Extracellular Metabolites Profile of Different Stages Colorectal Cancer Cell Lines

Metabolic footprinting involves the determination of metabolites excreted or secreted by the cells. This study aimed to identify the differential extracellular metabolites in colorectal cancer (CRC) cells for the determination of molecular changes that occur as CRC progresses. CRC cells at different stages ie; SW 1116 (stage A), HT 29 and SW 480 (stage B), HCT 15 and DLD-1 (stage C), and HCT 116 (stage D) were grown in culture. The media in which the cells were grown are subjected to metabolomics profiling using Liquid Chromatography Mass Spectrometry-Quadrupole Time of Flight (LC/MS Q-TOF). Statistical and metabolic pathway analysis was performed using Metaboanalyst software and identification of metabolites was determined by the METLIN database. A total of 27 differential extracellular metabolites were identified in CRC cells of different stages compared to stage A cells. Data from the Partial least squares-discriminant analysis (PLS-DA) score plot shows a clear separation between CRC cells of different stages with a few overlaps between stage B and C. Further analysis using variable importance in projection (VIP) revealed 14 differential extracellular metabolites that were most significant in differentiating CRC cells of the advanced stages from stage A which are 5-hydroxy-L-tryptophan, indoleacetaldehyde, 4,5-dimethylthiazole, 8-oxodiacetoxyscirpenol, bisnorbiotin, 5-amino-6-(5'phosphoribosylamino) uracil, glyceryl 5-hydroxydecanoate, sphinganine, 8,8-diethoxy-2,6-dimethyl-2-octanol, l-cystine, thiamine acetic acid, phytosphingosine, PE (20:4(5Z,8Z,11Z,14Z)/22:6(4Z,7Z,10Z,13Z,16Z,19Z)), N-(2R-hydroxypentacosano-yl)-2S-amino-1,3S,4R-octadecanetriol. The different expressions of metabolites may indicate altered metabolic pathways in the more advanced CRC cells compared to stage A. This study highlights the importance of conducting both metabolomics profiling of extracellular and intracellular to generate a more complete understanding on the molecular changes that occur as CRC progresses.

SAR11 Cells Rely on Enzyme Multifunctionality to Transport and Metabolize a Range of Polyamine Compounds

In the ocean surface layer and cell culture, the polyamine transport protein PotD of SAR11 bacteria is often one of the most abundant proteins detected. Polyamines are organic cations produced by all living organisms and are thought to be an important component of dissolved organic matter (DOM) produced in planktonic ecosystems. We hypothesized that SAR11 cells transport and metabolize multiple polyamines and use them as sources of carbon and nitrogen. Metabolic footprinting and fingerprinting were used to measure the uptake of five polyamine compounds (putrescine, cadaverine, agmatine, norspermidine, and spermidine) in two SAR11 strains that represent the majority of SAR11 cells in the surface ocean environment, Ca. Pelagibacter st. HTCC7211 and C. P. ubique st. HTCC1062. Both strains transported all five polyamines and concentrated them to micromolar or millimolar intracellular concentrations. Both strains could use most of the polyamines to meet their nitrogen requirements, but we did not find evidence of use as carbon sources. We propose potABCD transports cadaverine, agmatine, and norspermidine, in addition to its usual substrates of spermidine and putrescine, and that spermidine synthase, speE, is reversible, catalyzing the breakdown of spermidine and norspermidine, in addition to its usual biosynthetic role. These findings provide support for the hypothesis that enzyme multifunctionality enables streamlined cells in planktonic ecosystems to increase the range of DOM compounds they oxidize.