TY - JOUR

T1 - Host and symbiont intraspecific variability: The case of Paramecium calkinsi and “Candidatus Trichorickettsia mobilis”

AU - Sabaneyeva, E.

AU - Castelli, M.

AU - Szokoli, F.

AU - Benken, K.

AU - Lebedeva, N.

AU - Salvetti, A.

AU - Schweikert, M.

AU - Fokin, S.

AU - Petroni, G.

PY - 2018

Y1 - 2018

N2 - Newly isolated strains of the ciliate Paramecium calkinsi and their cytoplasmic bacterial endosymbionts were characterized by a multidisciplinary approach, including live observation, ultrastructural investigation, and molecular analysis. Despite morphological resemblance, the characterized P. calkinsi strains showed a significant molecular divergence compared to conspecifics, possibly hinting for a cryptic speciation. The endosymbionts were clearly found to be affiliated to the species “Candidatus Trichorickettsia mobilis” (Rickettsiales, Rickettsiaceae), currently encompassing only bacteria retrieved in an obligate intracellular association with other ciliates. However, a relatively high degree of intraspecific divergence was observed as well, thus it was possible to split “Candidatus Trichorickettsia” into three subspecies, one of which represented so far only by the newly characterized endosymbionts of P. calkinsi. Other features distinguished the members of each different subspecies. In particular, the endosymbionts of P. calkinsi resided in the cytoplasm and possessed numerous peritrichous flagella, although no motility was evidenced, whereas their conspecifics in other hosts were either cytoplasmic and devoid of flagella, or macronuclear, displaying flagellar-driven motility. Moreover, contrarily to previously analyzed “Candidatus Trichorickettsia” hosts, infected P. calkinsi cells frequently became amicronucleate and demonstrated abnormal cell division, eventually leading to decline of the laboratory culture.

AB - Newly isolated strains of the ciliate Paramecium calkinsi and their cytoplasmic bacterial endosymbionts were characterized by a multidisciplinary approach, including live observation, ultrastructural investigation, and molecular analysis. Despite morphological resemblance, the characterized P. calkinsi strains showed a significant molecular divergence compared to conspecifics, possibly hinting for a cryptic speciation. The endosymbionts were clearly found to be affiliated to the species “Candidatus Trichorickettsia mobilis” (Rickettsiales, Rickettsiaceae), currently encompassing only bacteria retrieved in an obligate intracellular association with other ciliates. However, a relatively high degree of intraspecific divergence was observed as well, thus it was possible to split “Candidatus Trichorickettsia” into three subspecies, one of which represented so far only by the newly characterized endosymbionts of P. calkinsi. Other features distinguished the members of each different subspecies. In particular, the endosymbionts of P. calkinsi resided in the cytoplasm and possessed numerous peritrichous flagella, although no motility was evidenced, whereas their conspecifics in other hosts were either cytoplasmic and devoid of flagella, or macronuclear, displaying flagellar-driven motility. Moreover, contrarily to previously analyzed “Candidatus Trichorickettsia” hosts, infected P. calkinsi cells frequently became amicronucleate and demonstrated abnormal cell division, eventually leading to decline of the laboratory culture.

KW - Atomicforcemicroscopy(AFM);Bacterialendosymbionts;Ciliophora;Fluorescenceinsituhydridization(FISH);rRNAgeneinsertions;Symbiosis

KW - Atomic force microscopy (AFM)

KW - Bacterial endosymbionts

KW - Ciliophora

KW - Fluorescence in situ hydridization (FISH)

KW - rRNA gene insertions

KW - Symbiosis

UR - http://www.scopus.com/inward/record.url?scp=85039168608&partnerID=8YFLogxK

UR - https://www.elibrary.ru/item.asp?id=35484324https://www.elibrary.ru/item.asp?id=35484324

U2 - 10.1016/j.ejop.2017.12.002

DO - 10.1016/j.ejop.2017.12.002

M3 - Article

VL - 62

SP - 79

EP - 94

JO - European Journal of Protistology

JF - European Journal of Protistology

SN - 0932-4739

ER -