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Disclosure of the differences of Mesorhizobium loti under the free-living and symbiotic conditions by comparative proteome analysis without bacteroid isolation.

Tatsukami Y, Nambu M, Morisaka H, Kuroda K, Ueda M - BMC Microbiol. (2013)

Bottom Line: The lifestyle of rhizobia remains largely unknown, although genome and transcriptome analyses have been carried out.In proteome analysis, high separation performance is required to analyze complex biological samples.Therefore, we used a liquid chromatography-tandem mass spectrometry system, equipped with a long monolithic silica capillary column, which is superior to conventional columns.

View Article: PubMed Central - HTML - PubMed

Affiliation: Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.

ABSTRACT

Background: Rhizobia are symbiotic nitrogen-fixing soil bacteria that show a symbiotic relationship with their host legume. Rhizobia have 2 different physiological conditions: a free-living condition in soil, and a symbiotic nitrogen-fixing condition in the nodule. The lifestyle of rhizobia remains largely unknown, although genome and transcriptome analyses have been carried out. To clarify the lifestyle of bacteria, proteome analysis is necessary because the protein profile directly reflects in vivo reactions of the organisms. In proteome analysis, high separation performance is required to analyze complex biological samples. Therefore, we used a liquid chromatography-tandem mass spectrometry system, equipped with a long monolithic silica capillary column, which is superior to conventional columns. In this study, we compared the protein profile of Mesorhizobium loti MAFF303099 under free-living condition to that of symbiotic conditions by using small amounts of crude extracts.

Result: We identified 1,533 and 847 proteins for M. loti under free-living and symbiotic conditions, respectively. Pathway analysis by Kyoto Encyclopedia of Genes and Genomes (KEGG) revealed that many of the enzymes involved in the central carbon metabolic pathway were commonly detected under both conditions. The proteins encoded in the symbiosis island, the transmissible chromosomal region that includes the genes that are highly upregulated under the symbiotic condition, were uniquely detected under the symbiotic condition. The features of the symbiotic condition that have been reported by transcriptome analysis were confirmed at the protein level by proteome analysis. In addition, the genes of the proteins involved in cell surface structure were repressed under the symbiotic nitrogen-fixing condition. Furthermore, farnesyl pyrophosphate (FPP) was found to be biosynthesized only in rhizobia under the symbiotic condition.

Conclusion: The obtained protein profile appeared to reflect the difference in phenotypes under the free-living and symbiotic conditions. In addition, KEGG pathway analysis revealed that the cell surface structure of rhizobia was largely different under each condition, and surprisingly, rhizobia might provided FPP to the host as a source of secondary metabolism. M. loti changed its metabolism and cell surface structure in accordance with the surrounding conditions.

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Schematic representation of the lifestyle under the symbiotic condition compared to the free-living condition. The illustration shows the changes in the lifestyles of M. loti: the lifestyle model under the (a) free-living and (b) symbiotic conditions. The central carbon metabolic pathway is essential under both conditions. Under the symbiotic condition, nitrogen is fixed by electrons from the TCA cycle or other energy metabolism and is provided to the host legume or used for amino acid biosynthesis. Moreover, the flagellum and pilus are lost, and the cell wall, which is mainly composed of peptidoglycan, may become thin or disappear. In contrast, FPP is synthesized to provide to the host legume. Under the free-living condition, LPS is secreted extracellularly as a nod factor to infect the host legume.
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Figure 5: Schematic representation of the lifestyle under the symbiotic condition compared to the free-living condition. The illustration shows the changes in the lifestyles of M. loti: the lifestyle model under the (a) free-living and (b) symbiotic conditions. The central carbon metabolic pathway is essential under both conditions. Under the symbiotic condition, nitrogen is fixed by electrons from the TCA cycle or other energy metabolism and is provided to the host legume or used for amino acid biosynthesis. Moreover, the flagellum and pilus are lost, and the cell wall, which is mainly composed of peptidoglycan, may become thin or disappear. In contrast, FPP is synthesized to provide to the host legume. Under the free-living condition, LPS is secreted extracellularly as a nod factor to infect the host legume.

Mentions: In order to detect the changes in M. loti between free-living and symbiotic conditions, we performed proteome analysis of M. loti. We used our LC-MS/MS system, equipped with a long monolithic silica capillary column, to successfully identify 1,658 proteins without bacteroid isolation and prefractionation. This analytical system opens up a new horizon for symbiotic proteome analysis from small amounts of unpurified crude biological samples. The protein profile indicated some interesting and unexpected results associated with the cell surface structure and metabolism, in accordance with the external environment of each condition (FigureĀ 5). The data set revealed that M. loti under the symbiotic condition simplifies the components of the cell surface, such as flagellum, pilus, and cell wall. In addition, we found that M. loti under the symbiotic condition provided not only a nitrogen source but also FPP, which is a source of secondary metabolism. Our data should be helpful in carrying out detailed studies on the change of these 2 conditions of rhizobia.


