12 research outputs found
The neotypification of Frontonia vernalis (Ehrenberg, 1833) Ehrenberg, 1838 and the description of Frontonia paravernalis sp. nov. trigger a critical revision of frontoniid systematics
Background: Among Oligohymenophorea (Ciliophora, Alveolata) the subclass Peniculia stands as one of the most
well-known groups. Frontonia is the largest genus of Peniculia, and its representatives are spread in any type of
water bodies as well as in soil. At a first glance, Frontonia species exhibit an overall similar morphology, and form a
well-recognizable taxon of ciliates. Despite the general morphological homogeneity, the phylogenetic analysis
based on the 18S rDNA sequencing showed that Frontonia is a non-monophyletic group. The systematics of this
genus should be deeply reviewed, although additional issues complicate the task solving. First, type species of the
genus is not yet clearly established, and no type material is available. In this context, the situation of F. vernalis, one
of the first Frontonia ever described, is somehow puzzled: the description of this ciliate made by Ehrenberg (in 1833
and 1838) contains several inaccuracies and subsequent misidentifications by other authors occurred. Moreover, the
18S rDNA sequence of a putative F. vernalis is available on GenBank, but no morphological description of the
correspondent specimens is provided; thus, in our opinion, it should be only prudently associated with F. vernalis or
at least indicated as “F. vernalis”.
Results: In the present work, we provide the neotypification of F. vernalis newly found in Italy, presenting its
multidisciplinary description and its neotype material. Similarly, we describe a novel species bearing Chlorella-like
endosymbionts, Frontonia paravernalis sp. nov., retrieved in two far distant locations (Italy, Russia). A critical
discussion on the status of Frontonia taxonomy and phylogeny is also presented, based on the 18S rDNA
sequencing of both these two newly collected species and other 14 frontoniids isolated in different parts of the
world. Finally, in the present study F. leucas was neotypified and proposed as the type species of the genus.
Conclusions: Green frontoniids form a monophyletic clade of freshwater organisms characterized by having a
single contractile vacuole and bearing intracytoplasmatic Chlorella-like symbionts. With the neotypification of F.
vernalis and F. leucas a fundamental step in Frontonia systematics was taken, and the bases for further taxonomic
studies were laid
Computational models for liposomes generation and extrusion
This work aim to illustrate a computational model able to simulate the process of generation of a population of liposome and their extrusion. This model can also simulate the entrapment of molecules inside the liposme and their ripartition during the extrusion
Characterization of novel verrucomicrobial endo- and ectosymbionts of ciliates: a comparative phylogenetic and genomic study.
The aim of the present PhD project is to investigate bacterial endosymbionts
and ectosymbionts of ciliates, belonging to Phylum Verrucomicrobia,
from a genomic and phylogenetic point of view.
The first goal of this study is to improve the knowledge about
the diversity and distribution of verrucomicrobial endosymbionts in
ciliates. Therefore it was decided to focus on genus Euplotes due to its
propensity to harbor symbiotic bacteria and due to preliminary data
report on the presence of symbiotic Verrucomicrobia in some Euplotes
strains from our laboratory culture collection.
The second goal of this study is the characterization from a genomic
point of view of an already known ectosymbionts of the ciliate
Euplotidium itoi, the so called Epixenosome.
