Contribution of trimethylamine N-oxide on the growth and pressure tolerance of deep-sea bacteria

Trimethylamine N-oxide(TMAO) is widely dispersed in marine environments and plays an important role in the biogeochemical cycle of nitrogen. Diverse marine bacteria utilize TMAO as carbon and nitrogen sources or as electron acceptor in anaerobic respiration. Alteration of respiratory component according to the pressure is a common trait of deep-sea bacteria. Deep-sea bacteria from dif ferent genera harbor high hydrostatic pressure(HHP) inducible TMAO reductases that are assumed to be constitutively expressed in the deep-sea piezosphere and facilitating quick reaction to TMAO released from ?sh which is a potential nutrient for bacterial growth. However, whether deep-sea bacteria universally employ this strategy remains unknown. In this study, 237 bacterial strains affliated to 23 genera of Proteobacteria,Bacteroidetes, Firmicutes and Actinobacteria were isolated from seawater, sediment or amphipods collected at dif ferent depths. The pressure tolerance and the utilization of TMAO were examined in 74 strains. The results demonstrated no apparent correlation between the depth where the bacteria inhabit and their pressure tolerance, regarding to our samples. Several deep-sea strains from the genera of Alteromonas, Halomonas,Marinobacter, Photobacterium, and Vibrio showed capacity of TMAO utilization, but none of the isolated Acinebacter, Bacillus, Brevundimonas, Muricauda, Novosphingobium, Rheinheimera, Sphingobium and Stenotrophomonas did, indicating the utilization of TMAO is a species-speci?c feature. Furthermore, we noticed that the ability of TMAO utilization varied among strains of the same species. TMAO has greater impact on the growth of deep-sea isolates of Vibrio neocaledonicus than shallow-water isolates. Taken together, the results describe for the ?rst time the TMAO utilization in deep-sea bacterial strains, and expand our understanding of the physiological characteristic of marine bacteria.     

2008年贵州罕见低温雨雪冰冻灾害成因及影响分析

2008年1月下半月到2月上半月,贵州所遭遇的历史罕见的低温雨雪冰冻灾害,具有降温幅度大、持续时间长、影响范围广、冰冻灾害重等特点.文中分析了这次灾害的可能成因及其影响.分析表明,2007年8月发生的拉尼娜事件所造成的大气环流异常是导致贵州大范围持续低温雨雪冰冻灾害的重要原因.乌拉尔山地区环流场偏高,中亚至蒙古国西部直到俄罗斯远东地区偏低的环流异常持续时间长,有利于冷空气自西北向东南活动:西太平洋副热带高压异常偏西偏北及青藏高原南缘的南支槽异常稳定活跃,有利于暖湿气流不断向云贵高原输送,为贵州雨(雪)天气提供更充足的水汽来源.分析还表明,逆温层的长时间维持是贵州大范围冻雨持续出现的主要原因.这场低温冰冻灾害给贵州春运、能源电力、农业、林业、居民生活等造成了极大的影响.     

Contribution of trimethylamine N-oxide on the growth and pressure tolerance of deep-sea bacteria

Trimethylamine N-oxide (TMAO) is widely dispersed in marine environments and plays an important role in the biogeochemical cycle of nitrogen. Diverse marine bacteria utilize TMAO as carbon and nitrogen sources or as electron acceptor in anaerobic respiration. Alteration of respiratory component according to the pressure is a common trait of deep-sea bacteria. Deep-sea bacteria from different genera harbor high hydrostatic pressure (HHP) inducible TMAO reductases that are assumed to be constitutively expressed in the deep-sea piezosphere and facilitating quick reaction to TMAO released from fish which is a potential nutrient for bacterial growth. However, whether deep-sea bacteria universally employ this strategy remains unknown. In this study, 237 bacterial strains affiliated to 23 genera of Proteobacteria, Bacteroidetes, Firmicutes and Actinobacteria were isolated from seawater, sediment or amphipods collected at different depths. The pressure tolerance and the utilization of TMAO were examined in 74 strains. The results demonstrated no apparent correlation between the depth where the bacteria inhabit and their pressure tolerance, regarding to our samples. Several deep-sea strains from the genera of Alteromonas, Halomonas, Marinobacter, Photobacterium, and Vibrio showed capacity of TMAO utilization, but none of the isolated Acinebacter, Bacillus, Brevundimonas, Muricauda, Novosphingobium, Rheinheimera, Sphingobium and Stenotrophomonas did, indicating the utilization of TMAO is a species-specific feature. Furthermore, we noticed that the ability of TMAO utilization varied among strains of the same species. TMAO has greater impact on the growth of deep-sea isolates of Vibrio neocaledonicus than shallow-water isolates. Taken together, the results describe for the first time the TMAO utilization in deep-sea bacterial strains, and expand our understanding of the physiological characteristic of marine bacteria.