Reproductive biology of Hemitripterus villosus in the Bohai Strait,China

To understand the reproductive biology of Hemitripterus villosus in the Bohai Strait,and fill the key knowledge gap in verifying reproductive seasonality and documenting gonadotropin dependent reproductive cycle of this species,a year-round detail study was conducted for the first time.In total,263 individuals were randomly sampled off the coasts of the Bohai Strait.Results show that and the overall female-to-male ratio(1.35:1)did not differ significantly from the 1:1 sex ratio.The length and weight relationship for females and males were regressed,depicting an isometric growth for both sexes.Four reproductive phases of the complete gonadotropin dependent reproductive cycle in both sexes were identified.The monthly variations in the gonadosomatic and hepatosomatic indexes for both sexes further indicated that this species spawns a single batch of eggs per year and the peak spawning period is from October to December.The average diameter of eggs ranged from 2.10 to 3.57 mm.The length at first sexual maturity was 224.87 mm for females and 241.26 mm for males.Significant positive relationships between absolute fecundity and fish size,and also gonadal weight were observed.H.villosus from the Bohai Strait exhibited smaller body size,smaller egg diameter,lower gonadosomatic index,lower absolute fecundity,and higher population extinction risk than the other populations’studied previously.Our findings contribute to understanding the status of this isolated westernmost population,and we emphasize that more efficient protection measures for the species and control measures are urgently required to improve the coastal environment in the Bohai Strait.

Transient expression of the enhanced green fluorescent protein(egfp) gene in Sargassum horneri

Sargassum horneri is a macroalga widespread in North Asia-Pacific region, and these years its bloom has caused huge damage to the environment and the economic in China. To make up the blank on genetic engineering research, a transient transformation system for the multicellular marine brown alga S . horneri was established in this research. The algae used in this research were collected from the Yellow Sea of China and verified as a same species S . horneri with analysis of molecular markers. The S . horneri parietal leaves were transformed with the enhanced green fluorescent gene as the reporter by micro-particle bombardment. The results show that green fluorescent protein (GFP) is an eff ective transgene reporter for S . horneri and that particle bombardment is a suitable method for transformation of S . horneri . Through selection of four diff erent promoters for EGFP and six groups’ bombardment characters, the highest transformation efficiency approximately 1.31% was got with the vector pEGFP-N1 at bombardment characters 900 spi and 6 cm distance. This research paves a way for the further research and application of S . horneri .

Extraction of electrons by magnetite and ferrihydrite from hydrogen-producing Clostridium bifermentans by strengthening the acetate production pathway

Conductive mineral nanoparticles, such as magnetite, can promote interspecies electron transfer between syntrophic partners.However, the effect of magnetite has only been inferred in intraspecific electron output. Herein, a hydrogen-producing strain,namely, Clostridium bifermentans, which holds several electron output pathways, was used to study the effect of magnetite on the intraspecific electron output manner. Additionally, insulated amorphous ferrihydrite, which was used as an extracellular electron acceptor, was selected to compare with magnetite. Electrons, which were originally used to generate hydrogen, were shunted with the addition of magnetite and ferrihydrite, which resulted in the reduction of hydrogen production and accumulation of Fe(II). Interestingly, more electrons(39.7% and 53.5%) were extracted by magnetite and ferrihydrite, respectively, which led to less production of butyrate and more acetate. More importantly, the increased electron extraction efficiency suggested that electroactive microorganisms can switch metabolic pathways to adapt to electron budget pressure in intraspecific systems. This work broadens the understanding of the interaction between iron oxides and fermentative hydrogen-producing microbes that hold the capacity of Fe(III) reduction.

