Inhibitory effect and mechanism of algicidal bacteria on Chaetomorpha valida.

Chaetomorpha valida, filamentous green tide algae, poses a significant threat to both aquatic ecosystems and aquaculture. Vibrio alginolyticus Y20 is a new algicidal bacterium with an algicidal effect on C. valida. This study aimed to investigate the physiological and molecular responses of C. valida to exposure to V. alginolyticus Y20. The inhibitory effect of V. alginolyticus Y20 on C. valida was content dependent, with the lowest inhibitory content being 3 × 105 CFU mL-1. The microscopic results revealed that C. valida experienced severe morphological damage under the influence of V. alginolyticus Y20, with a dispersion of intracellular pigments. V. alginolyticus Y20 caused the decrease in chlorophyll-a content and Fv/Fm in C. valida. At the molecular level, V. alginolyticus Y20 downregulated the expression of genes related to photosynthetic pigment synthesis, light capture, and electron transport. Furthermore, V. alginolyticus Y20 induced oxidative damage to algal cells. The production of reactive oxygen species significantly increased after 11 days of exposure. Malondialdehyde content significantly increased, and the cell membranes were severely damaged by lipid peroxidation. The content of superoxide dismutase and peroxidase also markedly increased, whereas catalase content decreased significantly. Additionally, peroxisomes were inhibited due to the downregulation of PEX expression, leading to irreversible oxidative damage to algal cells. Our findings provided a new theoretical basis for exploring the interaction between algicidal bacteria and green tide algae at the molecular level.

Functional characterization of secologanin synthase-like homologous genes suggests their involvement in the biosynthesis of diverse metabolites in the secoiridoid biosynthetic pathway of Camptotheca acuminata Decne.

The assignment of functions based on homology has recently been challenged by the frequent discovery of functional divergence among homologous gene family members of enzymes involved in plant secondary metabolism. Secologanin synthase (SLS) is the key CYP450 enzyme that acts critically in the biosynthesis of Strychnos alkaloid scaffold. In this study, to fully elucidate the mechanism that underlies metabolic variation, the CYP450 paralogs that participate in oxidative transformation of the secoiridoid pathway were functionally characterized by combining multitiered strategies of metabolite profiling, phylogenetic analyses, biochemistry assays and reverse genetics techniques. Five CaSLSs-like homologous genes were mined and isolated from an integrative multi-omics database of Camptotheca acuminata. Protein sequences, structural comparisons, and phylogenetic analyses confirmed that CaSLS1-2 and CaSLS4-5 were grouped into the SLS clade, and only CaSLS3 clustered into the 7DLH clade. Five homologs, including two previously identified enzymatic genes, were thus designated as CaSLAS1, CaSLAS2, Ca7DLH, CaSLS4 and CaSLS5. Enzymatic assays of the recombinant proteins in yeast showed that CaSLAS1 and CaSLAS2 displayed multi-catalytic activities of SLS, secologanic acid synthase (SLAS) and secoxyloganin synthase (SXS). Additionally, the reactions of CaSLASs enzymes generated stereospecific isomers of secoiridoid products, and a new product of secoxyloganin was observed. CaSLS5, a third SLS enzyme isoform that catalyzes the formation of secologanin, was reported for the first time. However, CaSXS enzymatic activities in vitro had little physiological impact on the biosynthesis of camptothecin (CPT) in Camptotheca acuminata. The primary and secondary roles of CaSLSs-like genes in secoiridoid metabolism were confirmed by virus-induced gene silencing (VIGS) in plant leaves. Efficient silencing and transcriptional downregulation of CaSLAS2, compared with the CaSLAS1 homologs, resulted in a greater reduction of the accumulation of CPT within silenced plants, and CaSLS5 had barely any effect on the contents of metabolites in planta. Thus, CaSLAS2, rather than CaSLAS1, appeared to function as a major participant in the biosynthesis of CPT, and there were redundant functions in the CaSLSs-like enzymes. Consistent with such roles, CaSLAS2 was ubiquitously expressed at very high levels in Camptotheca tissues, and CaSLAS2 was specifically expressed in young leaves. In contrast, CaSLS5 was poorly expressed in every tissue tested. Our findings demonstrate that homologs that belong to the CYP72 gene family are functionally diverse and exhibit divergence and thereby uncover an expanding group of enzymatic genes that determine the chemo-diversity of the iridoid pathway.

