Project description:Nitrification, the oxidation of ammonia via nitrite to nitrate, has always been considered to be a two-step process catalysed by chemolithoautotrophic microorganisms oxidizing either ammonia or nitrite. No known nitrifier carries out both steps, although complete nitrification should be energetically advantageous. This functional separation has puzzled microbiologists for a century. Here we report on the discovery and cultivation of a completely nitrifying bacterium from the genus Nitrospira, a globally distributed group of nitrite oxidizers. The genome of this chemolithoautotrophic organism encodes the pathways both for ammonia and nitrite oxidation, which are concomitantly activated during growth by ammonia oxidation to nitrate. Genes affiliated with the phylogenetically distinct ammonia monooxygenase and hydroxylamine dehydrogenase genes of Nitrospira are present in many environments and were retrieved on Nitrospira contigs in new metagenomes from engineered systems. These findings fundamentally change our picture of nitrification and point to completely nitrifying Nitrospira as key components of nitrogen-cycling microbial communities.
Project description:Nitrite-oxidizing bacteria are vital players in the global nitrogen cycle that convert nitrite to nitrate during the 2nd step of nitrification. Within this functional guild, the genus Nitrospira is among the most widespread and phylogenetically and physiologically diverse nitrite oxidizers and its members drive nitrite oxidation in many natural and biotechnological ecosystems. Despite their ecological and biotechnological importance, our understanding of Nitrospira’s energy metabolism is still limited. The main bottleneck for a detailed biochemical characterization of Nitrospira is biomass production, since they are slow-growing organisms and fastidious to culture. In this study, we cultured Nitrospira moscoviensis in a continuous stirred tank reactor system (CSTR) allowing constant biomass harvesting. Additionally, this cultivation setup enabled accurate control of physicochemical parameters and thus avoided fluctuating levels of nitrite and accumulation of nitrate. We performed transcriptome analysis and confirmed constant gene expression profiles in the chemostat culture over a period of two weeks. The transcriptomic data supports the predicted core metabolism of N. moscoviensis, including the reductive TCA cycle as a CO2 fixation pathway, the novel bd-like oxidase as terminal oxidase and the octaheme nitrite reductase involved in nitrogen assimilation. Additionally, the expression of multiple copies of respiratory complexes suggests functional differentiation of these copies within the respiratory chain. Transcriptome analysis also suggests a soluble and a membrane-bound gamma subunit as part of the nitrite oxidoreductase (NXR), the enzyme catalyzing nitrite oxidation. Overall, the transcriptome data provided novel insights into the metabolism of Nitrospira supporting the genome-based prediction of key pathways. Moreover, the application of a CSTR to cultivate Nitrospira is an important foundation for future proteomic and biochemical characterizations, which are crucial for a better understanding of canonical and complete nitrifying microorganisms.
Project description:The etiologic agent of bubonic plague, Yersinia pestis, senses cell density-dependent chemical signals to synchronize transcription between cells of the population in a process named quorum sensing. Though the closely related enteric pathogen Y. pseudotuberculosis uses quorum sensing system to regulate motility, the role of YpeIR quorum sensing in Y. pestis has been unclear. YpeIR is one of the AHL quorum sensing system in Y. pestis. In this study we performed transcriptional profiling experiments to identify Y. pestis YpeIR quorum sensing regulated functions at 37°C.
Project description:Investigation of gene expression dynamics associated with male strobilus induction in Cryptomeria japonica in response to gibberellic acid (GA) treatment. [SUBMITTER_CITATION]: Transcriptome Analysis in Male Strobilus Induction by Gibberellin Treatment in Cryptomeria japonica D. Don Manabu Kurita 1,?, Kentaro Mishima 2,*,? , Miyoko Tsubomura 2, Yuya Takashima 2 , Mine Nose 2, Tomonori Hirao 2 and Makoto Takahashi 2 Forests 2020, 11(6), 633
Project description:Improvement of chilling tolerance is a key strategy to face potential menace from abnormal temperature in rice production, which depends on the signaling network triggered by receptors. However, little is known about the QTL genes encoding membrane complexes for sensing cold. Here, Chilling-tolerance in Gengdao/japonica rice 1 (COG1) was isolated from a chromosome segment substitution line containing a QTL (qCS11-jap) for chilling sensitivity. The major gene COG1 was found to confer chilling tolerance in japonica rice. In natural rice populations, only the haplogroup1 encoded a functional COG1. Evolutionary analysis showed that COG1 originated from Chinese O. Rufipogon and was fixed in japonica rice during domestication. COG1, a membrane-localized LRR-RLP, targeted and activated the kinase OsSERL2 in a cold-induced manner, promoting chilling tolerance. Furthermore, the cold signal transmitted by COG1-OsSERL2 activates OsMAPK3 in the cytoplasm. Our findings reveal a cold-sensing complex, which mediates signaling network for the chilling defense in rice.