Taxonomy is the science of defining and naming groups of biological organisms based on shared characteristics and, more recently, on evolutionary relationships. With the birth of novel genomics/bioinformatics techniques and the increasing interest in microbiome studies, a further advance of taxonomic discipline appears not only possible but highly desirable. The present work proposes a new approach to modern taxonomy, consisting in the inclusion of novel descriptors in the organism characterization: (1) the presence of associated microorganisms (e.g.: symbionts, microbiome), (2) the mitochondrial genome of the host, (3) the symbiont genome. This approach aims to provide a deeper comprehension of the evolutionary/ecological dimensions of organisms since their very first description. Particularly interesting, are those complexes formed by the host plus associated microorganisms, that in the present study we refer to as “holobionts”. We illustrate this approach through the description of the ciliate Euplotes vanleeuwenhoeki sp. nov. and its bacterial endosymbiont “Candidatus Pinguicoccus supinus” gen. nov., sp. nov. The endosymbiont possesses an extremely reduced genome (~ 163 kbp); intriguingly, this suggests a high integration between host and symbiont.

Allophylus serratusmediated silver nanoparticles biosynthesis, characterization, and antimicrobial activity were described. The synthesis of silver nanoparticles was confirmed by visual observation: UV-Vis spectrum, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and Fourier Transform Infra-Red (FTIR). UV-Vis spectroscopy studies showed that the absorption spectra of synthesized silver nanoparticles from leaf and callus extracts had absorbance peak range of 440 nm and 445 nm, respectively. The X-RD pattern revealed the presence of crystalline, dominantly spherical silver nanoparticles in the sample having size ranging from 42 to 50 nm. The XRD peaks 38.2°, 44.1°, 64.1°, and 77.0° for leaf extract and 38.1°, 44.3°, 64.5°, 77.5°, and 81.33° for callus extract can be assigned the plane of silver crystals (111), (200), (220), and (311), respectively, and indicate that the silver nanoparticles are face-centered, cubic, and crystalline in nature. SEM and EDS analysis also confirmed the presence of silver nanoparticles. The FTIR results showed the presence of some biomolecules in extracts that act as reducing and capping agent for silver nanoparticles biosynthesis. The synthesized silver nanoparticles showed significant antibacterial activity againstKlebsiella pneumoniaeandPseudomonas aeruginosa.

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Holospora spp. and “Candidatus Gortzia infectiva”, known as Holospora-like bacteria (HLB), are commonly found as nuclear endosymbionts of ciliates, especially the Paramecium genus. HLB are related by phylogenetic relationships, morphological features, and life-cycles, which involve two alternating morphotypes: reproductive and infectious forms (RF, IF). In this paper we describe a novel species belonging to the “Ca. Gortzia” genus, detected in P. multimicronucleatum, a ciliate for which infection by an HLB has not been reported, discovered in India. This novel endosymbiont shows unusual and surprising features with respect to other HLB, such as large variations in IF morphology and the occasional ability to reproduce in the host cytoplasm. We propose the name of “Candidatus Gortzia shahrazadis” for this novel HLB. Moreover, we report two additional species of HLB from Indian Paramecium populations: “Ca. Gortzia infectiva” (from P. jenningsi), and H. obtusa (from P. caudatum); the latter is the first record of Holospora from a tropical country. Although tropical, we retrieved H. obtusa at an elevation of 706 m corresponding to a moderate climate not unlike conditions where Holospora are normally found, suggesting the genus Holospora does exist in tropical countries, but restricted to higher elevations.

The subclass Peniculia (Oligohymenophorea, Intramacronucleata) is one of the most known groups of the phylum Ciliophora, being composed by very notorious representatives, such as Paramecium and Frontonia. Nevertheless, phylogenetic relationships among genera within this subclass are still far from being resolved. Moreover, for several members of the group the characterization by molecular markers is still lacking, such as for Wenrichia, Clathrostoma, Paraclathrostoma, Didieria and, to date, also for Neobursaridium. The finding of one strain of Neobursaridium gigas from India led to the first molecular characterization of this uncommonly sampled ciliate. The 18S rDNA sequence and the COI sequence were obtained and used for phylogenetic analyses. Moreover, the partial mitochondrial genome of N. gigas was sequenced, annotated and employed for phylogenomics analysis. To increase the sampling effort for the Paramecium clade, several newly obtained 18S rDNA sequences of parameciids are herein presented. Unexpectedly, the inclusion of N. gigas's molecular data in phylogenetics/phylogenomics analyses did not help to solve the complex evolution relationships inside Peniculia. Conversely, it raised new and intriguing questions about Paramecium phylogeny, since N. gigas clustered inside Paramecium clade as sister species of Paramecium bursaria in all the performed analyses. A critical revision of past and present data led to rename N. gigas as Paramecium gigas (Balech, 1941) comb. nov., and triggered the revision of genus Paramecium, with the proposal of the new subgenus Gigaparamecium subgen. nov. Hypotheses on the evolution of giant morphologies in ciliates are also discussed.