Characterization of Candidatus Nitrotoga and its Competitiveness in Co-Culture with Nitrospira

• Main Author: Wegen, Simone
• Other Authors: Spieck, Eva (PD Dr.)
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky 2017
• Subjects: Nitrifikation; Nitrit-oxidierende Bakterien; Nitrotoga; Nischendifferenzierung; Nitrification; nitrite-oxidizing bacteria; niche partitioning; 570 Biowissenschaften; Biologie; 42.30 Mikrobiologie; ddc:570; permafrost
• Online Access: http://nbn-resolving.de/urn:nbn:de:gbv:18-90392; https://ediss.sub.uni-hamburg.de/handle/ediss/7603

Nitrification is a crucial microbial process during nitrogen removal in wastewater treatment plants (WWTPs) and recirculating aquaculture systems (RAS), where ammonia-oxidizing microbes (AOM) and nitrite oxidizing bacteria (NOB) prevent the accumulation of highly toxic ammonia and nitrite. NOB of the genus Nitrospira are usually detected in activated sludge or biofilters. However, Nitrotoga was recently reported as the main NOB in WWTPs, alone or in coexistence with Nitrospira. Their frequent detection in the same habitat raises the question of niche separation between these two genera. The candidate genus Nitrotoga was first described as a cold-tolerant NOB with a distinct large periplasm. In contrast to Nitrospira-like NOB, only a few Nitrotoga members have been enriched, cultured, and characterized. Since their 16S rRNA gene sequences are nearly identical (> 99% similarity), assigning species within the genus based on sequence data alone is difficult. Four highly enriched Nitrotoga cultures sampled from different habitats were available for a comparative characterization, including physiology, phylogeny, and morphology. Based on results from these tests, cultures were selected for competition experiments with Nitrospira to determine factors enabling niche partitioning. While they showed similar morphological features, each Nitrotoga culture was characterized by distinct physiological properties. Nitrotoga arctica (permafrost soil, active layer) and Nitrotoga BS (activated sludge) shared the same optimum temperature of 17°C, whereas Nitrotoga HW (biofilter RAS) and Nitrotoga 1052 (permafrost soil, bore core) grew best at 22°C. The cold adaption of the genus was confirmed by high activity down to 4°C but inhibition above 25 to 28°C. Regarding the pH, Nitrotoga tolerated alkalinity (about pH 8) better than acidity (about pH 6) in general. Nonetheless, Ntg. arctica and Nitrotoga HW had their optimum in the slightly acidic to neutral range, while Nitrotoga 1052 and Nitrotoga BS preferred slightly alkaline ...