Trichomonas vaginalisandMycoplasma hominis: new tales of two old friends

Trichomonas vaginalisis an anaerobic protist, responsible for the most prevalent non-viral sexually transmitted infection in humans. One of the most intriguing aspects ofT. vaginalispathobiology is the complex relationship with intracellular microbial symbionts: a group of dsRNA viruses belonging to family ofTotiviridae(T. vaginalisvirus), and eubacteria belonging to theMycoplasmagenus, in particularMycoplasma hominis. Both microorganisms seem to strongly influence the lifestyle ofT. vaginalis, suggesting a role of the symbiosis in the high variability of clinical presentation and sequelae during trichomoniasis. In the last few years many aspects of this unique symbiotic relationship have been investigated:M. hominisresides and replicates in the protozoan cell, andT. vaginalisis able to pass the bacterial infection to both mycoplasma-free protozoan isolates and human epithelial cells;M. hominissynergistically upregulates the proinflammatory response of human monocytes toT. vaginalis. Furthermore, the influence ofM. hominisoverT. vaginalismetabolism and physiology has been characterized. The identification of a novel species belonging to the class ofMollicutes(CandidatusMycoplasma girerdii) exclusively associated toT. vaginalisopens new perspectives in the research of the complex series of events taking place in the multifaceted world of the vaginal microbiota, both under normal and pathological conditions.

Microbial eukaryotes have adapted to hypoxia by horizontal acquisitions of a gene involved in rhodoquinone biosynthesis

Under hypoxic conditions, some organisms use an electron transport chain consisting of only complex I and II (CII) to generate the proton gradient essential for ATP production. In these cases, CII functions as a fumarate reductase that accepts electrons from a low electron potential quinol, rhodoquinol (RQ). To clarify the origins of RQ-mediated fumarate reduction in eukaryotes, we investigated the origin and function of rquA, a gene encoding an RQ biosynthetic enzyme. RquA is very patchily distributed across eukaryotes and bacteria adapted to hypoxia. Phylogenetic analyses suggest lateral gene transfer (LGT) of rquA from bacteria to eukaryotes occurred at least twice and the gene was transferred multiple times amongst protists. We demonstrate that RquA functions in the mitochondrion-related organelles of the anaerobic protist Pygsuia and is correlated with the presence of RQ. These analyses reveal the role of gene transfer in the evolutionary remodeling of mitochondria in adaptation to hypoxia.

Genetic diversity of Blastocystis in non-primate animals

Blastocystis is an anaerobic protist, commonly inhabiting the intestinal tract of both humans and other animals. Blastocystis is extremely diverse comprising 17 genetically distinct subtypes in mammals and birds. Pathogenicity of this enteric microbe is currently disputed and knowledge regarding its distribution, diversity and zoonotic potential is fragmentary. Most research has focused on Blastocystis from primates, while sampling from other animals remains limited. Herein, we investigated the prevalence and distribution of Blastocystis in animals held within a conservation park in South East England. A total of 118 samples were collected from 27 vertebrate species. The barcoding region of the small-subunit ribosomal RNA was used for molecular identification and subtyping. Forty one per cent of the species were sequence positive for Blastocystis indicating a high prevalence and wide distribution among the animals in the park. Six subtypes were identified, one of which is potentially novel. Moreover, the majority of animals were asymptomatic carriers, suggesting that Blastocystis is not pathogenic in animals. This study provides a thorough investigation of Blastocystis prevalence within a wildlife park in the UK and can be used as a platform for further investigations on the distribution of other eukaryotic gut microbes.

Lipid metabolism inGiardia: a post-genomic perspective

SUMMARYGiardia lamblia, a protozoan parasite, infects a wide variety of vertebrates, including humans. Studies indicate that this anaerobic protist possesses a limited ability to synthesize lipid moleculesde novoand depends on supplies from its environment for growth and differentiation. It has been suggested that most lipids and fatty acids are taken up by endocytic and non-endocytic pathways and are used byGiardiafor energy production and membrane/organelle biosynthesis. The purpose of this article is to provide an update on recent progress in the field of lipid research of this parasite and the validation of lipid metabolic pathways through recent genomic information. Based on current cellular, biochemical and genomic data, a comprehensive pathway has been proposed to facilitate our understanding of lipid and fatty acid metabolism/syntheses in this waterborne pathogen. We envision that the current review will be helpful in identifying targets from the pathways that could be used to design novel therapies to control giardiasis and related diseases.