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Genome-wide screen for temperature-regulated genes of the obligate intracellular bacterium, Rickettsia typhi.

Dreher-Lesnick SM, Ceraul SM, Rahman MS, Azad AF - BMC Microbiol. (2008)

Bottom Line: A large number of differentially expressed genes are still poorly characterized, and either have no known function or are not in the COG database.The microarray results were validated with quantitative real time RT-PCR.Further characterization of the identified genes may provide new insights into the ability of R. typhi to successfully transition between its mammalian and arthropod hosts.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Microbiology and Immunology, University of Maryland, 660 W, Redwood Street, Room HH324B, Baltimore, MD 21201, USA. sdreh001@umaryland.edu

ABSTRACT

Background: The ability of rickettsiae to survive in multiple eukaryotic host environments provides a good model for studying pathogen-host molecular interactions. Rickettsia typhi, the etiologic agent of murine typhus, is a strictly intracellular gram negative alpha-proteobacterium, which is transmitted to humans by its arthropod vector, the oriental rat flea, Xenopsylla cheopis. Thus, R. typhi must cycle between mammalian and flea hosts, two drastically different environments. We hypothesize that temperature plays a role in regulating host-specific gene expression, allowing R. typhi to survive in mammalian and arthropod hosts. In this study, we used Affymetrix microarrays to screen for temperature-induced genes upon a temperature shift from 37 degrees C to 25 degrees C, mimicking the two different host temperatures in vitro.

Results: Temperature-responsive genes belonged to multiple functional categories including among others, transcription, translation, posttranslational modification/protein turnover/chaperones and intracellular trafficking and secretion. A large number of differentially expressed genes are still poorly characterized, and either have no known function or are not in the COG database. The microarray results were validated with quantitative real time RT-PCR.

Conclusion: This microarray screen identified various genes that were differentially expressed upon a shift in temperature from 37 degrees C to 25 degrees C. Further characterization of the identified genes may provide new insights into the ability of R. typhi to successfully transition between its mammalian and arthropod hosts.

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Differentially expressed R. typhi genes in response to a shift in temperature from 37°C to 25°C according to gene functional group (COGs). Differentially expressed R. typhi genes were assigned their corresponding COG descriptors. (A) Comparison of number of genes per functional group found to be downregulated (white bars) versus upregulated (black bars) upon a shift down in temperature. (B) Summary of R. typhi genes according to functional group downregulated after a temperature shift. (C) Summary of R. typhi genes according to functional group upregulated after a temperature shift.
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Figure 1: Differentially expressed R. typhi genes in response to a shift in temperature from 37°C to 25°C according to gene functional group (COGs). Differentially expressed R. typhi genes were assigned their corresponding COG descriptors. (A) Comparison of number of genes per functional group found to be downregulated (white bars) versus upregulated (black bars) upon a shift down in temperature. (B) Summary of R. typhi genes according to functional group downregulated after a temperature shift. (C) Summary of R. typhi genes according to functional group upregulated after a temperature shift.

Mentions: The pattern and distribution of differentially expressed genes differs for many functional categories, or COGs (Figure 1A). As expected, more genes involved in translation (COG J), transcription (COG K), posttranslational modification and protein turnover (COG O), amino acid transfer and metabolism (COG E) are downregulated upon a shift to the lower temperature (Figure 1A,B). Genes that showed a decrease in fold change expression are listed by functional category in Table 1. This correlates to slower growth rates and doubling time observed for rickettsiae at lower temperatures [30-32]. Reducing environmental temperature thus seems to trigger a reduction in metabolic and transcriptional activity of rickettsiae.


Genome-wide screen for temperature-regulated genes of the obligate intracellular bacterium, Rickettsia typhi.

Dreher-Lesnick SM, Ceraul SM, Rahman MS, Azad AF - BMC Microbiol. (2008)

Differentially expressed R. typhi genes in response to a shift in temperature from 37°C to 25°C according to gene functional group (COGs). Differentially expressed R. typhi genes were assigned their corresponding COG descriptors. (A) Comparison of number of genes per functional group found to be downregulated (white bars) versus upregulated (black bars) upon a shift down in temperature. (B) Summary of R. typhi genes according to functional group downregulated after a temperature shift. (C) Summary of R. typhi genes according to functional group upregulated after a temperature shift.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2335108&req=5

Figure 1: Differentially expressed R. typhi genes in response to a shift in temperature from 37°C to 25°C according to gene functional group (COGs). Differentially expressed R. typhi genes were assigned their corresponding COG descriptors. (A) Comparison of number of genes per functional group found to be downregulated (white bars) versus upregulated (black bars) upon a shift down in temperature. (B) Summary of R. typhi genes according to functional group downregulated after a temperature shift. (C) Summary of R. typhi genes according to functional group upregulated after a temperature shift.
Mentions: The pattern and distribution of differentially expressed genes differs for many functional categories, or COGs (Figure 1A). As expected, more genes involved in translation (COG J), transcription (COG K), posttranslational modification and protein turnover (COG O), amino acid transfer and metabolism (COG E) are downregulated upon a shift to the lower temperature (Figure 1A,B). Genes that showed a decrease in fold change expression are listed by functional category in Table 1. This correlates to slower growth rates and doubling time observed for rickettsiae at lower temperatures [30-32]. Reducing environmental temperature thus seems to trigger a reduction in metabolic and transcriptional activity of rickettsiae.

Bottom Line: A large number of differentially expressed genes are still poorly characterized, and either have no known function or are not in the COG database.The microarray results were validated with quantitative real time RT-PCR.Further characterization of the identified genes may provide new insights into the ability of R. typhi to successfully transition between its mammalian and arthropod hosts.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Microbiology and Immunology, University of Maryland, 660 W, Redwood Street, Room HH324B, Baltimore, MD 21201, USA. sdreh001@umaryland.edu

ABSTRACT

Background: The ability of rickettsiae to survive in multiple eukaryotic host environments provides a good model for studying pathogen-host molecular interactions. Rickettsia typhi, the etiologic agent of murine typhus, is a strictly intracellular gram negative alpha-proteobacterium, which is transmitted to humans by its arthropod vector, the oriental rat flea, Xenopsylla cheopis. Thus, R. typhi must cycle between mammalian and flea hosts, two drastically different environments. We hypothesize that temperature plays a role in regulating host-specific gene expression, allowing R. typhi to survive in mammalian and arthropod hosts. In this study, we used Affymetrix microarrays to screen for temperature-induced genes upon a temperature shift from 37 degrees C to 25 degrees C, mimicking the two different host temperatures in vitro.

Results: Temperature-responsive genes belonged to multiple functional categories including among others, transcription, translation, posttranslational modification/protein turnover/chaperones and intracellular trafficking and secretion. A large number of differentially expressed genes are still poorly characterized, and either have no known function or are not in the COG database. The microarray results were validated with quantitative real time RT-PCR.

Conclusion: This microarray screen identified various genes that were differentially expressed upon a shift in temperature from 37 degrees C to 25 degrees C. Further characterization of the identified genes may provide new insights into the ability of R. typhi to successfully transition between its mammalian and arthropod hosts.

Show MeSH
Related in: MedlinePlus