Heterologous Production in the Synechocystis Chassis Suggests the Biosynthetic Pathway of Astaxanthin in Cyanobacteria.

Astaxanthin is a carotenoid species with the highest antioxidant capability. Its natural resource is very rare. The biosynthesis of astaxanthin from ß-carotene includes a hydroxylation step and a ketolation step, for which the corresponding enzymes have been characterized in a few species. However, the sequence of these two reactions is unclear, and may vary with different organisms. In this study, we aimed to elucidate this sequence in Synechocystis, which is an ideal cyanobacterial synthetic biology chassis. We first silenced the endogenous carotene oxygenase gene SyneCrtO to avoid its possible interference in the carotenoid metabolic network. We then introduced the ß-carotene ketolase gene from Haematococcus pluvialis (HpBKT) and the CrtZ-type carotene ß-hydroxylase gene from Pantoea agglomerans (PaCrtZ) to this δCrtO strain. Our pigment analysis demonstrated that both the endogenous CrtR-type carotene hydroxylase SyneCrtR and HpBKT have the preference to use ß-carotene as their substrate for hydroxylation and ketolation reactions to produce zeaxanthin and canthaxanthin, respectively. However, the endogenous SyneCrtR is not able to further catalyze the 3,3'-hydroxylation of canthaxanthin to generate astaxanthin. From our results, a higher accumulation of canthaxanthin and a much lower level of astaxanthin, as confirmed using liquid chromatography-tandem mass spectrometry analysis, were detected in our transgenic BKT+/CrtZ+/δCrtO cells. Therefore, we proposed that the bottleneck for the heterologous production of astaxanthin in Synechocystis might exist at the hydroxylation step, which requires a comprehensive screening or genetic engineering for the corresponding carotene hydroxylase to enable the industrial production of astaxanthin.

Analysis of Potential Risk Factors for Cement Leakage into Paraspinal Veins after Vertebroplasty for Acute Osteoporotic Vertebral Fractures Based on a 3D Reconstruction Technique: A Retrospective Matched Case-Control Study.

OBJECTIVE: Pulmonary embolism, cardiac embolism, and even cerebral embolism due to paraspinal vein leakage (PVL) are increasingly reported, and their risk factors need to be adequately investigated for prevention. To this end, this study investigated the correlation of the distribution and morphological characteristics of fracture lines with the occurrence of PVL after percutaneous vertebroplasty (PVP), which has not been previously reported. METHODS: Patients with acute single-segment thoracolumbar osteoporotic vertebral compression fractures (OVCFs) treated with PVP at our institution from January 2019 to July 2022 were selected for a matched case-control study. The case and control groups included those with and without PVL, respectively, matched at a 1:1 ratio based on general clinical characteristics. Additionally, fracture map and heatmap analysis was performed in both groups. In addition to the general clinical characteristics, the vertebral height ratio, puncture angle, delivery rate, and indexes were assessed via the three-dimensional CT reconstruction fracture line mapping technique, namely, the distribution of fracture lines, fracture line length, main fracture line shape, location of fracture line involvement, and number of fracture line branches, were compared between the two groups. The Wilcoxon rank-sum test, t tests, analysis of variance, and conditional logistic regression were used for statistical analysis. RESULTS: Among 658 patients with OVCFs, 54 who did and 54 who did not develop PVL were included in this study. Significant differences in the puncture angle, fracture line distribution (MR-1, ML-2, MM-2, MR-2, ML-3, MM-3, LL-1, LM-1, LL-2, LM-2), fracture line involvement of the posterior wall, total fracture line length, and main fracture line length were found between the two groups (p < 0.05). Logistic univariate analysis showed significant differences in the puncture angle, fracture line distribution (MR-1, ML-2, MM-2, MR-2, ML-3, MM-3, LL-1, LL-2, LM-2, LL-3), total fracture line length, main fracture line length, and fracture line involvement of the posterior wall between the two groups (p < 0.05). Logistic multifactorial analysis showed that the fracture line distribution (UR-3, ML-3, LM-2, LR-2) and main fracture line length were independent risk factors for the development of PVL in both groups. In addition, the fracture maps and heatmaps showed a greater degree of fracture line encapsulation and more extensive involvement in the middle and lower regions of the vertebral body in the PVL group than in the control group. CONCLUSIONS: Through a three-dimensional computed tomography reconstruction-based fracture line mapping technique, this study revealed for the first time that the distribution of fracture lines (UR-3, ML-3, LM-2, LR-2) and main fracture line length were independent risk factors for PVL after PVP in patients with acute single-segment thoracolumbar OVCFs. In addition, we hypothesized that the fracture line-vein traffic branch that may appear within 2 weeks after injury in acute OVCF patients may be one of the mechanisms influencing the above potential independent risk factors associated with PVL.

