IV. RESULTS AND DISCUSSION
2.4.2.4. Identification of stress response masses
2.4.2.4. Identification of stress response masses
As for the growth curves metabolomes, all masses found to be increased or decreased in each of the different stress responses were crosschecked using the MassTRIX database, and the annotation was done using the published genome of the M31 strain as a reference (Mongodin et al., 2005). The metabolome modifications occurring under the different stress conditions assayed rendered similar percentages of annotable metabolites. Only 13% of the total stress discriminative masses (increased or decreased) could be identified, whereas the rest remained unidentified. Of the annotated masses, 28% could be associated to glycerolipid, glycerophospholipid and fatty acid metabolisms, and to the biosynthesis of unsaturated fatty acid pathways, being the most important those shown in Tables 18, 19, and 20. Although the rest of the identified metabolites were associated to alpha-‐linolenic acid (13%), glyoxylate and dicarboxylate (9%) and cyano-‐aminoacids (6%) metabolisms, and 44% were distributed in different metabolic pathways (Table S2, S3, S4). These metabolites did not allow us to speculate about a clear physiological response of S. ruber during the stress conditions.
However, the analysis of metabolites associated to lipids and phospholipids showed that all three stresses produced a different transition on the fatty acid saturation/unsaturation ratios and in the length of their acyl chains. These results are consistent with the fact that, under environmental stress conditions, specific alterations in the membrane lipid–fatty acid composition are required for survival of the cell and, concurrently, the membrane lipids are suggested to serve as endogenous reserves providing carbon/energy for maintenance requirements (DiRusso & Nystrom, 1998).. To mantain the membrane fluidity and functions, enzymatic remodeling or degradation of fatty acids and lipids can occur (DiRusso & Nystrom, 1998).. In this sense, glycerophospholipids can alter their acyl chain structure by changing the ratio of (1) saturation to unsaturation, (2) cis to trans unsaturation, (3) branched to unbranched structures and type of branching, and (4) acyl chain length (Denich et al, 2003)(Figure 26). These alterations can occur simultaneously to achieve the desired level of fluidity, in this case, during anoxia, phospholipids with a high number of double bonds (such as 1-‐Acyl-‐sn-‐glycerol 3-‐phosphate (R=C23:10); Table 18) decreased in intensity (especially in the cellular soluble and insoluble fractions), while phospholipids with a low number of double bonds (such as 1-‐Acyl-‐sn-‐
glycerol 3-‐phosphate (R=C12:5)) increased (mainly in the extracellular fraction). These results were consistent with the description of the masses shown in Table 17, where the number of masses that increased during anoxia was higher in the extracellular fraction. Similarly, during dilution stress the phospholipids with a high number of double bonds decreased in intensity or remained undetected (especially in the cellular soluble and insoluble fractions), while phospholipids with a low number of double bonds increased (Table 19).
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Table 18. Proposed elemental composition of common masses increased or decreased under oxygen stress conditions (16 h) and identified by the Masstrix database. The intensity of masses and the metabolic pathways involved are also specified. * R=Cn:N; indicates the characteristics of acyl chains, where Cn is the number of carbons (length) comprising the chains and N the number of double bonds. UD= under detection limit; S= detected under stress condition; I= increased value with respect to the control; D= decreased value with respect to the control. Values in brackets represent number of times.
