Nanobacteria - Are They Alive?

Apr 23, 2008 By Lisa Zyga feature
Calcium carbonate crystals (nanobacteria-like particles) have a cellular appearance, but the new study shows that nanobacteria are not alive. Image credit: Martel and Young. ©2008 PNAS.

Tiny particles called nanobacteria have intrigued researchers in many ways since their discovery 20 years ago, but perhaps the most controversial question they pose is whether or not they are alive.

Nanobacteria – which sometimes go by the name “nanobes” or “calcifying nanoparticles” – don’t seem to fit scientists’ criteria for life. Researchers at a workshop hosted by the National Academy of Sciences for this specific reason concluded that the minimal cellular size of life on Earth must exceed 200 nm in diameter in order to contain the cellular machinery based on DNA replication. But nanobacteria can be as small as 80 nm – so, unless they contain some novel replicating mechanism, it seems unlikely that they constitute a form of life.

That’s just one piece of evidence against living nanobacteria named in a recent study by Jan Martel of Chang Gung University in Taiwan and John Ding-E Young from The Rockefeller University in New York, which was published in PNAS. Martel and Young have studied healthy human blood serum that contains what they call “nanobacteria-like particles” (NLP), composed of the compound calcium carbonate (CaCO3), or limestone. The researchers performed a series of experiments showing that the tiny particles contain no traces of DNA or RNA, and suggest that their formation can be explained by non-biological means.

“We believe that this study provides substantive proof that nanobacteria are not living entities,” Young told PhysOrg.com. “Some previous studies have hinted that this is the case, but have not provided a chemical composition or formulation that could explain the nanobacteria phenomenon in its entirety.”

One thing about nanobacteria that’s clear is that they’re very widespread, occurring in practically all human material tested. Under an electron microscope, nanobacteria (and the NLPs) look like typical bacteria, and even resemble cells undergoing division. They’re also hardy: when the researchers bombarded the NLPs with 30 kGy (kiloGray) of gamma radiation, it didn’t prevent them from growing in cultures, in accordance with previous studies.

Another bacteria-like property of NLPs is that they have the ability to nucleate hydroxyapatite (HAP), a calcium phosphate crystal that largely composes the bones and teeth of humans and animals. Previous research has suggested that this might be how the nanobacteria self-replicate. When Martel and Young investigated this issue in their study, however, they found that HAP only forms around NLPs under certain conditions. For example, when mixed with some crystal-growth-inhibiting proteins, NLPs stop nucleating HAP, indicating that HAP is not really necessary for NLP formation.

Instead, their experiments lead Martel and Young to suggest a chemical rather than biological model for NLP formation. Based on this hypothesis, they could control the speed and shape of NLP formation in vitro by simply varying the substrates needed for the precipitation of calcium carbonate.

These findings could also shed light on nanobacteria that have shown up in a variety of other areas, from sandstones of the Triassic and Jurassic eras to meteorite fragments from Mars. The chemical process that the researchers describe here for nanobacteria formation could be the same for these nanobacteria, as well.

“Nanobacteria have been heralded as the smallest cellular forms on Earth and as candidates to explain how cellular life began on Earth and other extraterrestial bodies, like meteorites and Mars,” Young said. “Our results clearly disprove that nanobacteria are living organisms. We have shown that all the previous vast body of literature in nanobacteria can actually be explained by a chemical and abiotic mechanism involving the simple deposition of limestone or calcium carbonate.”

Nano-pathogens?

Previous research has suggested that nanobacteria could be the cause of a wide variety of diseases, from kidney stones to atherosclerosis – a prospect which now must be tested with the new nanoparticles. Because they multiply faster in low-gravity environments, NASA is particularly concerned in light of astronauts’ increased risk for developing kidney stones. According to Martel and Young, these nanoparticles may be part of a much wider family of organic mineral complexes that seem to assemble and propagate as if they are alive – in fact, much like prions, the self-assembled proteins that cause mad cow disease.

“We believe that we have uncovered a whole family of organic mineral complexes that give the seeming appearance of replication and self-assembly as if they are live entities,” Young said. “They appear to be ubiquitous entities found in living and non-living substrates.”

Some researchers have even been developing antibodies to try to combat the “pathogenic” nanobacteria. A company called Nanobac Oy, owned by Nanobac Life Sciences and founded by the discoverers of nanobacteria, has antibodies that are commercially available and sells diagnostic kits for detecting the nanobacteria. The antibodies come from mice cells that have been immunized with nanobacteria obtained from cows.

To try to understand the nature of the reaction between the antibodies and nanobacteria, Martel and Young tested the antibodies on NLPs, which gave positive reaction, as expected. Surprisingly, however, the same antibodies also reacted with albumin, the most common protein in the blood serum. Since proteins like albumin can not possibly have been produced by any living bacteria, they’re probably attached to the calcium carbonate particles, and reacting with the antibodies, the researchers explain.

