Glycine Cleavage Powers Photoheterotrophic Growth of Chloroflexus aurantiacus in the Absence of H2

• Published in: Frontiers in microbiology Vol. 6
• Main Authors: He, Lian, Wang, Yaya, You, Le, Khin, Yadana, Tang, Joseph K.-H., Tang, Yinjie J.
• Format: Journal Article
• Language: English
• Published: Frontiers Media S.A 22-12-2015
• Subjects: 13C; 3-hydroxypropionate; C1 metabolism; CO2 fixation; formyltetrahydrofolate; Microbiology
• ISSN: 1664-302X; 1664-302X
• DOI: 10.3389/fmicb.2015.01467

Chloroflexus aurantiacus
is an anoxygenic phototrophic bacterium. Its unique CO
2
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 H
2(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 CO
2
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.