Relationships between Arctic and Antarctic Shewanella strains evaluated by a polyphasic taxonomic approach

As a result of the recent application of DNA-based technologies to investigate bacterial diversity in the polar marine environment, bacterial strains sharing significant 16S rRNA gene sequence similarities were isolated from both the Arctic and the Antarctic sea waters. Three selected marine bacterial isolates (BSw20248, BSw20661 and BSw10166) from two Arctic regions (the Greenland Sea and Canada Basin) and from Antarctica (Prydz Bay) were studied to determine their evolutionary relationships and phylogenetic position using a polyphasic taxonomic approach, including phenotypic characterization and genotypic analyses. These bacterial isolates proved to belong to the same species and were identified as Shewanella frigidimarina. Differences in phenotypic properties observed among them revealed a diversity of ecotypes for adaptation to the changing ecological or geographical conditions. It provided the evidence that Shewanella frigidimarina has a bipolar, or even global, distribution in the marine environment.     

Beneficial effects of <Emphasis Type="Italic">Bacillus licheniformis</Emphasis> on the intestinal microflora and immunity of the white shrimp, <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>

When Bacillus licheniformis was administered to the white shrimp, Litopenaeus vannamei, although the total bacterial counts in the intestinal tract of the shrimp remained constant, Vibrio numbers significantly decreased (P < 0.05). Haemocyte counts together with phenoloxidase and superoxide dismutase activities of the shrimp were significantly higher (P < 0.05) in treatments than in the control. Thus, administration of B. licheniformis can improve the white shrimp's intestinal microflora and its immune ability.     

不同pH和盐度下海洋细菌对赤潮藻生长和产毒的影响

研究了在可控生态条件下。一株分离自厦门西海域沉积物的海洋细菌S10在不同pH和盐度条件下对赤潮原因种塔玛亚历山大藻(Alexandrium tamarense)生长和产毒的影响．结果表明。实验用藻株适宜生长pH为6～8,适宜盐度为20～34;该藻株在不同pH及不同盐度条件下,藻细胞毒力差异显著,且随着pH升高而下降。随着盐度增加而加大,到盐度为30时达到最高值。然后逐渐下降;菌株Sl0(1．02×10^l0cells·ml^-1)在pH7～9和盐度15～34下均能有效抑藻生长和产毒。且在pH7、盐度34时其抑藻生长作用最强;在pH7时抑藻产毒效果较好,且其抑藻产毒作用强度不随盐度变化而异．     

Study on the ecological safety of algacides: a comprehensive strategy for their screening

The ecological safety of 14 algacidal materials were appraised using algal growth inhibition tests as well as toxicity test for zooplankton and fish and prawn juveniles. In addition, an integrative analysis for evaluating their potential as algacides was made by comparing the 24-h LC₅₀ and ratio of efficiency to safety (RES) of each material. The results showed that the growth of algae tested were not affected after 96 h of exposure to diallyl trisulfide even when the concentration was 10 mg L⁻¹; there was a similar toxicity between garlic solution and diallyl trisulfide on seven species of aquatic organisms tested. Moreover, both prawn juveniles had lower resistances to garlic solution and diallyl trisulfide than the other 12 materials. According to the RES, green tea, garlic solution, diallyl trisulfide, and the Chinese medical herbs Cortex Fraxini, Herba Houttuyniae, Semen Arecae, and Rhizoma Coptidis are better algacides than the other materials tested in this study.     

Molecular and stable isotopic evidence for the occurrence of nitrite-dependent anaerobic methane-oxidizing bacteria in the mangrove sediment of Zhangjiang Estuary,China

Applied Microbiology and Biotechnology - Nitrite-dependent anaerobic methane oxidation (n-damo), which is mediated by “Candidatus Methylomirabilis oxyfera-like” bacteria, is unique in...