The present study aimed to analyze the metaproteome of the microbial community comprising harmful algal bloom (HAB) in the Daechung reservoir, Korea. HAB samples located at GPS coordinates of 36°29’N latitude and 127°28’E longitude were harvested in October 2013. Microscopic observation of the HAB samples revealed red signals that were presumably caused by the autofluorescence of chlorophyll and phycocyanin in viable cyanobacteria. Metaproteomic analysis was performed by a gelbased shotgun proteomic method. Protein identification was conducted through a two-step analysis including a forward search strategy (FSS) (random search with the National Center for Biotechnology Information (NCBI), Cyanobase, and Phytozome), and a subsequent reverse search strategy (RSS) (additional Cyanobase search with a decoy database). The total number of proteins identified by the two-step analysis (FSS and RSS) was 1.8-fold higher than that by one-step analysis (FSS only). A total of 194 proteins were assigned to 12 cyanobacterial species (99 mol%) and one green algae species (1 mol%). Among the species identified, the toxic microcystin-producing Microcystis aeruginosa NIES-843 (62.3%) species was the most dominant. The largest functional category was proteins belonging to the energy category (39%), followed by metabolism (15%), and translation (12%). This study will be a good reference for monitoring ecological variations at the meta-protein level of aquatic microalgae for understanding HAB.

Abstract
INTRODUCTION
MATERIALS AND METHODS
    1. Sample preparation
    2. SDS-PAGE and gel slicing
    3. MS analysis of HAB samples
    4. Bioinformatic analysis
RESULTS AND DISCUSSION
    1. Microscopic observation of HAB inthe Daechung Reservoir
    2. Results of metaproteomic analysis bytwo strategies
    3. Microalgae profiles of HAB inthe Daechung Reservoir
    4. Characteristics of the HAB metaproteomein the Daechung Reservoir
CONCLUSIONS
REFERENCES

• Jong-Soon Choi(Biological Disaster Analysis Team, Korea Basic Science Institute/Graduate School of Analytical Science and Technology, Chungnam National University) Corresponding author
• Yun Hwan Park(Division of Environmental Science and Ecological Engineering, Korea University)
• Soo Hyeon Kim(Biological Disaster Analysis Team, Korea Basic Science Institute/Graduate School of Analytical Science and Technology, Chungnam National University)
• Ju Seong Park(Biological Disaster Analysis Team, Korea Basic Science Institute/Graduate School of Analytical Science and Technology, Chungnam National University)
• Yoon-E Choi(Division of Environmental Science and Ecological Engineering, Korea University) Corresponding author