Bacterial foraging facilitates aggregation of Chlamydomonas microsphaera in an organic carbon source-limited aquatic environment

Ranran Zhao; Guowei Chen; Li Liu; Wei Zhang; Yifei Sun; Baoguo Li; Gang Wang

doi:10.1016/j.envpol.2020.113924

Bacterial foraging facilitates aggregation of Chlamydomonas microsphaera in an organic carbon source-limited aquatic environment

Environ Pollut. 2020 Apr:259:113924. doi: 10.1016/j.envpol.2020.113924. Epub 2020 Jan 7.

Authors

Ranran Zhao¹, Guowei Chen², Li Liu¹, Wei Zhang³, Yifei Sun⁴, Baoguo Li⁴, Gang Wang⁴

Affiliations

¹ Department of Civil Engineering, Hefei University of Technology, Hefei, 230009, China.
² Department of Civil Engineering, Hefei University of Technology, Hefei, 230009, China; State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, 210098, China. Electronic address: gwchen@hfut.edu.cn.
³ Department of Plant, Soil and Microbial Sciences, and Environmental Science and Policy Program, Michigan State University, East Lansing, MI, 48824, United States.
⁴ Department of Soil and Water Sciences, China Agricultural University, Beijing, 100193, China.

PMID: 31926396
DOI: 10.1016/j.envpol.2020.113924

Abstract

Microalgal aggregation is a key to many ecosystem functions in aquatic environments. Yet mechanistic understanding of microalgae aggregation, especially the interactions with ubiquitous bacteria populations, remains elusive. We reported an experimental study illustrating how the emerging bacterial populations interacted with a model microalga (Chlamydomonas microsphaera) cells and the consequent aggregation patterns. Results showed that the emergence of bacterial populations significantly stimulated C. microsphaera aggregation. Both bacterial and C. microsphaera motilities were remarkably excited upon coculturing, with the mean cell velocity being up to 2.67 and 1.80 times of those of separate bacterial and C. microsphaera cultures, respectively. The stimulated bacterial and C. microsphaera cell velocity upon coculturing would likely provide a mechanism for enhanced probability of cell-cell collisions that led to amplified aggregation of C. microsphaera population. Correlation analysis revealed that bacterial resource foraging (for polysaccharides) was likely a candidate mechanism for stimulated cell motility in an organic carbon source-limited environment, whereby C. microsphaera-derived polysaccharides serve as the sole organic carbon source for heterotrophic bacteria which in turns facilitates bacteria-C. microsphaera aggregation. Additional analysis showed that bacterial populations capable of successive decomposing algal-derived organic matters dominated the cocultures, with the top five abundant genera of Brevundimonas (24.78%), Shinella (17.94%), Sphingopyxis (11.62%), Dongia (5.82%) and Hyphomicrobium (5.45%). These findings provide new insights into full understanding of microalgae-bacteria interactions and consequent microbial aggregation characteristics in aquatic ecosystems.

Keywords: C. microsphaera aggregation; Motility; Organic carbon source-limited environment; Resource foraging.

MeSH terms

Bacteria*
Carbon / metabolism*
Chlamydomonas / physiology*
Ecosystem
Microalgae

Substances

Carbon