Citral-loaded chitosan/carboxymethyl cellulose copolymer hydrogel microspheres with improved antimicrobial effects for plant protection.

The extensive use of chemical pesticides in agricultural production has caused great damage to the soil and ecological environment. Citral, a monoterpene aldehyde, has been shown to inhibit the growth of a variety of pathogenic fungi by affecting mitochondrial structure. However, the high volatility and chemical instability of citral may restrict its applications in the agricultural industries. In this study, a concise and facile method for the preparation of modified copolymer chitosan/carboxymethyl cellulose (CS/CMC) hydrogels microspheres loaded with citral was developed to increase and stabilize the bioavailability of this natural bioactive substance. Polyelectrolyte composite scaffold hydrogel microspheres were synthesized by polycationic chitosan (CS) and polyanionic carboxymethyl (CMC). Citral was embedded into the microspheres by coupling the carbonyl group of citral with the amino group of CS to form a Schiff base structure. The effects of three parameters including CS/CMC weight ratio, concentration of CMC and citral on the loading ratio were investigated and optimal loading of 68% was achieved based on single-factor experiments. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) were employed to confirm and characterize the structure and surface morphology of the microspheres. Both the XRD and FTIR spectra indicated that the microspheres contain -C=N- covalent bonds between CS and citral. The hydrogel microspheres with incorporated citral exhibited effective and improved in vitro antibacterial effects against E. coli, S. aureus and B. subtilis than non-loaded CS microspheres. Moreover, CS/CMC-citral-MPs showed a good antifungal effect in vivo in reducing disease incidence caused by the plant pathogenic fungus Botrytis cinerea in Solanum lycopersicum. Different from the previous applications of CS and citral in the preservation of picked fruits, citral was embedded into CS/CMC microspheres to achieve improved plant protection against Botrytis cinerea. The microspheres are a promising green antimicrobial agent against plant pathogens in crop protection and other fields.

Microplastics profile in a typical urban river in Beijing.

Municipal wastewater treatment plants (WWTPs) are known to be important point sources of microplastic pollution in the environment because they discharge large volumes of microplastic-containing effluents into nearby rivers. However, the fate of these microplastics once they enter the urban rivers is not well understood. The present study focused on the Qing River, a typical urban river in Beijing that receives effluents from four nearby WWTPs. We investigated the microplastic pollution profile both at the effluent outfalls from the WWTPs and in the river. Using micro Fourier-transform infrared spectroscopy, we identified and confirmed a total of 18 polymers from the river and effluent outfalls. The microplastics were then separated into four categories based on their shapes with the fragment group being the most abundant, followed by the fiber, film, and pellet groups. Abundance of microplastics was found to be slightly higher in the main body of the Qing River when sampled in November than in July. However, abundance levels from the effluent outfalls were similar in November and in July. Significant amounts of microplastics in the Qing river, up to 80%, were retained upstream of dams that are used for water storage. This result was also confirmed by a decrease in the polymer-diversity index downstream of the dams compared to upstream. A preliminary conclusion could be drawn that the microplastics in the Qing River are mainly released from the WWTPs and that most of these microplastics are retained in the river by dams.

Microplastics in sediments from an interconnected river-estuary region.

Microplastics are an emerging pollutant of international concern due to its wide distribution through various pathways. Estuary is an important pathway for land microplastics to enter into the oceans by rivers. In this study, we hypothesized that microplastics would sink into estuary sediment during diffusion and transmission from river before entering into the sea, which results in higher accumulation of microplastics in proximity to river-estuary than in the oceans. In order to demonstrate this hypothesis, sediment samples were collected from an estuary and its two main inputting rivers and the microplastics in these samples were analyzed. In the collected sediment samples, 19 types of polymers, including the three most common polymers (polyethylene, polyethylene terephthalate, and poly(propylene:ethylene)), were identified and confirmed by FT-IR. Eight types of polymers were consistently detected in all samples, while 11 types of polymers were occasionally found in some samples. These microplastics exhibited four shapes and their percentages followed the high-to-low order of film, fragment, fiber and pellet. A relatively lower abundance of microplastics was found in river sediments from Shuangtaizi River with an average of 170 ± 96 particles/kg d.w., compared to that from Daliao River with an average of 237 ± 129 particles/kg d.w., but it was higher than that from Liaohe Estuary with an average of 120 ± 46 particles/kg d.w. Furthermore, the highest concentration of microplastics was found at the mouth of rivers, showing high accumulation where the freshwater and saltwater meet. Results from this study, including the abundance, characteristics and spatial distribution of microplastic pollution in sediments from an interconnected river-estuary system, revealed the fate and distribution of microplastics in the river and estuary environment.

