The impacts of thermal heterogeneity across microhabitats on post-settlement selection of intertidal mussels.

Rapid genetic selection is critical for allowing natural populations to adapt to different thermal environments such as those that occur across intertidal microhabitats with high degrees of thermal heterogeneity. To address the question of how thermal regimes influence selection and adaptation in the intertidal black mussel Mytilisepta virgata, we continuously recorded environmental temperatures in both tidal pools and emergent rock microhabitats and then assessed genetic differentiation, gene expression patterns, RNA editing level, and cardiac performance. Our results showed that the subpopulations in the tidal pool and on emergent rocks had different genetic structures and exhibited different physiological and molecular responses to high-temperature stress. These results indicate that environmental heterogeneity across microhabitats is important for driving genetic differentiation and shed light on the importance of post-settlement selection for adaptively modifying the genetic composition and thermal responses of these intertidal mussels.

Exploring the adaptability of the secondary structure of mRNA to temperature in intertidal snails based on SHAPE experiments.

RNA-based thermal regulation is an important strategy for organisms to cope with temperature changes. Inhabiting the intertidal rocky shore, a key interface of the ocean, atmosphere and terrestrial environments, intertidal species have developed variable thermal adaptation mechanisms; however, adaptions at the RNA level remain largely uninvestigated. To examine the relationship between mRNA structural stability and species distribution, in the present study, the secondary structure of cytosolic malate dehydrogenase (cMDH) mRNA of Echinolittorina malaccana, Echinolittorina radiata and Littorina brevicula was determined using selective 2'-hydroxyl acylation analyzed by primer extension (SHAPE), and the change in folding free energy of formation (ΔGfold) was calculated. The results showed that ΔGfold increased as the temperature increased. The difference in ΔGfold (ΔΔGfold) between two specific temperatures (25 versus 0°C, 37 versus 0°C and 57 versus 0°C) differed among the three species, and the ΔΔGfold value of E. malaccana was significantly lower than those of E. radiata and L. brevicula. The number of stems of cMDH mRNA of the snails decreased with increasing temperature, and the breakpoint temperature of E. malaccana was the highest among these. The number of loops was also reduced with increasing temperature, while the length of the loop structure increased accordingly. Consequently, these structural changes can potentially affect the translational efficiency of mRNA. These results imply that there were interspecific differences in the thermal stability of RNA secondary structures in intertidal snails, and these differences may be related to snail distribution.

Electricity production enhancement in a constructed wetland-microbial fuel cell system for treating saline wastewater.

The use of constructed wetlands in combination with microbial fuel cells (CW-MFC) to treat saline wastewater may enhance electricity production by increasing the ionic strength, reducing internal resistance and stimulating microbes to accelerate electron transfer. In this study, salinity did not significantly inhibit the removal of TP and COD, but TN and NH4+-N removal efficiencies during saline wastewater treatment (ST) were significantly lower than during non-saline wastewater treatment (NT). However, salinity significantly increased the power density (16.4 mW m-2 in ST and 3.9 mW m-2 in NT, a 4-fold enhancement) by increasing the electron transfer rate and reducing internal resistance (140.29â€¯Ω in ST and 415.21â€¯Ω in NT). The peptides in extracellular polymeric substances (EPS) acted as electron shuttles to promote the migration of electrons and protons in ST. From start-up to stable operation, though the microorganisms in ST were reduced in diversity relative to NT, the proportion of electrochemically active bacteria (EAB), such as Ochrobactrum, significantly increased (p < 0.05) and gradually predominated in the microbial community.

Mesorhizobium acaciae sp. nov., isolated from root nodules of Acacia melanoxylon R. Br.

Three novel strains, RITF741T, RITF1220 and RITF909, isolated from root nodules of Acacia melanoxylon in Guangdong Province of China, have been previously identified as members of the genus Mesorhizobium, displaying the same 16S rRNA gene RFLP pattern. Phylogenetic analysis of 16S rRNA gene sequences indicated that the three strains belong to the genus Mesorhizobium and had highest similarity (100.0 %) to Mesorhizobium plurifarium LMG 11892T. Phylogenetic analyses of housekeeping genes recA, atpD and glnII revealed that these strains represented a distinct evolutionary lineage within the genus Mesorhizobium. Strain RITF741T showed >73 % DNA­DNA relatedness with strains RITF1220 and RITF909, but < 60 % DNA­DNA relatedness with the closest type strains of recognized species of the genus Mesorhizobium. They differed from each other and from their closest phylogenetic neighbours by presence/absence of several fatty acids, or by large differences in the relative amounts of particular fatty acids. While showing distinctive features, they were generally able to utilize a wide range of substrates as sole carbon sources based on API 50CH and API 20NE tests. The three strains were able to form nodules with the original host Acacia melanoxylon and other woody legumes such as Acacia aneura, Albizia falcataria and Leucaena leucocephala. In conclusion, these strains represent a novel species belonging to the genus Mesorhizobium based on the data obtained in the present and previous studies, for which the name Mesorhizobium acaciae sp. nov. is proposed. The type strain is RITF741T ( = CCBAU 101090T = JCM 30534T), the DNA G+C content of which is 64.1 mol% (T m).

