TY - JOUR

T1 - “Candidatus Mystax nordicus” Aggregates with Mitochondria of Its Host, the Ciliate Paramecium nephridiatum

AU - Korotaev , Aleksandr

AU - Benken, Konstantin

AU - Sabaneyeva , Elena

N1 - Publisher Copyright: © 2020 by the authors.

PY - 2020/6/1

Y1 - 2020/6/1

N2 - Extensive search for new endosymbiotic systems in ciliates occasionally reverts us to the endosymbiotic bacteria described in the pre-molecular biology era and, hence, lacking molecular characterization. A pool of these endosymbionts has been referred to as a hidden bacterial biodiversity from the past. Here, we provide a description of one of such endosymbionts, retrieved from the ciliate Paramecium nephridiatum. This curve-shaped endosymbiont (CS), which shared the host cytoplasm with recently described "Candidatus Megaira venefica", was found in the same host and in the same geographic location as one of the formerly reported endosymbiotic bacteria and demonstrated similar morphology. Based on morphological data obtained with DIC, TEM and AFM and molecular characterization by means of sequencing 16S rRNA gene, we propose a novel genus, "Candidatus Mystax", with a single species "Ca. Mystax nordicus". Phylogenetic analysis placed this species in Holosporales, among Holospora-like bacteria. Contrary to all Holospora species and many other Holospora-like bacteria, such as "Candidatus Gortzia", "Candidatus Paraholospora" or "Candidatus Hafkinia", "Ca. Mystax nordicus" was never observed inside the host nucleus. "Ca. Mystax nordicus" lacked infectivity and killer effect. The striking peculiarity of this endosymbiont was its ability to form aggregates with the host mitochondria, which distinguishes it from Holospora and Holospora-like bacteria inhabiting paramecia.

AB - Extensive search for new endosymbiotic systems in ciliates occasionally reverts us to the endosymbiotic bacteria described in the pre-molecular biology era and, hence, lacking molecular characterization. A pool of these endosymbionts has been referred to as a hidden bacterial biodiversity from the past. Here, we provide a description of one of such endosymbionts, retrieved from the ciliate Paramecium nephridiatum. This curve-shaped endosymbiont (CS), which shared the host cytoplasm with recently described "Candidatus Megaira venefica", was found in the same host and in the same geographic location as one of the formerly reported endosymbiotic bacteria and demonstrated similar morphology. Based on morphological data obtained with DIC, TEM and AFM and molecular characterization by means of sequencing 16S rRNA gene, we propose a novel genus, "Candidatus Mystax", with a single species "Ca. Mystax nordicus". Phylogenetic analysis placed this species in Holosporales, among Holospora-like bacteria. Contrary to all Holospora species and many other Holospora-like bacteria, such as "Candidatus Gortzia", "Candidatus Paraholospora" or "Candidatus Hafkinia", "Ca. Mystax nordicus" was never observed inside the host nucleus. "Ca. Mystax nordicus" lacked infectivity and killer effect. The striking peculiarity of this endosymbiont was its ability to form aggregates with the host mitochondria, which distinguishes it from Holospora and Holospora-like bacteria inhabiting paramecia.

KW - symbiosis

KW - Paramecium

KW - ciliates

KW - Holospora-like bacteria

KW - host–parasite interactions

KW - 16S rRNA gene sequencing

KW - full-cycle rRNA approach

KW - TEM

KW - fluorescence in situ hybridization

KW - Symbiosis

KW - 16S rRNA gene

KW - Fluorescence in situ hybridization

KW - Host-parasite interactions

KW - Ciliates

KW - Full-cycle rRNA approach

UR - https://www.mdpi.com/1424-2818/12/6/251

UR - http://www.scopus.com/inward/record.url?scp=85087527944&partnerID=8YFLogxK

U2 - 10.3390/D12060251

DO - 10.3390/D12060251

M3 - Article

VL - 12

JO - Diversity

JF - Diversity

SN - 1424-2818

IS - 6

M1 - 251

ER -