Uppsala University researchers have recently discovered that the predecessors of the Pontiac fever-causing bacteria, Legionella bacteria, began infecting eukaryotic cells, also known as plant cells, as early as two billion years ago. The infection starts when eukaryotes start to feed on different bacterias.
The results described in the study contribute to the chicken-or-egg debate on who came first, mitochondria or phagocytosis?
Ancestors of Legionella Bacteria Found to Infect Eukaryotic Cells 2 Billion Years Ago
Lionel Guy, the co-author of the study and an associate professor at the Department of Medical Biochemistry and Microbiology, explains that the team's study can help researchers further understand how harmful bacteria rose and how complex cells evolved eventually from simpler cells, reports PhysOrg.
Roughly two billion years ago, the ancestors of the legionella bacteria known to cause Legionnaires' disease or Pontiac fever already could avoid digestion by eukaryotes. Instead, the bacteria began using these eukaryotic cells.
Andrei Gulliaev, co-author and researcher at the Department of Medical Biochemistry and Microbiology, explains that the team discovered how the ancestors of the bacterial group that lived roughly two billion years in the past, at a time when eukaryotes were fully developed and were evolving from much simpler cells to the complex structures they have today. He adds that the team believes that the Legionellales bacteria group was among the first to infect eukaryotic cells.
The first step to a legionella bacteria infection is for a eukaryotic host, such as animals, humans, and amoebas, to bring the bacterium into its cells via phagocytosis. Next, the amoeba would digest the bacterium and use its components as an energy source. However, the bacteria have a molecular tool that prevents them from being digested by the cell and allows it to use the host as an energy source instead of multiplying.
In the study published in the journal Molecular Biology and Evolution, titled "Host-adaptation in Legionellales is 1.9 Ga, coincident with eukaryogenesis," researchers showcase that all Legionellales have similar molecular tools as legionella. The findings suggest that the ability to infect eukaryotes existed in the ancestor of the entire bacteria group. This means that phagocytosis is at least older since Legionallales already had the tool two billion years ago when eukaryotes were only in the early stages of evolution.
The findings also have major implications on the hot debate in evolutionary biology on whether mitochondria came first or phagocytosis. Based on the study, Lionel Guy explains that phagocytosis came first while mitochondria came much later.
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Understanding Eukaryotic Cells
Plant cells and animal cells are both eukaryotic, according to VisibleBody. These are cells found in animals, protists, fungi, and plants. They generally have a nucleus where their genetic material is stored. Additionally, eukaryotic cells tend to be bigger than prokaryotic cells. Although many eukaryotic cells consist of multiple cells, there are exceptions known as single-celled eukaryotes.
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