Environmentally relevant concentrations of mercury facilitate the horizontal transfer of plasmid-mediated antibiotic resistance genes.

Abundant antibiotic resistance genes (ARGs) are typically found in mercury (Hg)-contaminated aquatic environments. This phenomenon is partly attributed to the co-resistance, cross-resistance, and shared regulatory responses to Hg and antibiotics. However, it remains unclear whether and how Hg influences the conjugative transfer of ARGs mediated by mobilizable plasmids. In the present study, we found that Hg2+ at the environmentally relevant concentrations (0.001-0.5 mg L-1) facilitated the conjugative transfer of ARGs through the mobilizable plasmid RP4 from the donor Escherichia coli HB101 to the recipient E. coli K12. Exposure to Hg2+ significantly increases the formation of reactive oxygen species, malondialdehyde production, antioxidant enzyme activities, and cell membrane permeability, while decreasing the concentration of glutathione. Scanning electron microscopy and transmission electron microscopy showed that the cell membrane suffered from oxidative damage, which is beneficial for conjugative transfer. The expression of global regulatory genes (korA, korB, and trbA) negatively regulating conjugative transfer was restrained by Hg2+, while promoting the expression of positive regulatory genes involved in the mating pair formation system (trbBp and traF) and the DNA transfer and replication systems (trfAp and traJ). Although a high Hg2+ concentration (1.0 mg L-1) suppressed ARGs conjugative transfer, our results suggest that Hg2+ facilitates the dissemination of ARGs in aquatic environments at environmentally relevant concentrations. This study improves our understanding of ARGs dissemination in Hg-contaminated aquatic environments.

Gene expression in the microbial consortia of colonial Microcystis aeruginosa-a potential buoyant particulate biofilm.

Microcystis spp., notorious bloom-forming cyanobacteria, are often present in colony form in eutrophic lakes worldwide. Uncovering the mechanisms underlying Microcystis colony formation and maintenance is vital to controlling the blooms, but it has long been a challenge. Here, bacterial communities and gene expression patterns of colonial and unicellular forms of one non-axenic strain of Microcystis aeruginosa isolated from Lake Taihu were compared. Evidently, different microbial communities between them were observed through 16S rDNA MiSeq sequencing. Metatranscriptome analyses revealed that transcripts for pathways involved in bacterial biofilm formation, such as biosynthesis of peptidoglycan and arginine by Bacteroidetes, methionine biosynthesis, alginate metabolism, flagellum, and motility, as well as widespread colonization islands by Proteobacteria, were highly enriched in the colonial form. Furthermore, transcripts for nitrogen fixation and denitrification pathways by Proteobacteria that usually occur in biofilms were significantly enriched in the colonial Microcystis. Results revealed that microbes associated with Microcystis colonies play important roles through regulation of biofilm-related genes in colony formation and maintenance. Moreover, Microcystis colony represents a potential 'buoyant particulate biofilm', which is a good model for biofilm studies. The biofilm features of colonial Microcystis throw a new light on management and control of the ubiquitous blooms in eutrophic waters.

Case report: Clinical highlights and radiological classification of IgG4-related spinal pachymeningitis: A rare case series and updated review of the literature.

