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Naegleria fowleri: light and electron microscopy study of mitosis
Arturo González-Robles1, Ana Ruth Cristóbal-Ramos, Mónica González-Lázaro
1Department of Infectomic and Molecular Pathogenesis, Center for Research and Advanced Studies, Mexico City, Mexico.
Abstract:
DAPI and Feulgen stains were used as specific DNA markers for studying the mitosis process in Naegleria fowleri. Both DAPI and Feulgen stains reacted with DNA in the nuclei of the amoebae. Representative figures of N. fowleri mitotic nuclei with a defined arrangement according to the phase of the cell cycle were observed. A notable characteristic is that the nucleolus is present throughout the stages of mitosis. During metaphase, several deeply stained DNA condensations following an elongated pattern were observed, corresponding almost certainly to tightly grouped chromosomes. Ultrastructural observations demonstrated that the nucleus divides by cryptomitosis, a process in which the nuclear membrane does not disappear during the mitosis. Centrioles were not found, and a spindle of microtubules was observed running the length of the nucleus from pole to pole however, they did not come to a focal point.
Insights
This study visualizes the mitosis of Naegleria fowleri using DNA stains, revealing unique nuclear division characteristics. Key findings include the persistent nucleolus and a distinct cryptomitosis process without centrioles.
Area of Science:
- Cell Biology
- Microbiology
- Parasitology
Background:
- Naegleria fowleri is an opportunistic freshwater amoeba.
- Understanding its cell division is crucial for studying its biology and pathogenesis.
- Mitosis in free-living amoebae presents diverse and often atypical mechanisms.
Purpose of the Study:
- To investigate the process of mitosis in Naegleria fowleri.
- To characterize the nuclear division dynamics using specific DNA staining techniques.
- To describe the ultrastructural features of N. fowleri mitosis.
Main Methods:
- Application of DAPI and Feulgen stains as specific DNA markers.
- Microscopic observation of mitotic nuclei in Naegleria fowleri.
- Ultrastructural analysis of the nuclear division process.
Main Results:
- Both DAPI and Feulgen stains effectively marked DNA within N. fowleri nuclei.
- The nucleolus remained visible throughout all observed stages of mitosis.
- Mitosis occurred via cryptomitosis, characterized by an intact nuclear membrane and the absence of centrioles, with a non-focal spindle.
- Elongated DNA condensations, indicative of chromosomes, were observed during metaphase.
Conclusions:
- Naegleria fowleri undergoes a unique form of mitosis (cryptomitosis) with distinct nuclear and chromosomal behaviors.
- The persistent nucleolus and atypical spindle formation are notable features of N. fowleri cell division.
- The study provides detailed morphological insights into N. fowleri mitosis, contributing to the understanding of amoeboid cell division.
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