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Aluminum effects on marine phytoplankton: implications for a revised Iron Hypothesis (Iron-Aluminum Hypothesis)
No full textIn contrast to substantial studies and established knowledge of aluminum (Al) effects (mainly toxicity) on freshwater organisms and terrestrial plants, and even on human health, only a few studies of Al effects on marine organisms have been reported, and our understanding of the role of Al in marine biogeochemistry is limited. In this paper, we review the results of both field and laboratory experiments on the effects of Al on marine organisms, including Al toxicity to marine phytoplankton and the beneficial effects of Al on marine phytoplankton growth, and we discuss possible links of Al to the biological pump and the global carbon cycle. We propose a revised Iron (Fe) Hypothesis, i.e., the Fe-Al Hypothesis that introduces the idea that Al as well as Fe play an important role in the glacial-interglacial change in atmospheric CO2 concentrations and climate change. We propose that Al could not only facilitate Fe utilization, dissolved organic phosphorus utilization and nitrogen fixation by marine phytoplankton, enhancing phytoplankton biomass and carbon fixation in the upper oceans, but also reduce the decomposition and decay of biogenic matter. As a result, Al allows potentially more carbon to be exported and sequestered in the ocean depths through the biological pump. We also propose that Al binds to superoxide to form an Al-superoxide complex, which could catalyze the reduction of Fe(III) to Fe(II) and thus facilitate Fe utilization by marine phytoplankton and other microbes. Further ocean fertilization experiments with Fe and Al are suggested, to clarify the role of Al in the stimulation of phytoplankton growth and carbon sequestration in the ocean depths
Functional characterization of salt-tolerant microbial esterase WDEst17 and its use in the generation of optically pure ethyl (R)-3-hydroxybutyrate
No full textThe two enantiomers of ethyl 3-hydroxybutyrate are important intermediates for the synthesis of a great variety of valuable chiral drugs. The preparation of chiral drug intermediates through kinetic resolution reactions catalyzed by esterases/lipases has been demonstrated to be an efficient and environmentally friendly method. We previously functionally characterized microbial esterase PHE21 and used PHE21 as a biocatalyst to generate optically pure ethyl (S)-3-hydroxybutyrate. Herein, we also functionally characterized one novel salt-tolerant microbial esterase WDEst17 from the genome of Dactylosporangium aurantiacum subsp. Hamdenensis NRRL 18085. Esterase WDEst17 was further developed as an efficient biocatalyst to generate (R)-3-hydroxybutyrate, an important chiral drug intermediate, with the enantiomeric excess being 99% and the conversion rate being 65.05%, respectively, after process optimization. Notably, the enantio-selectivity of esterase WDEst17 was opposite than that of esterase PHE21. The identification of esterases WDEst17 and PHE21 through genome mining of microorganisms provides useful biocatalysts for the preparation of valuable chiral drug intermediates
An outbreak of sea cucumbers hinders coral recruitment
No full textAn outbreak of a small sessile sea cucumber, Ocnus sanya, occurred on the degraded Luhuitou coral reef in Sanya Bay, Hainan, China. This study explored the pattern of distribution of O. sanya on the reef and the impacts of the high abundance of O. sanya on post-settlement mortality of Pocillopora damicornis recruits. The density of O. sanya ranged from about 500 to over 2000 individuals m(-2) with 10.95-23.69% cover on hard substrate. Terracotta tiles with O. sanya on the surface accumulated 19.7% more surface sediment than those without sea cucumbers. Post-settlement P. damicornis recruits had significantly higher mortality on terracotta tiles with O. sanya than those without O. sanya after 21 d. Overall, O. sanya appears to increase sediment stress and inhibit coral recruitment, exacerbating the degradation of Luhuitou Reef. This study raises the possibility that such novel outbreak species could contribute significant additional stress on coral reefs at larger scales
Community differentiation of bacterioplankton in the epipelagic layer in the South China Sea
