A complex of iron and nucleic acid catabolites is a signal that triggers differentiation in a freshwater protozoan

Abstract

The polymorphic ciliated protozoan Tetrahymena vorax can undergo differentiation from the microstomal form, which normally feeds on bacteria and other particulate matter, into the macrostomal cell type, which is capable of ingesting prey ciliates. The process is triggered by exposure of the microstome to an inducer contained in stomatin, an exudate of the prey. To establish the identity of the signal, stomatin was fractionated by combinations of cation exchange, HPLC, and TLC, and the fractions were assayed for biological activity. Although no single active fraction of purified inducer was obtained, all fractions with activity contained ferrous iron and the nucleic acid catabolites hypoxanthine (6-oxypurine) and uracil (2,4-dioxopyrimidine), probably in a chelated form. The activity of synthetic complexes containing these three components is equivalent to stomatin. These results indicate a role for ferrous iron and its potential in chelated form to signal differentiation in certain protozoa and, perhaps, in other organisms as well.

Behavioral Effects of a Chemorepellent Receptor Knockout Mutation in Tetrahymena thermophila

“…Stomatin is found in the supernatant of Tetrahymena by using procedures that are very similar to our methods of obtaining the CSF (31). Stomatin causes transformation of the microstome form of T. vorax into the macrostomal form, which eats T. thermophila (31).…”

Microstome–macrostome transformation in the polymorphic ciliateTetrahymena voraxleads to mechanosensitivity associated with prey-capture behaviour

“…We studied behavioural and electrophysiological responses in polymorphous Tetrahymena vorax Kidder 1941, strain V 2 S. For induction of the transformation between the microstome and the macrostome form, and as prey species for the macrostome form, we used Tetrahymena thermophila, Nanney and McCoy 1952 (Buhse, 1967;Smith-Somerville et al, 2000). Both strains were obtained from the American Type Culture Collection.…”

“…This kairomone could be the complex mixture, i.e. stomatin that induces transformation in T. vorax (Williams, 1961;Buhse, 1966;Smith-Somerville et al, 2000;Arauz et al, 2009). Chemo-attraction to potential prey cells seems to be the main mechanism for food selection also in the carnivorous protozoa Didinum and Coleps (Seravin and Orlovskaja, 1977).…”

“…The cue that triggers the transformation in T. vorax is released by potential prey ciliates, such as Tetrahymena thermophila and Colpidium striatum. The cue is a mixture termed stomatin, which contains numerous components including Fe 2+ and nucleic acid catabolites (Smith-Somerville et al, 2000;Arauz et al, 2009). Receptors for inducing the transformation have not yet been indentified, but a rapid increase in cytosolic Ca 2+ concentration is an important step in the transmembrane signalling cascade (Ryals et al, 1999;Ryals et al, 2008).…”

Electrophysiological Properties of the Microstome and Macrostome Morph of the Polymorphic Ciliate Tetrahymena vorax

“…; Smith‐Somerville et al. ). Receptors for inducing the transformation have not yet been indentified, but a rapid increase in cytosolic Ca 2+ concentration is an important step in the transmembrane signalling cascade (Ryals et al.…”