促进我国环境微生物学的发展—“第十次全国环境微生物学术研讨会”专刊序言

我国是世界上环境污染最为严重的国家之一,环境治理工作日趋重要.随着分子生物学技术的发展,在环境微生物学领域的科研工作者的不懈努力下,我国在环境微生物学方面取得了许多重要成果,使微生物在环境保护中发挥着越来越重要的作用.为了展现国内环境微生物科研工作者取得的最新进展,<微生物学通报>针对"第十次全国环境微生物学术研讨会"组织出版了这期"环境微生物专刊",期望该专刊的出版有助于我国环境微生物学相关领域的交流和发展.     

Variation of physiological and antioxidative responses in tea cultivars subjected to elevated water stress followed by rehydration recovery

Water stress is a major limitation for plant survival and growth. Several physiological and antioxidative mechanisms are involved in the adaptation to water stress by plants. In this experiment, tea cultivars (TV-1, TV-20, TV-29 and TV-30) were subjected to drought stress by withholding water for 20 days followed by rehydration. An experiment was thus performed to test and compare the effect of dehydration and rehydration in growing seedlings of tea cultivars. The effect of drought stress and post stress rehydration was measured by studying the reactive oxygen species (ROS) metabolism in tea. Water stress decreased nonenzymic antioxidants like ascorbate and glutathione contents with differential responses of enzymic antioxidants in selected clones of Camellia sinensis indicating an oxidative stress situation. This was also apparent from increased lipid peroxidation, O₂ ⁻ and H₂O₂ content in water stress imposed plants. But the oxidative damage was not permanent as the plants recovered after rehydration. Comparatively less decrease in antioxidants, higher activities of POX, GR, CAT with higher phenolic contents suggested better drought tolerance of TV-1, which was also visible from the recovery study, where it showed lower ROS level and higher recovery of antioxidant property in response to rehydration, thus proving its better recovery potential. On the other hand, highest H₂O₂ and lipid peroxidation with decrease in phenolic content during stress in TV-29 suggested its sensitivity to drought. The antioxidant efficiency and biochemical tolerance in response to drought stress thus observed in the tested clones of Camellia sinensis can be arranged in the order as TV-30 > TV-1 > TV-29 > TV-20.     

Influence of long-term drought stress on osmolyte accumulation in sugar beet (Beta vulgaris L.) plants

Accumulation of various osmolytes was examined in plants of sugar beet cv. Janus grown under two soil water treatments: control (60% of the field water capacity; FWC) and drought (30–35% FWC). The water shortage started on the 61st day after emergence (DAE), at the stage of the beginning of tap-roots development and was imposed for 35 days. Osmotic potential of sugar beet plant organs, particularly tap-roots, was decreased significantly as a consequence of a long-term drought. Water shortage reduced univalent (K⁺, Na⁺) cations concentrations in the petioles and divalent (Ca²⁺, Mg²⁺) ions level in the mature and old leaves. Cation concentrations in the tap-roots were not affected by water shortage. The ratio of univalent to divalent cations was significantly increased in young leaves and petioles as a consequence of drought. Long-term water deficit caused a significant reduction of inorganic phosphorus (P_i) concentration in young and old leaves. Under the water stress condition, the concentration of proline was increased in all individual plant organs, except proline concentration in the youngest leaves. Drought treatment caused a significant increase of glycine betaine content in shoot without any change in tap-roots. Glucose concentrations were significantly increased only in tap-roots as the effect of drought. In response to water shortage the accumulation of sucrose was observed in all the examined leaves and tap-roots. Overall, a long-term drought activated an effective mechanism for osmotic adjustment both in the shoot and in the root tissues which may be critical to survival rather than to maintain plant growth but sugar beet organs accumulate different solutes as a response to water cessation.     

