PMID:15746329

Citation	Bollmann, A, Schmidt, I, Saunders, AM and Nicolaisen, MH (2005) Influence of starvation on potential ammonia-oxidizing activity and amoA mRNA levels of Nitrosospira briensis. Appl. Environ. Microbiol. 71:1276-82
Abstract	The effect of short-term ammonia starvation on Nitrosospira briensis was investigated. The ammonia-oxidizing activity was determined in a concentrated cell suspension with a NOx biosensor. The apparent half-saturation constant [Km(app)] value of the NH3 oxidation of N. briensis was 3 microM NH3 for cultures grown both in continuous and batch cultures as determined by a NOx biosensor. Cells grown on the wall of the vessel had a lower Km(app) value of 1.8 microM NH3. Nonstarving cultures of N. briensis showed potential ammonia-oxidizing activities of between 200 to 250 microM N h(-1), and this activity decreased only slowly during starvation up to 10 days. Within 10 min after the addition of fresh NH4+, 100% activity was regained. Parallel with activity measurements, amoA mRNA and 16S rRNA were investigated. No changes were observed in the 16S rRNA, but a relative decrease of amoA mRNA was observed during the starvation period. During resuscitation, an increase in amoA mRNA expression was detected simultaneously. The patterns of the soluble protein fraction of a 2-week-starved culture of N. briensis showed only small differences in comparison to a nonstarved control. From these results we conclude that N. briensis cells remain in a state allowing fast recovery of ammonia-oxidizing activity after addition of NH4+ to a starved culture. Maintaining cells in this kind of active state could be the survival strategy of ammonia-oxidizing bacteria in nature under fluctuating NH4+ availability.
Links	PubMed PMC1065156 Online version:10.1128/AEM.71.3.1276-1282.2005
Keywords	Acetylene/pharmacology; Ammonia/metabolism; Base Sequence; Culture Media; DNA, Bacterial/genetics; Enzyme Inhibitors/pharmacology; Genes, Bacterial; Kinetics; Nitrosomonadaceae/drug effects; Nitrosomonadaceae/genetics; Nitrosomonadaceae/metabolism; Oxidation-Reduction; Oxidoreductases/antagonists & inhibitors; Oxidoreductases/genetics; Oxidoreductases/metabolism; RNA, Bacterial/genetics; RNA, Bacterial/metabolism; RNA, Messenger/genetics; RNA, Messenger/metabolism; RNA, Ribosomal, 16S/genetics; RNA, Ribosomal, 16S/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
9PROT:O53984		GO:0004497: monooxygenase activity	ECO:0000270:		F		Figure 5 shows that amoA mRNA decreases during ammonium starvation and increases at ammonium introduction, while 16S rRNA levels do not change.	complete

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