Bradyrhizobium ganzhouense sp. nov., an effective symbiotic bacterium isolated from Acacia melanoxylon R. Br. nodules.

Three slow-growing rhizobial strains, designated RITF806(T), RITF807 and RITF211, isolated from root nodules of Acacia melanoxylon grown in Ganzhou city, Jiangxi Province, China, had been previously defined, based on amplified 16S rRNA gene restriction analysis, as a novel group within the genus Bradyrhizobium. To clarify their taxonomic position, these strains were further analysed and compared with reference strains of related bacteria using a polyphasic approach. According to 16S rRNA gene sequence analysis, the isolates formed a group that was closely related to 'Bradyrhizobium rifense' CTAW71, with a similarity value of 99.9%. In phylogenetic analyses of the housekeeping and symbiotic gene sequences, the three strains formed a distinct lineage within the genus Bradyrhizobium, which was consistent with the results of DNA-DNA hybridization. In analyses of cellular fatty acids and phenotypic features, some differences were found between the novel group and related species of the genus Bradyrhizobium, indicating that these three strains constituted a novel group distinct from any recognized species of the genus Bradyrhizobium. Based on the data obtained in this study, we conclude that our strains represent a novel species of the genus Bradyrhizobium, for which the name Bradyrhizobium ganzhouense sp. nov. is proposed, with RITF806(T) ( = CCBAU 101088(T) = JCM 19881(T)) as the type strain. The DNA G+C content of strain RITF806(T) is 64.6 mol% (T(m)).

[Cultivation and characterization of tumor spheres generated from human colorectal cancer cell lines].

OBJECTIVE: To study on the cultivation method for tumor spheres from colorectal cancer cell lines and identify whether resulting Colo205 spheroid cells display cancer stem cell characteristics. METHODS: Lovo, Colo205 and SW480 cells were seeded in serum free medium (SFM) with EGF and bFGF. Flow cytometry analysis, cell invasion assay and xenograft experiment were applied to examine the cell surface marker expression pattern, cell invasive ability and in vivo tumorigenicity of both Colo205 spheres and parental cells. CD44 expression of tumor spheroid cells was also analyzed after cultured with serum supplemented medium by flow cytometry. CD44, Musashi-1 and Oct4 mRNA were detected in these two cells by RT-PCR. RESULTS: Tumor spheres could be generated from three colorectal cancer cell lines in SFM. The formation and proliferation of tumor spheres were benefited from fresh SFM, cell dissociation reagent Accutase and the floating status of cancer cells. The overwhelming majority of spheroid cells were CD44+ cells. But CD44+ cells were gradually decreased when spheres cultured with serum supplemented medium. Colo205 spheres have higher Musashi-1 and Oct4 mRNA expression, tumor-initiating capability and invasive ability compared with those of parental cells. CONCLUSION: Tumor spheres in which enrich cancer stem cells can be generated and matained from colorectal cancer cell lines in SFM on floating-culture condition.

[The effect of Rac1 siRNA on the biological behaviors of gastrointestinal cancer cells].

OBJECTIVE: To explore the effect of Rac1 siRNA on the expression of Rac1 and the biological behaviors of gastrointestinal cancer cells. METHODS: Rac1 siRNA was transfected into human gastric cancer cell line SGC803 and colorectal cancer cell line Lovo by lipofectamine 2000. The expression of Rac1 in these cell lines were detected by Western blot and RT-PCR after 48 hours of the transfection. The effect of Rac1 on the proliferation of human gastric cancer cell line SGC803 and colorectal cancer cell line Lovo were tested by CCK8 kit. The motility of the transfected and the control cancer cells were assessed by Wound-healing assay and invasion assay. The apoptotic index was evaluated by Hoechst 33258 staining and FCM. RESULTS: Rac1 siRNA can down-regulated the expression of Rac1 on human gastric cancer cell line SGC803 and colorectal cancer cell line Lovo remarkably, and Rac1 siRNA can inhibit both the proliferation and motility of the transfectants. Analysis of apoptosis demonstrated that Rac1 siRNA can promote apoptosis of the gastric cancer cells and colorectal cancer cells. CONCLUSION: Rac1 play an important role in the regulation of biological behaviors of human gastric cancer and colorectal cancer cells, and the interference of Rac1 expression could provide a novel path in reversing the malignant phenotypes of these malignancies.