Investigation of PVA/ws-chitosan hydrogels prepared by combined γ-irradiation and freeze-thawing

γ-Irradiation combined with freeze-thawing, i.e. irradiation followed by freeze-thawing and freeze-thawing followed by irradiation, was applied to prepare poly(vinyl alcohol) (PVA)/water soluble chitosan (ws-chitosan) hydrogels for wound dressing. The properties of these hydrogels were investigated and compared to those prepared by freeze-thawing and by irradiation, respectively. Hydrogels made by irradiation followed by freeze-thawing show larger swelling capacity and mechanical strength, higher thermal stability, lower water evaporation rate, and are less turbid than those made by pure freeze-thawing and freeze-thawing followed by irradiation. Hydrogels made by irradiation alone cannot be used as wound dressing due to their poor mechanical strength. SEM results show that the final structure of hydrogels made by combined irradiation and freeze-thawing is mainly determined by the first processing step. It is found that the appropriate amount of ws-chitosan can endow hydrogels with large swelling capacity and mechanical strength. The presence of ws-chitosan provides the hydrogels with good antibacterial activity against Escherichia coli (E. coli).     

Relationship between road dust and ungulate density in Serengeti National Park,Tanzania

We measured the responses of ungulate grazers to roads by recording the density of dust on grasses and compared distance sampling of ungulates in Serengeti National Park (SNP), Tanzania. Data were collected on the east and west side of the Ngorongoro–Seronera main gravel road to test if road traffic and dust were important factors determining distribution patterns amongst grazers. Results indicate that dust increased progressively with traffic speed and volume during dry season. More dust was intercepted on the west than on the east side of the road mainly because of wind effects. Dust deposition (measured as density g grass g^?1 dust) was higher on short grasses than on long grasses during the dry and late‐dry seasons than during the wet season, when paired perpendicular distances up to 300 m were compared. Mean number of observed grazer species indicated that most fed further from the west side of the road than from the east perhaps to minimize higher density of dust commonly spread on foliage up to 200 m away from the road. Despite that most grazers avoided road side grass shoulders, supporting the ‘dust aversion hypothesis’, the test predictions from the ‘road disturbance’ and the ‘road attraction’ hypotheses did not support the responsive behaviours of grazers toward roads.     

Genotoxic and Histopathological Effects of Water Pollution on Two Fish Species, <Emphasis Type="Italic">Barbus capito pectoralis</Emphasis> and <Emphasis Type="Italic">Chondrostoma nasus</Emphasis> in the Büyük Menderes River,Turkey

The genotoxic and histopathological effects of water pollution were investigated on two fish species caught from the Buyuk Menderes River and from its tributary, the Cine Stream. The Buyuk Menderes basin is an important agricultural area in Turkey. The levels of copper, zinc, cadmium, cobalt, and lead were measured at the surface of the water and in gills, liver, and muscle tissue of Chondrostoma nasus and Barbus capito pectoralis. In some tissues, the concentrations of some of these metals exceeded acceptable levels for human consumption. Zinc was found to be the most abundant metal in water and tissues. Maximal metal accumulation was observed in the liver. To detect the genotoxic potential of contaminants, the formation of micronucleus in erythrocytes was used as indicator of chromosomal damage. The frequency of micronucleus formation did not show significant differences between locations and controls in B. capito pectoralis caught from three locations and C. nasus from two locations. The histological changes included significant decreases of the mean lengths of primary and secondary lamellae. In gills epithelia, we observed cellular proliferation that developed Because of secondary lamellae fusion, ballooning degenerations, or club deformation of secondary lamellae and cystic structures in secondary lamellae. In the liver, the changes included swollen and ruptured parenchymal cells, loss of cord structure, vacuoles filled with cellular debris, focal necrosis, and a significant increase in Kupffer cells.     

Martin Gibbs (1922–2006): Pioneer of 14C research, sugar metabolism & photosynthesis; vigilant Editor-in-Chief of Plant Physiology; sage Educator; and humanistic Mentor

The very personal touch of Professor Martin Gibbs as a worldwide advocate for photosynthesis and plant physiology was lost with his death in July 2006. Widely known for his engaging humorous personality and his humanitarian lifestyle, Martin Gibbs excelled as a strong international science diplomat; like a personal science family patriarch encouraging science and plant scientists around the world. Immediately after World War II he was a pioneer at the Brookhaven National Laboratory in the use of ¹⁴C to elucidate carbon flow in metabolism and particularly carbon pathways in photosynthesis. His leadership on carbon metabolism and photosynthesis extended for four decades of working in collaboration with a host of students and colleagues. In 1962, he was selected as the Editor-in-Chief of Plant Physiology. That appointment initiated 3 decades of strong directional influences by Gibbs on plant research and photosynthesis. Plant Physiology became and remains a premier source of new knowledge about the vital and primary roles of plants in earth’s environmental history and the energetics of our green-blue planet. His leadership and charismatic humanitarian character became the quintessence of excellence worldwide. Martin Gibbs was in every sense the personification of a model mentor not only for scientists but also shown in devotion to family. Here we pay tribute and honor to an exemplary humanistic mentor, Martin Gibbs.     