Along these two main goals, a very important milestone is the
production of an updated review on the knowledge about the phylum
Verrucomicrobia, a task not attended by anyone so far, but truly needed
due to increase of studies regarding Verrucomicrobi
The Azurin Coding Gene: Origin and Phylogenetic Distribution
Azurin is a bacterial-derived cupredoxin, which is mainly involved in electron transport reactions. Interest in azurin protein has risen in recent years due to its anticancer activity and its possible applications in anticancer therapies. Nevertheless, the attention of the scientific community only focused on the azurin protein found in Pseudomonas aeruginosa (Proteobacteria, Gammaproteobacteria). In this work, we performed the first comprehensive screening of all the bacterial genomes available in online repositories to assess azurin distribution in the three domains of life. The Azurin coding gene was not detected in the domains Archaea and Eucarya, whereas it was detected in phyla other than Proteobacteria, such as Bacteroidetes, Verrucomicrobia and Chloroflexi, and a phylogenetic analysis of the retrieved sequences was performed. Observed patchy distribution and phylogenetic data suggest that once it appeared in the bacterial domain, the azurin coding gene was lost in several bacterial phyla and/or anciently horizontally transferred between different phyla, even though a vertical inheritance appeared to be the major force driving the transmission of this gene. Interestingly, a shared conserved domain has been found among azurin members of all the investigated phyla. This domain is already known in P. aeruginosa as p28 domain and its importance for azurin anticancer activity has been widely explored. These findings may open a new and intriguing perspective in deciphering the azurin anticancer mechanisms and to develop new tools for treating cancer diseases
Do protocells preferentially retain macromolecular solutes upon division/fragmentation? A study based on the extrusion of POPC giant vesicles
A key process of protocell behaviour is their recursive growth and division. In order to be sustainable, the latter must be characterized by an even and homogeneous partition of the solute molecules initially present in the parent protocell among the daughter ones. Here we have investigated, by means of an artificial division model (extrusion of giant lipid vesicles) and confocal microscopy, the fate of solutes when a large vesicle fragments into many smaller vesicles. Solutes of low- and high-molecular weight such as pyranine, calcein, albumin-FITC, dextran-FITC and carbonic anhydrase have been employed. Although the vesicle extrusion brings about a release of their inner content in the environment, the results shown in this initial report indicate that macromolecules can be partially retained when compared with low-molecular weight ones. Results are discussed from the viewpoint of the life cycle of primitive cells. In particular, the findings suggest that a similar mechanism operating during the critical step of vesicle growth-division could have contributed to primitive evolution
Characterization of a Pseudokeronopsis Strain (Ciliophora, Urostylida) and Its Bacterial Endosymbiont “Candidatus Trichorickettsia” (Alphaproteobacteria, Rickettsiales)
Symbiotic associations between bacteria and ciliate protists are rather common. In particular,
several cases were reported involving bacteria of the alphaproteobacterial lineage Rickettsiales, but
the diversity, features, and interactions in these associations are still poorly understood. In this work,
we characterized a novel ciliate protist strain originating from Brazil and its associated Rickettsiales
endosymbiont by means of live and ultrastructural observations, as well as molecular phylogeny.
Though with few morphological peculiarities, the ciliate was found to be phylogenetically affiliated
with Pseudokeronopsis erythrina, a euryhaline species, which is consistent with its origin from a lagoon
with significant spatial and seasonal salinity variations. The bacterial symbiont was assigned to
“Candidatus Trichorickettsia mobilis subsp. hyperinfectiva”, being the first documented case of a
Rickettsiales associated with urostylid ciliates. It resided in the host cytoplasm and bore flagella,
similarly to many, but not all, conspecifics in other host species. These findings highlight the ability
of “Candidatus Trichorickettsia” to infect multiple distinct host species and underline the importance
of further studies on this system, in particular on flagella and their regulation, from a functional and
also an evolutionary perspective, considering the phylogenetic proximity with the well-studied and
non-flagellated Rickettsia
Holospora-like bacteria "Candidatus Gortzia yakutica" and Preeria caryophila: Ultrastructure, promiscuity, and biogeography of the symbionts
: Two already known representatives of Holospora-like bacteria, "Candidatus Gortzia yakutica" from Paramecium putrinum and Preeria caryophila, originally retrieved from the Paramecium aurelia complex, were found in new hosts: Paramecium nephridiatum and Paramecium polycaryum, respectively. In the present study, these bacteria were investigated using morphological and molecular methods. For "Ca. G. yakutica", the first details of the electron microscopic structure in the main and new hosts were provided. Regarding Pr. caryophila, the ultrastructural description of this species was implemented by several features previously unknown, such as the so called "membrane cluster" dividing periplasm from cytoplasm and fine composition of infectious forms before and during its releasing from the infected macronucleus. The new combinations of these Holospora-like bacteria with ciliate hosts were discussed from biogeographical and ecological points of view. Host specificity of symbionts as a general paradigm was critically reviewed as well
Host association and intracellularity evolved multiple times independently in the Rickettsiales
Abstract The order Rickettsiales (Alphaproteobacteria) encompasses multiple diverse lineages of host-associated bacteria, including pathogens, reproductive manipulators, and mutualists. Here, in order to understand how intracellularity and host association originated in this order, and whether they are ancestral or convergently evolved characteristics, we built a large and phylogenetically-balanced dataset that includes de novo sequenced genomes and a selection of published genomic and metagenomic assemblies. We perform detailed functional reconstructions that clearly indicates “late” and parallel evolution of obligate host-association in different Rickettsiales lineages. According to the depicted scenario, multiple independent horizontal acquisitions of transporters led to the progressive loss of biosynthesis of nucleotides, amino acids and other metabolites, producing distinct conditions of host-dependence. Each clade experienced a different pattern of evolution of the ancestral arsenal of interaction apparatuses, including development of specialised effectors involved in the lineage-specific mechanisms of host cell adhesion and/or invasion