Purpose: Hypertrophic pachymeningitis associated with immunoglobulin G4-related disease (IgG4-RD) has been rarely reported, and there is little information and no clear consensus on the management of IgG4-related spinal pachymeningitis (IgG4-RSP). The present study described its possible clinical features, including the symptoms, imaging, treatment and prognosis of patients with IgG4-RSP. Methods: We report three patients who presented with progressive neurological dysfunction due to spinal cord compression. Relevant articles were searched from the PubMed, Web of Science, and Embase databases, and the resulting literature was reviewed. Results: The literature review provided a summary of 45 available cases, which included three cases from our center. Progressive worsening of neurological impairment was observed in 22 patients (48.9%). The lesions involved the thoracic spine (n=28, 62.2%), cervical spine (n=26, 57.8%), lumbar spine (n=9, 20.0%), and sacral spine (n=1, 2.2%). Furthermore, the lesions were located in the dura mater (n=18, 40.0%), epidural space (n=17, 37.8%), intradural-extramedullary space (n=9, 20.0%), and intramedullary space (n=1, 2.2%). On magnetic resonance imaging (MRI), the lesions generally appeared as striated, fusiform, or less often lobulated oval changes, with homogeneous (n=17,44.7%) and dorsal (n=15,39.5%) patterns being the most common. Thirty-five patients had homogeneous T1 gadolinium enhancement. Early surgical decompression, corticosteroid treatment, and steroid-sparing agents offered significant therapeutic advantages. A good therapeutic response to disease recurrence was observed with the medication. Conclusion: The number of reported cases of IgG4-RSP remains limited, and patients often have progressive worsening of their neurological symptoms. The features of masses identified on the MRI should be considered. The prognosis was better with decompression surgery combined with immunosuppressive therapy. Long-term corticosteroid treatment and steroid-sparing agent maintenance therapy should be ensured. A systemic examination is recommended to identify the presence of other pathologies.

Gapless indica rice genome reveals synergistic contributions of active transposable elements and segmental duplications to rice genome evolution.

The ultimate goal of genome assembly is a high-accuracy gapless genome. Here, we report a new assembly pipeline that is used to produce a gapless genome for the indica rice cultivar Minghui 63. The resulting 397.71-Mb final assembly is composed of 12 contigs with a contig N50 size of 31.93 Mb. Each chromosome is represented by a single contig and the genomic sequences of all chromosomes are gapless. Quality evaluation of this gapless genome assembly showed that gene regions in our assembly have the highest completeness compared with the other 15 reported high-quality rice genomes. Further comparison with the japonica rice genome revealed that the gapless indica genome assembly contains more transposable elements (TEs) and segmental duplications (SDs), the latter of which produce many duplicated genes that can affect agronomic traits through dose effect or sub-/neo-functionalization. The insertion of TEs can also affect the expression of duplicated genes, which may drive the evolution of these genes. Furthermore, we found the expansion of nucleotide-binding site with leucine-rich repeat disease-resistance genes and cis-zeatin-O-glucosyltransferase growth-related genes in SDs in the gapless indica genome assembly, suggesting that SDs contribute to the adaptive evolution of rice disease resistance and developmental processes. Collectively, our findings suggest that active TEs and SDs synergistically contribute to rice genome evolution.

Hydrophobicity and iron coagulation of extracellular polymeric substance from colonial Microcystis.

