Co-culturing <i>Hyphomicrobium nitrativorans</i> strain NL23 and <i>Methylophaga nitratireducenticrescens</i> strain JAM1 allows sustainable denitrifying activities under marine conditions
Bibliographic record
Abstract
ABSTRACT Hyphomicrobium nitrativorans strain NL23 and Methylophaga nitratireducenticrescens strain JAM1 were the principal bacteria involved in the denitrifying activities of a methanol-fed, fluidized marine denitrification reactor. We believe that a tight relationship has developed between these two strains to achieve denitrification in the reactor under marine conditions. To characterize the potential synergy between strain JAM1 and strain NL23, we compared some of their physiological traits, and performed co-cultures. Pure cultures of strain JAM1 had a readiness to reduce nitrate (NO 3 −) with no lag phase for growth contrary to pure cultures of strain NL23, which has a 2-3 days lag phase before NO 3 − starts to be consumed and growth to occur. Compared to strain NL23, strain JAM1 has a higher μmax for growth and higher specific NO 3 − reduction rates. Antagonist assays showed no sign of exclusion by both strains. Planktonic co-cultures could only be performed on low NaCl concentrations for strain NL23 to survive. Denitrification rates were twice higher in the planktonic co-cultures than those measured in strain NL23 pure cultures. Biofilm co-cultures were performed for several months in a 500-mL bioreactor filled with Bioflow supports, and operated under fed-batch mode with increasing concentrations of NaCl for strain NL23 to acclimate to marine conditions. Under these conditions, the biofilm co-cultures showed sustained denitrifying activities and surface colonization by both strains. Increase in ectoine concentrations produced by strain JAM1 was observed in the biofilm with increasing NaCl concentrations. These results illustrate the capacity of both strains to act together in performing denitrification under marine environments. Although strain JAM1 did not contribute in better specific denitrifying activities in the biofilm co-cultures, its presence was essential for strain NL23 to survive in a medium with NaCl concentrations > 1.0%. We believe that ectoine is an important factor for the survival of strain NL23 in these environments.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".