Characterization of bacterial community associated with phytoplankton bloom in a eutrophic lake in South Norway using 16S rRNA gene amplicon sequence analysis.

Niranjan Nitin Parulekar,Mohan Kale,Anette Johansen,Urmila Kulkarni-Kale,Pandurang Kolekar,Andrew Jenkins,Hans Utkilen,Mona Sæbø,Synne Kleiven,Sangeeta Sawant,Todd Miller

doi:10.1371/journal.pone.0173408

Niranjan Nitin Parulekar, Mohan Kale + Show 9 more

Open Access

https://doi.org/10.1371/journal.pone.0173408

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Journal: PloS one	Publication Date: Mar 10, 2017
Citations: 73	License type: CC BY 4.0

Affiliation: Savitribai Phule Pune University

Abstract

Interactions between different phytoplankton taxa and heterotrophic bacterial communities within aquatic environments can differentially support growth of various heterotrophic bacterial species. In this study, phytoplankton diversity was studied using traditional microscopic techniques and the bacterial communities associated with phytoplankton bloom were studied using High Throughput Sequencing (HTS) analysis of 16S rRNA gene amplicons from the V1-V3 and V3-V4 hypervariable regions. Samples were collected from Lake Akersvannet, a eutrophic lake in South Norway, during the growth season from June to August 2013. Microscopic examination revealed that the phytoplankton community was mostly represented by Cyanobacteria and the dinoflagellate Ceratium hirundinella. The HTS results revealed that Proteobacteria (Alpha, Beta, and Gamma), Bacteriodetes, Cyanobacteria, Actinobacteria and Verrucomicrobia dominated the bacterial community, with varying relative abundances throughout the sampling season. Species level identification of Cyanobacteria showed a mixed population of Aphanizomenon flos-aquae, Microcystis aeruginosa and Woronichinia naegeliana. A significant proportion of the microbial community was composed of unclassified taxa which might represent locally adapted freshwater bacterial groups. Comparison of cyanobacterial species composition from HTS and microscopy revealed quantitative discrepancies, indicating a need for cross validation of results. To our knowledge, this is the first study that uses HTS methods for studying the bacterial community associated with phytoplankton blooms in a Norwegian lake. The study demonstrates the value of considering results from multiple methods when studying bacterial communities.

Highlights

In recent years, reports of cyanobacterial blooms in freshwater ecosystems attributed to eutrophication and global warming have increased [1,2,3,4,5,6]
In June and July, the concentration of microcystin was below the detection limit of 0.15 μg/l
This study is the first use of 16S rRNA targeted amplicon sequencing to characterize the bacterial communities associated with phytoplankton blooms in a eutrophic lake in Norway

Summary

Introduction

Reports of cyanobacterial blooms in freshwater ecosystems attributed to eutrophication and global warming have increased [1,2,3,4,5,6]. Cyanobacteria coexist and interact with heterotrophic bacterial groups commonly found in freshwater ecosystems [13, 14]. They may produce various dissolved organic compounds and fix atmospheric nitrogen, supplying heterotrophic bacteria with substrates for growth [15,16,17]. Such compounds can differentially support growth of heterotrophic bacteria species [18]. It is likely that the composition of cyanobacterial blooms will structure the associated heterotrophic bacterial populations [14]

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Discussion

Conclusion