Detection Cellular
fraction Exp m/z Proposed
composition Proposed name Intensity
of peak Metabolic pathways involved Decreased CI 387.13678 C14H24N2O9 N-‐Acetylmuramoyl-‐Ala (H+ replaced by Na+) UD Peptidoglycan biosynthesis Decreased CS 447.12901 C18H25NO10P 2-‐Acyl-‐sn-‐glycero-‐phosphoserine(R=C10:4)* UD Glycerophospholipid metabolism Decreased CS 404.18218 C18H30NO7P 1-‐Acyl-‐sn-‐glycero-‐3-‐phosphocholine(R=C9:4) UD Glycerophospholipid metabolism Decreased CS 404.18218 C18H30NO7P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphocholine(R=C9:4) UD Glycerophospholipid metabolism Decreased CS 443.20527 C19H35NO7P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoethanolamine
(R=C13:2) (H+ replaced by Na+) UD Glycerophospholipid metabolism Decreased CI 446.22852 C19H38NO7P 1-‐Acyl-‐sn-‐glycero-‐3-‐phosphocholine(R=C10:1)
(H+ replaced by Na+) UD Glycerophospholipid metabolism
Decreased CI 446.22852 C19H38NO7P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphocholine(R=C10:1)
(H+ replaced by Na+) UD Glycerophospholipid metabolism
Decreased CS 412.17283 C20H27O9 sn-‐3-‐D-‐Galactosyl-‐sn-‐2-‐acylglycerol (R=C10:5) UD Glycerolipid metabolism Decreased CS 507.12640 C21H25NO10P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoserine (R=C13:6)
(H+ replaced by Na+) UD Glycerophospholipid metabolism
Decreased CS 502.21295 C27H34O7P 1-‐Acyl-‐sn-‐glycerol 3-‐phosphate (R=C23:10) D (0.8) Glycerolipid and Glycerophospholipid metabolism
Decreased CI 529.31653 C27H47NO7P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoethanolamine
(R=C21:4) UD Glycerophospholipid metabolism
Decreased CS 548.29451 C28H45O9 sn-‐3-‐D-‐Galactosyl-‐sn-‐2-‐acylglycerol (R=C18:4)
(H+ replaced by Na+) UD Glycerolipid metabolism
Decreased CS 631.25129 C30H43NO10P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoserine (R=C22:7)
(H+ replaced by Na+) UD Glycerophospholipid metabolism
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Table 18. Proposed elemental composition of common masses increased or decreased under oxygen stress conditions (16 h) and identified by the Masstrix database.
Detection Cellular
fraction Exp m/z Proposed
composition Proposed name Intensity
of peak Metabolic pathways involved Decreased CI 699.40732 C34H63NO10P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoserine (R=C26:1)
(H+ replaced by Na+) UD Glycerophospholipid metabolism
Decreased CS 723.40814 C36H63NO10P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoserine (R=C28:3)
(H+ replaced by Na+) UD Glycerophospholipid
metabolism
Increased CI 358.11679 C16H22O7P 1-‐Acyl-‐sn-‐glycerol 3-‐phosphate (R=C12:5) I(2) Glycerolipid and Glycerophospholipid metabolism
Increased CS 296.19776 C17H27O4 1-‐Acylglycerol (R=C13:3) S Glycerolipid metabolism
Increased E 451.16090 C18H29NO10P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoserine (R=C10:2) I(1.5) Glycerophospholipid metabolism Increased E 307.26076 C18H36O2 Octadecanoic acid (H+ replaced by Na+) I (3) Unsaturated fatty acids biosynthesis Increased E 329.24518 C20H34O2 (8Z,11Z,14Z)-‐Icosatrienoic acid (H+ replaced by Na+) S Unsaturated fatty acids biosynthesis Increased E 391.35464 C24H48O2 Tetracosanoic acid (H+ replaced by Na+) I (4) Unsaturated fatty acids biosynthesis Increased CI 575.28350 C25H47NO10P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoserine (R=C17:0)
(H+ replaced by Na+) I (3) Glycerophospholipid metabolism
Increased CI 522.35542 C26H52NO7P 1-‐Acyl-‐sn-‐glycero-‐3-‐phosphocholine (R=C17:1) I (8) Glycerophospholipid metabolism Increased CI 522.35542 C26H52NO7P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphocholine (R=C17:1) I (8 ) Glycerophospholipid metabolism Increased E 664.52743 C36H74NO7P 1-‐Acyl-‐sn-‐glycero-‐3-‐phosphocholine (R=C27:0) S Glycerophospholipid metabolism Increased E 664.52743 C36H74NO7P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphocholine (R=C27:0) S Glycerophospholipid metabolism Increased E 658.49988 C37H69O9 sn-‐3-‐D-‐Galactosyl-‐sn-‐2-‐acylglycerol (R=C27:1) S Glycerolipid metabolism
Results and Discussion: Chapter 2
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The opposite situation was observed for temperature stress, where compounds with a high number of double bonds increased or were detected only under stress (for example, 1-‐Acyl-‐sn-‐glycero-‐3-‐
phosphocholine (R=C18:6)). Saturated compounds, such as 1-‐Acyl-‐sn-‐glycero-‐3-‐phosphocholine (R=C10:1), were reduced or remained undetected (Table 20). In this case, all identified compounds corresponded to CS and CI fractions, which disagree with the observation that membrane proteins, lipopolysaccharide, glycerophospholipids and enzymes could be released during temperature stress (Denich et al., 2003), since these kind of compounds were not recognized in the extracellular fraction.
