Changes in Free-Living and Particle-Associated Bacterial Communities Depending on the Growth Phases of Marine Green Algae, Tetraselmis suecica

Bum Soo Park,Won-Ji Choi,Jang-Seu Ki,Hansol Kim,Ruoyu Guo

doi:10.3390/jmse9020171

Abstract

Bacteria are remarkably associated with the growth of green algae Tetraselmis which are used as a feed source in aquaculture, but Tetraselmis-associated bacterial community is characterized insufficiently. Here, as a first step towards characterization of the associated bacteria, we investigated the community composition of free-living (FLB) and particle-associated (PAB) bacteria in each growth phase (lag, exponential, stationary, and death) of Tetraselmis suecica P039 culture using pyrosequencing. The percentage of shared operational taxonomic units (OTUs) between FLB and PAB communities was substantially high (≥92.4%), but their bacterial community compositions were significantly (p = 0.05) different from each other. The PAB community was more variable than the FLB community depending on the growth phase of T. suecica. In the PAB community, the proportions of Marinobacter and Flavobacteriaceae were considerably varied in accordance with the cell number of T. suecica, but there was no clear variation in the FLB community composition. This suggests that the PAB community may have a stronger association with the algal growth than the FLB community. Interestingly, irrespective of the growth phase, Roseobacter clade and genus Muricauda were predominant in both FLB and PAB communities, indicating that bacterial communities in T. suecica culture may positively affect the algae growth and that they are potentially capable of enhancing the T. suecica growth.

Highlights

In order to save the cost for algal production, there have been attempts to advance the algal-culture technique which enables gaining a higher biomass of this green algae
The green algae T. suecica and FLB in the culture appeared as a common, typical SThe green algae T. suecica and FLB in the culture appeared as a common, typical shaped growth curve (Figure 1), but the growth of FLB was faster than that of T. suecica
FLB and PAB communities were significantly distinct (p = 0.05), the PAB community was more affected depending on the growth phases of T. suecica than FLB community

Summary

Introduction

Marine green microalga genus Tetraselmis is well-known to have a high lipid content and fast growth [1,2], and it has been widely used in multiple industries, for example, a source of nutrition for invertebrates in aquaculture [3], feedstock of biofuel production [4], and cosmetic applications [5]. In order to save the cost for algal production, there have been attempts to advance the algal-culture technique which enables gaining a higher biomass of this green algae. Bacteria which have a symbiotic relationship to algae have been considered as a new factor to advance the algal-culture technique, allowing to gain a higher algal biomass Algal-culture techniques have been developed based on adjusting physiochemical factors (e.g., light intensity, nutrient limitation, temperature, pH, CO2 concentration, and salinity) which are well known to have an intimate association with algal growth [6,7].

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Conclusion