Effect of potassium citrate salts on the vapor-liquid equilibrium properties of aqueous solutions of alanine at different temperatures

Water activity measurements by isopiestic method have been carried out on the aqueous solutions of alanine + potassium di-hydrogen citrate (KH₂Cit) and alanine + tri-potassium citrate (K₃Cit) over a range of temperatures at atmospheric pressure. From these measurements, values of the vapor pressure of solutions were determined. The effect of temperature and charge on the anion of salts on the vapor–liquid equilibrium of the investigated systems has been studied. The experimental water activities have been correlated successfully with the segment-based local composition Wilson and NRTL models. The agreement between the correlations and the experimental data is good.     

Influence of ambient and enhanced ultraviolet-B radiation on the plant growth and physiological properties in two contrasting populations of Hippophae rhamnoides

Two contrasting sea buckthorn (Hippophae rhamnoides L.) populations from low and high altitude regions were employed to investigate the effects of prevailing and enhanced ultraviolet-B (UV-B) radiation on plant growth and physiological properties under a UV-B-enhanced/exclusion system. The experimental design included three UV-B regimes, including excluded (-UVB), near-ambient (NA) and enhanced UV-B (+UVB) radiation. Compared with the control (-UVB), NA caused the formation of smaller but thicker plant leaves in both sea buckthorn populations, paralleled with significant increments of carotenoids and UV-absorbing compounds as well as improved water economy. NA also induced more biomass partition from shoot to root, but CO(2) assimilation rate (A), photosynthetic area and biomass accumulation were unaffected. The low-altitude population seemed sensitive to +UVB, as indicated by the decreases in total biomass, A and ascorbic acid content (Asa, an antioxidant) compared with NA. However, little +UVB effect occurred on the high-altitude population, and we suggest that the higher tolerance of this population could be associated with its specific morphological and physiological characteristics, such as small but thick leaves and high-level of Asa content, as well as its greater physiological modification in response to NA, e.g., increases in protective compounds (carotenoids and UV-absorbing compounds) and improvement in water economy, in comparison to the low-altitude population, which form an effective adaptation strategy to enhanced UV-B stress.     

Algal communities at Gouqi Island in the Zhoushan archipelago, China

The kelp bed of Gouqi Island lies in the east of the East China Sea, in the Shengsi Archipelago. It is a key component of the island-reef ecosystem. This study evaluated kelp beds on intertidal and subtidal zones from 2004 to 2006. We evaluated seasonal variations in the community structure of macroalgae, and their relationship with water temperature, nitrogen and phytoplankton. The Gouqi Island kelp bed consists mainly of species of Sargassum. Sargassum horneri was the dominant species in subtidal zones, representing 90% of the total biomass. The dominant species in intertidal zones were S. fusiforme, S. horneri, S. thunbergii and Undaria pinnatifida. Fifty-four phytoplankton species were found in the Gouqi Island kelp bed, of which 51 species were found inside the kelp beds, 43 species outside the kelp beds, and 40 species were present both inside and outside the kelp beds. Diatoms were dominant both inside and outside the kelp beds. Except in winter, Skeletonema costatum was dominant, and its abundance in autumn was over 98% of the total abundance. Water temperature was found to be the primary factor influencing the growth of S. horneri in the Gouqi Island kelp bed. S. horneri grew slowly from November to March, and rapidly from March to June. The upper temperature limit for growth of S. horneri was about 18°C. Higher water temperatures can result in a decline in the kelp bed. Nitrogen seemed to be a limiting factor for macroalgal growth. This was particularly true for S. horneri and phytoplankton. Since nitrate is the primary nutrient for S. horneri, its absorption by S. horneri resulted in seasonal changes of nitrate in the ecosystem.