Figure 26: Possible glycerophospholipids modifications during environmental changes. The fluidity of biological membranes is influenced by changes in the phospholipids composition that involve modifications in the polar head groups (where R could be serine, choline, ethanolamine, glycerol, or inositol) and variations in the length and/or saturation level of their fatty acids chains (Denich et al., 2003).
A similar response was observed in the changes of the length of the acyl-‐chains of phospholipids under all stress conditions. For example, compounds with long acyl-‐chains (R=C26 to C28), such as 2-‐Acyl-‐sn-‐glycero-‐3-‐
phosphoserine (R=C28:3), decreased in intensity or remained undetected, whereas compounds with short acyl-‐chains (R=C10 to C17) increased (Tables 18 and 19). Exceptions to this rule were 1 and 2-‐Acyl-‐glycero-‐3-‐
phosphocholine, with short acyl-‐chains and low unsaturation (R=C10:1) that remained undetected during all stress conditions (Tables 18, 19 and 20); and the 1 and 2-‐Acyl-‐glycero-‐3-‐phosphocholine with long but saturated acyl chains (R=C27:0) that were detected only under oxygen depletion (Table 18).
In this sense, fatty acids with short chains have lower melting points than longer chain length. In addition, longer chains promotes the packaging of the acyl chains making the membrane environment more gel-‐like (Russell, 1989). Shorter chains, especially those with less than 12 carbons, cannot form hydrophobic interactions with other lipids and proteins, increasing the fluidity and inestability due to the motion of the free acyl chans ends (Denich et al., 2003).
Results and Discussion: Chapter 2
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Thereby, different interactions between these compounds would lead to adopt an optimal membrane fluidity preventing the collapse of the cells under adverse conditions since the adaptation to fluctuating fluidity conditions through chain lenght alterations can only be conducted in growing cells (Russell, 1989).
Also, during oxygen depletion, cell envelope components such as N-‐Acetylmuramoyl-‐Ala, involved in the first steps of biosynthesis of peptidoglycan, decreased (Table 20). The peptidoglycan of the cell wall is the primary stress-‐bearing structure that dictates cell shape, and cell shape can be also altered either genetically or environmentally (Huang et al., 2008). The decrease in these compounds could also be related to modificacions in the membrane composition which might have forced the cells to change shape as part of the adaptation process to the new environment or simply, cells were unable to synthetize these compounds in absent of oxygen, which also coud influence the cell structure.
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Table 19. Proposed elemental composition of common masses increased or decreased under dilution stress conditions (16 h) and identified by the Masstrix database. The intensity of masses and the metabolic pathways involved are also specified. * R=Cn:N; indicates the characteristics of acyl chains, where Cn is the number of carbons (length) comprising the chains and N the number of double bonds. UD= under detection limit; S= detected under stress condition; I= increased value with respect to the control; D= decreased value with respect to the control. Values in brackets represent the number of times.