Two classes of cytochrome P450 reductase genes and their divergent functions in Camptotheca acuminata Decne.

Cytochrome P450 monooxygenases (CYP450s) and their auxiliary cytochrome P450 reductases (CPRs) are important and commonly involved in the biosynthesis of camptothecin (CPT). To better understand the possible functions of CPRs in planta, we first isolated two CaCPRs genes from Camptotheca acuminata. Sequence analysis revealed the presence of common conserved FMN-, FAD- and NADPH-binding motifs in putative CaCPR1/CaCPR2 proteins. The two CaCPR paralogs were assigned to the Class I and Class II of CPRs, respectively, according to phylogenetic tree. The recombinant CrCYP72-CaCPR1 and CrCYP72-CaCPR2 enzymes and their substrate bioconversion rates of 23.09% and 35.23% demonstrated that both CaCPRs could support the enzyme activities of CrSLS1. Gene silencing of CaCPRs by VIGS led to downregulation of CaCPR1/CaCPR2 expression by 50-67%, accompanied with 10-15% slight decrease and 57-63% dramatic reduction for CaCPR1 and CaCPR2 individually in CPT accumulations. Moreover, CaCPR1/CaCPR2 displayed almost omnipresent expression patterns across Camptotheca tissues. While in comparison to constitutive expression of CaCPR1 gene, CaCPR2 and CYP450 genes were all dramatically phytohormone-induced expressed in leaves which were main tissues for isoprenoid and CPT biosynthesis. Our results suggested that, in Camptotheca seedlings, CaCPR2 had a distinct function from CaCPR1 that was clearly involved in the inducible specialized metabolism for CPT biosynthesis.

Gene identification and antimicrobial activity analysis of a novel lysozyme from razor clam Sinonovacula constricta.

Lysozymes are important immune effectors present in phylogenetically diverse organisms. They play vital roles in bacterial elimination during early immune responses. In the present study, a second invertebrate-type (i-type) lysozyme gene from razor clam Sinonovacula constricta (denoted as ScLYZ-2) was cloned by RACE and nested PCR methods. The full-length cDNA sequences of ScLYZ-2 were 1558 bp, including a 5' untranslated region (UTR) of 375 bp, an open reading frame of 426 bp, and a 3'-UTR of 757 bp with polyadenylation signal sequence (AATAAA) located upstream of the poly(A) tail. SMART analysis showed that ScLYZ-2 contains a signal peptide in the first 16 amino acid (AA) sequences and a destabilase domain located from 24 to 134 AA sequences. The deduced AA sequences of ScLYZ-2 were highly similar (42%-58%) to other known lysozyme genes of bivalve species. Multiple alignments of AA sequences showed that ScLYZ-2 possesses the classical i-type lysozyme family signature of two motifs ["MDVGSLSCGP(Y/F)QIK" and "CL(E/L/R/H)C(I/M)C"] and two catalytic residues (Glu35 and Asp46). Moreover, phylogenetic analysis showed that ScLYZ-2 is a new member of the i-type lysozyme family. In healthy razor clams, ScLYZ-2 was highly expressed in the hepatopancreas, followed by the gills, water pipes, and abdominal foot. Lysozyme activity and ScLYZ-2 expression levels were significantly upregulated in the hepatopancreas and gills after being infected with V. splendidus, V. harveyi, V. parahaemolyticus and S. aureus and M. luteus. Moreover, the recombinant ScLYZ-2 had strong antimicrobial activities against V. splendidus, V. harveyi, and V. parahaemolyticus. Furthermore, the minimal inhibitory concentration of the recombinant ScLYZ-2 against V. parahaemolyticus was 7.2 µmol/mL. Taken together, our results show that ScLYZ-2 plays an important role in the immune defense of razor clam by eliminating pathogenic microorganisms.

Factors that affect the growth and photosynthesis of the filamentous green algae, Chaetomorpha valida, in static sea cucumber aquaculture ponds with high salinity and high pH.

