Project description:Saccharomyces cerevisiae normally cannot assimilate mannitol, a promising brown macroalgal carbon source for bioethanol production. To date, the molecular mechanisms underlying this inability remain unknown. Here, we found that cells acquiring mannitol-assimilating ability appeared from wild-type S. cerevisiae strain during prolonged culture in mannitol medium. Our microarray analysis revealed that genes for putative mannitol dehydrogenase and hexose transporters were up-regulated in cells acquiring mannitol-assimilating ability. Take account of our other results including complementation analysis and cell growth data, we demonstrated that this acquisition of mannitol-assimilating ability was due to the spontaneous mutation in the gene encoding Tup1 or Cyc8. Tup1-Cyc8 is the general corepressor complex involved in the repression of many kinds of genes. Thus, it is suggested that the inability of wild-type S. cerevisiae to assimilate mannitol can be attributed to the transcriptional repression of a set of genes involved in mannitol utilization by Tup1-Cyc8 corepressor. In other words, Tup1-Cyc8 is a key regulator of mannitol metabolism in S. cerevisiae. We also showed that S. cerevisiae strain which carries mutant allele of TUP1 or CYC8 produced ethanol from mannitol efficiently. Especially, strain carrying mutant allele of CYC8 showed high tolerance to salt, which is superior to other ethanologenic microorganisms. This characteristic is highly beneficial to produce bioethanol from marine biomass. Taken together, Tup1-Cyc8 can be an ideal target to develop a yeast-algal bioethanol production system. To figure out how Mtl+ strains (cells acquiring ability to grow in mannitol medium) had acquired the ability to assimilate mannitol, we performed genome-wide analysis by using Nimblegen microarrays. Yeast Saccharomyces cerevisiae cells (wild-type BY4742 strain and two Mtl+ strains, MK3619 and MK3683) were grown at 30Â°C to the logarithmic phase in SC or SM media. Total RNA was purified and the 4 RNA samples (BY4742 cells in SC as control, MK3619 cells in SM, MK3683 cells in both SC and SM) were analyzed with Nimblegen microarrays.

Project description:Here, we established for the first time a proteomic analysis of B. methanolicus MGA3, and we used this approach to compare cells grown on methanol and mannitol at 50°C as well as cells grown on methanol at 37°C and 50°C. Bacillus methanolicus MGA3 is a facultative methylotroph of industrial relevance that is able to grow on methanol as its sole source of carbon and energy. The Gram-positive bacterium possesses a soluble NAD-dependent methanol dehydrogenase and assimilates formaldehyde via the ribulose monophosphate (RuMP) cycle. We used label-free quantitative proteomics to generate reference proteome data for this bacterium and compared the proteome of B. methanolicus MGA3 on two different carbon sources (methanol and mannitol) as well as two different growth temperatures (50°C and 37°C). From a total of approximately 1,200 different detected proteins, approximately 1,000 of these were used for quantification. While the levels of 213 proteins were significantly different at the two growth temperatures tested, the levels of 109 proteins changed significantly when cells were grown on different carbon sources. The carbon source strongly affected the expression of enzymes related to carbon metabolism, and in particular, both dissimilatory and assimilatory RuMP cycle enzyme levels were elevated during growth on methanol compared to mannitol. Our data also indicate that B. methanolicus has a functional TCA cycle that is differentially regulated on mannitol and methanol. Other proteins presumed to be involved in growth on methanol were constitutively expressed under the different growth conditions. Protein Identification: Raw data of gel slices with equal molecular weight were loaded together into the software package Progenesis LCMS Version. 4.1 (www.nonlinear.com), a software tool developed for label-free quantification of LC–MS data. Data was analyzed according to Progenesis LCMS analysis in Weisser et al., In brief, for data loading, the option "High Mass Accuracy Instrument" was selected. LC–MS data were normalized and aligned according to manufacturer’s specifications. In the aligning step manual seeding of "three to five" vectors along the retention time gradient was performed followed by automatic alignment. For the identification of peptide features in the corresponding mass spectrometry files, Mascot generic files (.mgf file format) are generated with Progenesis LCMS (using up to five tandem mass spectra for each feature with the top 200 fragment ion peaks ,charge deconvolution and de-isotopting activated). Mgf files were searched by Mascot 2.3 search engine against an amino acid database containing 20,399 entries including 3,418 MGA3 annotated proteins (downloaded from Uniprot on August 2013), 6,651 yeast proteins, 261 known mass spectrometry contaminants as forward entries and from all forward entries except the contaminats, a reverse decoy sequence. Parameters for precursor tolerance and fragment ion tolerance were set to ± 10 ppm and ± 0.6 Da, respectively. Mascot results were loaded into Scaffold v4.05, using the options for protein clustering and high mass accuracy PeptideProphet scoring.

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Comparative analysis of global gene expression profiles of Bacillus methanolicus MGA3 during growth with arabitol or mannitol

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