Metabolic commensalism and competition in a two-species microbial consortium
Metabolic commensalism and competition in a two-species microbial consortium
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DOI：
10.1128/aem.68.5.2495-2502.2002
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发表时间：
2002-05-01
影响因子：
4.4
通讯作者：
Molin, S
中科院分区：
文献类型：
--
作者：
Christensen, BB;Haagensen, JAJ;Molin, S
我们分析了代谢的相互作用和苯甲醇降解微生物的财团，包括两个物种，恶臭假单胞菌菌株R1和不动杆菌菌株C6，这两个都能够利用苯甲醇作为他们唯一的碳和能源的特定结构关系的重要性。生物体生长的表面附着的生物体（生物膜）在如何室或悬浮培养恒化器。在恒化器和流动室的流出物中测定恶臭假单胞菌RI和不动杆菌菌株C6的CFU数。当这两个物种在具有限制浓度的苯甲醇的恒化器中一起生长时，不动杆菌属菌株C6的数量超过恶臭假单胞菌RI（500：1），而在生物膜中的类似生长条件下，恶臭假单胞菌R1的数量高于不动杆菌属菌株C6（5：1）。为了解释这种差异，在生物膜中进行了微生物活性和结构关系的调查。将生长速率调节的rRNA启动子rrnBP 1和编码绿色荧光蛋白的不稳定变体的gfp基因之间的融合物插入恶臭假单胞菌RI中，使得可以监测恶臭假单胞菌R1细胞在生物膜中不同位置的生理活性。结合荧光原位杂交和扫描共聚焦激光显微镜显示，这两种生物体竞争或显示的相互作用，这取决于它们在生物膜中的相对物理定位。在生物膜形成的初始阶段，恶臭假单胞菌R1的生长活性显示在不动杆菌菌株C6的小菌落附近较高。高压液相色谱分析表明，在不动杆菌菌株C6单培养生物膜的流出物中，代谢中间体苯甲酸盐积累，而在双培养生物膜中，情况并非如此，这表明在这些生物膜中，不动杆菌菌株C6产生的过量苯甲酸盐泄漏到周围环境中，在那里它被恶臭假单胞菌R1代谢。几天后，恶臭假单胞菌R1细胞使不动杆菌菌株C6菌落过度生长，并形成新的结构，其中在生物膜的上层建立了不动杆菌菌株C6细胞的小菌落。通过这种方式，两种微生物形成了结构关系，使不动杆菌菌株C6接近具有高浓度苯甲醇的原液，并使恶臭假单胞菌R1受益于不动杆菌菌株C6泄漏的苯甲酸盐。我们的结论是，在恒化器中，生物体不能在固定位置建立，两种菌株将竞争主要碳源，苯甲醇，这显然使不动杆菌菌株C6的生长优势，可能是因为它将苯甲醇转化为苯甲酸酯，每单位时间的产率高于恶臭假单胞菌R1。然而，在生物膜中，生物体建立结构化的表面附着的聚生体，其中异质生态位发展，并且在这些条件下，对初级碳源的竞争不是生物量和种群结构的唯一决定因素。
We analyzed metabolic interactions and the importance of specific structural relationships in a benzyl alcohol-degrading microbial consortium comprising two species, Pseudomonas putida strain R1 and Acinetobacter strain C6, both of which are able to utilize benzyl alcohol as their sole carbon and energy source. The organisms were grown either as surface-attached organisms (biofilms) in How chambers or as suspended cultures in chemostats. The numbers of CFU of P. putida RI and Acinetobacter strain C6 were determined in chemostats and from the effluents of the flow chambers. When the two species were grown together in chemostats with limiting concentrations of benzyl alcohol, Acinetobacter strain C6 outnumbered P. putida RI (500:1),whereas under similar growth conditions in biofilms,P.putida R1 was present in higher numbers than Acinetobacter strain C6 (5:1). In order to explain this difference, investigations of microbial activities and structural relationships were carried out in the biofilms. Insertion into P. putida RI of a fusion between the growth rate-regulated rRNA promoter rrnBP1 and a gfp gene encoding an unstable variant of the green fluorescent protein made it possible to monitor the physiological activity of P. putida R1 cells at different positions in the biofilms. Combining this with fluorescent in situ hybridization and scanning confocal laser microscopy showed that the two organisms compete or display commensal interactions depending on their relative physical positioning in the biofilm. In the initial phase of biofilm development, the growth activity of P. putida R1 was shown to be higher near microcolonies of Acinetobacter strain C6. High-pressure liquid chromatography analysis showed that in the effluent of the Acinetobacter strain C6 monoculture biofilm the metabolic intermediate benzoate accumulated, whereas in the biculture biofilms this was not the case, suggesting that in these biofilms the excess benzoate produced by Acinetobacter strain C6 leaks into the surroundingenvironment, from where it is metabolized by P.putida R1. After a few days, Acinetobacter strain C6 colonies were overgrown by P. putida R1 cells and new structures developed, in which microcolonies of Acinetobacter strain C6 cells were established in the upper layer of the biofilm. In this way the two organisms developed structural relationships allowing Acinetobacter strain C6 to be close to the bulk liquid with high concentrations of benzyl alcohol and allowing P. putida R1 to benefit from the benzoate leaking from Acinetobacter strain C6. We conclude that in chemostats, where the organisms cannot establish in fixed positions, the two strains will compete for the primary carbon source, benzyl alcohol, which apparently gives Acinetobacter strain C6 a growth advantage, probably because it converts benzyl alcohol to benzoate with a higher yield per time unit than P. putida R1. In biofilms, however, the organisms establish structured, surface-attached consortia, in which heterogeneous ecological niches develop, and under these conditions competition for the primary carbon source is not the only determinant of biomass and population structure.