El-Khoury Nay, Bennaceur Imene, Verplaetse Emilie, Aymerich Stéphane, Lereclus Didier, Kallassy Mireille, Gohar Michel
Micalis Institute, Université Paris-Saclay, INRAE, AgroParisTech, 78350 Jouy-en-Josas, France.
Biotechnology Laboratory, UR EGP, Faculty of Science, Saint Joseph University, B.P. 11-514 6 Riad El Solh, Beirut 1107 2050, Lebanon.
Microorganisms. 2021 Feb 2;9(2):298. doi: 10.3390/microorganisms9020298.
During biofilm growth, the coexistence of planktonic and sessile cells can lead to dynamic exchanges between the two populations. We have monitored the fate of these populations in glass tube assays, where the 407 strain produces a floating pellicle. Time-lapse spectrophotometric measurement methods revealed that the planktonic population grew until the pellicle started to be produced. Thereafter, the planktonic population decreased rapidly down to a value close to zero while the biofilm was in continuous growth, showing no dispersal until 120 h of culture. We found that this decrease was induced by the presence of the pellicle, but did not occur when oxygen availability was limited, suggesting that it was independent of cell death or cell sedimentation and that the entire planktonic population has integrated the biofilm. To follow the distribution of recruited planktonic cells within the pellicle, we tagged planktonic cells with GFP and sessile cells with mCherry. Fluorescence binocular microscopy observations revealed that planktonic cells, injected through a 24-h-aged pellicle, were found only in specific areas of the biofilm, where the density of sessile cells was low, showing that spatial heterogeneity can occur between recruited cells and sessile cells in a monospecies biofilm.
在生物膜生长过程中，浮游细胞和固着细胞的共存会导致这两种细胞群体之间的动态交换。我们在玻璃管试验中监测了这些细胞群体的命运，在该试验中407菌株会形成漂浮的菌膜。延时分光光度测量方法显示，浮游细胞群体一直生长到菌膜开始形成。此后，在生物膜持续生长的过程中，浮游细胞群体迅速减少至接近零的值，且在培养120小时前未出现扩散现象。我们发现这种减少是由菌膜的存在诱导的，但在氧气供应受限的情况下不会发生，这表明它与细胞死亡或细胞沉降无关，且整个浮游细胞群体已整合到生物膜中。为了追踪被招募的浮游细胞在菌膜内的分布情况，我们用绿色荧光蛋白（GFP）标记浮游细胞，用红色荧光蛋白（mCherry）标记固着细胞。荧光双目显微镜观察显示，通过24小时龄的菌膜注入的浮游细胞仅出现在生物膜的特定区域，这些区域固着细胞的密度较低，这表明在单物种生物膜中，被招募的细胞和固着细胞之间可能会出现空间异质性。
