Human monocyte derived macrophages incubated with Legionella pneumophila derived extracellular vesicles (white), endoplasmic reticulum (green); nucleus (blue), mitochondria (orange).
© Institut Pasteur
Researchers led by scientists from the Institut Pasteur, Université de Paris, have discovered how the pathogenic bacterium Legionella pneumophila, that caused the deadly Legionella disease, overcomes its victim's immune system. Any intelligent [sic] design advocate will tell you, this must have been the intended outcome when the bacterium was being designed because nothing in nature evolves without the intent and intervention of their omniscient, omnipotent divine malevolence.
The organism does this by secreting a small regulatory strand of RNA which facilitates the survival and proliferation of L. pneumophila during infection.
The team's findings are published, open access, in the journal Nature Communications.
In their press release accompanying the publication of their research paper, the team say:
Intracellular pathogens adopt various strategies to circumvent immune defenses and proliferate inside the cells they infect. Legionella pneumophila has a large repository of effector proteins [1] that mimic host cell functions and are used by the pathogen to manipulate host signaling pathways to the pathogens advantage[2]. The teams of Carmen Buchrieser, head of the unit Biology of the Intracellular Bacteria at the Institut Pasteur and associated to CNRS, in collaboration with Gregory Lavieu at the Université de Paris and associated to Inserm and CNRS, have discovered that Legionella pneumophila secretes extracellular vesicles into the host cell during infection in which it packs small, regulatory RNA molecules. These regulatory RNAs mimic eukaryotic regulatory RNAs called micro RNAs that already exist naturally in the host cell. The researchers have discovered that these two bacterial RNAs, named RsmY and tRNA-Phe, function in the host cell in a microRNA-like manner. They downregulate RIG-I, a protein in the cell that detects foreign RNA molecules in order to initiate an immune response. The down regulation of the expression of RIG-I leads to a diminished host immune response and a better replication of Legionella pneumophila. This work sheds new light on the diverse, sophisticated strategies employed by intracellular pathogens for survival and development during infection.The team give more technical details in the abstract to their paper in Nature Communication:
AbstractObviously, if you subscribe to the childish Intelligent [sic] Design superstition, you have to believe that whatever malevolence designed L. pneumophila had a pretty good understanding of the human immune system and how to overcome it, in order to ensure the bacterium killed as many people as possible, because the organism appears to have no other function.
Legionella pneumophila is an intracellular bacterial pathogen that can cause a severe form of pneumonia in humans, a phenotype evolved through interactions with aquatic protozoa in the environment. Here, we show that L. pneumophila uses extracellular vesicles to translocate bacterial small RNAs (sRNAs) into host cells that act on host defence signalling pathways. The bacterial sRNA RsmY binds to the UTR of ddx58 (RIG-I encoding gene) and cRel, while tRNA-Phe binds ddx58 and irak1 collectively reducing expression of RIG-I, IRAK1 and cRel, with subsequent downregulation of IFN-β. Thus, RsmY and tRNA-Phe are bacterial trans-kingdom regulatory RNAs downregulating selected sensor and regulator proteins of the host cell innate immune response. This miRNA-like regulation of the expression of key sensors and regulators of immunity is a feature of L. pneumophila host-pathogen communication and likely represents a general mechanism employed by bacteria that interact with eukaryotic hosts.
Sahr, T., Escoll, P., Rusniok, C. et al.
Translocated Legionella pneumophila small RNAs mimic eukaryotic microRNAs targeting the host immune response.
Nature Communications 13, 762 (2022). https://doi.org/10.1038/s41467-022-28454-x
Copyright: © 2022 The authors. Published by Springer Nature Ltd.
Open access
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)
The alternative is that the bacterium evolved by a mindless, amoral, utilitarian process, but that would exclude a magic creator from the process, and that is something that no self-respecting Creationist will do, for fear of what the imaginary malevolence might do to them.
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