtained from 16 microalgae strains (under 11 genera, 7 classes) using two methods: a one-step extraction with ethanol/water and a three-step fractionating procedure using hexane, ethylacetate, and water successively. Measuring the total phenol content (TPC), total carotenoid content (TCC), and antioxidant activity of the extracts, indicating TPC and TCC, played an important role in determining the antioxidant activity of the microalgae. A weighted scoring system was used to evaluate the antioxidant activity, and the scores of microalgal samples from two extraction methods were calculated using the same system. Among the investigated microalgae, Euglena gracilis SCSIO-46781 had the highest antioxidant score, contributing to high TPC and TCC, followed by Arthrospira platensis SCSIO-44012, Nannochloropsis sp. SCSIO-45224, Phaeodactylum tricornutum SCSIO-45120, and Nannochloropsis sp. SCSIO-45006, respectively. Additionally, the above-mentioned five strains are currently being applied in commercial production, indicating this system could be effective not only for screening microalgal antioxidants, but also for screening microalgal species/strains with strong adaptation to environmental stress, which is a critical trait for their commercial cultivation.

Microalgal polysaccharides have been reported in many studies due to their uniqueness, biocompatibility, and high value, and Rhodosorus sp. SCSIO-45730 was an excellent source of polysaccharides and β-glucans. However, the polysaccharides from the red unicellular alga Rhodosorus sp. SCSIO-45730 have barely been studied. In this work, hot water extraction of Rhodosorus sp. SCSIO-45730 polysaccharides (RSP) was optimized using response surface methodology (RSM) based on Box–Behnken design (BBD). The maximum RSP yield (9.29%) was achieved under the optimum extraction conditions: liquid–solid ratio of 50.00 mL g−1; extraction temperature of 84 °C; extraction time of 2 h; and extraction times of 5 times. The results of physicochemical characterization showed that RSP had high sulfate and uronic acid with content of 19.58% and 11.57%, respectively, rough layered structure, and mainly contained glucose, galactose, xylose, and galacturonic acid with mass percentages of 34.08%, 28.70%, 12.46%, and 12.10%. Furthermore, four kinds of antioxidant assays were carried out, and the results indicated that RSP had strong scavenging activities on ABTS and hydroxyl radical and moderate scavenging activities on DPPH and ferrous chelating ability. These results indicated that RSP showed potential as a promising source of antioxidants applied in food, pharmaceutical, and cosmetics industry. Supplementary Information The online version contains supplementary material available at 10.1007/s10811-021-02646-2.

Enterovirus 71 (EV71) poses a major threat to public health globally due to severe and even fatal hand, foot, and mouth disease (HFMD). However, no effective antiviral agents are available to treat HFMD caused by this virus. Polysaccharides have been shown to exhibit antiviral activity, and polysaccharides extracted from Picochlorum sp. 122 (PPE) could potentially be used to treat HFMD, but reports on their antiviral activity are limited. In this study, the antiviral activity of PPE against EV71 was verified in Vero cells. PPE was shown to limit EV71 infection, as demonstrated using an MTT assay and by observing the cellular cytopathic effect. In addition, a decrease in VP1 RNA and protein levels indicated that PPE effectively inhibits proliferation of EV71 in Vero cells. An annexin V affinity assay also indicated that PPE protects host cells from apoptosis through the AKT and ATM/ATR signalling pathways. These results demonstrate that PPE has potential as an antiviral drug to treat HFMD caused by EV71.

