The Dynamics of the Bacterial Community of the Photobioreactor-Cultivated Green Microalga Haematococcus lacustris during Stress-Induced Astaxanthin Accumulation

Abstract

Haematococcus lacustris is a natural source of a valuable ketocarotenoid astaxanthin. Under autotrophic growth conditions, it exists in the form of a community with bacteria. The close coexistence of these microorganisms raises two questions: how broad their diversity is and how they interact with the microalga. Despite the importance these issues, little is known about microorganisms existing in Haematococcus cultures. For the first time, we characterize the dynamic of the H. lacustris microbiome of the microbiome of Haematococcus (a changeover of the bacterial associated species as function of the time) cultivated autotrophically in a photobioreactor based on 16S rRNA metabarcoding data. We found that Proteobacteria and Bacteroidetes are predominant phyla in the community. The Caulobacter bacterium became abundant during astaxanthin accumulation. These data were supported by microscopy. We discuss possible roles and interactions of the community members. These findings are of potential significance for biotechnology. They provide an insight into possible bacterial contamination in algal biomass and reveal the presence of bacteria essential for the algal growth.

Faecal Microbiota Divergence in Allopatric Populations of Podarcis lilfordi and P. pityusensis, Two Lizard Species Endemic to the Balearic Islands

“…Such differences are also evident at the level of alpha diversity, where we have found significant differences between samples of both species collected in spring, being P. pityusensis the species exhibiting the highest diversity values. Although these results should be interpreted with caution due to the pooled nature of the samples, there is evidence that microbiota analyses based on mixed samples are a viable measure to consider in population-level studies, providing estimates of the community-level diversity that are highly correlated with diversity estimates using individually sequenced samples [ 61 – 66 ]. The core microbiomes of both Podarcis species intersected in 13 ASVs from several genera commonly found in the gut communities of other lizard species ( Alistipes , Bacteroides , Breznakia , Desulfovibrio , Odoribacter , Oscillibacter , Parabacteroides , and Ruminococcaceae UBA1819; e.g .…”

Sequential Continuous Mixotrophic and Phototrophic Cultivation Might Be a Cost-Effective Strategy for Astaxanthin Production From the Microalga Haematococcus lacustris

“…A recent study investigating the daily dynamics of H. lacustris microbiome revealed interesting consortia between microalgae and bacteria. The findings provided an insight into possible bacterial contamination of the harvested algal biomass and also revealed the possible presence of a core microbiome which may be essential for the growth of the microalga although an interesting question whether there was a core H. lacustris microbiome still needed further confirmation ( Chekanov et al, 2021 ). In another recent study, Wen et al (2020) performed mass cultivation of H. lacustris in ORPs under the mixotrophic mode.…”

Effect of Abscisic Acid on Growth, Fatty Acid Profile, and Pigment Composition of the Chlorophyte Chlorella (Chromochloris) zofingiensis and Its Co-Culture Microbiome

“…The authors of the current study also noticed the microbiomes from cultures treated with the minimal and maximal concentrations of ABA (1 and 50 μM, respectively) had high relative abundances of PGPB genera, such as Paenibacillus , Dyadobacter, and Brevibacillus , which might increase macronutrient availability and are important elements of host–microbial interactions in plants–rhizosphere and microalgae–phycosphere systems [ 102 , 103 , 104 ]. On the other hand, the middle range concentrations of ABA (5 and 10 μM) resulted in stimulating the growth of the genera, some of which are known to accompany microalgal cultures in the photobioreactor systems and provide microalgae with organic substrates or act as parasitic organisms [ 48 , 105 ].…”

“…It is widely known that most of the microalgal strains exist in a close metabolic and regulatory relationship with bacterial species inhabiting their phycosphere [ 46 ]. The core microbiome of H. pluvialis cultures was studied in previous works and was shown to be affected under the conditions inducing carotenogenesis and lipogenesis [ 47 , 48 ]. It was discovered recently that the microbiome components could, in turn, affect the biomass production yield and astaxanthin biosynthesis rate in H. pluvialis under certain conditions [ 49 ].…”