The bloom-forming cyanobacterium Microcystis occurs mainly as colonial aggregates under the natural conditions. This paper investigated the hydrophobicity and iron coagulation of extracellular polymeric substances (EPSs) from colonial Microcystis in order to understand the impact of EPS on the water treatment process. The higher contents of dissolved EPS (dEPS) and bound EPS (bEPS, mucilaginous matrix around the cells), lower dEPS/bEPS ratio and greater negative zeta potential of bEPS and dEPS were found in colonial Microcystis compared with unicellular Microcystis. XAD resin fractionation analysis indicated that the hydrophobicity could be ranked in an order as follows: bEPS > dEPS > dissolved extracellular organic matter (dEOM) for all the Microcystis strains. Correlation analysis showed that there was a statistically significant correlation between the amounts of carbohydrate and dissolved organic carbon in the hydrophobic fraction of EOM (dEOM, dEPS and bEPS), indicating that the hydrophobicity of Microcystis EOM might be related to carbohydrate. The coagulation experiment showed that for each colonial Microcystis strain, the removal efficiency of bEPS was higher than that of dEPS within the pH range from 3 to 10. The implications of the EPS characteristics were further discussed with respect to water treatment.

Mining and characterization of novel EST-SSR markers of Parrotia subaequalis (Hamamelidaceae) from the first Illumina-based transcriptome datasets.

Parrotia subaequalis is an endangered Tertiary relict tree from eastern China. Despite its important ecological and horticultural value, no transcriptomic data and limited molecular markers are currently available in this species. In this study, we first performed high-throughput transcriptome sequencing of two individuals representing the northernmost (TX) and southernmost (SJD) population of P. subaequalis on the Illumina HiSeq 2500 platform. We gathered a total of 69,135 unigenes for P. subaequalis (TX) and 84,009 unigenes for P. subaequalis (SJD). From two unigenes datasets, 497 candidate polymorphic novel expressed sequence tag-simple sequence repeats (EST-SSRs) were identified using CandiSSR. Among these repeats, di-nucleotide repeats were the most abundant repeat type (62.78%) followed by tri-, tetra- and hexa-nucleotide repeats. We then randomly selected 54 primer pairs for polymorphism validation, of which 27 (50%) were successfully amplified and showed polymorphisms in 96 individuals from six natural populations of P. subaequalis. The average number of alleles per locus and the polymorphism information content values were 3.70 and 0.343; the average observed and expected heterozygosity were 0.378 and 0.394. A relatively high level of genetic diversity (HT = 0.393) and genetic differentiation level (FST = 0.171) were surveyed, indicating P. subaequalis maintained high levels of species diversity in the long-term evolutionary history. Additionally, a high level of cross-transferability (92.59%) was displayed in five congeneric Hamamelidaceae species. Therefore, these new transcriptomic data and novel polymorphic EST-SSR markers will pinpoint genetic resources and facilitate future studies on population genetics and molecular breeding of P. subaequalis and other Hamamelidaceae species.

Effects of long-term 4-nonylphenol dietary exposure on reproductive ability of Japanese quails (Coturnix japonica).

As an endocrine disruptor, 4-nonylphenol (4-NP) is widespread in the environment. Here, we investigated the effect of long-term 4-NP dietary exposure on Japanese quails (Coturnix japonica). A total of 72 quails were evenly divided into 24 cages (12 cages for the reproductive toxicity study and 12 cages for the histopathology study, with one male quail and two female quails in each cage) and fed with various doses of 4-NP in diet. The body weight in quails administered with 4-NP was significantly decreased (P < 0.05) in a time- and dose-dependent manner. The egg fertilization rate significantly decreased (P < 0.05) in all treated groups, which was 91.4%, 86.5%, 85.4%, and 86.2% in the control group, 10 mg·kg-1, 20 mg·kg-1, and 50 mg·kg-1 treatment groups, respectively. Moreover, the hatching rate was also significantly decreased (P < 0.05) in the 50 mg·kg-1 treatment group compared with the control group. Furthermore, the 14-day survival rate of young quails was significantly decreased (P < 0.05) in all treated groups, which was 98.0%, 91.1%, 89.8%, and 86.8% in the control group, 10 mg·kg-1, 20 mg·kg-1, and 50 mg·kg-1 treatment groups, respectively. Damaged spermatogenesis in male quails was found in all treated groups. In conclusion, oral administration of 4-NP impaired the gonads of male quails, leading to reproduction performance damage of Japanese quails.

Environmental factors influencing mucilage accumulation of the endangered Brasenia schreberi in China.

