Culture Age, Intracellular Ca2+ Concentration, and Protein Phosphorylation in Encystment-Induced Colpoda cucullus

Abstract

In Colpoda cucullus, intracellular Ca 2? mediates the encystment induction and protein phosphorylation that occur just prior to morphogenetic transformation into the resting form. When rapidly growing cells were stimulated to encyst, encystment was not readily induced, and the protein phosphorylation level was lower. On the other hand, in post-growing cells stimulated to encyst, the encystment rate and protein phosphorylation level were elevated. These results suggest that protein phosphorylation is closely linked to encystment induction. Why, then, are the protein phosphorylation level and encystment rate difficult to elevate in the rapidly growing cells? Fura 2 ratiometry showed that the intracellular Ca 2? concentration (F 340 /F 380 ratio) was raised in rapidly growing cells as well as in post-growing cells when the cells were stimulated to encyst. It is presumed that the Ca 2? -mediated signal transduction pathways for protein phosphorylation and encystment may be triggered in rapidly growing cells, but downstream certain steps may be suppressed by certain intracellular components.

Evidence for asymmetric cell fate and hypoxia induced differentiation in the facultative pathogen protist Colpoda cucullus

“…are free-living ciliates found occasionally as vegetative and cystic form in human urine tract (acute cystitis, chronic prostatitis) [3] and invertebrates. In recent years Colpoda cucullus has been intensively studied by a Japanese research group [4][5][6][7][8]. In the present paper we compare what is known about Colpoda cucullus cell differentiation to our findings in E. invadens [1,2] and Giardia (Niculescu VF 2014.…”

“…The Japanese researchers cultured Colpoda in a nutrient poor culture medium consisting only of 0.05% w/v dried wheat leaves infusion [4][5][6][7][8]. Low-density cultures (LD cultures) were inoculated with 10 3 vegetative cells/ml.…”

“…Low-density cultures (LD cultures) were inoculated with 10 3 vegetative cells/ml. Non-proliferating Aerobacter aerogenes cells [4][5][6] and Klebsiella pneumoniae [7,8] were added to the culture medium as a food source. Both A. aerogenes and K. pneumoniae are oxygen consuming bacteria (OCB) [9,10].…”

“…Unfortunatelly, the authors failed to report the amounts of bacteria added in culture, thus neglecting to consider the effects of hypoxia and different pO 2 It could be that the true inducer is a shift in hypoxia, similar to the hypoxic/hypoosmotic pressure in OCB sediments which shift E. invadens to ITD. Evidence for this assertion is the "overpopulation" (OP) mediated encystment observed in encystment assays inoculated with high Colpoda cell density [6,8]. The authors differentiate between "induced" (IND) and "not induced" (NI) encystment occuring in 1mM Tris-HCl pH 7,2 with or without Ca 2+ ions, and "spontaneous" (S) encystment occuring in culture medium (0.05% w/v infusion of dried wheat leaves).…”

“…For "induced" assays they suspended high density Colpoda populations (3x10 4 cells/ml) in 1mM TrisHCl pH 7,2/0,1mM CaCl 2 encystment medium referred to as HD/Ca 2+ (IND). For "not-induced" assays authors transferred low density populations of 1-2x10 3 cells/ml in encystment medium without Ca 2+ ions and bacteria referred to as LD/Tris (NI) [7] and [8]. It is not inducement by Ca 2+ ions, but rather hypoxic changes that occur during and after cell transfer (t0-t6) which in fact induce encystment.…”