Algae as an important environment for bacteria – phylogenetic relationships among new bacterial species isolated from algae FRANZ GOECKE 1 *, VERA THIEL † ,JUTTA WIESE 1 ,ANTJE LABES 1 AND JOHANNES F. IMHOFF 1 1 Kieler Wirkstoff-Zentrum at Helmholtz Centre for Ocean Research Kiel (GEOMAR), Am Kiel-Kanal 44, Kiel D-24106, Germany GOECKE F., THIEL V., WIESE J., LABES A. AND IMHOFF J.F. 2013. Algae as an important environment for bacteria – phylogenetic relationships among new bacterial species isolated from algae. Phycologia 52: 14–24. DOI: 10.2216/12–24.1.s1. Bacteria are an inherent part of the biotic environment of algae. Recent investigations revealed that bacterial communities associated with algae were generally highly host specific. Several new bacterial species and genera were isolated from algae, which suggested that algae were an interesting environment for discovery of new bacterial taxa; however, the distribution of the different phylogenetic groups among those isolates remained unclear, and this information could help to explain specific associations. We conducted a phylogenetic study based on 16S rRNA gene sequences available in GenBank, including 101 validly described bacterial species that were isolated from eukaryotic macro- and micro-algae from marine and freshwater environments. These species were distributed among six bacterial phyla, including: Bacteroidetes (42 species), Proteobacteria (36 species), and Firmicutes, Actinobacteria, Verrucomicrobia and Planctomycetes (23 species). Bacterial species and strains that carried out similar metabolic functions were found to colonize similar algal taxa or algal groups. This assumption was supported by information available from bacterial species descriptions: (1) Most of the bacteria described from microalgae grouped into the Roseobacter clade (Alphaproteobacteria), which indicated that members of this group were well adapted for life in close association with phytoplankton; and (2) 32% of the bacterial species, mainly isolates from macroalgae, were able to decompose macroalgal polysaccharides. Because algal-bacterial association are still under-studied in various algal groups, we expect a great number of new bacterial taxa to be discovered in the future. KEY WORDS: Enzyme, Macroalgae, Microbe-alga, Phytoplankton. INTRODUCTION Algae and their associated microbial communities form complex and highly dynamic ecosystems (Holmstro¨m et al. 2002). Bacteria are dominant among the primary colonizers of algae (Lachnit et al. 2009). While several bacterial species have been identified as causative agents of algal diseases, many bacterial associations are clearly beneficial for the algal host (Matsuo et al. 2005; Goecke et al. 2010; Seyedsayam- dost et al. 2011; Hollants et al. 2012). Many new bacterial species, genera and orders have been described from algae, suggesting that algae represent an interesting biotic environ- ment for discovery of new bacterial taxa, even if the origin does not necessarily indicate a specific association. Some of these bacteria specifically prefer growth on algal surfaces and may even show syntrophic associations. Others are less tightly associated with algae and may be ubiquitous in aquatic environments (Goecke et al. 2010). Several specific associations between algae and bacteria have been described (i.e. Biegala et al. 2002; Croft et al. 2005; Dimitrieva et al. 2006; Grossart & Simon 2007; Amin et al. 2009; Ga¨ rdes et al. 2010; Wagner-Do¨ bler et al. 2010; Hollants et al. 2011; Seyedsayamdost et al. 2011; Trias et al. 2012). Strain-specific preferences for certain substrates and strain-specific pro- or antifouling activities of algal metabolites play an important role in formation of these specific communities (Wahl et al. 2010; Sneed & Pohnert 2011). Conceptually, the surface chemistry of an alga is the sum of exuded secondary metabolites and extracellular exopoly- meric substances (EPS) present on the thallus. This complex mixture of compounds, presumably in equilibrium with the ambient water body (Lachnit et al. 2010; Salau¨n et al. 2012), is a primary source of nutrients for those bacteria attached to the surface. Also, the cell/thallus morphology and micro- topography of the algal surface play a role in the colonization and association with the microbiota and invertebrates (Wahl et al. 2010). Hence, each algal species can be considered to be a unique micro-environment. Utilization of substrates produced or released by the algae, including structural polysaccharide components of algal cell walls, is an important aspect of surface colonization by bacteria (Doubet & Quatrano 1982; Goecke et al. 2010; Bengtsson et al. 2011; Salau¨n et al. 2012). Bacteria may use the macroalga not only as surface for settlement but also as a source of substrates for their own nutrition (Johansen et al. 1999), and this is probably an important factor shaping specific macroalga-bacteria interactions. The macromolecu- lar composition of algal surfaces is characteristically different among the major evolutionary lineages of algae, linking specific life style or nutritional habits to specifically encountered biopolymers. Most of these algal macromole- cules are polysaccharides, which occur in sulfated (carra- geenans, fucans) or highly ionic (alginates) forms (Thomas et * Corresponding author (fgoecke@geomar.de). † Present address: The Pennsylvania State University, Depart- ment of Biochemistry and Molecular Biology, 231 South Frear Lab, University Park, PA 16802, USA Phycologia (2013) Volume 52 (1), 14–24 Published 4 January 2013 14