Brasenia schreberi J. F. Gmel. (Cabombaceae), a perennial freshwater macrophyte characterized by a thick mucilage on all underwater organs and especially young buds, has been widely cultivated as an aquatic vegetable in China for many years but is now listed as an endangered species due to anthropogenic impacts and habitat loss. Recent studies have demonstrated that different B. schreberi populations in China have low levels of genetic diversity but significantly different mucilage contents (MucC). Considering the importance of mucilage on both economic and ecological aspects, we examined mucilage-environment relationships in three B. schreberi cultivation sites. The results indicated that water permanganate index (CODMn), total N (TNw), electrical conductivity (ECw), dissolved oxygen (DOw), sediment organic carbon (SOC) and total N (TNs) were significant factors, which explained 82.2% of the variation in mucilage accumulation. The MucC and mucilage thickness (MucT) as well as single bud weight (SBW) of B. schreberi showed negative relationships with CODMn, TNw and ECw but positive relationships with SOC and TNs. Besides, high temperature may have a negative impact on mucilage accumulation of the species. Our study demonstrated that the mucilage accumulation of B. schreberi required good water quality and nutrient-enriched sediments, suggesting that habitat conservation, especially the quality of water, is important for maintaining B. schreberi populations.

Temporal and spatial distribution of Microcystis biomass and genotype in bloom areas of Lake Taihu.

Cyanobacterial blooms as a global environmental issue are of public health concern. In this study, we investigated the spatial (10 sites) and temporal (June, August and October) variations in: 1) their biomass based on chlorophyll-a (chl-a) concentration, 2) their toxic genotype based on gene copy ratio of mcyJ to cpcBA, and 3) their cpcBA genotype composition of Microcystis during cyanobacterial bloom in Lake Taihu. While spatial-temporal variations were found in chl-a and mcyJ/cpcBA ratio, only spatial variation was observed in cpcBA genotype composition. Samples from northwestern part had a higher chl-a, but mcyJ/cpcBA ratio didn't vary among the sites. High chl-a was observed in August, while mcyJ/cpcBA ratio and genotypic richness increased with time. The spatial variations in chl-a and mcyJ/cpcBA ratio and temporal variation in cpcBA genotype were correlated negatively with dissolved N and positively with dissolved P. Spatial distribution of Microcystis biomass was positively correlated with nitrite and P excluding October, but no correlation was found for spatial distribution of mcyJ/cpcBA ratio and cpcBA genotype. Spatial distribution of toxic and cpcBA genotypes may result from horizontal transport of Microcystis colonies, while spatial variation in Microcystis biomass was probably controlled by both nutrient-mediated growth and horizontal transport of Microcystis. The temporal variation in Microcystis biomass, toxic genotype and cpcBA genotype composition were related to nutrient levels, but cause-and-effect relationships require further study.

Effects of 4-nonylphenol in drinking water on the reproductive capacity of Japanese quails (Coturnix japonica).

4-nonylphenol (4-NP), a major degradation product of Nonylphenol ethoxylates (NPEOs), is widespread in environment. In this study, the effects of long-term 4-NP exposure in drinking water on Japanese quails (Coturnix japonica) were investigated. A total of 45 quails were evenly divided into 15 groups and administrated with various doses (0.1 µg L-1, 1.0 µg L-1, 10 µg L-1 and 100 µg L-1, which reflected the environmental concentrations of 4-NP) of 4-NP in drinking water. The results showed that 4-NP in drinking water had no effect on quails' food intake, but significantly decreased the quails' body weights (P < 0.05) in a time- and dose-dependent manner. The egg fertilization rates were also significantly decreased (P < 0.05) in all treatment groups. Moreover, the hatchability was significantly reduced (P < 0.05) in 10 µg L-1 and 100 µg L-1 groups, and the 14 d survival rates of young quails were significantly decreased (P < 0.05) in 1.0 µg L-1, 10 µg L-1 and 100 µg L-1 groups. Damaged spermatogenesis in male quails was observed in all treatment groups. Therefore, administration of 4-NP in drinking water impaired the reproductive ability of Japanese quails, and led to pathological lesions in the male gonads.

