AUTHOR=Hempel Priscilla P. , Keffer Jessica L. , Maresca Julia A. 

TITLE=RNA-Seq Reveals that Light and Darkness Are Different Stimuli in Freshwater Heterotrophic Actinobacteria

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.739005

DOI=10.3389/fmicb.2021.739005

ISSN=1664-302X

ABSTRACT=<p>Light is a ubiquitous source of both energy and information in surface environments, and regulates gene expression not only in photosynthetic microorganisms, but in a broad range of photoheterotrophic and heterotrophic microbes as well. Actinobacteria are keystone species in surface freshwater environments, where the ability to sense light could allow them to coordinate periods of nutrient uptake and metabolic activity with primary production. The model freshwater Actinobacteria <italic>Rhodoluna</italic> (<italic>R.</italic>) <italic>lacicola</italic> strain MWH-Ta8 and <italic>Aurantimicrobium</italic> (<italic>A.</italic>) <italic>photophilum</italic> strain MWH-Mo1 grow faster in the light than in the dark, but do not use light energy to support growth. Here, we characterize transcription throughout a light-dark cycle in <italic>R. lacicola</italic> and <italic>A. photophilum</italic>. In both species, some genes encoding carbohydrate metabolism and storage are upregulated in the light. However, expression of genes of the TCA cycle is only coordinated with light availability in <italic>R. lacicola.</italic> In fact, the majority of genes that respond to light and darkness in these two species are different, even though their light-responsive phenotypes are similar. The ability to respond to light and darkness may be widespread in freshwater Actinobacteria, but the genetic networks controlled by these two stimuli may vary significantly.</p>