Bacteria Help Amoeba Fight Viruses – News Home


Scientists from Austria and France describe a surprising combination of the amoeba and the single-celled chlamydia that lives in it, so the host amoeba is protected from the giant virus. While the molecular basis of this phenomenon remains to be elucidated, experiments have shown that chlamydia can prevent giant viruses of various species from multiplying in amoeba hosts, although it cannot prevent the virus from entering cells.

giant virus – An amazing group of DNA-containing eukaryotic viruses that stand out from other viruses in size virion, and along the length of the genome. They infect unicellular eukaryotes (Protists), especially amoeba. Many giant viruses are ruthless to their hosts and cause rapid cell lysis, releasing many new virions that assemble within the host cell. New virus particles infect new hosts and everything repeats itself. But it’s not just viruses that destroy protist life.Bacteria usually colonize inside them and become true gluttons, snatching away from their owners Adenosine triphosphate and valuable metabolites. However, the role of these clients is sometimes underestimated…

authors of the study post Recently in a magazine NASAannounced the discovery of a new giant virus, which they dubbed Viennavirus and assigned to the family Marseille viridae. Scientists have isolated particles of a new virus from wastewater.Intravenous virus infection of amoeba of the genus AcanthamoebaInclude, Acanthamoeba (figure 2). Interestingly, the cells were isolated from the same water sample from which the viper virus was isolated. A.the thiefContains intracellular bacteriaChlamydia Acanthamoeba parachlamydia. This bacterium survives at the expense of the host cell, from which it obtains ATP and metabolic intermediates.The authors of the study confirmed that there is Acanthamoeba Negatively affects amoeba viability, especially as they divide much more slowly than cells without a symbiotic “trailer”. Why do amoebas continue to contain chlamydia at their own expense, and why haven’t they evolved to develop protection against “hosters”?

米。 2. 棘阿米巴卡氏变形虫细胞中的维纳病毒病毒工厂

The researchers examined how the presence of chlamydia in amebic cells affects the course of infection caused by venoviruses. venavirus itself, like other giant viruses of the family Marseille viridaeIt is acutely lytic: the amoeba begins to lyse 12 hours after infection, and by 55 hours after infection, the original amoeba population is gone.

But if the amoeba has bacterial cells in it Acanthamoeba Something went wrong in the viral life cycle: virus factories (special parts of the cytoplasm where new virions are actively formed) do not form in infected amoeba, nor do new virions emerge.confirm its existence Acanthamoeba to amoeba A.the thief The ability to effectively fight off viruses, scientists have tried to infect amoeba cells of another species with chlamydia, Acanthamoeba castellaniand another strain A.the thief (PRA-115), without the symbionts, after which they were attacked by the viper virus.It turns out that in the absence of symbionts and A. castellaniiand A.the thief PRA-115 is efficiently cleaved by venavirus to produce viral progeny. But cells that received the coveted chlamydia were resistant to lysis.Therefore, in the presence of viper virus in the environment Pseudomonas acanthamoeba Instead of being useless from scratch, it becomes a protector that prevents viruses from multiplying in bacterial cells.

To answer the question of how exactly chlamydia protects the amoeba from the venom, you need to figure out which stage of the viral life cycle it blocks. To clarify this question, the scientists either infected the amoeba with both the virus and bacteria, or first with the bacteria and then with the virus (Figure 3). The results showed that in the case of co-infection with chlamydia and viper virus, virus factories were formed in the amoeba, and they could be detected in cells 12 and 24 hours after infection. However, viral replication was an order of magnitude lower in these cells than in cells without symbiotic bacteria. The authors of the study concluded that chlamydia does not interfere with the entry of the virus into cells, but prevents it from replicating. This hypothesis was confirmed in experiments using different infection protocols. It turns out that if the amoeba is first infected with a bacterium, and 12 hours after infection with a virus (twelve hours after infection with bacteria, the “relationship” between the host amoeba and chlamydia becomes relatively stable), then the virus factory can also be Viper virus was detected 12 hours after infection and no longer detected after 24 hours. The authors show that in this case, viral factories are still formed in amoeba cells, but they do not develop further and gradually disappear, interrupting viral replication.

米。 3. 变形虫细胞中静脉病毒行为的可视化

Surprising but protective Acanthamoeba Extends to other giant viruses, including those unrelated to venavirus! Amoeba-infected amoeba also obtained similar results to venoviruses. Mimic virus and Tupan virus – Giant viruses from another family (Viridae). Like venoviruses, chlamydia successfully inhibited the replication of these viruses in amoebae cells (Figure 4).Therefore, it can be said that bacteria Acanthamoeba Nonspecific protection against evolutionarily and structurally distant giant viruses for amoeba hosts.

米。 4. 细胞内衣原体不仅会阻止毒粒病毒在变形虫细胞中的繁殖,而且还会阻止其他两种巨型病毒——拟态病毒和图潘病毒——的繁殖

Unfortunately, regarding the mechanism of protection Acanthamoeba So far, nothing has been said for sure. It can be assumed that chlamydia comes into direct contact with a mature virus factory or virus particle, but within an amoeba, the bacterium is not self-contained – it is surrounded by a membrane that it receives when it enters the amoeba. A more plausible option seems to be for the bacteria to indirectly block the reproduction of the virus, somehow manipulating the host cell’s signaling pathways.

resource: Patrick Arthofer, Vincent Delafont, Anouk Willemsen, Florian Panhölzl and Matthias Horn. Defensive symbiosis against the giant amoeba virus // NASA. 2022. DOI:10.1073/pnas.2205856119。

Elizabeth Minina

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