Detection Cellular
fraction Exp. m/z Proposed
composition Proposed name Intensity
of peak Metabolic pathways involved Decreased CS 447.12901 C18H25NO10P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoserine (R=C10:4)* UD Glycerophospholipid metabolism Decreased CI 446.22852 C19H38NO7P 1-‐Acyl-‐sn-‐glycero-‐3-‐phosphocholine (R=C10:1)
(H+ replaced by Na+) UD Glycerophospholipid metabolism
Decreased CI 446.22852 C19H38NO7P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphocholine (R=C10:1)
(H+ replaced by Na+) UD Glycerophospholipid metabolism
Decreased CS 412.17283 C20H27O9 sn-‐3-‐D-‐Galactosyl-‐sn-‐2-‐acylglycerol (R=C10:5) UD Glycerolipid metabolism Decreased CS 507.12640 C21H27NO10P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoserine (R=C13:6)
(H+ replaced by Na+) UD Glycerophospholipid metabolism
Decreased CS 537.17354 C23H33NO10P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoserine (R=C15:5)
(H+ replaced by Na+) UD Glycerophospholipid metabolism
Decreased CI 503.20478 C24H35NO7P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoethanolamine
(R=C18:7) (H+ replaced by Na+) UD Glycerophospholipid metabolism Decreased CS 575.28344 C25H47NO10P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoserine (R=C17:0)
(H+ replaced by Na+) UD Glycerophospholipid metabolism
Decreased CS 502.21295 C27H34O7P 1-‐Acyl-‐sn-‐glycerol 3-‐phosphate (R=C23:10) UD Glycerolipid and
Glycerophospholipid metabolism Decreased CI 529.31653 C27H47NO7P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoethanolamine
(R=C21:4) UD Glycerophospholipid metabolism
Decreased CS 631.25137 C30H43NO10P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoserine (R=C22:7)
(H+ replaced by Na+) D (0.2) Glycerophospholipid metabolism
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Table 19. Proposed elemental composition of common masses increased or decreased under dilution stress conditions (16 h) and identified by the Masstrix database
Detection Cellular
fraction Exp. m/z Proposed
composition Proposed name Intensity
of peak Metabolic pathways involved Decreased CS 596.38499 C33H56O7P 1-‐Acyl-‐sn-‐glycerol 3-‐phosphate (R=C29:5) UD Glycerolipid and
Glycerophospholipid metabolism Decreased CS 723.40814 C36H63NO10P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoserine (R=C28:3)
(H+ replaced by Na+) UD Glycerophospholipid metabolism
Increased CI 302,06374 C8H16NO9P N-‐Acetyl-‐D-‐glucosamine 6-‐phosphate S Aminosugars metabolism and Phosphotransferase system (PTS) Increased CI 302,06374 C8H16NO9P N-‐Acetyl-‐D-‐mannosamine 6-‐phosphate S Aminosugars metabolism Increased CI 302,06374 C8H16NO9P N-‐Acetyl-‐alpha-‐D-‐glucosamine 1-‐phosphate S Aminosugars metabolism Increased CI 302,06374 C8H16NO9P N-‐Acetyl-‐D-‐galactosamine 6-‐phosphate S Galactose metabolism and
Phosphotransferase system (PTS) Increased CI 358,11683 C16H22O7P 1-‐Acyl-‐sn-‐glycerol 3-‐phosphate (R=C12:5) I(2) Glycerolipid metabolism
Glycerophospholipid metabolism
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Table 20. Proposed elemental composition of common masses increased or decreased under temperature stress conditions (16 h) and identified by the Masstrix database. The intensity of masses and the metabolic pathways involved are also specified. * R=Cn:N; indicates the characteristics of acyl chains, where Cn is the number of carbons (length) comprising the chains and N the number of double bonds. UD= under detection limit; S= detected under stress condition; I= increased value with respect to the control. Values in brackets represent the number of times.
