Fig 14 - uploaded by Giulio Petroni
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1 " Candidatus Midichloria mitochondrii " bacteria in an oocyte of the tick Ixodes ricinus. b indicates the bacteria, m indicates a mitochondrion. A group of five bacteria is clearly visible within one organelle, while other " Ca. M. mitochondrii " appear to be in the cytoplasm, engulfed by a host-derived membrane. Bar = 0.7 μm
Source publication
“Candidatus Midichloriaceae” (order Rickettsiales) is a family that encompasses obligate intracellular bacteria present in a wide range of hosts, from parasitic arthropods (ticks, fleas, bedbugs) to aquatic animals (e.g. sponges and corals) and protists, including pathogenic amoebae (genus Acanthamoeba). In addition, multiple studies have detected...
Citations
... Alternatively, it is possible that ticks could transmit this endosymbiont to humans and consequently to other ticks, completing a tick-to-human-to tick transmission route, similar to that described for tick-borne pathogens. Indeed, this endosymbiont has been detected in the blood of humans and mammals bitten by ticks [54]. ...
The bacteria of the families Rickettsiaceae and Anaplasmataceae, harbored by arthropod vectors, may cause disease in animals and humans. The aim of this study was to screen ectoparasites collected from cats and dogs in Attica, Greece for the bacteria of the Rickettsiales group, by molecular methods. The ectoparasites examined were Ctenocephalides felis fleas and Rhipicephalus sanguineus s.l., Rhipicephalus sp., and Ixodes sp. ticks. Rickettsia felis was detected in 4.8% of C. felis fleas, and Rickettsia conorii was detected in 7.3% of R. sanguineus s.l. ticks. Ehrlichia canis was found in one R. sanguineus s.l. tick, and Wolbachia pipientis was detected in the majority of fleas. Another endosymbiont, Cancidatus Midichloria mitochondrii (Cancidatus Midichloriaceae), was detected in one Ixodes sp.. This is the first report of R. conorii and E. canis in R. sanguineus s.l. ticks in this study area. Given the fact that Greece is considered endemic for spotted fever group rickettsioses, further investigation of these rickettsial pathogens’ distribution in their vectors and hosts could enhance our knowledge of their epidemiology, in order to assess their potential implications for public health in this metropolitan area.
... In many cases, these emerging diseases appear as skin pathologies, as is the case of red mark syndrome (RMS) affecting rainbow trout Oncorhynchus mykiss (Ferguson et al., 2006;Lloyd et al., 2008;Oidtmann et al., 2013;Schmidt et al., 2018;Schmidt-Posthaus et al., 2009;Verner-Jeffreys et al., 2008). RMS is a disease consisting of single or multiple skin lesions usually localized on the trunk of fish approaching market size (Castelli et al., 2016a). Farmers are forced to downgrade the fish to highly manufactured items because of its reduced market value (e.g., fish balls and baby food), thus causing a substantial economic damage. ...
Red mark syndrome (RMS) is a disease of farmed rainbow trout, Oncorhynchus mykiss (Walbaum, 1792), one of the most widespread freshwater farmed species in Europe. The disease emerges at water temperatures below 16 °C and consists of one or more bright red skin lesions on the fish body. Mortality due to RMS is reportedly rare, but the disease leads to downgrading of the product and subsequent economic losses. Despite the disease impact, the causative agent for RMS is still formally undetermined although increasing evidence points to a bacterium ascribed to the Midichloriaceae family (order Rickettsiales), hereafter referred to as RMS-Midichloria like organism (RMS-MLO).
Intriguingly, recently deposited sequences revealed the presence of RMS-MLO-like bacteria associated with Ichthyophthirius multifiliis, a common protozoan skin parasite of freshwater fish frequently harboring bacterial endosymbionts. Therefore, we hypothesized that I. multifiliis could be a vehicle for RMS-MLO. This was tested by infecting RMS-diseased rainbow trout with I. multifiliis theronts, and subsequently investigating the presence of RMS-MLO in tomonts detached from the fish.
Real time PCR analyses showed clearly that I. multifiliis previously exposed to RMS-affected fish become positive to RMS-MLO suggesting that this bacterium can be at least transiently acquired and carried by the protozoan. Moreover, statistical analyses suggested a possible level of vertical transmission in I. multifiliis from one trophic stage to the next one. Further studies will be necessary to prove whether I. multifiliis has a role in the horizontal transfer of RMS-MLO bacteria from diseased RMS fish to healthy ones.
Placozoa is an enigmatic phylum of simple, microscopic, marine metazoans1,2. Although intracellular bacteria have been found in all members of this phylum, almost nothing is known about their identity, location and interactions with their host3–6. We used metagenomic and metatranscriptomic sequencing of single host individuals, plus metaproteomic and imaging analyses, to show that the placozoan Trichoplax sp. H2 lives in symbiosis with two intracellular bacteria. One symbiont forms an undescribed genus in the Midichloriaceae (Rickettsiales)7,8 and has a genomic repertoire similar to that of rickettsial parasites9,10, but does not seem to express key genes for energy parasitism. Correlative image analyses and three-dimensional electron tomography revealed that this symbiont resides in the rough endoplasmic reticulum of its host’s internal fibre cells. The second symbiont belongs to the Margulisbacteria, a phylum without cultured representatives and not known to form intracellular associations11–13. This symbiont lives in the ventral epithelial cells of Trichoplax, probably metabolizes algal lipids digested by its host and has the capacity to supplement the placozoan’s nutrition. Our study shows that one of the simplest animals has evolved highly specific and intimate associations with symbiotic, intracellular bacteria and highlights that symbioses can provide access to otherwise elusive microbial dark matter.
