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Review
. 2022 Feb 19;7(2):32.
doi: 10.3390/tropicalmed7020032.

Moonlighting in Rickettsiales: Expanding Virulence Landscape

Ana Luísa Matos  1 , Pedro Curto  1 , Isaura Simões  1   2
Affiliations
Review

Moonlighting in Rickettsiales: Expanding Virulence Landscape

Ana Luísa Matos et al. Trop Med Infect Dis. .

Abstract

The order Rickettsiales includes species that cause a range of human diseases such as human granulocytic anaplasmosis (Anaplasma phagocytophilum), human monocytic ehrlichiosis (Ehrlichia chaffeensis), scrub typhus (Orientia tsutsugamushi), epidemic typhus (Rickettsia prowazekii), murine typhus (R. typhi), Mediterranean spotted fever (R. conorii), or Rocky Mountain spotted fever (R. rickettsii). These diseases are gaining a new momentum given their resurgence patterns and geographical expansion due to the overall rise in temperature and other human-induced pressure, thereby remaining a major public health concern. As obligate intracellular bacteria, Rickettsiales are characterized by their small genome sizes due to reductive evolution. Many pathogens employ moonlighting/multitasking proteins as virulence factors to interfere with multiple cellular processes, in different compartments, at different times during infection, augmenting their virulence. The utilization of this multitasking phenomenon by Rickettsiales as a strategy to maximize the use of their reduced protein repertoire is an emerging theme. Here, we provide an overview of the role of various moonlighting proteins in the pathogenicity of these species. Despite the challenges that lie ahead to determine the multiple potential faces of every single protein in Rickettsiales, the available examples anticipate this multifunctionality as an essential and intrinsic feature of these obligates and should be integrated into available moonlighting repositories.

Keywords: Anaplasma spp.; Ehrlichia spp.; Orientia spp.; Rickettsia spp.; Rickettsiales; moonlighting; multitasking; pathogenicity; protein function; virulence factors.

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Conflict of interest statement

The authors declare that they have no conflict of interest. The funders had no role in the writing of the manuscript.

Figures

Figure 1
Figure 1
The multiple roles of the reported moonlighting/multitasking proteins in Rickettsiales. Created with BioRender.com.
Figure 2
Figure 2
Examples of the multitasking proteins and their roles among the different members of the Rickettsiales: Anaplasma (A.), Ehrlichia (E.), Orientia (O.), Rickettsia (R.), and Wolbachia (W.). Details on each protein are provided in the text. Created with BioRender.com.
See this image and copyright information in PMC

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