Detection Cellular
fraction Exp m/z Proposed
composition Proposed name Intensity
of peak Metabolic pathways involved Decreased CS 447.12901 C18H25NO10P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoserine (R=C10:4) UD Glycerophospholipid metabolism Decreased CS 446.22842 C19H38NO7P 1-‐Acyl-‐sn-‐glycero-‐3-‐phosphocholine (R=C10:1)
(H+ replaced by Na+) UD Glycerophospholipid metabolism
Decreased CI 446.22842 C19H38NO7P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphocholine (R=C10:1)
(H+ replaced by Na+) UD Glycerophospholipid metabolism
Decreased CS 507.12640 C21H27NO10P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoserine (R=C13:6)
(H+ replaced by Na+) UD Glycerophospholipid metabolism
Decreased CI 503.20478 C24H35NO7P
2-‐Acyl-‐sn-‐glycero-‐3 phosphoethanolamine (R=C18:7)
(H+ replaced by Na+)
UD Glycerophospholipid metabolism Decreased CI 554.33586 C28H52O7P 1-‐Acyl-‐sn-‐glycerol 3-‐phosphate (R=C24:2)
(H+ replaced by Na+) UD Glycerolipid and Glycerophospholipid
metabolism
Decreased CI 554.33586 C30H50O7P 1-‐Acyl-‐sn-‐glycerol 3-‐phosphate (R=C26:5) UD Glycerolipid and Glycerophospholipid metabolism
Decreased CS 723.40814 C36H63NO10P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoserine (R=C28:3)
(H+ replaced by Na+) UD Glycerophospholipid metabolism
Increased CI 216.13584 C11H19O4 1-‐Acylglycerol (R=C7:1) I (3) Glycerolipid metabolism
Increased CI 358.11682 C16H22O7P 1-‐Acyl-‐sn-‐glycerol 3-‐phosphate (R=C12:5) I (3) Glycerolipid and Glycerophospholipid metabolism
Increased CS 296.19782 C17H27O4 1-‐Acylglycerol (R=C13:3) S Glycerolipid metabolism
Increased CI 425.15708 C18H29NO7P 2-‐Acyl-‐sn-‐glycero-‐phosphoethanolamine (R=C12:4)
(H+ replaced by Na+) S Glycerophospholipid metabolism
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Table 20. Proposed elemental composition of common masses increased or decreased under temperature stress conditions (16 h) and identified by the Masstrix database
Detection Cellular
fraction Exp m/z Proposed
composition Proposed name Intensity
of peak Metabolic pathways involved Increased CI 443.20501 C19H35NO7P 2-‐Acyl-‐sn-‐glycero-‐phosphoethanolamine (R=C13:2)
(H+ replaced by Na+) I (3) Glycerophospholipid metabolism
Increased CS 497.14391 C22H27NO10P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoserine (R=C14:7) I (1.5) Glycerophospholipid metabolism Increased CS 450.27458 C22H42O7P 1-‐Acyl-‐sn-‐glycero-‐3-‐phosphate (R=C18:1) S Glycerolipid and Glycerophospholipid
metabolism
Increased CS 450.27458 C27H39O4 1-‐Acylglycerol (R=C23:7) (H+ replaced by Na+) S Glycerolipid metabolism Increased CS 504.30932 C25H46NO7P 1-‐Acyl-‐sn-‐glycero-‐3-‐phosphocholine (R=C16:3) S Glycerophospholipid metabolism Increased CS 504.30932 C25H46NO7P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphocholine (R=C16:3) S Glycerophospholipid metabolism Increased CI 575.28348 C25H47NO10P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphoserine (R=C17:0)
(H+ replaced by Na+) I(3) Glycerophospholipid metabolism
Increased CS 526.29135 C27H44NO7P 1-‐Acyl-‐sn-‐glycero-‐3-‐phosphocholine (R=C18:6) S Glycerophospholipid metabolism Increased CS 526.29135 C27H44NO7P 2-‐Acyl-‐sn-‐glycero-‐3-‐phosphocholine (R=C18:6) S Glycerophospholipid metabolism
Results and Discussion: Chapter 2
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Finally, the identification of discriminative masses extracted from the statistical model, which defined a differentiation between the control versus T16 and T40, showed similar characteristics of the identified masses at 16 h (Table 20). Thus, from temperature metabolome composition analysis between 16 and 40 h, only 7% of the total masses that increased or decreased could be annotated, remaining unidentified the majority of them. Of the annotated masses, 39% of them could be associated to metabolic pathways involving fatty acids whereas the rest of metabolites were associated to pathways involving aminoacids (6%), alpha-‐linolenic (3%), and sugars metabolisms (2%) (Table S5). However, an increase of unsaturated fatty acids and a decrease of compounds as 12-‐methyltetradecanoic acid, involved in the two component system, responsible for the biofilm formation, mobility and virulence, were observed at low temperature (Table 21).