Effects of various organic carbon sources on the growth and biochemical composition of Chlorella pyrenoidosa.

The aim of this study was to investigate the effects of various organic carbon sources (glucose, galactose, fructose, sucrose, maltose, lactose and starch) on the growth and biochemical composition of Chlorella pyrenoidosa. Monosaccharides were found to exert stronger stimulative effects on the algal growth than disaccharides and starch. After 10-day culture, addition of 0.5-5.0 g L(-1) glucose and galactose significantly reduced the cellular protein contents by 27.7-63.7% and 22.6-60.5%, respectively, and significantly increased the carbohydrate contents by 103.2-266.5% and 91.9-240.0%, respectively. However, addition of 0.5-5.0 g L(-1) disaccharides and starch did not significantly affect the contents of lipid, protein and carbohydrate. Similar to the normal nitrogen condition, the cellular biochemical composition was not significantly affected by addition of 3.0 g L(-1) disaccharides and starch under the low nitrogen condition. Finally, the significance of this work in the biotechnological application of mixotrophic cultivation of C. pyrenoidosa was further discussed.

Effects of paraquat on photosynthetic pigments, antioxidant enzymes, and gene expression in Chlorella pyrenoidosa under mixotrophic compared with autotrophic conditions.

Only limited information is available on herbicide toxicity to algae under mixotrophic conditions. In the present study, we studied the effects of the herbicide paraquat on growth, photosynthetic pigments, antioxidant enzymes, and gene expression in Chlorella pyrenoidosa under mixotrophic compared with autotrophic conditions. The mean measured exposure concentrations of paraquat under mixotrophic and autotrophic conditions were in the range of 0.3-3.4 and 0.6-3.6 µM, respectively. Exposure to paraquat for 72 h under both autotrophic and mixotrophic conditions induced decreased growth and chlorophyll (Chl) content, increased superoxide dismutase and peroxidase activities, and decreased transcript abundances of three photosynthesis-related genes (light-independent protochlorophyllide reductase subunit, photosystem II protein D1, and ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit [rbcL]). Compared with autotrophic conditions, the inhibition percentage of growth rate under mixotrophic conditions was lower at 0.8 µM paraquat, whereas it was greater at 1.8 and 3.4 µM paraquat. With exposure to 0.8-3.4 µM paraquat, the inhibition rates of Chl a and b content under mixotrophic conditions (43.1-52.4% and 54.6-59.7%, respectively) were greater compared with autotrophic conditions, whereas the inhibition rate of rbcL gene transcription under mixotrophic conditions (35.7-44.0%) was lower. These data showed that similar to autotrophic conditions, paraquat affected the activities of antioxidant enzymes and decreased Chl synthesis and transcription of photosynthesis-related genes in C. pyrenoidosa under mixotrophic conditions, but a differential susceptibility to paraquat toxicity occurred between autotrophically versus mixotrophically grown cells.

Bacterial community structure in cooling water and biofilm in an industrial recirculating cooling water system.

Microbial fouling is a serious problem in open recirculating cooling water systems. The bacterial communities that cause it have not been fully understood. In this study, we analyzed the community structure of free-living bacteria and particle-attached bacteria in cooling water, and bacteria in biofilm collected from the wall of the water reservoir in an industrial recirculating cooling water system by construction of a 16S rRNA gene clone library. Based on amplified ribosomal DNA restriction analysis, clones of all three libraries were clustered into 45 operational taxonomic units (OTUs). Thirteen OTUs displaying 91-96% sequence similarity to a type strain might be novel bacterial species. Noted differences in community structure were observed among the three libraries. The relative species richness of the free-living bacteria in cooling water was much lower than that of particle-attached bacteria and bacteria in biofilm. The majority of the free-living bacterial community (99.0%) was Betaproteobacteria. The predominant bacteria in the particle-attached bacterial community were Alphaproteobacteria (20.5%), Betaproteobacteria (27.8%) and Planctomycetes (42.0%), while those in the biofilm bacterial community were Alphaproteobacteria (47.9%), Betaproteobacteria (11.7%), Acidobacteria (13.1%) and Gemmatimonadetes (11.3%). To control microbial fouling in industrial recirculating cooling water systems, additional physiological and ecological studies of these species will be essential.

