Svercel Miroslav, Saladin Bianca, van Moorsel Sofia J, Wolf Sarah, Bagheri Homayoun C
Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, CH-8057, Switzerland.
BMC Res Notes. 2011 Sep 13;4:357. doi: 10.1186/1756-0500-4-357.
Little is known about interactions between filamentous heterotrophs and filamentous cyanobacteria. Here, interactions between the filamentous heterotrophic bacteria Fibrella aestuarina (strain BUZ 2) and Fibrisoma limi (BUZ 3) with an axenic strain of the autotrophic filamentous cyanobacterium Nostoc muscorum (SAG 25.82) were studied in mixed cultures under nutrient rich (carbon source present in medium) and poor (carbon source absent in medium) conditions.
F. aestuarina BUZ 2 significantly reduced the cyanobacterial population whereas F. limi BUZ 3 did not. Physical contact between heterotrophs and autotroph was observed and the cyanobacterial cells showed some level of damage and lysis. Therefore, either contact lysis or entrapment with production of extracellular compounds in close vicinity of host cells could be considered as potential modes of action.The supernatants from pure heterotrophic cultures did not have an effect on Nostoc cultures. However, supernatant from mixed cultures of BUZ 2 and Nostoc had a negative effect on cyanobacterial growth, indicating that the lytic compounds were only produced in the presence of Nostoc.The growth and survival of tested heterotrophs was enhanced by the presence of Nostoc or its metabolites, suggesting that the heterotrophs could utilize the autotrophs and its products as a nutrient source. However, the autotroph could withstand and out-compete the heterotrophs under nutrient poor conditions.
Our results suggest that the nutrients in cultivation media, which boost or reduce the number of heterotrophs, were the important factor influencing the outcome of the interplay between filamentous heterotrophs and autotrophs. For better understanding of these interactions, additional research is needed. In particular, it is necessary to elucidate the mode of action for lysis by heterotrophs, and the possible defense mechanisms of the autotrophs.
关于丝状异养菌与丝状蓝细菌之间的相互作用，人们了解甚少。在此，研究了丝状异养细菌河口纤维杆菌（菌株BUZ 2）和泥质纤维菌（BUZ 3）与自养丝状蓝细菌地木耳（SAG 25.82）的无菌菌株在营养丰富（培养基中存在碳源）和营养贫瘠（培养基中不存在碳源）条件下混合培养时的相互作用。
河口纤维杆菌BUZ 2显著减少了蓝细菌数量，而泥质纤维菌BUZ 3则没有。观察到异养菌与自养菌之间存在物理接触，并且蓝细菌细胞显示出一定程度的损伤和裂解。因此，接触裂解或在宿主细胞附近产生细胞外化合物导致的捕获都可被视为潜在的作用方式。纯异养培养物的上清液对念珠藻培养物没有影响。然而，BUZ 2与念珠藻混合培养物的上清液对蓝细菌生长有负面影响，表明裂解化合物仅在有念珠藻存在时产生。念珠藻或其代谢产物的存在增强了受试异养菌的生长和存活，这表明异养菌可以将自养菌及其产物作为营养源。然而，在营养贫瘠条件下，自养菌能够抵御并胜过异养菌。
我们的结果表明，培养基中的营养物质，其增加或减少了异养菌的数量，是影响丝状异养菌与自养菌相互作用结果的重要因素。为了更好地理解这些相互作用，还需要进行更多研究。特别是，有必要阐明异养菌的裂解作用方式以及自养菌可能的防御机制。