No full textThe South China Sea (SCS) is the largest marginal sea in the western tropical Pacific Ocean and is characterized by complex physicochemical environments. To date, the biogeographic patterns of the microbial communities have rarely been reported at a basin scale in the SCS. In this study, the bacterial assemblages inhabiting the epipelagic zone across 110 degrees E to 119 degrees E along 14 degrees N latitude were uncovered. The vertical stratification of both bacterial taxa and their potential functions were revealed. These results suggest that the water depth-specific environment is a driver of the vertical bacterioplankton distribution. Moreover, the bacterial communities were different between the eastern stations and the western stations, where the environmental conditions were distinct. However, the mesoscale eddy did not show an obvious effect on the bacterial community due to the large distance between the sampling site and the center of the eddy. In addition to the water depth and longitudinal location of the samples, the heterogeneity of the phosphate and salinity concentrations also significantly contributed to the variance in the epipelagic bacterial community in the SCS. To the best of our knowledge, this study is the first to report that the variability in epipelagic bacterioplankton is driven by the physicochemical environment at the basin scale in the SCS. Our results emphasize that the ecological significance of bacterioplankton can be better understood by considering the relationship between the biogeographic distribution of bacteria and the oceanic dynamics processes
Soliseptide A, A Cyclic Hexapeptide Possessing Piperazic Acid Groups from Streptomyces solisilvae HNM30702
No full textSoliseptide A (1), a cyclic hexapeptide possessing piperazic acid groups, together with two known azalomycin derivatives (2 and 3) were isolated from Streptomyces solisilvae HNM30702. Their structures were determined through spectroscopic methods and single crystal X-ray diffraction analysis. Soliseptide A (1) possessed a cyclic hexapeptide core featured with two piperazic acid units rarely discovered in nature, and exhibited weak antibacterial and antiviral activities. Besides, compounds 2 and 3 displayed significant fungicidal effects
Type II toxin/antitoxin system ParE(SO)/CopA(SO) stabilizes prophage CP4So in Shewanella oneidensis
No full textToxin/antitoxin (TA) loci are commonly found in mobile genetic elements such as plasmids and prophages. However, the physiological functions of these TA loci in prophages and cross-regulation among these TA loci remain largely unexplored. Here, we characterized a newly discovered type II TA pair, ParE(SO)/CopA(SO), in the CP4So prophage in Shewanella oneidensis. We demonstrated that ParE(SO)/CopA(SO) plays a critical role in the maintenance of CP4So in host cells after its excision. The toxin ParE(SO) inhibited cell growth, resulting in filamentous growth and eventually cell death. The antitoxin CopA(SO) neutralized the toxicity of ParE(SO) through direct protein-protein interactions and repressed transcription of the TA operon by binding to a DNA motif in the promoter region containing two inverted repeats [5-GTANTAC (N)(3) GTANTAC>-3]. CopA(SO) also repressed transcription of another TA system PemK(SO)/PemI(SO) in megaplasmid pMR-1 of S. oneidensis through binding to a highly similar DNA motif in its promoter region. CopA(SO) homologs are widely spread in Shewanella and other Proteobacteria, either as a component of a TA pair or as orphan antitoxins. Our study thus illustrated the cross-regulation of the TA systems in different mobile genetic elements and expanded our understanding of the physiological function of TA systems
Adsorption of phosphorus by calcium-flour biochar: Isotherm, kinetic and transformation studies
No full textDischarging phosphorus (P)-contaminated water directly into the aquatic environment leads to resource loss and eutrophication. Thus, removing P from waste streams is imperative. In this study, calcium decorated biochar (Ca-BC) in different mass ratios of Ca to BC was designed to effectively adsorb P from solution. Ca-BC was characterized through X-ray diffraction (XRD) analysis, followed by isotherm and kinetic adsorption experiments. The decorated Ca on the BC surface was found to have preferred P adsorption ability. A design of calcium hydroxide (Ca(OH)(2)) to flour in a mass ratio of 2:1 was found to have a maximum adsorption capacity of 314.22 mg g(-1) for P. The Langmuir and pseudo-second-order models fit the sorption process adequately. XRD analysis indicated that the preferable adsorption ability to P was due to the reaction of Ca(OH)(2) and PO34-, forming the hydroxylapatite (Ca-5(PO4)(3)(OH)) crystal. The P in solution was transformed to the crystal. Thus, Ca-BC is an environmental friendly and low-cost sorbent for P removal. (C) 2017 Elsevier Ltd. All rights reserved
