<i>Methanospirillum</i> Respiratory mRNA
Biomarkers Correlate with Hydrogenotrophic Methanogenesis Rate during
Growth and Competition for Hydrogen in an Organochlorine-Respiring
Mixed Culture
Annette R. Rowe
Cresten B. Mansfeldt
Gretchen L. Heavner
Ruth E. Richardson
10.1021/es303061y.s001
https://acs.figshare.com/articles/journal_contribution/_i_Methanospirillum_i_Respiratory_mRNA_Biomarkers_Correlate_with_Hydrogenotrophic_Methanogenesis_Rate_during_Growth_and_Competition_for_Hydrogen_in_an_Organochlorine_Respiring_Mixed_Culture/2456671
Molecular biomarkers hold promise for inferring rates
of key metabolic
activities in complex microbial systems. However, few studies have
assessed biomarker levels for simultaneously occurring (and potentially
competing) respirations. In this study, methanogenesis biomarkers
for <i>Methanospirillum hungatei</i> were developed, tested,
and compared to <i>Dehalococcoides mccartyi</i> biomarkers
in a well-characterized mixed culture. Proteomic analyses of mixed
culture samples (<i>n</i> = 4) confirmed expression of many <i>M. hungatei</i> methanogenesis enzymes. The mRNAs for two oxidoreductases
detected were explored as quantitative biomarkers of hydrogenotrophic
methanogenesis: a coenzyme F<sub>420</sub>-reducing hydrogenase (FrcA)
and an iron sulfur protein (MvrD). As shown previously in <i>D. mccartyi</i>, <i>M. hungatei</i> transcript levels
correlated linearly with measured (<i>R</i> = 0.97 for FrcA, <i>R</i> = 0.91 for MvrD; <i>n</i> = 7) or calculated
respiration rate (<i>R</i> = 0.81 for FrcA, <i>R</i> = 0.62 for MvrD; <i>n</i> = 35) across two orders of magnitude
on a log–log scale. The average abundance of MvrD transcripts
was consistently two orders of magnitude lower than FrcA, regardless
of experimental condition. In experiments where <i>M. hungatei</i> was competing for hydrogen with <i>D. mccartyi</i>, transcripts
for the key respiratory hydrogenase HupL were generally less abundant
per mL than FrcA and more abundant than MvrD. With no chlorinated
electron acceptor added, HupL transcripts fell below both targets.
These biomarkers hold promise for the prediction of in situ rates
of respiration for these microbes, even when growing in mixed culture
and utilizing a shared substrate which has important implications
for both engineered and environmental systems. However, the differences
in overall biomarker abundances suggest that the strength of any particular
mRNA biomarker relies upon empirically established quantitative trends
under a range of pertinent conditions.
2013-01-02 00:00:00
respiration rate
HupL transcripts
methanogenesis biomarkers
hungatei methanogenesis enzymes
mRNA biomarker
biomarker abundances
Methanospirillum Respiratory mRNA Biomarkers Correlate
hydrogenase HupL
biomarker levels
Hydrogenotrophic Methanogenesis Rate
hydrogenotrophic methanogenesis
MvrD transcripts
culture samples
Methanospirillum hungatei
inferring rates
hungatei transcript levels
iron sulfur protein
Proteomic analyses
chlorinated electron acceptor
FrcA
Dehalococcoides mccartyi biomarkers