“Since nanobacteria have now been disproved as living entities, it is unlikely that they can produce diseases as bacteria would,” Young added. “Their common distribution in living and non-living environments – from blood to soil to meteorites – must be taken into account when speculating a role for them in disease. This is not to say that such nanoparticles are incapable of causing disease – with which they may very well be involved – but any such claims must be rigorously established through verifiable documentation, which is lacking at the present moment.”

More information: Martel, Jan, and Ding-E Young, John. “Purported nanobacteria in human blood as calcium carbonate nanoparticles.” Proceedings of the National Academy of Sciences. April 8, 2008. vol. 105, no. 14, 5549-5554.

Copyright 2008 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.

Explore further: Tough foam from tiny sheets

add to favorites email to friend print save as pdf

Related Stories

Recommended for you

Tough foam from tiny sheets

16 hours ago

Tough, ultralight foam of atom-thick sheets can be made to any size and shape through a chemical process invented at Rice University.

Graphene surfaces on photonic racetracks

Jul 28, 2014

In an article published in Optics Express, scientists from The University of Manchester describe how graphene can be wrapped around a silicon wire, or waveguide, and modify the transmission of light through it.

Simulating the invisible

Jul 28, 2014

Panagiotis Grammatikopoulos in the OIST Nanoparticles by Design Unit simulates the interactions of particles that are too small to see, and too complicated to visualize. In order to study the particles' behavior, he uses ...

Building 'invisible' materials with light

Jul 28, 2014

A new method of building materials using light, developed by researchers at the University of Cambridge, could one day enable technologies that are often considered the realm of science fiction, such as invisibility ...

User comments : 9

Adjust slider to filter visible comments by rank

Display comments: newest first

MikeMarianiMD,FAAP
5 / 5 (1) Apr 23, 2008
I concur with the assessment that nanobacteria are not living, yet I wonder what justifies the assertion that they can not produce diseases. Lead, for example, is not alive, but lead toxicity is a significant disease.
The scientists are apparently not physicians.
OregonWind
not rated yet Apr 23, 2008
"I wonder what justifies the assertion that they can not produce diseases"

That is not what the article is telling us.

earls
4 / 5 (1) Apr 24, 2008
While Bio isn't my specific field of interest, this is definitely intriguing. Is it yet known what exactly the dividing line between "alive" and "not-live (dead?)" exist? Just what exactly is the simplest form of life and what "triggers" its "aliveness?" Do molecules simply become so large and/or complex that the physics of quantum mechanics creates a recursive replication process?! Yet evolves!?
Mercury_01
5 / 5 (1) Apr 24, 2008
%u201COur results clearly disprove that nanobacteria are living organisms. We have shown that all the previous vast body of literature in nanobacteria can actually be explained by a chemical and abiotic mechanism involving the simple deposition of limestone or calcium carbonate.%u201D

with that kind of reasoning, they could disprove life alltogether. " Perhaps I am not alive, but simply a chemical and mechanical deposition of elements! I say if it defies entropy, it's a lifeform.
earls
not rated yet Apr 24, 2008
I made that assumption once too Merc, but life does not defy entropy any more than heavy atoms do.

Life may do so temporarily, but everything dies and decays thereby keeping in step with overall entropy.

Take the galaxy article under space/earth science... They defy entropy by growing larger and evolving, but (supposedly) they too will some day decay to nothing.

Unless you consider galaxies alive (which is debatable based on the definition there of), nothing defies entropy so your definition doesn't really work.
Mercury_01
4 / 5 (1) Apr 24, 2008
Good point. in a physical sense, nothing can forever escape the laws of thermodynamics, but in a world where bare compounds can decompose in a matter of minutes, life runs the other way in defiance and becomes more complex as it finds new ways to express the finer points of the nature of the universe. And if it werent for nucleic decay, humans might find a way to keep thier race alive long after the heavens go dark and planets are forgotten, and on into infinity. So in a way, lifeforms defy entropy. This has always been an interesting topic for me personally, with far reaching implications. I choose to draw the line of life further into the realm most would call "inanimate". Or, rather, perhaps there is no line, but varying degrees of conciousness within matter.
Soylent
5 / 5 (1) Apr 26, 2008
I say if it defies entropy, it's a lifeform.


1) Crystals of salt are alive?

2) No closed system defies entropy. Not life, not anything else. Just put a lifeform in a closed container without light, food and oxygen and watch it decay as it cannot get low entropy forms of energy with which it can organize its internal structure.
ontheinternets
5 / 5 (1) Apr 27, 2008
"alive" and "life" are words in the English language which were created and defined by people. Like any English word, it may be subject to ongoing change. You can select an acceptable definition and see if these things fall within it. It's also okay to go with your gut a bit about whether or not you want these things to fall within the definition -- and if your choice disagrees with our current definitions of the words, then you've got to update them. It's not set in stone and I'd go so far to say that it's not necessarily as important or interesting as understanding precisely what these things are and how they operate.
mrlewish
not rated yet Apr 28, 2008
Well, isn't part of this Galaxy alive?