Comparative transcriptomic insights into the mechanisms of electron transfer in Geobacter co-cultures with activated carbon and magnetite

Both activated carbon and magnetite have been reported to promote the syntrophic growth of Geobacter metallireducens and Geobacter sulfurreducens co-cultures, the first model to show direct interspecies electron transfer (DIET); however, differential transcriptomics of the promotion on co-cultures with these two conductive materials are unknown. Here, the comparative transcriptomic analysis of G. metallireducens and G. sulfurreducens co-cultures with granular activated carbon (GAC) and magnetite was reported. More than 2.6-fold reduced transcript abundances were determined for the uptake hydrogenase genes of G. sulfurreducens as well as other hydrogenases in those co-cultures to which conductive materials had been added. This is consistent with electron transfer in G. metallireducens-G. sulfurreducens co-cultures as evinced by direct interspecies electron transfer (DIET). Transcript abundance for the structural component of electrically conductive pili (e-pili), PilA, was 2.2-fold higher in G. metallireducens, and, in contrast, was 14.9-fold lower in G. sulfurreducens in co-cultures with GAC than in Geobacters co-cultures without GAC. However, it was 9.3-fold higher in G. sulfurreducens in co-cultures with magnetite than in Geobacters co-cultures. Mutation results showed that GAC can be substituted for the e-pili of both strains but magnetite can only compensate for that of G. sulfurreducens, indicating that the e-pili is a more important electron acceptor for the electron donor strain of G. metallireducens than for G. sulfurreducens. Transcript abundance for G. metallireducens c-type cytochrome gene GMET_RS14535, a homologue to c-type cytochrome gene omcE of G. sulfurreducens was 9.8-fold lower in co-cultures with GAC addition, while that for OmcS of G. sulfurreducens was 25.1-fold higher in co-cultures with magnetite, than in that without magnetite. Gene deletion studies showed that neither GAC nor magnetite can completely substitute the cytochrome (OmcE homologous) of G. metallireducens but compensate for the cytochrome (OmcS) of G. sulfurreducens. Moreover, some genes associated with central metabolism were up-regulated in the presence of both GAC and magnetite; however, tricarboxylic acid cycle gene transcripts in G. sulfurreducens were not highly-expressed in each of these amended co-cultures, suggesting that there was considerable redundancy in the pathways utilised by G. sulfurreducens for electron transfer to reduce fumarate with the amendment of GAC or magnetite. These results support the DIET model of G. metallireducens and G. sulfurreducens and suggest that e-pili and cytochromes of the electron donor strain are more important than that of the electron acceptor strain, indicating that comparative transcriptomics may be a promising route by which to reveal different responses of electron donor and acceptor during DIET in co-cultures.

The differentiation of iron-reducing bacterial community and iron-reduction activity between riverine and marine sediments in the Yellow River estuary

Rivers are the primary contributors of iron and other elements to the global oceans.Iron-reducing bacteria play an important biogeochemical role in coupling the iron and carbon redox cycles.However,the extent of changes in community structures and iron-reduction activities of iron-reducing bacteria in riverine and coastal marine sediments remains unclear.This study presents information on the spatial patterns and relative abundance of iron-reducing bacteria in sediments of the Yellow River estuary and the adjacent Bohai Sea.High-throughput sequencing of bacterial 16S rRNA found that the highest relative abundances and diversities were from the estuary(Yellow River-Bohai Sea mixing zone).Pseudomonas,Thiobacillus,Geobacter,Rhodoferax,and Clostridium were the most abundant putative iron-reducing bacteria genera in the sediments of the Yellow River.Vibrio,Shewanella,and Thiobacillus were the most abundant in the sediments of the Bohai Sea.The putative iron-reducing bacterial community was positively correlated with the concentrations of total nitrogen and ammonium in coastal marine sediments,and was significantly correlated with the concentration of nitrate in river sediments.The riverine sediments,with a more diverse iron-reducing bacterial community,exhibited increased activity of Fe(III)reduction in enrichment cultures.The estuary-wide high abundance of putative iron-reducing bacteria suggests that the effect of river-sea interaction on bacterial distribution patterns is high.The results of this study will help the understanding of the biogeochemical cycling of iron in riverine and coastal marine environments.