High reproducibility of ammonia-oxidizing bacterial communities in parallel sequential batch reactors.
OBJECTIVE
To investigate whether the ammonia-oxidizing bacterial (AOB) communities of replicate nitrifying bioreactors (i) co-evolve or diverge over time and (ii) are stable or dynamic during periods of complete nitrification.


RESULTS
Three sequential batch reactors (SBR) were inoculated with sludge from a municipal wastewater treatment plant, fed with ammonium-enriched tap water and operated in parallel for 134 days. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) demonstrated co-evolvement of the AOB communities over time. During start-up, temporary decreases in nitrification were noticed, and the AOB community rate of change values (Delta(t(week))) were medium to high (12-22%). During the adjacent period of complete nitrification, low AOB community dynamics were observed (Delta(t(week)) < 5%). Further pragmatic processing of the DGGE profiles revealed a high range-weighted richness and a medium functional organization of the AOB communities.


CONCLUSIONS
After a start-up period, high functional stability and low dynamics of the AOB communities were observed. Deterministic rather than stochastic driving forces led to AOB community co-evolvement in the replicate SBR.


CONCLUSIONS
Replicates in identical set-ups are reproducible, and pragmatic processing of DGGE patterns is a straightforward tool to score and compare the functionality of the bacterial communities.
Wittebolle
L
L
Laboratory of Microbial Ecology & Technology, Ghent University, Gent, Belgium.
Van Vooren
N
N
Verstraete
W
W
Boon
N
N
D000641:Ammonia / Q000378:metabolism; D001419:Bacteria / Q000235:genetics / Q000254:growth & development* / Q000302:isolation & purification*; D019149:Bioreactors; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S; D012722:Sewage; D013997:Time Factors
D012336:RNA, Ribosomal, 16S; D012722:Sewage; D000641:Ammonia