Different co‐occurring bacteria enhance or decrease the growth of the microalga Nannochloropsis sp. CCAP211/78

Abstract

Marine photosynthetic microalgae are ubiquitously associated with bacteria in nature. However, the influence of these bacteria on algal cultures in bioreactors is still largely unknown. In this study, eighteen different bacterial strains were isolated from cultures of Nannochloropsis sp. CCAP211/78 in two outdoor pilot-scale tubular photobioreactors. The majority of isolates was affiliated with the classes Alphaproteobacteria and Flavobacteriia. To assess the impact of the eighteen strains on the growth of Nannochloropsis sp. CCAP211/78, 24-well plates coupled with custom-made LED boxes were used to simultaneously compare replicate axenic microalgal cultures with addition of individual bacterial isolates. Co-culturing of Nannochloropsis sp. CCAP211/78 with these strains demonstrated distinct responses, which shows that the technique we developed is an efficient method for screening the influence of harmful/beneficial bacteria. Two of the tested strains, namely a strain of Maritalea porphyrae (DMSP31) and a Labrenzia aggregata strain (YP26), significantly enhanced microalgal growth with a 14% and 12% increase of the chlorophyll concentration, respectively, whereas flavobacterial strain YP206 greatly inhibited the growth of the microalga with 28% reduction of the chlorophyll concentration. Our study suggests that algal production systems represent a 'natural' source to isolate and study microorganisms that can either benefit or harm algal cultures.

A closer look into the microbiome of microalgal cultures

“…Applying the different bacterial communities to axenic cultures of the respective other Phaeodactylum strains could give further insight on the actual impact and the possible cause vs. consequence of the different bacterial communities on the different strains. Specific positive and negative effect of different bacterial species on microalgal growth has been demonstrated before (Tait et al, 2019;Ling et al, 2020;Lian et al, 2021).…”

“…In cultivation systems, microalgae co-exist together with bacteria, which either have been associated with the microalgae since isolation or they have been introduced later through air or non-sterile handling. Only in a very few cases, and at a small scale, can microalgae in culture be maintained axenically ( Biondi et al, 2018 ; Lian et al, 2021 ).…”

The seaweed holobiont: from microecology to biotechnological applications

“…Microalgae have been proposed as an alternative source of plant biostimulants because there is potential for increased raw material standardization and cost reduction (Chiaiese et al ., 2018 ). Microalgae are also ubiquitously associated with bacteria in nature, and their interactions, which can be both beneficial or detrimental to microalgae, can greatly affect aquatic ecosystem productivity and stability (Chhun et al ., 2021 ; Lian et al ., 2021 ). Therefore, harnessing these interactions could help improve microalgal yield and thus biostimulant production.…”

Producing high value unsaturated fatty acid by whole‐cell catalysis using microalga: A case study with Tribonema minus

“…In this way, the lipid content of Tribonema minus is increased from 15.5% (first stage) to 49.0% (second stage) (Zhou et al, 2019). However, such cultivation mode still lives at the mercy of the weather, and has the risk of cultivation failure by microbial contamination (Lian et al, 2021;Steichen et al, 2020). Therefore, a more convenient and effective method is urgently needed to enhance the lipid accumulation of heterotrophic Tribonema sp.…”