“Candidatus Gortzia shahrazadis”, a Novel Endosymbiont of Paramecium multimicronucleatum and a Revision of the Biogeographical Distribution of Holospora-Like Bacteria

Abstract

<i>Holospora</i> spp. and "<i>Candidatus</i> Gortzia infectiva", known as <i>Holospora</i>-like bacteria (HLB), are commonly found as nuclear endosymbionts of ciliates, especially the <i>Paramecium</i> 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 "<i>Ca</i>. Gortzia" genus, detected in <i>P. multimicronucleatum</i>, 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 "<i>Candidatus</i> Gortzia shahrazadis" for this novel HLB. Moreover, we report two additional species of HLB from Indian <i>Paramecium</i> populations: "<i>Ca</i>. Gortzia infectiva" (from <i>P. jenningsi</i>), and <i>H. obtusa</i> (from <i>P. caudatum</i>); the latter is the first record of <i>Holospora</i> from a tropical country. Although tropical, we retrieved <i>H. obtusa</i> at an elevation of 706 m corresponding to a moderate climate not unlike conditions where <i>Holospora</i> are normally found, suggesting the genus <i>Holospora</i> does exist in tropical countries, but restricted to higher elevations.