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首页> 外文期刊>Applied and Environmental Microbiology >Are Readily Culturable Bacteria in Coastal North Sea Waters Suppressed by Selective Grazing Mortality?
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Are Readily Culturable Bacteria in Coastal North Sea Waters Suppressed by Selective Grazing Mortality?

机译：选择性放牧死亡率能抑制北海沿海地区的现成细菌吗？

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We studied the growth of six culturable bacterial lineages from coastal North Sea picoplankton in environmental samples under different incubation conditions. The grazing pressure of heterotrophic nanoflagellates (HNF) was reduced either by double prefiltration through 0.8-μm-pore-size filters or by 10-fold dilutions with 0.2-μm (pore-size) prefiltered seawater. We hypothesized that those γ-proteobacterial genera that are rapidly enriched would also be most strongly affected by HNF regrowth. In the absence of HNF, the mean protein content per bacterial cell increased in both treatments compared to environmental samples, whereas the opposite trend was found in incubations of unaltered seawater. Significant responses to the experimental manipulations were observed in Alteromonas, Pseudoalteromonas, and Vibrio populations. No treatment-specific effects could be detected for members of the Roseobacter group, the Cytophaga latercula-C. marinoflava lineage, or the NOR5 clade. Statistical analysis confirmed a transient increase in the proportions of Alteromonas, Pseudoalteromonas, and Vibrio cells at reduced HNF densities only, followed by an overproportional decline during the phase of HNF regrowth. Cells from these genera were significantly larger than the community average in the dilution treatments, and changes in their relative abundances were negatively correlated with HNF densities. Our findings suggest that bacteria affiliated with frequently isolated genera such as Alteromonas, Pseudoalteromonas, and Vibrio might be rare in coastal North Sea picoplankton because their rapid growth response to changing environmental conditions is counterbalanced by a higher grazing mortality.
机译：我们研究了在不同孵化条件下环境样品中北海微微浮游生物的六个可培养细菌谱系的生长。异养纳米鞭毛藻（HNF）的放牧压力通过使用0.8-μm孔径的过滤器进行两次预过滤或用0.2-μm（孔径）的过滤水稀释10倍来降低。我们假设那些迅速富集的γ-变形杆菌属也将受到HNF再生的最大影响。在没有HNF的情况下，与环境样品相比，两种处理中每个细菌细胞的平均蛋白质含量均增加，而在未改变海水温育条件下发现相反的趋势。在Alteromonas，Pseudoalteromonas和Vibrio种群中观察到对实验操作的重要反应。没有发现针对玫瑰杆菌属（Cytophaga Latercula-C）成员的治疗特异性作用。 marinoflava血统，或NOR5进化枝。统计分析证实，仅在降低的HNF密度下，Alternomonas，Pseudoalteromonas和Vibrio细胞的比例会短暂增加，然后在HNF再生阶段过度下降。在稀释处理中，这些属的细胞明显大于群落平均数，并且其相对丰度的变化与HNF密度呈负相关。我们的研究结果表明，与频繁分离的属（如Alteromonas，Pseudoalteromonas和Vibrio）相关的细菌在北海小海域浮游动物中可能很少见，因为它们对变化的环境条件的快速生长反应被较高的放牧死亡率所抵消。

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