[Stable isotopes of zooplankton and their applications in the research of aquatic ecosystems]. / æµ®æ¸¸åŠ¨ç‰©ç¨³å®šç¢³ã€æ°®åŒä½ç´ ç‰¹å¾åŠå ¶åœ¨æ°´ç”Ÿæ€ç³»ç»Ÿç ”ç©¶ä¸­çš„åº”ç”¨.

Zooplankton plays a mediating role in the food web of aquatic ecosystems, the stable carbon and nitrogen isotopes (δ13C and δ15N) of which have been widely used to study the utilization of food resources, material cycling pathways, and trophic relationships. The δ13C and δ15N values of zooplankton have been used to predict primary productivity, sources and sinks of pollutants and environmental changes. To better use δ13C and δ15N of zooplankton as ecological and environmental indicators, it is particularly important to understand their temporal and spatial variations and the influencing factors. Based on related literature, we synthesized spatial and temporal variations in δ13C and δ15N of zooplankton in different aquatic ecosystems and taxa groups, and the use of δ13C and δ15N indicators for ecological processes and environmental changes. The δ13C and δ15N of zooplankton are largely affected by its food sources, and its stable isotope compositions are in turn affected by primary productivity and nitrogen sources. We proposed that the combination of δ13C and δ15N in zooplankton with transportation and transformation of emerging pollutants would form a multi-means, multi-disciplinary and multi-scale research direction in the fields of earth science and biology.

Degradation of recalcitrant aliphatic and aromatic hydrocarbons by a dioxin-degrader Rhodococcus sp. strain p52.

This study investigates the ability of Rhodococcus sp. strain p52, a dioxin degrader, to biodegrade petroleum hydrocarbons. Strain p52 can use linear alkanes (tetradecane, tetracosane, and dotriacontane), branched alkane (pristane), and aromatic hydrocarbons (naphthalene and phenanthrene) as sole carbon and energy sources. Specifically, the strain removes 85.7 % of tetradecane within 48 h at a degradation rate of 3.8 mg h(-1) g(-1) dry cells, and 79.4 % of tetracosane, 66.4 % of dotriacontane, and 63.9 % of pristane within 9-11 days at degradation rates of 20.5, 14.7, and 20.3 mg day(-1) g(-1) dry cells, respectively. Moreover, strain p52 consumes 100 % naphthalene and 55.3 % phenanthrene within 9-11 days at respective degradation rates of 16 and 12.9 mg day(-1) g(-1) dry cells. Metabolites of the petroleum hydrocarbons by strain p52 were analyzed. Genes encoding alkane-hydroxylating enzymes, including cytochrome P450 (CYP450) enzyme (CYP185) and two alkane-1-monooxygenases, were amplified by polymerase chain reaction. The transcriptional activities of these genes in the presence of petroleum hydrocarbons were detected by reverse transcription-polymerase chain reaction. The results revealed potential of strain p52 to degrade petroleum hydrocarbons.

Inhibition of Microcystis aeruginosa by the extracellular substances from an Aeromonas sp.

Growth of Microcystis aeruginosa could be inhibited significantly within 24 h by the extracellular substances prepared from Aeromonas sp. strain FM. During the treatment, the concentration of extracellular soluble carbohydrates increased significantly in algal culture. Morphological and ultrastructural changes in M. aeruginosa cells, including breakage of the cell surface, secretion of mucilage, and intracellular disorganization of thylakoids, were observed. HPLC-MS analysis showed that the extracellular substances of Aeromonas sp. strain FM were a mixture of free amino acids, tripeptides, and clavulanate. Among these, the algae-lysis effects of lysine and clavulanate were confirmed.

Bacterial community of iron tubercles from a drinking water distribution system and its occurrence in stagnant tap water.

Bacteria in drinking water distribution systems can cause deterioration of the water quality, and the microbial quality of tap water is closely related to consumer health. In the present study, the potential effects of bacteria attached to cast iron pipes on tap water in a distribution system were investigated. Comparison of the bacterial community composition of pipe tubercles with that of stagnant tap water samples based on a denaturing gradient gel electrophoresis analysis of the 16S rRNA gene revealed that the communities were related. Specifically, the main bacterial members were identical to each other. The bacterial community was found to be dominated by Firmicutes, Actinobacteria, and Proteobacteria, which included Rhizobium, Pseudomonas, Lactococcus, Brevundimonas, Rheinheimera, Arthrobacter, Bacillus, and Herbaspirillum. Heterotrophic bacteria proliferation was observed during the period of stagnation, followed by a decrease of assimilable organic carbon and a slight increase of microbially available phosphorus. These findings indicated that the regrowth of bacteria might be boosted by the release of nutrients such as phosphorus from the pipe walls, as well as the decline of residual chlorine during stagnation. Inorganic contaminants at low levels, including Al, Mn, Zn, Pb, Cr, Cu, and Ni, were detected in tubercles and were concentrated in particulates from tap water following the release of iron during stagnation.

Algicidal activity of a dibenzofuran-degrader Rhodococcus sp.

Rhodococcus sp. strain p52, a previously isolated dibenzofuran degrader, could effectively inhibit the growth of cyanobacteria, including species of Microcystis, Anabaena, and Nodularia. When strain p52 was inoculated at the concentration of 7.7×10(7) CFU/ml, 93.5% of exponentially growing Microcystis aeruginosa (7.3×10(6) cells/ml initially) was inhibited after 4 day. The threshold concentration for its algicidal activity against M. aeruginosa was 7.7×10(6) CFU/ml. Strain p52 exerted algicidal effect by synthesizing extracellular substances, which were identified as trans-3-indoleacrylic acid, DL-pipecolic acid, and L-pyroglutamic acid. The effective concentrations of trans-3-indoleacrylic acid and DL-pipecolic acid against M. aeruginosa were tested to be 0.5 mg/l and 5 mg/l, respectively.