Mirror life (also called mirror-image life) is a
hypothetical form of life using
mirror-reflected molecular building blocks. The possibility of mirror life was first discussed by
Louis Pasteur
Louis Pasteur (, ; 27 December 1822 – 28 September 1895) was a French chemist, pharmacist, and microbiologist renowned for his discoveries of the principles of vaccination, Fermentation, microbial fermentation, and pasteurization, the la ...
. This alternative life form has never been discovered in nature, although certain mirror-image components of molecular machinery have been synthesized in the laboratory and, in principle, entire mirror organisms could be created.
In December 2024, a broad coalition of scientists, including leading synthetic biology researchers and Nobel laureates, warned that the creation of mirror life, could cause "unprecedented and irreversible harm" to human health and ecosystems worldwide.
The potential for mirror bacteria to escape immune defenses and invade natural ecosystems might lead to "pervasive lethal infections in a substantial fraction of plant and animal species, including humans." Given these risks, the scientists concluded that mirror organisms should not be created without compelling evidence of safety.
Homochirality
Many of the essential molecules for life on Earth can exist in two mirror-image forms, often called "left-handed" and "right-handed", where handedness refers to the direction in which polarized light skews when beamed through a pure solution of the molecule, but living organisms do not use both.
RNA
Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself (non-coding RNA) or by forming a template for the production of proteins (messenger RNA). RNA and deoxyrib ...
and
DNA
Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...
contain only right-handed
sugar
Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose
Glucose is a sugar with the Chemical formula#Molecular formula, molecul ...
s;
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
s made by the ribosome are exclusively composed of left-handed
amino acids
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the Proteinogenic amino acid, 22 α-amino acids incorporated into p ...
. This phenomenon is known as
homochirality
Homochirality is a uniformity of chirality, or handedness. Objects are chiral when they cannot be superposed on their mirror images. For example, the left and right hands of a human are approximately mirror images of each other but are not their ow ...
.
It is not known whether homochirality emerged before or after life, whether the building blocks of life must have this particular chirality, or indeed whether life needs to be homochiral. Protein chains built from amino acids of mixed chirality tend not to fold or function well, but mirror-image proteins have been constructed that have identical function but on substrates of opposite handedness.
[
]
The concept
Advances in synthetic biology
Synthetic biology (SynBio) is a multidisciplinary field of science that focuses on living systems and organisms. It applies engineering principles to develop new biological parts, devices, and systems or to redesign existing systems found in nat ...
, like synthesizing viruses since 2002, partially synthetic bacteria in 2010, and synthetic ribosomes in 2013, may lead to the possibility of fully synthesizing a living cell from small molecules, which could enable synthesizing mirror cells from mirrored versions (enantiomer
In chemistry, an enantiomer (Help:IPA/English, /ɪˈnænti.əmər, ɛ-, -oʊ-/ Help:Pronunciation respelling key, ''ih-NAN-tee-ə-mər''), also known as an optical isomer, antipode, or optical antipode, is one of a pair of molecular entities whi ...
s) of life's building-block molecules. Some proteins have been synthesized in mirror-image versions, including polymerase
In biochemistry, a polymerase is an enzyme (Enzyme Commission number, EC 2.7.7.6/7/19/48/49) that synthesizes long chains of polymers or nucleic acids. DNA polymerase and RNA polymerase are used to assemble DNA and RNA molecules, respectively, by ...
in 2016.
Reconstructing regular lifeforms in mirror-image form, using the mirror-image (chiral) reflection of their cellular components, could be achieved by substituting left-handed amino acids with right-handed ones, in order to create mirror reflections of proteins, and likewise substituting right-handed with left-handed nucleic acids. Because the phospholipid
Phospholipids are a class of lipids whose molecule has a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue (usually a glycerol molecule). Marine phospholipids typ ...
s of cell membranes are also chiral, American geneticist George Church proposed using an achiral fatty acid instead of mirror-image phospholipids for the membrane.
Electromagnetic force (chemistry) is unchanged under such molecular reflection transformation (P-symmetry
In physics, a parity transformation (also called parity inversion) is the flip in the sign of ''one'' Three-dimensional space, spatial coordinate. In three dimensions, it can also refer to the simultaneous flip in the sign of all three spatial co ...
). There is a small alteration of weak interactions under reflection, which can produce very small corrections that theoretically favor the natural enantiomers of amino acids and sugars, but it is unknown if this effect is large enough to affect the functionality of mirror biomolecules or explain homochirality in nature.
Mirror animals would need to feed on reflected food, produced by reflected plants. Mirror viruses would not be able to attack natural cells, just as natural viruses would not be able to attack mirror cells.
Mirror life presents potential dangers. For example, a chiral-mirror version of cyanobacteria
Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteri ...
, which only needs achiral nutrients and light for photosynthesis
Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...
, could take over Earth's ecosystem due to lack of natural enemies, disturbing the bottom of the food chain by producing mirror versions of the required sugars. Some bacteria can digest L-Glucose; exceptions like this would give some rare lifeforms an unanticipated advantage.
Direct applications
Direct application of mirror-chiral organisms can be mass production of enantiomer
In chemistry, an enantiomer (Help:IPA/English, /ɪˈnænti.əmər, ɛ-, -oʊ-/ Help:Pronunciation respelling key, ''ih-NAN-tee-ə-mər''), also known as an optical isomer, antipode, or optical antipode, is one of a pair of molecular entities whi ...
s (mirror-image) of molecules produced by normal life.
