Exploring the potential of algae/bacteria interactions
Graphical abstract
Introduction
Algae are phototrophs that occur in freshwater and marine environments. They vary from small unicellular microalgae, such as cyanobacteria and diatoms, to large multicellular macroalgae, such as giant kelp. They are primary producers that synthesize organic compounds from carbon dioxide, thereby supporting heterotrophic organisms (consumers) that decompose organics and recycle elements. Ecological studies have identified specific phylogenetic groups of heterotrophic bacteria to occur in close association with specific algae [1]. For instance, Lachnit et al. analyzed biofilm communities attaching onto three different species of macroalgae in different seasons, suggesting that marine macroalgae harbor species-specific and temporally adapted epiphytic bacterial biofilms on their surfaces [2]. In addition to biofilm bacteria, algal exudates may also influence planktonic organisms (e.g., heterotrophic bacteria) in the vicinity of algae, and the term ‘phycosphere’ has been coined to describe a region where algal exudates are influential upon co-occurring organisms [3]. A number of studies have demonstrated specific combinations of algae and bacteria to occur in phycospheres, suggesting the presence of their specific interactions. To cite an instance, two heterotrophic bacterial phyla, Proteobacteria (e.g., Roseobacter and Sulfitobacter) and Bacteroidetes (e.g., Cytophaga and Flavobacterium), appear to be consistently associated with diatoms [1, 4]. On the other hand, it has also been shown that heterotrophic bacteria influence algal behaviors in various ways, including the stimulation of growth, morphogenesis, spore germination, and colonization [5]. These interactions are of ecological and biogeochemical importance, since they are considered to be fundamental factors in shaping aquatic communities.
Algae are also the focus of research for their application to biotechnology processes, such as water treatment and bioenergy production [6]. Bacteria may co-occur in these processes and affect biotechnological outcomes in various ways [7]. Moreover, studies have attempted to exploit algae/bacteria interactions in designed consortia, such as those for microbial solar cells (MSCs) [8••]. The design of microbial consortia is a recently proposed direction in biotechnology; for instance, an article has suggested that a synthesis of knowledge from studies of sophisticated natural interactions is expected to create an exciting tool for synthetic biology in which the assembled parts are not just genes, but organisms and communities [9]. Although such examples are currently very limited, complex algae/bacteria interactions are considered to provide attractive opportunities for synthetic biotechnology.
In the present article, we first review algae/bacteria interactions in the natural environment that are potentially relevant to biotechnology processes. We next summarize biotechnology processes that exploit consortia of algae and bacteria with a particular focus on designed consortia for MSCs. On the basis of these instances, this article suggests that a better understanding of mechanisms underlying algae/bacteria interactions will facilitate the development of more efficient and/or as-yet-unexploited biotechnology processes.
Section snippets
Algae/bacteria interactions in the natural environment
Extensive studies have been performed to elucidate algae/bacteria interactions in the natural environment. These studies have revealed different types of interactions to shape specific partnerships between algae and bacteria. According to previous studies [10], this article categorizes their interactions into three types, namely, nutrient exchange, signal transduction and gene transfer (Figure 1). Among them, nutrient exchange has been considered the most common type of interactions. Algae
Algae/bacteria interactions for biotechnology
Algae have attracted great attention due to their beneficial features for biotechnology processes, for example, wastewater treatment [33] and biofuel production [34, 35, 36]. Bacteria generally occur in these processes and affect biotechnological outcomes in various ways. An important concern in biofuel production is that bacteria consume algal products (e.g., oils [35], hydrogen [37] and other chemicals [38]), resulting in the decrease in product yields. In contrast, studies have also shown
Conclusions
Algae/bacteria interactions in natural and engineered ecosystems are complex and contribute largely to their growth and biotechnological outcomes. Although much more work is needed to fully understand complex interactions between algae and bacteria, workers have attempted to exploit some of these interactions to develop and improve biotechnology processes. Furthermore, it has been suggested that an understanding of sophisticated natural interactions will create exciting tools for synthetic
References and recommended reading
Papers of particular interest, published within the period of review, have been highlighted as:
• of special interest
•• of outstanding interest
Acknowledgement
We thank Ayako Matsuzawa for technical assistance.
References (49)
- et al.
Consortia of cyanobacteria/microalgae and bacteria: biotechnological potential
Biotechnol Adv
(2011) - et al.
Light/electricity conversion by defined cocultures of Chlamydomonas and Geobacter
J Biosci Bioeng
(2013) - et al.
Mutualistic interactions between vitamin B12-dependent algae and heterotrophic bacteria exhibit regulation
Environ Microbial
(2012) - et al.
The chloroplast genome of the diatom Seminavis robusta: new features introduced through multiple mechanisms of horizontal gene transfer
Mar Genomics
(2014) - et al.
Widespread decay of vitamin-related pathways: coincidence or consequence?
Trends Genet
(2013) - et al.
Advances in microalgae engineering and synthetic biology applications for biofuel production
Curr Opin Chem Biol
(2013) - et al.
Trends in biohydrogen production: major challenges and state-of-the-art developments
Environ Technol
(2013) - et al.
Photolysis of iron-siderophore chelates promotes bacterial–algal mutualism
Proc Natl Acad Sci U S A
(2009) - et al.
Involvement of indole-3-acetic acid produced by the growth-promoting bacterium Azospirillum spp. in promoting growth of Chlorella vulgaris
J Phycol
(2008) - et al.
Algal–bacterial processes for the treatment of hazardous contaminants: a review
Water Res
(2006)
Interactions between diatoms and bacteria
Microbiol Mol Biol Rev
Epibacterial community patterns on marine macroalgae are host specific but temporally variable
Environ Microbiol
Significance of microalgal–bacterial interactions for aquaculture
Rev Aquaculture
Bacterial community composition differs with species and toxigenicity of the diatom Pseudo-nitzschia
Aqua Microb Ecol
Chemical interactions between marine macroalgae and bacteria
Mar Ecol Prog Ser
Getting in touch with your friends
Science
Coral-associated micro-organisms and their roles in promoting coral health and thwarting diseases
Proc R Soc B Biol Sci
Associations and dynamics of Vibrionaceae in the environment, from the genus to the population level
Front Microbiol
A bacterial facultative parasite of Gracilaria conferta
Dis Aqua Org
Release of dissolved carbohydrates by Emiliania huxleyi and formation of transparent exopolymer particles depend on algal life cycle and bacterial activity
Environ Microbiol
Unicellular cyanobacterium symbiotic with a single-celled eukaryotic alga
Science
Screening and selection of growth-promoting bacteria for Dunaliella cultures
Algal Res
Chlamydomonas reinhardtii thermal tolerance enhancement mediated by a mutualistic interaction with vitamin B12-producing bacteria
ISME J
Cited by (233)
Formation and adaptation of algal–bacterial granular sludge in real Chinese liquor brewing wastewater treatment
2024, Journal of Environmental Chemical EngineeringPotential applications of microalgae–bacteria consortia in wastewater treatment and biorefinery
2024, Bioresource TechnologyRealization process of microalgal biorefinery: The optional approach toward carbon net-zero emission
2023, Science of the Total Environment