title: Response of the bacterial symbiont Holospora caryophila to different growth conditions of its host.
abstract: Previous studies on bacterial symbionts of ciliates have shown that some symbionts can be maintained relatively well under standard laboratory conditions whereas others are frequently lost, especially when the host is cultivated at a high division rate. In this study, the variation in infection level by the endosymbiont Holospora caryophila within its host population Paramecium octaurelia was investigated in response to three alimentary treatments and a subsequent starvation phase. The response of the ciliates was determined as a nearly exponential growth rate with different slopes in each treatment, proportional to the amount of food received. The initial infection level was higher than 90%. After 24 days of exponential host's growth, the prevalence remained stable at approximately 90% in all treatments, even after a subsequent starvation phase of 20 days. However, at intermediate time-points in both the feeding and the starvation phase, fluctuations in the presence of the intracellular bacteria were observed. These results show that H. caryophila is able to maintain its infection under the tested range of host growth conditions, also due to the possibility of an effective re-infection in case of partial loss.
authors: Protistology-Zoology Unit, Department of Biology, University of Pisa, 56126 Pisa, Italy.
authors: Michele
authors: M
authors: Castelli
authors: Protistology-Zoology Unit, Department of Biology, University of Pisa, 56126 Pisa, Italy.
authors: Olivia
authors: O
authors: Lanzoni
authors: Protistology-Zoology Unit, Department of Biology, University of Pisa, 56126 Pisa, Italy; Department of Invertebrate Zoology, St Petersburg State University, 199034 St. Petersburg, Russia.
authors: Sergei I
authors: SI
authors: Fokin
authors: Institute of Hydrobiology, Technische Universität Dresden, 01217 Dresden, Germany; Microbiology, Institute of Biology II, University of Freiburg, 79104 Freiburg, Germany.
authors: Martina
authors: M
authors: Schrallhammer
authors: Protistology-Zoology Unit, Department of Biology, University of Pisa, 56126 Pisa, Italy. Electronic address: giulio.petroni@unipi.it.
authors: Giulio
authors: G
authors: Petroni
mesh_terms: D000704:Analysis of Variance; D042281:Holosporaceae / Q000502:physiology*; D010247:Paramecium / Q000254:growth & development / Q000382:microbiology*; D013559:Symbiosis; D013997:Time Factors
keywords: Ciliates; Endosymbiosis; Macronuclear; Paramecium; Parasites