Disclosure of the differences of Mesorhizobium loti under the free-living and symbiotic conditions by comparative proteome analysis without bacteroid isolation.

Tatsukami Y, Nambu M, Morisaka H, Kuroda K, Ueda M - BMC Microbiol. (2013)

Schematic representation of the lifestyle under the symbiotic condition compared to the free-living condition. The illustration shows the changes in the lifestyles of M. loti: the lifestyle model under the (a) free-living and (b) symbiotic conditions. The central carbon metabolic pathway is essential under both conditions. Under the symbiotic condition, nitrogen is fixed by electrons from the TCA cycle or other energy metabolism and is provided to the host legume or used for amino acid biosynthesis. Moreover, the flagellum and pilus are lost, and the cell wall, which is mainly composed of peptidoglycan, may become thin or disappear. In contrast, FPP is synthesized to provide to the host legume. Under the free-living condition, LPS is secreted extracellularly as a nod factor to infect the host legume.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750425&req=5

Figure 5: Schematic representation of the lifestyle under the symbiotic condition compared to the free-living condition. The illustration shows the changes in the lifestyles of M. loti: the lifestyle model under the (a) free-living and (b) symbiotic conditions. The central carbon metabolic pathway is essential under both conditions. Under the symbiotic condition, nitrogen is fixed by electrons from the TCA cycle or other energy metabolism and is provided to the host legume or used for amino acid biosynthesis. Moreover, the flagellum and pilus are lost, and the cell wall, which is mainly composed of peptidoglycan, may become thin or disappear. In contrast, FPP is synthesized to provide to the host legume. Under the free-living condition, LPS is secreted extracellularly as a nod factor to infect the host legume.
Mentions: In order to detect the changes in M. loti between free-living and symbiotic conditions, we performed proteome analysis of M. loti. We used our LC-MS/MS system, equipped with a long monolithic silica capillary column, to successfully identify 1,658 proteins without bacteroid isolation and prefractionation. This analytical system opens up a new horizon for symbiotic proteome analysis from small amounts of unpurified crude biological samples. The protein profile indicated some interesting and unexpected results associated with the cell surface structure and metabolism, in accordance with the external environment of each condition (FigureĀ 5). The data set revealed that M. loti under the symbiotic condition simplifies the components of the cell surface, such as flagellum, pilus, and cell wall. In addition, we found that M. loti under the symbiotic condition provided not only a nitrogen source but also FPP, which is a source of secondary metabolism. Our data should be helpful in carrying out detailed studies on the change of these 2 conditions of rhizobia.

Bottom Line: The lifestyle of rhizobia remains largely unknown, although genome and transcriptome analyses have been carried out.In proteome analysis, high separation performance is required to analyze complex biological samples.Therefore, we used a liquid chromatography-tandem mass spectrometry system, equipped with a long monolithic silica capillary column, which is superior to conventional columns.

View Article: PubMed Central - HTML - PubMed

Affiliation: Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.

ABSTRACT

Background: Rhizobia are symbiotic nitrogen-fixing soil bacteria that show a symbiotic relationship with their host legume. Rhizobia have 2 different physiological conditions: a free-living condition in soil, and a symbiotic nitrogen-fixing condition in the nodule. The lifestyle of rhizobia remains largely unknown, although genome and transcriptome analyses have been carried out. To clarify the lifestyle of bacteria, proteome analysis is necessary because the protein profile directly reflects in vivo reactions of the organisms. In proteome analysis, high separation performance is required to analyze complex biological samples. Therefore, we used a liquid chromatography-tandem mass spectrometry system, equipped with a long monolithic silica capillary column, which is superior to conventional columns. In this study, we compared the protein profile of Mesorhizobium loti MAFF303099 under free-living condition to that of symbiotic conditions by using small amounts of crude extracts.

Result: We identified 1,533 and 847 proteins for M. loti under free-living and symbiotic conditions, respectively. Pathway analysis by Kyoto Encyclopedia of Genes and Genomes (KEGG) revealed that many of the enzymes involved in the central carbon metabolic pathway were commonly detected under both conditions. The proteins encoded in the symbiosis island, the transmissible chromosomal region that includes the genes that are highly upregulated under the symbiotic condition, were uniquely detected under the symbiotic condition. The features of the symbiotic condition that have been reported by transcriptome analysis were confirmed at the protein level by proteome analysis. In addition, the genes of the proteins involved in cell surface structure were repressed under the symbiotic nitrogen-fixing condition. Furthermore, farnesyl pyrophosphate (FPP) was found to be biosynthesized only in rhizobia under the symbiotic condition.

Conclusion: The obtained protein profile appeared to reflect the difference in phenotypes under the free-living and symbiotic conditions. In addition, KEGG pathway analysis revealed that the cell surface structure of rhizobia was largely different under each condition, and surprisingly, rhizobia might provided FPP to the host as a source of secondary metabolism. M. loti changed its metabolism and cell surface structure in accordance with the surrounding conditions.

Show MeSH
Related in: MedlinePlus