Hahn M W, Moore E R, Höfle M G
GBF-National Research Center of Biotechnology, AG Microbial Ecology, D-38124 Braunschweig, Germany.
Appl Environ Microbiol. 1999 Jan;65(1):25-35. doi: 10.1128/AEM.65.1.25-35.1999.
A facultatively filamentous bacterium was isolated from eutrophic lake water and was identified as Flectobacillus sp. strain MWH38 (a member of the Cytophaga-Flavobacterium-Bacteroides phylum) by comparative 16S rRNA gene sequence analysis. Filament formation by Flectobacillus sp. strain MWH38 and filament formation by Flectobacillus major, the closest known relative of strain MWH38, were studied in chemostat cultures under grazing pressure by the bacterivorous flagellate Ochromonas sp. strain DS and without predation at several growth rates. The results clearly demonstrated that filament formation by the two flectobacilli is growth rate controlled and thus independent of the presence of a predator. However, flagellate grazing positively influenced bacterial growth rates by decreasing bacterial biomass and thus indirectly stimulated filament formation. The results of investigations of cell elongation and filament formation by Comamonas acidovorans PX54 (a member of the beta subclass of the class Proteobacteria) supported the recent proposal that in this species the mechanism of filament formation is growth rate controlled. The finding that the grazing defense mechanism consisting of filament formation is growth rate controlled in the flectobacilli investigated and C. acidovorans PX54 (i.e., in bacteria belonging to divergent evolutionary phyla) may indicate that this mechanism is a phylogenetically widely distributed defense strategy against grazing.
从富营养化湖水中分离出一种兼性丝状细菌，通过比较16S rRNA基因序列分析，将其鉴定为弯曲杆菌属菌株MWH38（噬纤维菌-黄杆菌-拟杆菌门的成员）。在恒化器培养中，研究了弯曲杆菌属菌株MWH38及其已知最近亲缘种大弯曲杆菌在食菌鞭毛虫赭纤虫属菌株DS的捕食压力下以及在几种生长速率下无捕食情况下的丝状形成。结果清楚地表明，这两种弯曲杆菌的丝状形成受生长速率控制，因此与捕食者的存在无关。然而，鞭毛虫的捕食通过降低细菌生物量对细菌生长速率产生了积极影响，从而间接刺激了丝状形成。对食酸丛毛单胞菌PX54（变形菌纲β亚类的成员）的细胞伸长和丝状形成的研究结果支持了最近的提议，即在该物种中，丝状形成机制受生长速率控制。在所研究的弯曲杆菌和食酸丛毛单胞菌PX54（即属于不同进化门的细菌）中，由丝状形成组成的捕食防御机制受生长速率控制这一发现可能表明，这种机制是一种在系统发育上广泛分布的针对捕食的防御策略。
