In the poly(A)+RNA isolated from the ciliate Paramecium primaurelia is found a discrete and abundant mRNA species of high molecular weight (corresponding to about 9,000 nucleotides). This mRNA species has size and abundance characteristics that identify it tentatively as the message coding for the variant cell-surface antigens. After microinjection of the high molecular weight mRNA into amphibi...

The AMP-dependent stimulation of the cyanide-insensitive respiration of Paramecium mitochondria was investigated. The nucleotides exhibiting a stimulatory effect on the cyanide-insensitive oxidation of pyruvate (+ malate) in a medium supplemented with EDTA or carboxyatractyloside were, in decreasing order of efficiency, AMP, GMP, IMP, UMP and TMP. On the other hand, ADP, ATP and cyclic AMP were...

PP63 (parafusin) is a 63 kDa phosphoprotein which is very rapidly (within 80 ms) dephosphorylated (to P63) during triggered trichocyst exocytosis; this occurs selectively in exocytosis-competent Paramecium tetraurelia strains. In the present work, two cDNAs coding for PP63/parafusin have been isolated, one of which is a new isoform. These isoforms are 99.6% identical and are derived from two di...

In most studies dealing with the laboratory cultivation of paramecia (Paramecium bursaria), Klebsiella pneumoniae bacteria are used to inoculate the medium. However, Klebsiella pneumoniae is a typical pathogen, and its use is always associated with a risk of infection. The aim of the present research was to examine non-pathogenic bacteria strains as components of the medium for Paramecium bursa...

Behavioural responses to different accelerations below 1 g and up to 5 g were investigated in Paramecium biaurelia by using a centrifuge microscope on Earth and in space during a recent space flight. Increased stimulation (hypergravity) enhanced the negative gravitactic and the gravikinetic responses in Paramecium biaurelia within seconds. Cells did not adapt to altered gravitational conditions...

Paramecium tetraurelia is attracted to acetate and biotin by swimming smoothly and fast up gradients of these attractants, and turning immediately and slowing down when leaving these stimuli. We use a group of mutants, each with a different defect in an identified ion conductance, to show that these two stimuli open different ion channels, and the behaviors that occur upon application of stimul...

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...

We cloned a guanylyl cyclase of 280 kDa from the ciliate Paramecium which has an N-terminus similar to that of a P-type ATPase and a C-terminus with a topology identical to mammalian adenylyl cyclases. Respective signature sequence motifs are conserved in both domains. The cytosolic catalytic C1a and C2a segments of the cyclase are inverted. Genes coding for topologically identical proteins wit...

According to text book definition, parasites reduce the fitness of their hosts whereas mutualists provide benefits. But biotic and abiotic factors influence symbiotic interactions, thus under certain circumstances parasites can provide benefits and mutualists can harm their host. Here we addressed the question which intrinsic biotic factors shape a symbiosis and are crucial for the outcome of t...