Light Modulates the Physiology of NonphototrophicActinobacteria

Abstract

Light is a source of energy and an environmental cue that is available in excess in most surface environments. In prokaryotic systems, conversion of light to energy by photoautotrophs and photoheterotrophs is well understood, but the conversion of light to information and the cellular response to that information have been characterized in only a few species. Our goal was to explore the response of freshwaterActinobacteria, which are ubiquitous in illuminated aquatic environments, to light. We found thatActinobacteriawithout functional photosystems grow faster in the light, likely because sugar transport and metabolism are upregulated in the light. Based on the action spectrum of the growth effect and comparisons of the genomes of threeActinobacteriawith this growth rate phenotype, we propose that the photosensor in these strains is a putative CryB-type cryptochrome. The ability to sense light and upregulate carbohydrate transport during the day could allow these cells to coordinate their time of maximum organic carbon uptake with the time of maximum organic carbon release by primary producers.IMPORTANCESunlight provides information about both place and time. In sunlit aquatic environments, primary producers release organic carbon and nitrogen along with other growth factors during the day. The ability ofActinobacteriato coordinate organic carbon uptake and utilization with production of photosynthate enables them to grow more efficiently in the daytime, and it potentially gives them a competitive advantage over heterotrophs that constitutively produce carbohydrate transporters, which is energetically costly, or produce transporters only after detection of the substrate(s), which delays their response. Understanding how light cues the transport of organic carbon and its conversion to biomass is key to understanding biochemical mechanisms within the carbon cycle, the fluxes through it, and the variety of mechanisms by which light enhances growth.

Bacterium Lacking a Known Gene for Retinal Biosynthesis Constructs Functional Rhodopsins

“…S1). Maresca et al (2019) reported that Aurantimicrobium spp. grow more rapidly in the light than in the dark.…”

Dysbiosis of the Saliva Microbiome in Patients With Polycystic Ovary Syndrome

“…Lactobacillales is considered a beneficial gut bacteria, playing a role in infection control, metabolism regulation, and inflammation/allergy modulation ( Pessione, 2012 ). As mentioned above, Actinobacteria , which may be modulated by light, are able to coordinate organic carbon uptake and utilization, accompanied by the production of photosynthate that enhances growth during the daytime ( Maresca et al., 2019 ). Actinobacteria have been found to be reduced during periodontal diseases ( Kornman and Loesche, 1982 ; Kanoe et al., 1995 ) and metabolic diseases ( Long et al., 2017 ).…”

Genome streamlining, proteorhodopsin, and organic nitrogen metabolism in freshwater nitrifiers

“…Photolyase-related proteins in GL MAGs were identified by searching for the following features: K01669, COG0415, PF03441, PF00875, PF04244, SSF48173, SSF52425. Reference proteins (n=56) spanning the previously defined families of photolyases and cryptochromes (33) were obtained from UniProt, along with aquatic bacterial sequences described by Maresca and colleagues (34). The reference sequences were aligned using MAFFT (27), and sequences from GL MAGs were added using the MAFFT --addfragments option.…”

“…The other shares an FAD-binding domain with photolyases but the C-terminal region has no recognizable domains (Fig 5b). This protein is widespread in aquatic bacteria and has not been functionally characterized, though an actinobacterial homolog was suggested to be involved in light sensing and regulation (86). Beyond photolyases, NspiraGL also encode uracil-DNA glycosylase (UNG), which removes misincorporated uracil from DNA.…”