Effects of dietary carbohydrate to lipid ratio on growth, feed utilization, body composition and digestive enzyme activities of golden pompano (Trachinotus ovatus)
No full textAn 8-week feeding trial was conducted to investigate the effects of dietary carbohydrate to lipid ratio (CHO: L) on growth, feed utilization, body composition and digestive enzyme activities of golden pompano, Trachinotus ovatus. Five iso-nitrogenous (450g/kg protein) and iso-energetic (19MJ/kg gross energy) diets with varying CHO: L ratios of 0.68, 1.02, 1.62, 2.61 and 4.35, respectively, were fed to triplicate groups of 30 fish (average 13.8 +/- 0.1g). Results showed that dietary CHO: L ratios did not show any significant influence on survival of golden pompano (p>.05) but significantly affected its growth performance and feed utilization (p<.05). Fish fed diets with CHO: L ratios at 1.62 and 2.61 exhibited the highest final body weight, weight gain ratio, specific growth rate, feed efficiency ratio and protein efficiency ratio. Fish body lipid and liver glycogen contents were also significantly influenced by CHO: L ratio (p<.05). Hepatic amylase activity increased firstly and then decreased as the dietary CHO: L ratio increased, while lipases activity decreased with increasing dietary CHO:L level. The regression model analysis showed that the most suitable dietary CHO: L ratio (protein 450g/kg) to reach the highest weight gain ratio is 2.38
Identification and characterization of a locus putatively involved in colanic acid biosynthesis in Vibrio alginolyticus ZJ-51
No full textColanic acid (CA) is a group I extracellular polysaccharide (EPS) that contributes to resistance against adverse environments in many members of the Enterobacteriaceae. In the present study, a genetic locus EPSC putatively involved in CA biosynthesis was identified in Vibrio alginolyticus ZJ-51, which undergoes colony morphology variation between translucent/smooth (ZJ-T) and opaque/rugose (ZJ-O). EPSC in ZJ-T carries 21 ORFs and resembles the CA cluster of Escherichia coli K-12. The deletion of EPSC led to decreased EPS and biofilm formation in both genetic backgrounds but no alternation of lipopolysaccharide. The loss of this locus also changed the colony morphology of ZJ-O on the 2216E plate and reduced the motility of ZJ-T. Compared with ZJ-T, ZJ-O lacks a 10-kb fragment (eps(T)) in EPSC containing homologs of wecA, wzx and wzy that are essential for O-antigen synthesis. However, the deletion or overexpression of eps(T) resulted in no change of colony morphology, biofilm formation or EPS production. This study reported at the first time a genetic locus EPSC that may be involved in colanic acid synthesis in V. alginolyticus ZJ-51, and found that it was related to EPS biosynthesis, biofilm formation, colony morphology and motility, which may shed light on the environmental adaptation of the vibrios
Butyratibacter algicola gen. nov., sp nov., a marine bacterium from the culture broth of Picochlorum sp 122
No full textA Gram-stain-negative, motile, non-spore-forming, ovoid or rod-shaped bacterium, designated strain B15(T), was isolated from the culture broth of a marine microalga, Picochlorum sp. 122. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain B15(T) forms a stable cluster with Lutibaculum baratangense KCTC 22669(T) (95.4% 16S rRNA gene sequence similarity), Tepidamorphus gemmatus CB-27A(T) (94.9 %) and Microbaculum marinum HSF11(T) (94.6 %) in the family Rhodobiaceae. Optimal growth of strain B15(T) was observed at 33 degrees C, pH 8-9 and in the presence of 3% (w/v) NaCl. The only detected ubiquinone of strain B15(T) was Q-10, and the G+C content of the genomic DNA was 66.3 mol%. The major fatty acid profile comprised C-19 : 0 cyclo omega 8c, C-18 : 1 omega 7c/omega 6c and C-17 : 1 iso I/anteiso B. The major polar lipids of strain B15(T) were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, two unidentified aminolipids, and one unidentified lipid. Comprehensive analyses based on polyphasic characterization of strain B15(T) indicated that it represents a novel species of a new genusin the family Rhodobiaceae, for which the name Butyratibacter algicola gen. nov., sp. nov. is proposed. The type strain of the type species is B15(T) (= KCTC 52552(T) = MCCC 1K03221(T))