The infection of enterovirus 71 (EV71) resulted in hand, foot, and mouth disease and may lead to severe nervous system damage and even fatalities. There are no effective drugs to treat the EV71 virus and it is crucial to find novel drugs against it. Polysaccharide isolated from Durvillaea antarctica green algae has an antiviral effect. In this study, D. antarctica polysaccharide (DAPP) inhibited the infection of EV71 was demonstrated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), reverse transcription polymerase chain reaction, flow cytometry, and western blot. MTT assay showed that DAPP had no toxicity on Vero cells at the concentration 250 μg/ml. Furthermore, DAPP significantly reduced the RNA level of EV71 in a dose-dependent manner. Moreover, DAPP inhibited the Vero cells apoptosis induced by EV71 via the P53 signaling pathway. Meanwhile, the expression of signal transducer and activator of transcription 1 and mammalian target of rapamycin were increased and the proinflammatory cytokines were significantly inhibited by DAPP. Taken together, these results suggested that DAPP could be a potential pharmaceutical against the infection of EV71 virus.

With the increase of global energy consumption, bioenergy from microalgae has been recognized as a potential alternative choice. A novel carbohydrate-rich microalgal strain, isolated from Xisha Islands (China), was identified as Rhodosorus sp. SCSIO-45730. To accumulate biomass for bioenergy production, strategies of phosphate optimization and chitosan flocculation were used to evaluate its potential for the production of biomass, total carbohydrates, and β-glucans. The biomass of this alga reached 12.3 ± 0.1 g L−1 in vertical bubble column photobioreactors at the phosphate concentration of 120 mg L−1, and the productivities of total carbohydrates and β-glucans maximized up to 242.6 ± 2.3 mg L−1 day−1 and 108.1 ± 4.0 mg L−1 day−1, respectively. Simultaneously, flocculation results demonstrated that the recovery rate of the biomass, total carbohydrates, and β-glucans were over 90% at a low chitosan concentration of 3 mg L−1. The flocs were easily collected and washed through a 300-mesh bolting cloth, presenting an ultralow harvest cost of 2.93 US$ per tonne of biomass. In summary, addition of suitable phosphate and flocculation with low chitosan concentration could be effective strategies to enhance the commercial potential of Rhodosorus sp. SCSIO–45730 as a feedstock for biofuel and β-glucans.

Arthrospira platensis, a well-known cyanobacterium, is widely applied not only in human and animal nutrition but also in cosmetics for its high amounts of active products. The biochemical composition plays a key role in the application performance of the Arthrospira biomass. The present study aimed to evaluate the growth and biochemical composition characteristics of A. platensis, cultured with a nitrogen-free and seawater-supplemented medium in an outdoor raceway pond in winter. The results showed that the biomass yield could achieve 222.42 g m−2, and the carbohydrate content increased by 247% at the end of the culture period (26 d), compared with that of the starter culture. The daily and annual areal productivities were 3.96 g m−2 d−1 and 14.44 ton ha−1 yr−1 for biomass and 2.88 g m−2 d−1 and 10.53 ton ha−1 yr−1 for carbohydrates, respectively. On the contrary, a profound reduction was observed in protein, lipid, and pigment contents. Glucose, the main monosaccharide in the A. platensis biomass, increased from 77.81% to 93.75% of total monosaccharides. Based on these results, large-scale production of carbohydrate-rich A. platensis biomass was achieved via a low-cost culture, involving simultaneous nitrogen deficiency and supplementary seawater in winter.

The microalga Porphyridium accumulates high-value compounds such as phycoerythrin, polyunsaturated fatty acids, and polysaccharides, and thus, the extraction of these compounds could significantly expand the value of Porphyridium biomass. In the present study, a novel fractional extraction strategy based on the characteristics of these compounds was established using cold water, 95% ethanol, and hot water. The yield of phycoerythrin, lipids, and polysaccharides was 63.3, 74.3, and 75.2%, respectively. The phycoerythrin exhibited excellent fluorescence characteristics but had low purity. The crude lipid was dark with poor fluidity. Digalactosyldiacylglycerol and sulphoquinovosyldiacylglycerol containing C20:5 and C20:4 were the most abundant glycerolipids, while glucose, xylose, and galactose constituted the intracellular polysaccharides that had covalently bound to proteins (8.01%), uronic acid (4.13%), and sulfate (8.31%). Compared with polysaccharides and crude lipids, crude phycoerythrin showed the best antioxidant activity. Overall, the three-step fractional extraction process was feasible for Porphyridium, however, further purification is necessary for downstream applications.