Chaetomorpha valida, dominant filamentous green algae, can be harmful to sea cucumber growth in aquaculture ponds of China. In order to understand the environmental factors affecting the growth of C. valida in sea cucumber aquaculture ecosystems, a combination of field investigations and laboratory experiments were conducted. Field surveys over one year revealed that C. valida survived in sea cucumber aquaculture ponds in salinities ranging from 24.3 ± 0.01‰ to 32.0 ± 0.02‰ and a pH range of 7.5 ± 0.02-8.6 ± 0.04. The high salinity and pH during the period of low C. valida biomass from January to May lay the foundation for its rapid growth in the following months of June to October. Many factors interact in the field environment, thus, laboratory experiments were conducted to determine the isolated effects of pH and salinity on C. valida growth. In laboratory experiments, samples were incubated under different salinity and pH conditions at 25 °C, with a light intensity of 108 µmol photon·m-2·s-1, and a photoperiod of 12 L:12 D. Results showed that salinity and pH significantly affect the growth and F v/F m (quantum yield of photosynthesis) of C. valida (p < 0.01). C. valida grew the longest at a salinity of 34‰ and a pH of 8.0. At 34‰ salinity, C. valida grew to 26.44 ± 5.89 cm in 16 days. At a pH of 8.0, C. valida grew to 67.96 ± 4.45 cm in 32 days. F v/F m was 0.635 ± 0.002 at a salinity of 32‰, and 0.550 ± 0.006 to 0.660± 0.001 at pH 7.0 to 8.5. Based on these results, we conclude that C. valida can bloom in sea cucumber ponds due to the high salinity and pH of coastal sea waters, which promote growth and maintain the photosynthetic activity of C. valida.

Functional characterization of two ABC transporters in Sinonovacula constricta gills and their barrier action in response to pathogen infection.

P-glycoprotein (P-gp or ABCB1) and multidrug resistance associated proteins (MRPs or ABCC) belonging to the family of ATP-binding cassette (ABC) transporters protect aquatic organisms from various toxicants and pathogen exposure. The function of ABC transporters of Sinonovacula constricta in response to pathogens was explored by cloning the complete cDNA of ABCB1 and ABCC5 of S. constricta through the rapid amplification of cDNA ends. Tissue-specific expression showed that ABCB1 and ABCC5 have the highest expression in hemocytes and gills among eight examined tissues, respectively. The transport activities of ABCB1 and ABCC5 in the gills were severely inhibited after their corresponding inhibitor treatments. The expression levels and transport activities of ABCB1 and ABCB5 were also investigated by using S. constricta samples infected by Vibrio parahaemolyticus at a final concentration of 107 CFU/mL. Results showed that the mRNA expression levels of ABCB1 and ABCC5 were significantly down-regulated when exposed to V. parahaemolyticus at 6 h and 12 h (P < 0.05) and then recovered to normal level at 24 h and 48 h. Consistently, the activities of the two ABC transporters display the same trends as the mRNA expression levels. The results, combined with that of previous investigations, indicated that these activities may be an innate immune response in S. constricta. Immunohistochemical results justified the tissue localization of P-gp in the interface between external environment and tissues. Taken together, our findings demonstrated that ABC transporters form an active, physiological barrier at the tissue-environment interface in S. constricta gills in response to pathogen infection, and they might play a vital role in adaptation and response to environmental stress and the immune defense.

ß-Integrin mediates LPS-induced coelomocyte apoptosis in sea cucumber Apostichopus japonicus via the integrin/FAK/caspase-3 signaling pathway.

Lipopolysaccharides (LPS) can induce the apoptosis of coelomocytes in Apostichopus japonicus (A. japonicus), and ß-integrin serves as an apoptotic inhibitor during this process. However, the underlying mechanism in invertebrates is largely unknown. Integrin/focal adhesion kinase (FAK) signaling pathway modulates the apoptosis in vertebrates. In this study, a novel FAK was identified from A. japonicus (designated as AjFAK) by ß-integrin (designated as AjITGB) -mediated GST-pull down assay. This interaction was further validated in the LPS-exposed coelomocytes through co-immunoprecipitation and immunofluorescence analyses. To investigate the functional role of AjFAK in AjITGB-mediated coelomocyte apoptosis, we cloned the full-length cDNA of AjFAK and characterized its relationship with AjITGB through real-time PCR. The mRNA expression levels of AjFAK exhibited consistent expression patterns with those of AjITGB in our previous work with 0.48- and 0.22-fold decreases at 12 and 96 h in LPS-exposed coelomocytes and in Vibrio splendidus challenged sea cucumber, respectively. Moreover, the expression level of AjFAK decreased to 0.35-fold in AjITGB knockdown treatment by specific small interference RNA (siRNA). We further performed an assay for the apoptotic rate of coelomocytes in AjITGB, AjFAK, and AjITGB/AjFAK silencing conditions and found that their apoptotic percentages increased to 26%, 25%, and 30%, respectively, compared with those of the control. Finally, the expression levels of four caspases from A. japonicus were also investigated to determine the apoptotic effector. After AjITGB or AjFAK was silenced, the mRNA levels of caspase-3 were 6.6-fold and 2.5-fold higher than those of the control, respectively. In addition, the enzymatic activity of caspase-3 was enhanced to 1.82- and 1.79-fold that of the control in the two groups. However, no significant changes were detected in caspase-2/6/8. All our results supported that ß-integrin mediated the LPS-induced coelomocyte apoptosis in sea cucumber via the integrin/FAK/caspase-3 signaling pathway.

