Entamoeba Shows Reversible Variation in Ploidy under Different Growth Conditions and between Life Cycle Phases

Abstract

Under axenic growth conditions, trophozoites of Entamoeba histolytica contain heterogenous amounts of DNA due to the presence of both multiple nuclei and different amounts of DNA in individual nuclei. In order to establish if the DNA content and the observed heterogeneity is maintained during different growth conditions, we have compared E. histolytica cells growing in xenic and axenic cultures. Our results show that the nuclear DNA content of E. histolytica trophozoites growing in axenic cultures is at least 10 fold higher than in xenic cultures. Re-association of axenic cultures with their bacterial flora led to a reduction of DNA content to the original xenic values. Thus switching between xenic and axenic growth conditions was accompanied by significant changes in the nuclear DNA content of this parasite. Changes in DNA content during encystation-excystation were studied in the related reptilian parasite E. invadens. During excystation of E. invadens cysts, it was observed that the nuclear DNA content increased approximately 40 fold following emergence of trophozoites in axenic cultures. Based on the observed large changes in nuclear size and DNA content, and the minor differences in relative abundance of representative protein coding sequences, rDNA and tRNA sequences, it appears that gain or loss of whole genome copies may be occurring during changes in the growth conditions. Our studies demonstrate the inherent plasticity and dynamic nature of the Entamoeba genome in at least two species.

The Macrophage Migration Inhibitory Factor Homolog of Entamoeba histolytica Binds to and Immunomodulates Host Macrophages

“…First, E. histolytica infection results in disruption of the mucosal barrier, which might lead to infiltration of bacteria into the lamina propria. Second, trophozoites feed on gut flora; hence, invading parasites could carry bacterial products, including LPS (46,47). As reported previously, EhMIF in combination with LPS increased TNF-␣ production by macrophages in vitro.…”

Recent insights into Entamoeba development: Identification of transcriptional networks associated with stage conversion

“…Upon further passage, the bacterial populations may change and whether certain bacterial species predominate is not known. It has been observed for some recently axenized E. histolytica clinical isolates that bacterial flora, when provided exogenously, is beneficial to inducing encystation (Mukherjee et al, 2008). Furthermore, it has also recently been demonstrated that there is differential DNA content in parasites grown as long-term axenic cultures compared with those grown under xenic conditions (Mukherjee et al, 2008).…”

Recent advances in Entamoeba biology: RNA interference, drug discovery, and gut microbiome

“…As an example, cell division in Entamoeba is poorly understood, especially related to our understanding of the mechanism regulating chromatin pairing and segregation during cell division. Entamoeba exist as multinucleated polyploid cells in vitro and in vivo 66 , suggesting that the parasites are able to mitigate issues arising due to gene copy number. Given the atypical cell cycle in Entamoeba 33 , one could be enticed to hypothesize that amoebic RNA is involved in genome stabilization during cellular division.…”