*Enantiopure drug
An enantiopure drug is a pharmaceutical available in one specific enantiomeric form. Most biomolecules (proteins, sugars, etc.) are present in only one of many chiral forms, so different enantiomers of a chiral drug molecule bind differently (or ...
s - some pharmaceuticals have shown different activity depending on enantiomeric form,
*Aptamer
Aptamers are oligomers of artificial ssDNA, RNA, Xeno nucleic acid, XNA, or peptide that ligand, bind a specific target molecule, or family of target molecules. They exhibit a range of affinities (Dissociation constant, KD in the pM to μM rang ...
s ( L-ribonucleic acid aptamers): "That makes mirror-image biochemistry a potentially lucrative business. One company that hopes so is Noxxon Pharma in Berlin. It uses laborious chemical synthesis to make mirror-image forms of short strands of DNA or RNA called aptamers, which bind to therapeutic targets such as proteins in the body to block their activity. The firm has several mirror-aptamer candidates in human trials for diseases including cancer; the idea is that their efficacy might be improved because they aren't degraded by the body's enzymes. A process to replicate mirror-image DNA could offer a much easier route to making the aptamers, says Sven Klussmann, Noxxon Pharma's chief scientific officer."
* L-Glucose, enantiomer of standard glucose
Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ...
, Tests showed that it tastes likes standard sugar, but is not metabolized the same way. However, it was never marketed due to excessive manufacturing costs. More recent research allows cheap production with high yields; however the authors state that it is not usable as a sweetener due to laxative effects.
In fiction
The creation of a mirror human is the basis of the 1950 short story " Technical Error" by Arthur C. Clarke
Sir Arthur Charles Clarke (16 December 191719 March 2008) was an English science fiction writer, science writer, futurist, inventor, undersea explorer, and television series host.
Clarke co-wrote the screenplay for the 1968 film '' 2001: A ...
. In this story, a physical accident transforms a person into his mirror image, speculatively explained by travel through a fourth physical dimension. H. G. Wells
Herbert George Wells (21 September 1866 – 13 August 1946) was an English writer, prolific in many genres. He wrote more than fifty novels and dozens of short stories. His non-fiction output included works of social commentary, politics, hist ...
' ''The Plattner Story
"The Plattner Story" is a short story by English writer H. G. Wells, first published in 1896 in ''The New Review''. It was included in '' The Plattner Story and Others'', a collection of short stories by Wells first published in 1897, and in '' T ...
'' (1896) is based on a similar idea.
In the 1970 ''Star Trek'' novel '' Spock Must Die!'' by James Blish
James Benjamin “Jimmy” Blish () was an American science fiction and fantasy writer. He is best known for his ''Cities in Flight'' novels and his series of ''Star Trek'' novelizations written with his wife, J. A. Lawrence. His novel ''A Case ...
, the science officer of the USS Enterprise is replicated in mirror form by a transporter mishap. He locks himself in the sick bay where he is able to synthesize mirror forms of basic nutrients needed for his survival.
An alien machine that reverses chirality, and a blood-symbiont that functions properly only when in one chirality, were central to Roger Zelazny
Roger Joseph Zelazny (May 13, 1937 – June 14, 1995) was an American fantasy and science fiction writer known for his short stories and novels, best known for '' The Chronicles of Amber''. He won the Nebula Award three times (out of 14 nominatio ...
's 1976 novel ''Doorways in the Sand
''Doorways in the Sand'' is a science fiction novel by American writer Roger Zelazny. Featuring both detective fiction and comic elements, it was originally published in serial form in the magazine ''Analog Science Fiction and Science Fact''; t ...
''.
On the titular planet of Sheri S. Tepper's 1989 novel ''Grass
Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family (biology), family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and spe ...
'', some lifeforms have evolved to use the right-handed isomer of alanine
Alanine (symbol Ala or A), or α-alanine, is an α-amino acid that is used in the biosynthesis of proteins. It contains an amine group and a carboxylic acid group, both attached to the central carbon atom which also carries a methyl group sid ...
.
In the ''Mass Effect
''Mass Effect'' is a military science fiction media franchise created by Casey Hudson. The franchise depicts a distant future where humanity and several alien civilizations have colonized the galaxy using technology left behind by Elder race, a ...
'' series, chirality of amino acids in foodstuffs is discussed often in both dialogue and encyclopedia files.
In the 2014 science fiction novel '' Cibola Burn'' by James S. A. Corey, the planet Ilus has indigenous life with partially-mirrored chirality. This renders human colonists unable to digest native flora and fauna, and greatly complicates conventional farming. Consequently, the colonists have to rely upon hydroponic farming and food importation.
In the 2017 Daniel Suarez novel ''Change Agent'', an antagonist, Otto, nicknamed the "Mirror Man", is revealed to be a genetically-engineered mirror human. Serving as an assassin due to his complete immunity to neurotoxins, which he coats himself with in the form of a cologne-like aerosol, he views other humans with disdain and causes them to feel an inexplicable repulsion by his very presence.
The concept is used during Ryan North
Ryan North (born October 20, 1980) is a Canadian writer and computer programmer.
He is the creator and author of ''Dinosaur Comics'', and has written for the comic series of ''Adventure Time'' and Marvel Comics' '' The Unbeatable Squirrel Girl'' ...
's 2023 run on Fantastic Four
The Fantastic Four, often abbreviated as FF, is a superhero team appearing in American comic books published by Marvel Comics. The team debuted in '' The Fantastic Four'' #1 ( cover-dated November 1961), helping usher in a new level of realism i ...
as an existential threat towards the human population.
See also
*Xenobiology
Xenobiology (XB) is a subfield of synthetic biology, the study of synthesizing and manipulating biological devices and systems. The name "xenobiology" derives from the Greek word ''xenos'', which means "stranger, alien". Xenobiology is a form o ...
* Mirror matter – A hypothetical form of matter that interacts only weakly with normal matter, which could form mirror planets, potentially inhabited by mirror matter life.
*
Notes
References
{{Reflist
Chirality
Synthetic biology
Hypothetical life forms