Identification and characterization of a novel PRR of fibrinogen-related protein in Apostichopus japonicus.

Fibrinogen-related proteins (FREPs) play important roles in innate immunity by recognizing pathogen associated molecular patterns on pathogenic bacteria surfaces via conserved fibrinogen-like domain (FBG). In this paper, the full-length cDNA of Apostichopus japonicus FREP (designated as AjFREP) was cloned combined with rapid amplification of cDNA ends (RACE) and transcriptome sequencing. The full-length cDNA of AjFREP was of 2110 bp with an open reading frame (ORF) of 1659 bp. SMART analysis revealed that the AjFREP contained a typical signal peptide of 19 amino acid residues, a FBG and two unusual epidermal growth factor-like domains (EGFs). Multiple sequence alignments suggested that FBG domain shared a remarkably high structural conservation in polypeptide binding site and Ca2+ binding site. Tissue distribution analysis revealed that AjFREP was constitutively expressed in all examined tissues with the largest magnitude in coelomocytes, indicating AjFREP might play an important role in immune defense. The mRNA level of AjFREP in coelomocytes was sharply up-regulated by Vibrio splendidus challenge, and reached its peak expression at 48 h. Knock-down AjFREP by specific siRNA could significantly repress the coelomocyte phagocytosis rate. Meantime, the survival number of V. splendidus in the coelomic fluid was promoted. All these current results indicated that AjFREP might be involved in pathogen clearance through mediating coelomocytes phagocytosis activity.

Divergent immune roles of two fucolectin isoforms in Apostichopus japonicus.

The F-type lectin (fucolectin) family represents a new group with innate immunity. In this study, two fucolectin isoforms (designated as AjFTL-1 and AjFTL-2) were identified in sea cucumber (Apostichopus japonicus) through rapid amplification of cDNA ends. Full-length cDNAs of AjFTL-1 and AjFTL-2 measured 2134 and 1286 bp, encoding two secreted proteins comprising 317 and 181 amino acid residues, respectively. The signal peptide, l-fucose binding motif ("HX(26)RXDX(4)R/K") and cation binding sequence motif ("h2DGx") were conserved in AjFTL-1 and AjFTL-2. However, AjFTL-1 contains an additional complement control protein domain. Multiple sequence alignments supported that AjFTL-1 and AjFTL-2 are new members of the F-type lectin family. Tissues distribution analysis indicated that both AjFTL-1 and AjFTL-2 were widely expressed in all tested tissues, featuring differential expression patterns. Vibrio splendidus infection in vivo can significantly upregulate the mRNA transcripts of the two genes, with a larger magnitude observed in AjFTL-1. By contrast, lipopolysaccharide stimulation in vitro can markedly induce the expression level of AjFTL-2 but not that of AjFTL-1. Silencing AjFTL-2 by siRNA can suppress the AjNOS transcript, whereas injection of the recombinant protein of AjFTL-2 can significantly induce AjNOS expression. By contrast, the loss- and gain-of-function of AjFTL-1 caused no effect on the expression of AjNOS. Our present study provides evidence supporting that AjFTL-1 and AjFTL-2 play diverse roles in the innate immune defense of sea cucumbers toward bacterial infection.

Cloning, expression analysis and functional characterization of an interleukin-1 receptor-associated kinase 4 from Apostichopus japonicus.