Differences in microcystin production and genotype composition among Microcystis colonies of different sizes in Lake Taihu.

The cyanobacterium Microcystis, which occurs as colonies of different sizes under natural conditions, can produce toxic microcystins (MCs). To monitor the toxicity and assess the risk of Microcystis blooms in Lake Taihu, it is important to investigate the relationship between MC production and Microcystis colony size. In this study, we classified Microcystis collected from Zhushan Bay of Lake Taihu during blooms into four classes with size of <50 µm, 50-100 µm, 100-270 µm and >270 µm and studied their differences in MC production and genetic structure. The results showed that colonies with size of <50, 50-100, 100-270 and >270 µm produced 12.2 ± 11.2%, 19.5 ± 7.9%, 61.3 ± 12.6%, and 7.0 ± 9.6% of total MC, respectively. The proportion of cell density of colonies with size of 50-100, 100-270 and >270 µm was positively correlated with MC concentration during blooms, while that of colonies with size of <50 µm was negatively correlated. The MC cell quota tended to be higher during blooms in colonies with larger size except that of colonies with size of 100-270 µm was higher than that of colonies with size of >270 µm from June 11 to September 16. Colonies with size of <50 µm showed the highest proportion of the less toxic MC congener MC-RR, and colonies with size of >100 µm showed higher proportion of the most toxic MC congener MC-LR than colonies with size of <100 µm. Real-time PCR indicated that larger colonies had higher proportion of potential toxic genotype. Principal component analysis of PCR-denaturing gradient gel electrophoresis profile showed that cpcBA and mcyJ genotype compositions were different between colonies with size of <50 µm and colonies with size of >50 µm, and cpcBA genotype composition was also different among colonies with size of 50-100 µm, 100-270 µm and >270 µm. These results indicated that MC cell quota and congener composition were different in Microcystis colonies with different sizes in Lake Taihu during blooms, and the differences in MC production in colonies with different size resulted chiefly from the difference in their genotype composition. Therefore, the authorities of water quality monitoring and drinking water supply service in Lake Taihu should be alert that the toxicity of Microcystis colony with different size was different during blooms, and the high abundance of colonies larger than 50 µm could be an indicator of relatively high bloom toxicity.

Microcystis genotype succession and related environmental factors in Lake Taihu during cyanobacterial blooms.

From spring to autumn, heavy Microcystis blooms always occur in Lake Taihu, although environmental conditions vary markedly. We speculated that Microcystis genotype succession could play an important role in adaptation to environmental changes and long-term maintenance of the high Microcystis biomass. In this study, we investigated Microcystis genotype succession pattern and the related environmental variables in Lake Taihu during cyanobacterial blooms. Denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction -amplified the genus-specific cpcBA and mcyJ gene fragments was used to monitor the variations of Microcystis genotype and potential microcystin (MC)-producing Microcystis genotype compositions during blooms biweekly in three sites (Meiliang Bay, lake center, and Gonghu Bay) and CANOCO 4.5 for Windows were used for the multivariate statistical analysis of their relationships to environmental variables. DGGE patterns indicated that the number of dominant cpcBA genotype per sample increased from spring to autumn. Principal component analysis ordination plots of DGGE profiles showed clear temporal distribution pattern, but not spatial distribution pattern based on both cpcBA and mcyJ genotype compositions. These results indicated there were relatively gradual successions of Microcystis cpcBA and mcyJ genotype compositions in each site, and no distinct spatial difference among the three sites. Redundancy analyses of the gel patterns showed that, in all the three sites, three environmental factors (nitrate, pH, and chemical oxygen demand) were correlated significantly to successions of both cpcBA and mcyJ genotypes except for mcyJ genotype in the lake center. Spearman's correlations indicated that the three environmental variables were also strongly correlated with chl a and MC concentrations. These results suggested that the environmental factors affecting succession of Microcystis community composition might also influence the growth of Microcystis and MC production.

