First detailed microscopy evidence of ‘nanobacteria’(kurzweilai.net)
kurzweilai.net
First detailed microscopy evidence of ‘nanobacteria’
http://www.kurzweilai.net/irst-detailed-microscopy-evidence-of-nanobacteria-at-the-lower-size-limit-of-life?utm_source=KurzweilAI+Daily+Newsletter&utm_campaign=8d0828414b-UA-946742-1&utm_medium=email&utm_term=0_6de721fb33-8d0828414b-281895037
5 comments
What they actually said was "This is the smallest a cell can be and still accommodate enough material to sustain life" - this was shortened in the lede.
But "as small as life can get" is a thing that has been studied, eg for Mars Sample-Return missions, they have to figure out a safe filter size (chapter 3): http://science.nasa.gov/media/medialibrary/2013/01/17/ESF_Ma...
An important distinction is whether these organisms can live 'independently' - a virus relies on a host. Quoting from the doc above: it is believed that theoretically a coccoid[1] cell with the minimum number of genes to be free living in an environment other than a living host would have a minimum cell diameter of approximately 0.15–0,2 μm. - which is around about the size of the beasties in the parent article.
They did consider smaller biological entities though, like gene transfer agents[2], and recommended filters such that nothing over 0.05μm is released under any circumstances, and that there's only a 1 in a million chance of anything smaller than 0.01μm escaping.
[1] Spherical. http://en.wikipedia.org/wiki/Coccoid
[2] http://en.wikipedia.org/wiki/Gene_transfer_agent
But "as small as life can get" is a thing that has been studied, eg for Mars Sample-Return missions, they have to figure out a safe filter size (chapter 3): http://science.nasa.gov/media/medialibrary/2013/01/17/ESF_Ma...
An important distinction is whether these organisms can live 'independently' - a virus relies on a host. Quoting from the doc above: it is believed that theoretically a coccoid[1] cell with the minimum number of genes to be free living in an environment other than a living host would have a minimum cell diameter of approximately 0.15–0,2 μm. - which is around about the size of the beasties in the parent article.
They did consider smaller biological entities though, like gene transfer agents[2], and recommended filters such that nothing over 0.05μm is released under any circumstances, and that there's only a 1 in a million chance of anything smaller than 0.01μm escaping.
[1] Spherical. http://en.wikipedia.org/wiki/Coccoid
[2] http://en.wikipedia.org/wiki/Gene_transfer_agent
Prions self replicate, but require the host to have the correctly folded protein.[1] Of course there's viruses too, which are self replicating but need to infect some other organism.
Maybe crystals? Now we're getting in to the potentially wonky question of 'what is life?'
1. http://en.wikipedia.org/wiki/Prion
Edit: grammar for clarity.
Maybe crystals? Now we're getting in to the potentially wonky question of 'what is life?'
1. http://en.wikipedia.org/wiki/Prion
Edit: grammar for clarity.
Prions are not considered alive under any reasonable definition of life. They're infectious, but you can't really call it replication as they just trigger a conformational change in the correctly folded prion protein
Yes, that's true. I should not have included the word 'self' with regard to prions.
Are viruses considered 'alive'?
Are viruses considered 'alive'?
No. Viruses require a live host in order to replicate. That sounds tautological, but I'm not sure how else to say it briefly.
It's begging the question... every 'living' organism also requires a favorable environment in order to replicate
Couple of things stood out:
The DNA has been sequenced but the article reports that "The bacterial cells have densely packed spirals that are probably DNA". To me it seems strange not to know the gross anatomy but to be able to sequence the DNA; I can see how it could happen.
Also "The images revealed dividing cells, indicating the bacteria were healthy and not starved to an abnormally small size." but the write up says they appear to need other bacteria to function properly - and suggests the pili are involved in that. If they can stay healthy and divide in an environment without other bacteria then what do they need the other bacteria for, entertainment??
These parts appear to be based on the asbtract viz. "Ultrastructural features potentially related to cell and genome size minimization include tightly packed spirals inferred to be DNA, few densely packed ribosomes and a variety of pili-like structures that might enable inter-organism interactions that compensate for biosynthetic capacities inferred to be missing from genomic data."