Enterovirus 71 (EV71) pose a critical threat in global public health and may lead to severe and even lethal cases of hand-foot-and-mouth disease (HFMD). No effective antiviral agents are available to the masses for treatment of HFMD caused by EV71. Polysaccharide provides a good clinical application for antivirus. Polysaccharides extracted from Picochlorum sp. 122 (PPE) is a kind of seaweed Polysaccharides, the reports on its antiviral activity are limited. In this study, the antiviral activity was verified in Vero cells. Briefly, PPE has been demonstrated to restrain EV71 infection through MTT assay and cellular cytopathic effect. In addition, the decrease of the nucleic acid and protein levels of VP1 indicated PPE effectively inhibited the proliferation of EV71 in Vero cells. Furthermore, the annexinV-affinity assay suggested that PPE protected host cells from apoptosis. The mechanistic investigations revealed that PPE restrained EV71-induced host-cells apoptosis by AKT and ATM/ATR signaling pathways. In conclusion, these results demonstrate PPE is a hopeful antiviral drug for the infection of EV71.

To improve the yields of specific value-added compounds from Arthrospira platensis, one generally accepted method is to obtain mutant strains with increased target component content and growth rate. In the present study, mutation breeding of seawater A. platensis SCSIO-44012 (the wild type strain, hereafter WT) through space-flight carriage by Shijian-10 satellite was carried out. After returning to earth, 183 single filaments were picked out, 43 of which survived. During the following consecutive subcultures, one out of the 43 mutant strains, named A. platensis SCSIO-44012-H11 (hereafter H11), showed stable advantages in high levels of polysaccharides production. The biomass yield, total sugar content, and total sugar productivity of H11 remained stable at 0.88 g L−1, 24.82% DW, and 21.78 mg L−1 d−1, respectively, from the 10th to 35th generations of subculture, which were 8.6%, 62.26%, and 73.68%, respectively, higher than that of WT. The biochemical compositions of polysaccharide extracts (PSE) from H11 and WT also exhibited significant differences. The total sugar content of H11 PSE reached 55.37%, 2.49 times as much as that of WT PSE. The PSE from H11 was enriched in the component cutting off 100 kDa, accounting for 89.32% of the total polysaccharides, whereas WT PSE was mainly composed of the component with a molecular weight between 10 kDa and 50 kDa. The predominant monosaccharide of H11 PSE was glucose, followed by rhamnose, which accounted for 84.53% and 8.13% of the total monosaccharides, respectively. By comparison, glucose and rhamnose occupied 27.33% and 35.41%, respectively, in PSE from WT. Furthermore, the PSE from H11 showed strong ferrous ion-chelating activity and moisture retention capacity. These results indicated the feasibility of H11 as a polysaccharides feedstock applied in cosmetics, nutraceuticals, and medicines.

