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CIliates as NAtural Reservoir of potentially PATHOgenic BACTERia: an ecological, functional and evolutionary genomic investigation

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Can symbiotic bacteria become pathogenic?

EU-funded researchers have studied symbiotic bacteria that are present in a group of protozoans called ciliates to determine their potential danger to human and animal health.


Recent studies have shown that certain protozoan organisms such as Acanthamoeba can harbour microorganisms in a symbiotic relationship. Although normally benign, these opportunistic microbes can prove to be pathogenic to humans and animals. For instance, tropical weather conditions, compromised immune systems, poor hygiene and overcrowding can facilitate such undesirable transformations. The CINAR PATHOBACTER (Ciliates as natural reservoir of potentially pathogenic bacteria: An ecological, functional and evolutionary genomic investigation) project was an international network that also included non-European countries. The consortium characterised symbiotic bacteria living in ciliates that showed phylogenetic affinities to pathogenic bacteria. It also conducted a comprehensive ecological, functional and evolutionary genomic investigation in symbiotic organisms, particularly those from tropical regions. Researchers systematically sampled ciliates from many countries, including Brazil and India, and screened them for bacterial pathogens. This included an evolutionary genomic analysis of the available genome sequence of the bacterial symbionts of the ciliate Polynucleobacter necessarius. Analysis of the genome of symbiont Holospora caryophila is underway.. Ecophysiological evolutionary epidemiological studies on ciliates and their symbionts were also performed. Project activities were aimed at identifying the key factors that facilitate bacterial colonisation in the ciliates and mechanisms through which symbiosis is achieved. Such studies may also reveal the factors relevant to pathogenicity in bacterial symbionts and ciliates. Applications include prediction of pathogenicity where their close proximity to humans and animals can facilitate their transformation into infectious forms deleterious to our health. CINAR PATHOBACTER results and their possible developments will benefit those industries dealing with wastewater and sanitation treatment. They are also of potential interest to aquaculture and related industries.


Symbiotic, bacteria, pathogenic, ciliates, Acanthamoeba, symbionts

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