Botryococcus braunii is a colony-forming green alga that accumulates large amounts of liquid hydrocarbons within the colony. The utilization of B. braunii for biofuel production is however hindered by its low biomass productivity. Here we describe a novel bacterial ectosymbiont (BOTRYCO-2) that confers higher biomass productivity to B. braunii. 16S rDNA analysis indicated that the sequence of BOTRYCO-2 shows low similarity (<90%) to cultured bacterial species and located BOTRYCO-2 within a phylogenetic lineage consisting of uncultured alphaproteobacterial clones. Fluorescence in situ hybridization (FISH) studies and transmission electric microscopy indicated that BOTRYCO-2 is closely associated with B. braunii colonies. Interestingly, FISH analysis of a water bloom sample also found BOTRYCO-2 bacteria in close association with cyanobacterium Microcystis aeruginosa colonies, suggesting that BOTRYCO-2 relatives have high affinity to phytoplankton colonies. A PCR survey of algal bloom samples revealed that the BOTRYCO-2 lineage is commonly found in Microcystis associated blooms. Growth experiments indicated that B. braunii Ba10 can grow faster and has a higher biomass (1.8-fold) and hydrocarbon (1.5-fold) yield in the presence of BOTRYCO-2. Additionally, BOTRYCO-2 conferred a higher biomass yield to BOT-22, one of the fastest growing strains of B. braunii. We propose the species name ‘Candidatus Phycosocius bacilliformis’ for BOTRYCO-2.
Platysiphon verticillatus, a brown alga endemic to the Arctic, was described based on vegetative specimens collected at Inglefield Bay, West Greenland. The species is distinctive in having a lanceolate blade-like thallus terminated by a terete portion, both covered with hair-like assimilatory filaments. Punctaria glacialis was described from Eastern Greenland, and the species differs from other Punctaria species in lacking hairs and plurilocular zoidangia. Unilocular zoidangia were reported, but instead of zoids being released they formed cell walls in situ developing the appearance of plurilocular zoidangia. However, the fate of the zoids, as well as the walled cells was not traced, and the life history of the alga has remained unclear. By comparing DNA sequences (cox1, cox3, and rDNA ITS2) of specimens morphologically referable to Platysiphon verticillatus and Punctaria glacialis collected at Baffin Island, as well as re-examining morphology and studying crude cultures, we concluded that they are the same taxonomic entity. Furthermore, their cox3 sequence and vegetative morphology agreed with those of the type specimen of Punctaria glacialis. Consequently, we propose Platysiphon glacialis comb. nov. The life cycle could not be completed in culture, but we hypothesize that in situ germination of the unizoids produces reduced gametophytes housed in peripheral tissue of erect sporophytic thalli.
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