Algal β-glucans have received attention in recent years, but little is understood for the pattern and molecular mechanism of β-glucans accumulation in Chlorella, a more economically feasible microalga. In the present study, P-limited conditions were found to substantially inhibit the microalgal growth, reduce the lipid and protein production but induce the accumulation of β-glucans and total carbohydrate of Chlorella sorokiniana SCSIO 46784 during the early phase of growth. Comparative transcriptomics analysis of the microalga for the specific time point under P-limited and P-replete conditions identified key genes involved in β-glucans metabolism and revealed the probable molecular mechanism of the β-glucans accumulation. The significant up- and down-regulation of genes encoding β-glucans synthesis- and degradation-related enzymes coincided with a rapid increase in β-glucans production. The reduced synthesis of certain sugars (starch, sucrose, UDP-L-rhamnose, and UDP-sulfoquinovose) might provide more carbon precursors for β-glucans biosynthesis. The suppression of lipids (fatty acid, triacylglycerol, sulfoquinovosyl diacylglycerol, and monogalactosyldiacylglycerol) synthesis presumably shunted carbon flux toward carbohydrates and β-glucans biosynthesis. In addition, the down-regulation of multiple genes related to carbon fixation (CO2 concentrating mechanism and Calvin cycle) and central carbon metabolism (pentose phosphate pathway, glycolysis/gluconeogenesis, and tricarboxylic acid cycle) might contribute to the inferior growth of C. sorokiniana SCSIO 46784 under P-limited conditions. To our knowledge, this is the first report to reveal the metabolic insights into β-glucans in Chlorella. This study provides not only the useful information for understanding the biosynthesis and accumulation of β-glucans but also potential gene targets for genetic modification to improve the production of β-glucans in Chlorella.

Microalgae of the genus Porphyridium show great potential for large-scale commercial cultivation, as they accumulate large quantities of B-phycoerythrin (B-PE), long chain polyunsaturated fatty acids (LC-PUFAs) and exopolysaccharide (EPS). The present study aimed to adjust culture nitrogen concentrations to produce Porphyridium biomass rich in B-PE, LC-PUFAs and EPS. Porphyridium purpureum SCS-02 was cultured in ASW culture medium with low nitrogen supply (LN, 3.5 mM), medium nitrogen supply (MN, 5.9 mM) or high nitrogen supply (HN, 17.6 mM). HN significantly enhanced the accumulation of biomass, intracellular protein, B-PE and eicosapentaenoic acid. LN increased the intracellular carbohydrate and arachidonic acid content, and promoted the secretion of EPS. The total lipids content was almost unaffected by nitrogen concentration. Based on these results, a semi-continuous two-step process was proposed, which included the production of biomass rich in B-PE and LC-PUFAs with sufficient nitrogen, and induced EPS excretion with limited nitrogen and strong light.

A Gram-stain-negative, yellow, non-spore-forming, strictly aerobic bacterium, designated C3T, was isolated from a cyanobacterial culture pond. Cells were halophilic, rod-shaped and able to move by gliding. Growth of strain C3T was observed at 15–30 °C (optimum 25 °C), pH 6.0–9.0 (optimum pH 7.5), and in the presence of 1–7 % (w/v) NaCl (optimum 2–3 %). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain C3T formed a distinct lineage within the family Flavobacteriaceae and exhibited the highest similarity (95.21 %) to the type strains of Maribacter dokdonensis, Maribacter arcticus, Maribacter orientalis and Maribacter stanieri, and ‘Maribacter caenipelagi’ HD-44. The only isoprenoid quinone present within strain C3T was menaquinone 6 (MK-6). The G+C content of genomic DNA was 41.5 mol%. The major polar lipids were phosphatidylethanolamine and three unidentified lipids. The predominant cellular fatty acids (>5 % of the total fatty acids) were iso-C15 : 1 G, iso-C15 : 0, iso-C15 : 0 3-OH, iso-C17 : 0 3-OH, and summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c). On the basis of the phenotypic, chemotaxonomic and phylogenetic characteristics, strain C3T represents a novel species of the genus Maribacter, for which the name Maribacter flavus sp. nov. is proposed. The type strain is C3T ( = KCTC 42508T = CGMCC 1.15112T).

