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GNPS - Growth Rate-Dependent Coordination of Catabolism and Anabolism in the Archaeon Methanococcus maripaludis under Phosphate Limitation

ABSTRACT: Catabolic and anabolic processes are finely coordinated in microbes to provide optimized fitness under varying environmental conditions. Understanding this coordination and the resulting physiological traits identifies fundamental microbial strategies of acclimation. Here, we characterized the systems-level physiology of Methanococcus maripaludis, a niche-specialized methanogenic archaeon, at different growth rates under phosphate (i.e., anabolic) limitation. We observed a decoupling of catabolism and anabolism resulting in lower biomass yield relative to catabolically limited cells. In addition, the mass abundance of several coarse-grained proteome sectors exhibited a linear relationship with growth rate, most notably ribosomes and their biogenesis. Accordingly, cellular RNA content also correlated with growth rate. Although the methanogenesis proteome sector was invariant, the metabolic capacity for methanogenesis correlated with growth rate suggesting translationally independent regulation. These observations are in stark contrast to the physiology of M. maripaludis under formate (i.e., catabolic) limitation, where cells keep an invariant proteome including ribosomal content and a high methanogenesis capacity across a wide range of growth rates. Our findings reveal that although highly niche-specialized, M. maripaludis employs fundamentally different strategies to coordinate global physiology during anabolic phosphate and catabolic formate limitation.

INSTRUMENT(S): TripleTOF 5600

ORGANISM(S): Methanococcus Maripaludis S2 (ncbitaxon:267377)

SUBMITTER: Alfred M. Spormann James R. Williamson

PROVIDER: MSV000087621 | GNPS | Mon Jun 14 20:32:00 BST 2021

SECONDARY ACCESSION(S): PXD026700

REPOSITORIES: GNPS

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Project description:Hydrogenotrophic methanogenic Archaea are defined by a H2 requirement for growth. Despite this requirement, many hydrogenotrophs are also capable of growth with formate as an electron donor for methanogenesis. Hydrogenotrophs respond to H2 starvation both phenotypically and at the level of gene expression; however, the responses during growth on formate have not been characterized. Here we report that during continuous culture of Methanococcus maripaludis under defined nutrient conditions, growth yields relative to methane production decreased markedly with either H2 excess or formate excess, suggesting that energy spilling occurs. Using microarray analysis, we show that the expression of genes encoding F420-dependent steps of methanogenesis, including one of two formate dehydrogenases, increased with H2 starvation, but with formate occurred at high levels regardless of limitation or excess. One gene, encoding H2-dependent methylene-tetrahydromethanopterin dehydrogenase, decreased in expression with either H2 limitation or formate limitation. Expression of genes for the second formate dehydrogenase, molybdenum-dependent formylmethanofuran dehydrogenase, and molybdenum transport increased specifically with formate limitation. Of the two formate dehydrogenases, only the first could support growth on formate in batch culture where formate was in excess. The strain was grown by continuous culture in a one-liter fermenter (New Brunswick Scientific, Edison, NJ) at 37M-BM-0C (FEMS Microbiol Lett 238: 85-91, 2004). Medium and gas compositions were modified from those for non-limiting conditions (BMC Microbiol 9: 149, 2009). The medium contained 380 mM sodium formate in place of NaCl. The agitation rate was 250 revolutions per minute. The gas mixture initially supplied to the chemostat was H2/Ar/CO2/1% H2S (21/125/40/14 mLs min-1) (Proc Natl Acad Sci USA 104: 8930-8934, 2007). After the OD increased above 0.6 (24 h), the medium flow was turned on at 0.083 L/h. Medium was either non-limiting (described above), formate limiting (modified to contain 200 mM sodium formate and 180 mM NaCl), nitrogen limiting (2 mM NH4Cl), or phosphate limiting (0.08 mM K2HPO4). Also at this point, gas flow through the vessel was shut off, a 1 psi check valve was installed on the exhaust line to maintain positive pressure within the vessel while also allowing for exhaust of gaseous metabolic byproducts, and a 1% Na2S9H2O feed was started into the vessel at 0.83 mL/h. 48 hours later, samples were taken for physiological measurements or microarray analysis. Samples were collected for microarray analysis as follows: 1.5 mLs of chemostat culture (OD660 ~0.65) was centrifuged at 13,000 x g for 30 seconds and supernatant was discarded. The pellet was immediately placed in a dry ice/ethanol bath and stored at -80C until RNA extraction and microarrays could be performed. Total RNA from each sample was compared against a reference RNA pool that was generated in bulk from a mid-log phase culture of MM901. Total RNA from samples and reference were directly labeled with Cy3 or Cy5, and were hybridized to the tiling array. After hybridization and washing according to array manufacturer's instructions, the arrays were scanned by Microarray Scanner (Agilent Technologies, Santa Clara, CA). Dye-flip experiments were done for each sample.

Project description:Cheap and renewable feedstocks such as the one carbon substrate formate are emerging for sustainable production in a growing chemical industry. By quantitatively analyzing physiology, transcriptome, proteome in chemostat cultivations in combination with computational analyses, we investigated the acetogen Acetobacterium woodii as a potential host for bioproduction from formate alone and together with autotrophic and heterotrophic co-substrates. Continuous cultivations with a specific growth rate of 0.05 h-1 on formate showed high specific substrate uptake rates (47 mmol g‑1 h‑1). Co-utilization of formate with H2, CO, CO2 or fructose was achieved without catabolite repression and with acetate as the sole metabolic product. A transcriptomic comparison of all growth conditions revealed a distinct adaptation of A. woodii to growth on formate as 570 genes were changed in their transcription. Transcriptome and proteome showed higher expression of the Wood-Ljungdahl pathway during growth on formate and gaseous substrates, underlining its function during utilization of one carbon substrates. Flux balance analysis showed varying flux levels for the WLP (0.7-16.4 mmol/g/h) and major differences in redox and energy metabolism. Growth on formate, H2/CO2, and formate+H2/CO2 resulted in low energy availability (0.20-0.22 ATP/acetate) which was increased during co-utilization with CO or fructose (0.31 ATP/acetate for formate+H2/CO/CO2, 0.75 ATP/acetate for formate+fructose). Unitrophic and mixotrophic conversion of all substrates was further characterized by high energetic efficiencies. In silico analysis of bioproduction of ethanol and lactate from formate and autotrophic and heterotrophic co-substrates showed promising energetic efficiencies (70-92%). Collectively, our findings reveal A. woodii as a promising host for flexible and simultaneous bioconversion of multiple substrates, underline the potential of substrate co-utilization to improve the energy availability of acetogens and encourage metabolic engineering of acetogenic bacteria for the efficient synthesis of bulk chemicals and fuels from sustainable one carbon substrates.

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GNPS - Growth Rate-Dependent Coordination of Catabolism and Anabolism in the Archaeon Methanococcus maripaludis under Phosphate Limitation

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