es8b01066_si_001.pdf (1.9 MB)
Seasonal Gene Expression and the Ecophysiological Implications of Toxic Microcystis aeruginosa Blooms in Lake Taihu
journal contribution
posted on 2018-08-31, 00:00 authored by Xiangming Tang, Lauren E. Krausfeldt, Keqiang Shao, Gary R. LeCleir, Joshua M. A. Stough, Guang Gao, Gregory L. Boyer, Yunlin Zhang, Hans W. Paerl, Boqiang Qin, Steven W. WilhelmHarmful
cyanobacterial blooms represent an increasing threat to
freshwater resources globally. Despite increased research, the physiological
basis of how the dominant bloom-forming cyanobacteria, Microcystis spp., proliferate and then maintain high population densities through
changing environmental conditions is poorly understood. In this study,
we examined the transcriptional profiles of the microbial community
in Lake Taihu, China at 9 stations sampled monthly from June to October
in 2014. To target Microcystis populations, we collected
metatranscriptomic data and mapped reads to the M. aeruginosa NIES 843 genome. Our results revealed significant temporal gene
expression patterns, with many genes separating into either early
or late bloom clusters. About one-third of genes observed from M. aeruginosa were differentially expressed between
these two clusters. Conductivity and nutrient availability appeared
to be the environmental factors most strongly associated with these
temporal gene expression shifts. Compared with the early bloom season
(June and July), genes involved in N and P transport, energy metabolism,
translation, and amino acid biosynthesis were down-regulated during
the later season (August to October). In parallel, genes involved
in regulatory functions as well as transposases and the production
of microcystin and extracellular polysaccharides were up-regulated
in the later season. Our observation indicates an eco-physiological
shift occurs within the Microcystis spp. transcriptome
as cells move from the rapid growth of early summer to bloom maintenance
in late summer and autumn.