The microalga, Nannochloropsis, is receiving increased attention for their potential application as a biodiesel feedstock and an aquaculture feed. Nannochloropsis cultured in different environments has been shown to possess different growth characteristics and the biochemical composition. The biochemical composition are critical as they dictate applicability and profitably of the species. In the present study, the outdoor productivity of Nannochloropsis oceanica SCS-1981 was investigated in a novel open pond that was completely powered by solar-electricity. Using this technique, the maximum cell density in the solar-powered open pond was 1.1 × 108 cell mL−1, with proteins the dominant biochemical component (53.1% of dry weight). Additionally, the microalga accumulated a high content of eicosapntemacnioc acid (EPA) comprising nearly 3% of the dry weight. Probiotics, such as Phaeodactylibacter, were present in the culture pond, which was a gram-negative bacteria that has been reported to have a positive effect on the absorption and immune system of cultured animal. The results of the study indicated that N. oceanica was suitable for aquiculture feeds. The productivity of biomass was 5.8 g m−2 d−1, which was similar to traditional raceway ponds. Considering that the solar-powered open pond requires no additional energy input, the costs of culturing can be significantly reduced. This culturing method is easy to work with and would be an easy technique to be used in the culturing of Nannochloropsis as living aquaculture feeds. The study will greatly promote the low-cost cultivation of microalgae for aquaculture feed purposes.

A laboratory study was conducted on biomass and lipid production by Scenedesmus sp. and the removal of total nitrogen (TN) and total phosphorus (TP) from filtered anaerobically digested piggery wastewater. The dry weight (DW), lipid content and productivity, total nitrogen, and total phosphorus removal rate were assessed in five media: modified soil extract (MSE) medium, 5 % anaerobic digested wastewater (ADWW), 10 % ADWW, 15 % ADWW, and 5 % ADWW supplemented with NaNO3. The highest biomass productivity appeared in the 15 % ADWW group, which was 20.4 % higher than MSE group. The highest lipid content was found in the 5 % ADWW group (31.60 %), while the highest lipid productivity was in the 10 % ADWW group (27.01 mg L−1 day−1). Compared with the 5 % ADWW group, the 5 % ADWW group supplemented with NaNO3 had a similar biomass amount but lower lipid content and productivity. The fatty acids percentage of Scenedesmus sp. showed a slight difference in different media, but with the four dominant fatty acids (C16:0, C18:1, C18:2, C18:3) accounting for 87 % of the total fatty acids, suggests that Scenedesmus sp. in ADWW medium was no different than MSE in terms of lipid composition and content. TN removal rates were 82.85, 82.51, 85.85, 91.28, and 78.71 % in groups 1 to 5, and TP removal rates were 53.05, 88.53, 87.77, 88.72, and 80.64 %. Our experiment also shows the feasibility of using ADWW as a substitute of all the elements of MSE medium except for carbon, which would significantly reduce the costs of microalgal culture.

To explore the molecular mechanism of triploidy effect in the pearl oyster Pinctada fucata , two RNA-seq libraries were constructed from the mantle tissue of diploids and triploids by Roche-454 massive parallel pyrosequencing. The identification of differential expressed genes (DEGs) between diploid and triploid may reveal the molecular mechanism of triploidy effect. In this study, 230 down-regulated and 259 up-regulated DEGs were obtained by comparison between diploid and triploid libraries. The gene ontology and KEGG pathway analysis revealed more functional activation in triploids and it may due to the duplicated gene expression in transcriptional level during whole genome duplication (WGD). To confirm the sequencing data, a set of 11 up-regulated genes related to growth and development control and regulation were analyzed by RT-qPCR in independent experiment. According to the validation and annotation of these genes, it is hypothesized that the set of up-regulated expressed genes had the correlated expression pattern involved in shell building or other interactive probable functions during triploidization. The up- regulation of growth-related genes may support the classic hypotheses of ‘energy redistribution’ from early research. The results provide valuable resources to understand the molecular mechanism of triploidy effect in both shell building and producing high-quality seawater pearls.