Both kind of compounds could be related to modifications in the cell membrane, but they could also act as diffusible signaling factors (DSF) mediating an additional metabolic response to low temperature (Ryan &
Dow, 2008). Compounds as 12-‐methyltetradecanoic and hexadecanoic acid (Table 21) have been identified as main compounds in the whole fatty acid pattern of Actinobacteria isolated from Antartic snow, which could provide new insights into the physiological adaptation of this microorganisms to extreme low temperatures (Antony et al., 2009). On the other hand, by two component system, both compounds could also act as communication molecules allowing S. ruber cells to monitor the environment for other cells and to alter its behavior at a population-‐wide scale in response to changes (Waters & Bassler, 2005). Rigidification of the membrane appears to be the primary signal perceived by a bacterium when exposed to low temperature.
The perception and transduction of the signal occurs through a two-‐component signal transduction pathway,typically comprising paired histidine protein kinase (HK) and response regulator (RR) proteins implicated in comunication molecules perception, joining them as ligands and initiating the metabolic response (Shivaji & Prakash, 2010). Thus, a possible strategy adopted by S. ruber in order to adapt to prolonged cold incubation (40 h) could involve both, changes in the fatty acid composition as well as changes in the cell communication, which could lead to increase the final resistence of cells, changing the culturability pattern (Antony et al., 2009; Weichart & Kjelleberg, 1996).
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Table 21. Some proposed elemental composition of common masses increased or decreased under temperature stress conditions (40h) and identified by the Masstrix database. The intensity of masses and the metabolic pathways involved are also specified. UD= under detection limit; I= increased value with respect to the control; D= decreased value with respect to the control. Values in brackets represent the number of times.
Detection Cellular
fraction Exp. m/z Proposed
composition Proposed name Intensity
of peak Metabolic pathways involved
Decreased E 215.13877 C10H18N2O3 Dethiobiotin D(0.7) Biotin metabolism
Decreased E 221.09205 C11H12N2O3 5-‐Hydroxy-‐L-‐tryptophan UD Tryptophan metabolism Decreased E 237.08690 C11H12N2O4 L-‐Formylkynurenine D(0.5) Tryptophan metabolism
Decreased CI 336.08574 C11H17N3O7S S-‐Formylglutathione UD Methane and Microbial metabolism in diverse environments
Decreased E 243.23178 C15H30O2 12-‐Methyltetradecanoic acid D(0.2) Two component system
Decreased CI 241.25253 C16H32O Hexadecanal UD Fatty acids metabolism
Decreased E 400,34218 C23H45NO4 L-‐Palmitoylcarnitine UD Fatty acid metabolism
Decreased CI 611.35530 C34H52O8 beta-‐D-‐Glucuronoside (H+ replaced by Na+) D(0.5) Starch and sucrose metabolism and Pentose and glucuronate
interconversions
Decreased E 760,48704 C41H72NO8P Phosphatidylethanolamine; (H+ replaced by Na+) UD Glycerophospholipid metabolism Increased CS 173.02102 C3H9O6P sn-‐Glycerol 3-‐phosphate I(0.5) Glycerolipid and Glycerophospholipid
metabolism
Increased E 330.99530 C6H14O10P2 (R)-‐5-‐Diphosphomevalonate (H+ replaced by Na+) I(0.6) Unsaturated fatty acids biosynthesis Increased CS 173.02102 C8H6O3 alpha-‐Oxo-‐benzeneacetic acid (H+ replaced by Na+) I(0.5) Amino acid metabolism
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Table 21. Some proposed elemental composition of common masses increased or decreased under temperature stress conditions (40h) and identified by the Masstrix database.
Detection Cellular
fraction Exp. m/z Proposed
composition Proposed name Intensity
of peak Metabolic pathways involved Increased CS 173.02102 C8H6O3 2-‐Carboxybenzaldehyde (H+ replaced by Na+) I(0.5) Nafhthalene and anthracene
degradation
Increased E 251.19807 C14H28O2 Tetradecanoic acid (H+ replaced by Na+) I(0.2) Unsaturated fatty acids biosynthesis Increased E 279.22946 C16H32O2 Hexadecanoic acid (H+ replaced by Na+) I(2) Unsaturated fatty acids biosynthesis Increased E 335.29206 C20H40O2 Icosanoic acid (H+ replaced by Na+) I(2) Unsaturated fatty acids biosynthesis
Results and Discussion: Chapter 2
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