Proteome Analysis of Enriched Heterocysts from Two Hydrogenase Mutants from Anabaena sp. PCC 7120

Abstract

Cyanobacteria are oxygenic photosynthetic prokaryotes and play a crucial role in the Earth's carbon and nitrogen cycles. The photoautotrophic cyanobacterium Anabaena sp. PCC 7120 has the ability to fix atmospheric nitrogen in heterocysts and produce hydrogen as a byproduct through a nitrogenase. In order to improve hydrogen production, mutants from Anabaena sp. PCC 7120 are constructed by inactivation of the uptake hydrogenase (ΔhupL) and the bidirectional hydrogenase (ΔhoxH) in previous studies. Here the proteomic differences of enriched heterocysts between these mutants cultured in N2‐fixing conditions are investigated. Using a label‐free quantitative proteomics approach, a total of 2728 proteins are identified and it is found that 79 proteins are differentially expressed in the ΔhupL and 117 proteins in the ΔhoxH variant. The results provide for the first time comprehensive information on proteome regulation of the uptake hydrogenase and the bidirectional hydrogenase, as well as systematic data on the hydrogen related metabolism in Anabaena sp. PCC 7120.

Proteogenomic Analysis Provides Novel Insight into Genome Annotation and Nitrogen Metabolism in Nostoc sp. PCC 7120

“…Our proteogenomic strategy unambiguously identified 5,519 proteins by at least two unique peptides or by a single peptide combined with manual validation, which confirmed 5,519 proteins already annotated in CyanoBase database. To our knowledge, this is the most comprehensive annotation of Nostoc 7120 genome to date ( 37 , 38 ). Figure 2A depicts the distributions of all known peptides identified from each search engine.…”

Photosynthetic hydrogen production: Novel protocols, promising engineering approaches and application of semi‐synthetic hydrogenases

“…To achieve a greater understanding of how cell metabolism and bioenergetics navigate during H 2 photoproduction and to identify potential targets for further metabolic engineering, a system‐level omics approach, which includes genomics, transcriptomics, proteomics, and metabolomics analysis, is necessary. Most of the omics approaches have been focused on understanding the metabolism of nitrogenase‐based H 2 production (see, e.g., Aryal et al, 2013; Bernstein et al, 2015; Ekman et al, 2011; Kourpa et al, 2019; Sadler et al, 2016; Stensjö et al, 2007). The differential proteomes of N 2 ‐fixing and non‐N 2 ‐fixing cultures of both Nostoc sp.…”

“…4.0% (in the PAR region) and a maximal hydrogen concentration of 6.89%. However, it is also important to note that inactivation of uptake hydrogenase reprograms cell metabolism (Ekman et al, 2011; Kourpa et al, 2019) and may significantly decrease the duration of the H 2 production process and cell fitness, particularly under a high C/N environment (Kosourov et al, 2014).…”

Quantitative Proteomics Reveals the Protein Regulatory Network of Anabaena sp. PCC 7120 under Nitrogen Deficiency

“…Cyanobacteria are a group of multiform Gram-negative prokaryotes that perform oxygenic photosynthesis, which can assimilate inorganic nutrients from the environment and act a pivotal role in the global carbon and nitrogen cycles. , Their growth can be restricted by the exhausted essential nutrients, such as nitrogen, iron, and phosphate . In the absence of combined nitrogen, some species of diazotrophic filamentous cyanobacteria can differentiate into heterocysts, a process that contributes to balance nitrogen fixation and photosynthesis and to protect oxygen-sensitive nitrogenase from oxygen in the environment. , In addition, diazotrophic cyanobacteria regulate their energy metabolism and photosynthetic system to favor nitrogen fixation upon nitrogen starvation. − Hence, cyanobacteria have developed a wide array of molecular mechanisms to respond to nitrogen deficiency …”

“…It is noteworthy that the differentiation process can be inhibited if the nitrogen source is replenished during the time period of 9 to 12 h . By 24 h, the period of adaptation to the nitrogen deficiency, nearly all the heterocysts are mature with a full ability to fix nitrogen for the growth of cyanobacterial cells. , Although proteomic analyses have revealed the cellular mechanisms for nitrogen fixation and heterocyst differentiation in Anabaena 7120, − the previous studies on Anabaena 7120 focused mostly on the proteome changes caused by individual gene deletions or the specific proteomic changes occurring at a certain point after exposure to nitrogen stress. ,,− Additionally, these previous studies present several limitations due to the immaturity of the technology at the time they were published, such as low coverage of the proteome. Thus, it is necessary to explore the overall dynamic changes in the intracellular proteome of Anabaena 7120 in response to nitrogen stress with the proteomic technologies available nowadays.…”