Interleukin 1 receptor-associated kinase 4 (IRAK4) is a key factor in TLR-mediated host immune function. In this study, an IRAK4 homologue molecule was identified from Apostichopus japonicus (designated as AjIRAK4) by RACE approach. The full-length cDNA of AjIRAK4 was of 2024 bp containing an open reading frame of 1311 bp encoding a 436-amino-acid (aa) residue polyprotein with the typical death domain (10-113aa) and the kinase domain (160-426aa). The mRNA transcripts of AjIRAK4 displayed constitutively expressed in all examined tissues with highest expression in the muscles (7.20-fold increase compared to the coelomocytes). The pathogen Vibrio splendidus challenge and LPS exposure could both significantly up-regulate the mRNA expression of AjIRAK4. Silencing AjIRAK4 in vitro and in vivo could inhibit the expression of TLR members at mRNA and protein levels, suggesting AjIRAK4 was an important component of TLR cascade in sea cucumber. More importantly, knockdown of AjIRAK4 by specific siRNA resulted in the significant promotion of coelomocyte apoptosis by 1.82-fold increase in vitro and 1.95-fold in vivo. Taken together, all our results suggested that AjIRAK4 might be served as coelomocyte apoptosis regulator via TLR cascade.

Analysis of gut microbiota revealed Lactococcus garviaeae could be an indicative of skin ulceration syndrome in farmed sea cucumber Apostichopus japonicus.

Accumulative evidence has supported the pivotal roles of gut microbiota in shaping host health in a wide range of animals. However, the relationship between gut microbiota and sea cucumber disease is poorly understood. Using the Illumina sequencing of bacterial 16 S rRNA gene, we investigated the divergence of gut bacterial communities between healthy and skin ulceration syndrome (SUS) diseased Apostichopus japonicus. The results showed that bacterial phylotypes in both groups were closely related at phylum level with predominant component of Proteobacteria (>90%). However, Firmicutes and Verrucomicrobia displayed opposite trends in two groups with higher abundance of Firmicutes and lower of Verrucomicrobia in diseased group. Further KEGG enrichment revealed that bacterial-mediated infectious diseases and signal transduction pathways were significantly induced in the SUS group. We also identified one OTU of Lactococcus garvieae from Firmicutes exhibited significantly different abundances in diseased sea cucumber as compared to healthy subjects. The relative abundance of the species was 27.67% ±â€¯10.52% in diseased group compared to 2.78% ±â€¯2.59% in healthy sea cucumber. Three virulence genes of hlyⅢ, fbp and pva encoded by L. garvieae were investigated by qPCR, and were found to be significantly induced (P < 0.05) in diseased sea cucumbers as compared to healthy ones. All our results supported that L. garvieae might be a potential pathogen for SUS outbreak and could be served as a bio-indicator for this disease monitoring.

[Analysis of eleven mineral elements for eight benthic marine diatoms using AAS].

Eleven mineral-elements, Mg, Fe, K, Ca, Mn, Zn, Cu, Ni, Pb, Cr and Cd, for eight benthic marine diatoms were determined by using flame atomic absorption spectrophotometry (AAS). This method is rapid with high precision and accuracy. The relative standard deviation, correlative coefficient and recovery rate are less then 6.85%, 0.9989-0.9999 and 95%-103%, respectively. The results show that there are high mineral-element levels in the eight benthic diatoms, with Mg>Fe>K>Ca> Mn>Zn among them, while the contents of Ni and Cu are poor, and there are little Pb, Cr and Cd in benthic diatoms. The contents of Mg, K and Mn in Navicula seminulum Grun are maximum elements, with (17.2240 +/- 0.0302) mg x g(-1) SD and (1.7885 +/- 0.0939) mg x g(-1) SD, (0.2253 +/- 0.0011) mg x g(-1) SD respectively. There were the most contents of Fe (4.2314 +/- 0.0309) mg x g(-1) SD and Zn (0.1167 +/- 0.0029) mg x g(-1) SD, Cu (0.0227 +/- 0.0007) mg x g(-1) SD and Ni (0.0147 +/- 0.0005) mg x g(-1) SD in Hantzschia amphioxys (Ehr.) Grun. var. leptocephala Ostrup. The element of maximum content in Nitzschia sp. was Ca (6.3537 +/- 0.0412 mg x g(-1) SD). The experimental results indicate that the eight benthic diatom species could prove useful feed species for benthic animal species grown in aquaculture such as abalone, sea urchin and sea cucumber.