Angucyclines are aromatic polyketides with antimicrobial, antitumor, antiviral and enzyme inhibition activities. In this study, a new pair of degenerate primers targeting the cyclase genes that are involved in the aromatization of the first and/or second ring of angucycline, were designed and evaluated in a PCR protocol targeting the jadomycin cyclase gene of Streptomyces venezuelae ISP5230. The identity of the target amplicon was confirmed by sequencing. After validation, the primers were used to screen 49 actinomycete isolates from three different marine sponges to identify putative angucycline producers. Seven isolates were positively identified using this method. Sequence analysis of the positive amplicons confirmed their identity as putative angucycline cyclases with sequence highly similar to known angucycline cyclases. Phylogenetic analysis clustered these positives into the angucycline group of cyclases. Furthermore, amplifications of the seven isolates using ketosynthase-specific primers were positive, backing the results using the cyclase primers. Together these results provided strong support for the presence of angucycline biosynthetic genes in these isolates. The specific primer set targeting the cyclase can be used to identify putative angucycline producers among marine actinobacteria, and aid in the discovery of novel angucyclines.

In this report, the diversity of Actinobacteria associated with the marine sponge Hymeniacidon perleve collected from a remote island of the South China Sea was investigated employing classical cultivation and characterization, 16S rDNA library construction, 16S rDNA-restriction fragment length polymorphism (rDNA-RFLP) and phylogenetic analysis. A total of 184 strains were isolated using seven different media and 24 isolates were selected according to their morphological characteristics for phylogenetic analysis on the basis of their 16S rRNA gene sequences. Results showed that the 24 isolates were assigned to six genera including Salinispora, Gordonia, Mycobacterium, Nocardia, Rhodococcus and Streptomyces. This is the first report that Salinispora is present in a marine sponge from the South China Sea. Subsequently, 26 rDNA clones were selected from 191 clones in an Actinobacteria-specific 16S rDNA library of the H. perleve sample, using the RFLP technique for sequencing and phylogenetic analysis. In total, 26 phylotypes were clustered in eight known genera of Actinobacteria including Mycobacterium, Amycolatopsis, Arthrobacter, Brevibacterium, Microlunatus, Nocardioides, Pseudonocardia and Streptomyces. This study contributes to our understanding of actinobacterial diversity in the marine sponge H. perleve from the South China Sea.

Microorganisms of millions species exist in every corner of the Earth, and form a dynamic genetic reservoir that are not clearly revealed and categorized due to barrier in current cultivation technology. Their applications in biomedical and environmental aspects are more than satisfactory. However, the situation has drastically changed during the turn of the century because of the rapid development of phylogenetic studies based on rRNA sequencing independent of standard laboratory cultivation. More recently, high throughput sequencing technology which enables direct sequencing of community DNA for metagenomic analyses are making a direct impact on our understanding of microbial diversity, ecology, and secondary metabolism. In this review, we highlight some recent progress and innovation on metagenomic research with an emphasis on natural product drug discovery. The rapid path of accumulating decoded metagenomics would be an efficient guide on direct access to the genomes of numerous non-culturable microorganisms for their genomic diversity and associated chemical prosperity for potential medicinal applications.

In order to investigate the composition and diversity of prokaryotes in marine surface sediment from site XSCS13 at northern South China Sea.We extracted environment total DNA directly from the sediment and amplified 16S rRNA genes from the total DNA, thereby constructing 16S rRNA clone libraries of both archaea and bacteria. Then we selected positive clones randomly from the library and identified them by the method of restriction fragment length polymorphism (RFLP). After that, the unique RFLP pattern corresponded sequences were sequenced, BLAST and then constructed into a phylogenetic tree.Most of the clones were sequences from uncultured microbes. For the Archaea part: the community was mainly comprised of 3 phyla: Crenarchaeota, Thaumarchaeota and Euryarchaeota, among which Crenarchaeota was the dominant class with the percentage of 71%, while Euryarchaeota took the least with only 3 clones. The main group of Crenarchaeota was Marine Group I, taking 61% of all. For the bacteria part, all together 9 phyla were included: 32.6% of Proteobacteria, 3% of Verrucomicrobia, 5.2% of Bacteroidete, 4.44% of Acidobacteria, 6% of Chloroflexi, 3.7% of Firmicute, 5.2% of Planctomycete, 11.1% of Gemmatimonadete and 4.44% of Actinobacteria. Unlike archaea, there's no overwhelming preponderant phylum in bacterium, each phylum was relatively distributed in balanced proportions. Proteobacteria had 3 classes involved: alpha-Proteobacteri, gamma-Proteobacteria and delta-Proteobacteria, and gamma-Proteobacteria stood out with 54.5% of proportion. In addition, over half of all the clones were related to reduction reaction of sulfate and generation of methane.The research indicated that prokaryote diversity in marine surface sediment from site XSCS13 at northern South China Sea was quite plentiful, and a great mass of abundant microbial resources still remained unknown. Furthermore, the community structure of archaea and bacteria showed that the sampling site may be in a cold spring area with abundant methane.