Phylogenetic diversity and specificity of bacteria associated with Microcystis aeruginosa and other cyanobacteria.

Interactions between bacteria and cyanobacteria have been suggested to have a potential to influence harmful algal bloom dynamics; however, little information on these interactions has been reported. In this study, the bacterial communities associated with five strains of Microcystis aeruginosa, three species of other Microcystis spp., and four representative species of non-Microcystis cyanobacteria were compared. Bacterial 16S rDNA fragments were amplified and separated by denaturing gradient gel electrophoresis (DGGE) followed by DNA sequence analysis. The similarities among bacterial communities associated with these cyanobacteria were compared to the digitized DGGE profiles using the cluster analyses. The bacterial community structure of all cyanobacterial cultures differed. Cluster analysis showed that the similarity values among M. aeruginosa cultures were higher than those of other cyanobacterial cultures. Sequence analysis of DGGE fragments indicated the presence of bacteria including, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Bacteroidetes and Actinobacteria in the cyanobacterial cultures. Members of the Sphingomonadales were the prevalent group among the Microcystis-associated bacteria. The results provided further evidence for species-specific associations between cyanobacteria and heterotrophic bacteria, which are useful for understanding interactions between Microcystis and their associated bacteria.

[Effects of gamma linolenic acid on atherosclerosis induced by cholesterol-rich diet in rats].

OBJECTIVE: To study the effect of gamma linolenic acid (GLA) on atherogenesis in rats. METHOD: Sixty healthy male rats were randomly divided into 6 groups: normal contro 1, fed by normal feed; atherogenesis mode 1, fed by high lipid diet; positive control group 0.9 mg x kg(-1) x d(-1) of lovastatin and group IV 250 mg x kg(-1) x d(-1) duoxikang; high dose of 375 mg x kg(-1) x d(-1) GLA; low dose of 187.5 mg x kg(-1) x d(-1) GLA. After the model group received atherogenic diet for six weeks, serum triglyceride (TG), total cholesterol (TC), low density lipoprotein cholesterol (LDL-C) and high density lipoprotein cholesterol (HDL-C) were detected by enzyme method to confirm the formation of atherogenic. After fed for another five weeks, morphologic atherosclerosis of aorta in rats was observed by HE staining methods. The blood samples were collected and serum TC, TG, HDL-C, LDL-C, T-AOC, HL, LPL, NO, NOS, MDA and GSH were determined. RESULT: GLA attenuated the formation of atherosclerotic plaques, inhibited the level of serum TC, TG, MDA, OX-LDL, NO, NOS, HL, LPL and LDL-C and increased the level of T-AOC. CONCLUSION: GLA might significantly attenuate the development of atherosclerosis in rats fed with high lipid diet through improving the antioxidation capacity of the body.

Biosorption of uranium by lake-harvested biomass from a cyanobacterium bloom.

The aim of this work was to study some basic aspects of uranium biosorption by powdered biomass of lake-harvested cyanobacterium water-bloom, which consisted predominantly of Microcystis aeruginosa. The optimum pH for uranium biosorption was between 4.0 and 8.0. The batch sorption reached the equilibrium within 1 h. The isotherm fitted the Freundlich model well. Although the Langmuir model fitted the experiment data well at pH 3.0, 5.0 and 7.0, it did not fit at pH 9.0 and 11.0 at all. This implies that different biosorption mechanisms may be involved at different pH values. 0.1 N HCl was effective in uranium desorption. The results indicated that the naturally abundant biomass of otherwise nuisance cyanobacterium bloom exhibited good potential for application in removal of uranium from aqueous solution.