Glycine Cleavage Powers Photoheterotrophic Growth of Chloroflexus aurantiacus in the Absence of H 2

Lian He; Yaya Wang; Le You; Yadana Khin; Joseph K-H Tang; Yinjie J Tang

doi:10.3389/fmicb.2015.01467

Glycine Cleavage Powers Photoheterotrophic Growth of Chloroflexus aurantiacus in the Absence of H 2

Front Microbiol. 2015 Dec 22:6:1467. doi: 10.3389/fmicb.2015.01467. eCollection 2015.

Authors

Lian He¹, Yaya Wang², Le You¹, Yadana Khin², Joseph K-H Tang³, Yinjie J Tang¹

Affiliations

¹ Department of Energy, Environmental and Chemical Engineering, Washington University St. Louis, MO, USA.
² Department of Chemistry and Biochemistry, Clark University Worcester, MA, USA.
³ Department of Chemistry and Biochemistry, Clark UniversityWorcester, MA, USA; The Biodesign Institute, Arizona State UniversityTempe, AZ, USA.

Abstract

Chloroflexus aurantiacus is an anoxygenic phototrophic bacterium. Its unique CO2 fixation pathway and primitive light-harvesting antenna complexes have attracted extensive research attentions. In this work, we investigated the photoheterotrophic growth of C. aurantiacus J-10-fl using acetate [at 55°C and without H2(g)]. The results indicate that glycine can promote anaerobic biomass production in a minimal medium by threefold to fivefold. Via (13)C-metabolite analysis, we observed that glycine was involved in serine synthesis. Instead of being used as a major carbon source, glycine was degraded to produce C1 units and NAD(P)H. Tracer experiments also suggest that photoheterotrophic cultures growing with a exogenous glycine source exhibited capabilities of assimilating CO2 via multiple routes (including the 3-hydroxypropionate pathway). Finally, glycylglycine, a commonly used culture buffer, also significantly enhanced photoheterotrophic growth of C. aurantiacus, probably due to its thermal or enzymatic breakdown to glycine.

Keywords: 13C; 3-hydroxypropionate; C1 metabolism; CO2 fixation; formyltetrahydrofolate.