A semi-quantitative GeLC-MS analysis of temporal proteome expression in the emerging nosocomial pathogen Ochrobactrum anthropi - PubMed (original) (raw)

A semi-quantitative GeLC-MS analysis of temporal proteome expression in the emerging nosocomial pathogen Ochrobactrum anthropi

Robert Leslie James Graham et al. Genome Biol. 2007.

Abstract

Background: The alpha-Proteobacteria are capable of interaction with eukaryotic cells, with some members, such as Ochrobactrum anthropi, capable of acting as human pathogens. O. anthropi has been the cause of a growing number of hospital-acquired infections; however, little is known about its growth, physiology and metabolism. We used proteomics to investigate how protein expression of this organism changes with time during growth.

Results: This first gel-based liquid chromatography-mass spectrometry (GeLC-MS) temporal proteomic analysis of O. anthropi led to the positive identification of 131 proteins. These were functionally classified and physiochemically characterized. Utilizing the emPAI protocol to estimate protein abundance, we assigned molar concentrations to all proteins, and thus were able to identify 19 with significant changes in their expression. Pathway reconstruction led to the identification of a variety of central metabolic pathways, including nucleotide biosynthesis, fatty acid anabolism, glycolysis, TCA cycle and amino acid metabolism. In late phase growth we identified a number of gene products under the control of the oxyR regulon, which is induced in response to oxidative stress and whose protein products have been linked with pathogen survival in response to host immunity reactions.

Conclusion: This study identified distinct proteomic profiles associated with specific growth points for O. anthropi, while the use of emPAI allowed semi-quantitative analyses of protein expression. It was possible to reconstruct central metabolic pathways and infer unique functional and adaptive processes associated with specific growth phases, thereby resulting in a deeper understanding of the physiology and metabolism of this emerging pathogenic bacterium.

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Figures

Figure 1

Figure 1

Theoretical two-dimensional map of the soluble sub-proteome of O. anthropi. Diamonds, early growth phase; squares, both growth conditions; triangles, late growth phase.

Figure 2

Figure 2

Functional categorisation of identified proteins from the soluble sub-proteome of O. anthropi. Gray bars, early growth phase; black bars, late growth phase.

Figure 3

Figure 3

Overview of identified proteins from the soluble sub-proteome of O. anthropi at the early growth phase. Cellular localization was predicted based upon the use of PSortB v2.0.4 [41,42], SignalP v3.0 [43,44], and SecretomeP v2.0 [45,46].

Figure 4

Figure 4

Overview of identified proteins from the soluble sub-proteome of O. anthropi present in both growth conditions. Cellular localization was predicted based upon the use of PSortB v2.0.4 [41,42], SignalP v3.0 [43,44], and SecretomeP v2.0 [45,46].

Figure 5

Figure 5

Overview of identified proteins from the soluble sub-proteome of O. anthropi present in late growth conditions. Cellular localization was predicted based upon the use of PSortB v2.0.4 [41,42], SignalP v3.0 [43,44], and SecretomeP v2.0 [45,46].

Figure 6

Figure 6

Differential expression profile of proteins common to both growth phases of O. anthropi. Fold changes of ≥1.5 or ≤0.5 are significant.

Figure 7

Figure 7

Proposed model for induction of the OxyR regulon in O. anthropi. Oxidized oxyR regulates expression of the OxyR regulon in response to oxidative and nitrosative stress, inducing trxC, grxA, gorA and other OxyR regulon genes. ahpC, alkyl hydroperodide reductase I; fhuF, ferric reductase; fur, ferric uptake repressor; GSSH/GSH, oxidized/reduced glutathione; GorA, glutathione reductase; GrxA, glutaredoxin A; katG, catalase (hydroperoxidase I); OMP agn43, outer membrane protein; oxyS, regulatory RNA; RNO, reactive nitrogen species; ROS, reactive oxygen species; TP, thiol peroxidase; TR, thioredoxin 2. (Adapted (with kind permission of Springer Science and Business Media) from Figure 2a [70].)

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