Fate of particle-bound bacteria ingested by Calanus pacificus
Fate of particle-bound bacteria ingested by Calanus pacificus
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太平洋哲水蚤摄入的颗粒结合细菌的命运
DOI：
10.3354/meps097299
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发表时间：
1993
影响因子：
2.5
通讯作者：
F. Azam
中科院分区：
文献类型：
--
作者：
S. Lawrence;A. Ahmad;F. Azam
附着在颗粒上的细菌可以被海洋哲水蚤类桡足类摄取，从而潜在地在细菌和后生动物之间提供直接的营养联系，前提是微生物被动物消化。如果一些细菌在肠道中存活，它们可能在粪便颗粒溶解和破碎（通过胞外酶）和分解中发挥作用。我们研究了太平洋哲水蚤是否能同化细菌生物量，以及是否有相当一部分摄入的细菌活着进入粪球。我们喂成年女性桡足类的冻融硅藻（梭形刺囊藻和角毛藻属）。其已经被用3 H-亮氨酸标记的海水细菌的自然群体定殖。在摄食和随后的肠道清除后43 h，桡足类保留了26%至31%的标记，表明与适当大小的颗粒结合的细菌生物质的相当大一部分可以直接作为该桡足类的材料和能量来源。在摄食细菌性食物的桡足类的粪球中，细菌的浓度很高（10 ~ 101° ml-1），但在摄食无菌食物的桡足类的粪球中却不存在。当摄食细菌食物的桡足类新鲜排出的粪球在海水中培养时，粪球中的细菌丰度增加，在16 ℃时产生的最小比生长速率为0.08 h'（世代时间g = 8.7 h），在22 ℃时产生的最小比生长速率为0.19和0.20 h'（世代时间g = 3.6和3.5 h）。由于细菌在粪粒中生长，我们在新鲜排泄的粪粒中发现的至少一些细菌必须在肠道通道中存活。为了确定细菌是否赋予桡足类粪粒氨肽酶活性，比较了在未定殖和定殖的冻融硅藻上产生的粪粒的酶活性。该比较表明，粪粒中的细菌占粪粒氨肽酶活性的68%至84%，表明内部细菌在粪粒溶解和破碎中的潜在作用。我们的结论是，这些桡足类附着的细菌喂养不仅有助于连接微生物循环与放牧食物链，但由于通过活菌进入粪球，也可能影响粪球降解。
Bacteria bound to particles can be ingested by marine calanoid copepods, thus potentially providing a direct trophic link between bacteria and metazoa provided the microbes are digested by the animals. If some bacteria survive gut passage, they might play a role in fecal pellet solubilization and fragmentation (via ectoenzymes) and decomposition. We examined whether Calanus pacificus could assimilate bacterial biomass and whether a significant fraction of the ingested bacteria passed into the fecal pellets alive. We fed adult female copepods on freeze-thawed diatoms (Cylindrotheca fusiformis and Chaetoceros sp.) which had been colonized by natural populations of seawater bacteria labeled with 3H-leucine. The copepods retained 26 to 31 % of the label 43 h after ingestion and subsequent gut clearance, indicating that a substantial fraction of bacterial biomass bound to particulates of appropriate size can be directly ava~lable to this copepod as a source of material and energy. Bacteria were present at very high concentrations (10' to 101° ml-l) in the fecal pellets of copepod fed on bacterized food, but were absent in the fecal pellets of copepods fed axenic food. When fecal pellets freshly ejected by copepods fed bacterized food were incubated in seawater, bacteria abundances in them increased, yielding minimum specific growth rates of 0.08 h' (generation time g = 8.7 h) at 16 "C and 0.19 and 0.20 h' ( g = 3.6 and 3.5 h) at 22 "C. Since bacteria grew within the fecal pellets, at least some of the bacteria we found in the freshly egested fecal pellets must have survived gut passage In order to determine whether bacteria imparted aminopeptidase activity to copepod fecal pellets, the enzyme activity of fecal pellets produced on uncolonized and colonized freeze-thawed diatoms was compared. This comparison showed that bacteria in the fecal pellets account for 68 to 84 %of the aminopeptidase activity of fecal pellets, indicating a potential role for the interior bacteria in fecal pellet solubilization and fragmentation. We conclude that feeding of these copepods on attached bacteria not only serves to link the microbial loop with the grazing food chain but, because of the passage of viable bacteria into the fecal pellet, may also influence fecal pellet degradation.