Rapid Induction of Cellular Strain Specificity by Newly Acquired Cytoplasmic Components in Amoebas

Abstract

A new strain-specific character was induced in amoebas by bacterial endosymbionts after only 10 to 15 cell generations of symbiosis. The nuclei of changed amoebas not only became incompatible with the cytoplasm of the original strain, but also exerted a strong lethal effect on intact amoebas of the same original strain.

Nuclear Lethal Effect and Nucleocytoplasmic Incompatibility Induced by Endosymbionts in Amoeba proteus1

“…As suggested previously (14), exposure to the symbionts appears to induce the D nuclei to direct the synthesis of a new lethal factor specific to xD amoebae. The cytoplasm of newly infected D amoebae as well as that of established xD amoebae has been found to contain a unique polypeptide with a molecular weight of 29,000, which can be detected by two-dimensional electrophoresis (Ahn & Jeon, in preparation).…”

“…The present study was designed to investigate the time course of the acquisition of two phenotypic characters by strain xD of Amoeba proteus, namely the lethal effect on cells of the parent D strain and nucleocytoplasmic incompatibility. Previously, we infected strain D amoebae by intracellular injection of about 400 symbiotic bacteria per amoeba (14). It took about 3 weeks for the symbionts to attain a full complement, typically 42,000 bacteria per amoeba (1).…”

Genetic and Physiological Interactions in the Amoeba‐Bacteria Symbiosis1

“…Nuclei of xD amoebae are no longer compatible with the cytoplasm of D amoebae, the original strain (Jeon and Jeon 1976). When D amoebae are infected with XB either by intracellular injection or by induced phagocytosis, their nuclei become incompatible with the cytoplasm of D amoebae within a few wk (Lorch and Jeon 1981). Thus, XB cause nucleocytoplasmic incompatibility among amoebae.…”

“…Newly acquired nuclear lethal effect . Nuclei of xD amoebae are not only incompatible with the cytoplasm of D amoebae but also exert a strong lethal effect on D amoebae (Lorch and Jeon 1981). When the nucleus of an xD amoeba is transplanted into a D amoeba containing its own nucleus, the latter loses viability.…”

Bacterial Endosymbionts as Extrachromosomal Elements in Amebas

“…Meanwhile, the endosymbionts have other physiological and biochemical effects on the host, such as causing accelerated growth during induced infection (15), conferring temperature sensitivity (15), inducing nucleocytoplasmic incompatibility (23,24), and inducing the synthesis of new lethal factors (24,25).…”