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

Abstract

Background Harmful cyanobacterial blooms have attracted wide attention all over the world as they cause water quality deterioration and ecosystem health issues. Microcystis aeruginosa associated with a large number of bacteria is one of the most common and widespread bloom-forming cyanobacteria that secret toxins. These associated bacteria are considered to benefit from organic substrates released by the cyanobacterium. In order to avoid the influence of associated heterotrophic bacteria on the target cyanobacteria for physiological and molecular studies, it is urgent to obtain an axenic M. aeruginosa culture and further investigate the specific interaction between the heterotroph and the cyanobacterium. Results A traditional and reliable method based on solid-liquid alternate cultivation was carried out to purify the xenic cyanobacterium M. aeruginosa FACHB-905. On the basis of 16S rDNA gene sequences, two associated bacteria named strain B905–1 and strain B905–2, were identified as Pannonibacter sp. and Chryseobacterium sp. with a 99 and 97% similarity value, respectively. The axenic M. aeruginosa FACHB-905A (Microcystis 905A) was not able to form colonies on BG11 agar medium without the addition of strain B905–1, while it grew well in BG11 liquid medium. Although the presence of B905–1 was not indispensable for the growth of Microcystis 905A, B905–1 had a positive effect on promoting the growth of Microcystis 905A. Conclusions The associated bacteria were eliminated by solid-liquid alternate cultivation method and the axenic Microcystis 905A was successfully purified. The associated bacterium B905–1 has the potentiality to promote the growth of Microcystis 905A. Moreover, the purification technique for cyanobacteria described in this study is potentially applicable to a wider range of unicellular cyanobacteria.

In vivo Inhibition of the 3-Dehydroquinate Synthase by 7-Deoxysedoheptulose Depends on Promiscuous Uptake by Sugar Transporters in Cyanobacteria

“…For E. coli a weak growth inhibition could be observed when cultivated in minimal medium, but not in complex medium ( Supplementary Figure 3 ). It might be possible that some heterotrophic bacteria are able to metabolize 7dSh, as it is reported that the cocultivation of cyanobacteria with heterotrophic bacteria can support the growth of the cyanobacteria ( Zheng et al, 2018 ; Gao et al, 2020 ).…”

Generation of miniploid cells and improved natural transformation procedure for a model cyanobacterium Synechococcus elongatus PCC 7942

“…Effects of agar concentration, plating method, and additions of reactive oxygen species scavengers on cyanobacterial growth on solid media Cyanobacterial cultivation and the generation of mutants are challenging due to their slower growth rate (Hayashi et al, 2011;Burnap, 2015;Gao et al, 2020). A very concentrated inoculum is required to grow cyanobacteria on a solid medium.…”

“…There are many factors controlling the generation of fully segregated mutants, which include cyanobacterial strain background, lab conditions, and types of mutations ( Lea-Smith et al, 2016 ). Compared to heterotrophic bacteria, the growth rate of cyanobacteria is slow ( Burnap, 2015 ; Jaiswal et al, 2022 ), especially in solid medium ( Hayashi et al, 2011 ; Gao et al, 2020 ), which further confers a challenge for cyanobacterial transformation. Previous studies have tried to determine the optimum conditions for the growth of multiple cyanobacteria on solid media.…”

Genomic Insights on the Functional Capabilities of the Cyano-Sphere of Edible Andean Nostoc Macrocolonies (Llayta)

“…Filaments accumulate into a mucilaginous matrix rich in a complex polysaccharide enclosed by an outer envelope in Nostoc species capable of forming macrocolony. Nostoc macrocolonies can be observed as sheet-like or spherical forms with green to brown colorations, depending upon the species, dehydration state, and local environment [17][18][19][20][21][22]32]. In natural environments, macrocolonies of filamentous diazotrophic Nostoc are colonized by diverse microorganisms involved in biogeochemical cycles and ecosystem services [33].…”

“…The natural life cycle of primary producers may involve mutualistic, antagonistic, or commensal interactions with cyanophages, fungi, and heterotrophic bacteria. Positive or negative outcomes from such interactions have been previously discussed in Nostoc macrocolonies [18,19] and reported in Andean Nostoc macrocolonies [20][21][22]. However, studies on identifying members of the bacterial community associated with edible Llayta macrocolonies have been a pending issue.…”