A total of 110 culturable actinobacteria associated with seagrass (Thalassia hemprichii) were isolated using six different culture media, and their bioactivity potentials were analysed based on their genetic background on polyketide synthetase (PKS) and nonribosomal peptide synthetase (NRPS) gene sequences. Though the using of RFLP technique for sequencing and phylogenetic analysis, these selected 33 culturable isolates identified as belonging to ten genera of actinobacteria including Streptomyces, Micromonospora, Saccharomonospora, Mycobacterium, Actinomycetospora, Nonomuraea, Verrucosispora, Nocardiopsis, Microbacterium and Glycomyces. Four of the strains were unable to be assigned to currently known species and might be candidates of novel species. To our knowledge, this is the first report about culturable actinobacteria associated with seagrass and the isolate classified as Verrucosispora was first recorded to be isolated from plant. Most of the isolates harbor NRPS and PKS genes, which might indicate that these strains have great potential in production of bioactive natural compounds.

The bacterial diversity of deep-sea sediments collected from the South China Sea (B111), the Andaman Sea (ADM), and the Indian Ocean (P10) was investigated through the construction of 16S recombinant deoxyribonucleic acid (DNA) clone libraries for sequencing. The structure of the bacterial community and their phylogenetic relationships were analyzed using the Mothur software. The nutrient and heavy metal content of the sediments were also analyzed. In total, 263 valid sequences were obtained from 300 sequenced clones. There were 151 operational taxonomic units (OTUs) that belong to Actinobacteria, Proteobacteria, Planctomycetes, Bacteroidetes, Gemmatimonadetes, Nitrospira, Chloroflexi, Acidobacteria, WS3, BRC1, OD1, and numerous unclassified bacteria. The Chao1 and Shannon indices showed that B111 had the highest diversity, but P10 had the richest OTUs. The P < 0.05 value of the parsimony index, LIBSHUFF, and weighted UniFrac analyses indicated important distinctions in the structure and diversity of the bacterial communities. These differences are related to the nutrient and heavy metal content of the sediments. The present study clearly demonstrates the wide bacterial diversity in deep-sea sediments from the South China Sea, the ADM, and the P10, including a large number of unknown bacteria. Due to the different geographical locations of the sediments, the structures of their bacterial communities are also remarkably distinct. Key words: Deep-sea sediments, bacterial diversity, bacterial community structure.

Finding a series of archaeal 16S rRNA gene universal primer applied strategies to detect complex microbial diversity in environmental samples, especially with rapidly development of next generation sequencing technology challenge.We used Oligocheck soft to simulate two pairs of archaeal 16S rRNA gene universal primers with RDP (Ribosomal database project) database 16S rRNA gene sequences matching percentage. In succession, the sediment sample was constructed for two clone libraries by using two pairs of archaeal 16S rRNA gene universal primers.The soft simulation matched percentage result suggests that primer f109/r958 is better than primer f21/r958. This result is consistent with RFLP and diversity index analyses by two clone libraries.Multi-primers and properly primer are used to recovery environmental microbiology diversity, which will be advanced in environmental microbial resolution.