LOCALIZATION OF CYTOPLASMIC NUCLEIC ACID DURING GROWTH AND ENCYSTMENT OF ENTAMOEBA INVADENS

Abstract

With a modified color-translating ultraviolet microscope, the distribution of material showing an absorption maximum at 265 m~t was studied in samples from whole cultures of Entamoeba invadens at intervals during growth and from cysts allowed to mature under controlled conditions. Absorption by the cytoplasm in general gradually increased as trophozoites approached the period of maximum encystment. In late trophozoites and precystic forms, the absorbing material was concentrated into small bodies which coalesced to form large crystalloids of very high specific absorption. Maximum crystallization occurred in early cysts, where cytochcmical tests have shown the large crystalloids to be ribonucleoprotein. Electron micrographs show that the crystalloids are composed of particles 200 to 300 A in diameter. During cyst maturation the amount of absorbing material per cyst is not visibly reduced, but the large bodies fragment into smaller units until finally there is only a very high diffuse absorption over the entire cyst. From these and other results the hypothesis is advanced that the large crystalloids ("chromatoid bodies") are a manifestation of a special parasite-host adaptive mechanism; ribonucleoprotein is synthesized under favorable conditions, crystallized in the resistant cyst stage, and dispersed in the newly excysted amebae thereby enabling them to establish themselves in a new host by a period of quick growth.

The genome and transcriptome of the enteric parasite Entamoeba invadens, a model for encystation

“…These proteins may be involved in formation of the chromatoid bodies, RNP structures that are found in Entamoeba cysts [69]. In addition, DNA repair pathway genes such as the Rad1 homolog EIN_013450 and the Rad52 homolog EIN_094590 have increased expression and may facilitate nuclear division, which occurs late in encystation [70].…”

ULTRASTRUCTURE OF BACTERIZED AND AXENIC TROPHOZOITES OF ENTAMOEBA HISTOLYTICA WITH PARTICULAR REFERENCE TO HELICAL BODIES

“…Characteristic of those several species of Entamoeba studied thus far (4-6, 29, 30), these structures form linearly arranged aggregates that are the typical crystalline chromatoid bodies seen under the light RoSENBAUM AND WITTNER Bacterized and Axenic Trophozoites of Entamoeba Histolytica 3 7 3 microscope (15,18,20) . Studies by Barker (4,6) have emphasized their largely ribonucleoprotein nature in E. invadens . Both packed and fragmented or dispersed RNP bodies were present in the cytoplasm of axenic and bacterized trophozoites of E .…”

“…Furthermore, preparation of material for electron microscopic, as well as cytochemical studies, becomes simpler once bacterial associates are eliminated . Thus far, only E. invadens from the snake (6,12,29,36) has been studied from axenic culture with the electron microscope (30) .…”

Ribonucleoprotein‐Containing Vesicles in Cysts of Naegleria gruberi*

“…For studies on ultraviolet absorption, wet mounts of cysts and pre-cystic stages were made on quartz slides and studied with a modified color-translating ultraviolet microscope, Model UV-91 (Scientific Specialties Corp., Boston, Massachusetts). Details on the use of this instrument are given in ( 2 ) . Acridine orange staining of similar stages were performed for dark-field and fluorescence microscopy as reported previously (15).…”