Isolation of axenic cyanobacterium and the promoting effect of associated bacterium on axenic cyanobacterium

Abstract

In order to avoid the influence of associated bacteria on the target cyanobacteria for physiological and molecular studies, a traditional and reliable method based on solid-liquid alternate cultivation is carried out to purify the non-axenic cyanobacterium Microcystis aeruginosa FACHB-905. On the basis of 16S rDNA gene sequences, two associated bacteria named strain B905-1 and strain B905-2, are identified as Pannonibacter sp. and Chryseobacterium sp. with a 99% and 97% similarity value, respectively. To better investigate the general interaction between the bacterium and the cyanobacterium, the effect of strain B905-1 on the axenic cyanobacterium M. aeruginosa FACHB-905A is studied. Results indicate that the axenic M. aeruginosa FACHB-905A could not form colonies on BG11 agar medium without the addition of strain B905-1, while it grows well in BG11 liquid medium. Although the presence of B905-1 was not indispensable for the growth of M. aeruginosa FACHB-905A, B905-1 had a positive effect on promoting the growth of M. aeruginosa FACHB-905A. The purification technique for cyanobacteria described in this study is potentially applicable to a wider range of filamentous cyanobacteria.