2 research outputs found
Characterizing the Metabolic Trade-Off in <i>Nitrosomonas europaea</i> in Response to Changes in Inorganic Carbon Supply
The link between the nitrogen and
one-carbon cycles forms the metabolic basis for energy and biomass
synthesis in autotrophic nitrifying organisms, which in turn are crucial
players in engineered nitrogen removal processes. To understand how
autotrophic nitrifying organisms respond to inorganic carbon (IC)
conditions that could be encountered in engineered partially nitrifying
systems, we investigated the response of one of the most extensively
studied model ammonia oxidizing bacteria, <i>Nitrosomonas europaea</i> (ATCC19718), to three IC availability conditions: excess gaseous
and excess ionic IC supply (40× stoichiometric requirement),
excess gaseous IC supply (4× stoichiometric requirement in gaseous
form only), and limiting IC supply (0.25× stoichiometric requirement).
We found that, when switching from excess gaseous and excess ionic
IC supply to excess gaseous IC supply, <i>N. europaea</i> chemostat cultures demonstrated an acclimation period that was characterized
by transient decreases in the ammonia removal efficiency and transient
peaks in the specific oxygen uptake rate. Limiting IC supply led to
permanent reactor failures (characterized by biomass washout and failure
of ammonia removal) that were preceded by similar decreases in the
ammonia removal efficiency and peaks in the specific oxygen uptake
rate. Notably, both excess gaseous IC supply and limiting IC supply
elicited a previously undocumented increase in nitric and nitrous
oxide emissions. Further, gene expression patterns suggested that
excess gaseous IC supply and limiting IC supply led to consistent
up-regulation of ammonia respiration genes and carbon assimilation
genes. Under these conditions, interrogation of the <i>N. europaea</i> proteome revealed increased levels of carbon fixation and transport
proteins and decreased levels of ammonia oxidation proteins (active
in energy synthesis pathways). Together, the results indicated that <i>N. europaea</i> mobilized enhanced IC scavenging pathways for
biosynthesis and turned down respiratory pathways for energy synthesis,
when challenged with excess gaseous IC supply and limiting IC supply
Characterizing the Metabolic Trade-Off in <i>Nitrosomonas europaea</i> in Response to Changes in Inorganic Carbon Supply
The link between the nitrogen and
one-carbon cycles forms the metabolic basis for energy and biomass
synthesis in autotrophic nitrifying organisms, which in turn are crucial
players in engineered nitrogen removal processes. To understand how
autotrophic nitrifying organisms respond to inorganic carbon (IC)
conditions that could be encountered in engineered partially nitrifying
systems, we investigated the response of one of the most extensively
studied model ammonia oxidizing bacteria, <i>Nitrosomonas europaea</i> (ATCC19718), to three IC availability conditions: excess gaseous
and excess ionic IC supply (40× stoichiometric requirement),
excess gaseous IC supply (4× stoichiometric requirement in gaseous
form only), and limiting IC supply (0.25× stoichiometric requirement).
We found that, when switching from excess gaseous and excess ionic
IC supply to excess gaseous IC supply, <i>N. europaea</i> chemostat cultures demonstrated an acclimation period that was characterized
by transient decreases in the ammonia removal efficiency and transient
peaks in the specific oxygen uptake rate. Limiting IC supply led to
permanent reactor failures (characterized by biomass washout and failure
of ammonia removal) that were preceded by similar decreases in the
ammonia removal efficiency and peaks in the specific oxygen uptake
rate. Notably, both excess gaseous IC supply and limiting IC supply
elicited a previously undocumented increase in nitric and nitrous
oxide emissions. Further, gene expression patterns suggested that
excess gaseous IC supply and limiting IC supply led to consistent
up-regulation of ammonia respiration genes and carbon assimilation
genes. Under these conditions, interrogation of the <i>N. europaea</i> proteome revealed increased levels of carbon fixation and transport
proteins and decreased levels of ammonia oxidation proteins (active
in energy synthesis pathways). Together, the results indicated that <i>N. europaea</i> mobilized enhanced IC scavenging pathways for
biosynthesis and turned down respiratory pathways for energy synthesis,
when challenged with excess gaseous IC supply and limiting IC supply