The DNA has been sequenced but the article reports that "The bacterial cells have densely packed spirals that are probably DNA". To me it seems strange not to know the gross anatomy but to be able to sequence the DNA; I can see how it could happen.
Also "The images revealed dividing cells, indicating the bacteria were healthy and not starved to an abnormally small size." but the write up says they appear to need other bacteria to function properly - and suggests the pili are involved in that. If they can stay healthy and divide in an environment without other bacteria then what do they need the other bacteria for, entertainment??
These parts appear to be based on the asbtract viz. "Ultrastructural features potentially related to cell and genome size minimization include tightly packed spirals inferred to be DNA, few densely packed ribosomes and a variety of pili-like structures that might enable inter-organism interactions that compensate for biosynthetic capacities inferred to be missing from genomic data."
> To me it seems strange not to know the gross anatomy but to be able to sequence the DNA; I can see how it could happen.
As far as I understand, DNA sequencing is about breaking target into pieces and using clever tricks to fish out nucleotydes and determine their order. It seems to me that you don't need to know where and how DNA is exactly located to be able to brute-force its sequence.
As far as I understand, DNA sequencing is about breaking target into pieces and using clever tricks to fish out nucleotydes and determine their order. It seems to me that you don't need to know where and how DNA is exactly located to be able to brute-force its sequence.
That's what I meant by "I can see how it could happen". I guess I imagined that they would have confirmed the major features with further microscopy prior to publication; perhaps that's harder than I imagined but once you've seen STM images of atoms it seems like recognising DNA in a sample should be easy.
> "The images revealed dividing cells, indicating the bacteria were healthy and not starved to an abnormally small size." but the write up says they appear to need other bacteria to function properly - and suggests the pili are involved in that. If they can stay healthy and divide in an environment without other bacteria then what do they need the other bacteria for, entertainment??
I require food and water to function properly, but I'm not currently eating or drinking. These microbes were isolated using filteration, so presumably they were surrounded by other bacteria to leech from, right up to the point they were isolated.
I require food and water to function properly, but I'm not currently eating or drinking. These microbes were isolated using filteration, so presumably they were surrounded by other bacteria to leech from, right up to the point they were isolated.
"the images revealed dividing cells" - with the present participle "dividing" - to me suggested isolation prior to division; hence the question.
The solution you proffer is the expected situation but then the images would be prior to isolation or they'd show _divided_ cells (which is entirely uninteresting and tautological I think).
The solution you proffer is the expected situation but then the images would be prior to isolation or they'd show _divided_ cells (which is entirely uninteresting and tautological I think).
> To me it seems strange not to know the gross anatomy but to be able to sequence the DNA; I can see how it could happen.
They're just looking at an image of the cell and seeing these unknown structures. They cannot be sure what it is. It is impossible to determine whether its DNA or not from the image.
Quite independent of this, we can take a sample containing the organism and sequence its DNA without knowing where it originated from in the source cell. DNA is purified for sequencing from other cell structures by chemical and mechanical methods.
They're just looking at an image of the cell and seeing these unknown structures. They cannot be sure what it is. It is impossible to determine whether its DNA or not from the image.
Quite independent of this, we can take a sample containing the organism and sequence its DNA without knowing where it originated from in the source cell. DNA is purified for sequencing from other cell structures by chemical and mechanical methods.
Maybe they wanted to sound careful. I guess that densely packed spirals which take up a significant part of the miniscule volume would almost have to be the DNA, after all 1 Mbp need to have a certain volume, but I don't know the specifics and how bacteria tend to pack their DNA.
Mimivirus (https://en.wikipedia.org/wiki/Mimivirus), a virus which is actually twice the size of these nanobacteria has already prompted some debate about the relationship of viruses to the kingdoms of "life" and, for some, a reevaluation of what we mean by "life". These bacteria are likely to add to that debate.
Genetically these bacteria are apparently not that small--on the order of a million DNA bases. We already know of smaller bacteria with just a few hundred thousand bases (e.g. M. genitalium.) And so from the perspective of "minimal life", these may not be all that special.
Midiclorians... finally!
And then these bacteria come pretty close to virus and cell organelles, raising questions of when to call a parasite "life" or "not life".