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

by ca98am79 • 11 years ago

51 17 11 years ago

kurzweilai.net

pbhjpbhj3• 11 years ago

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."

bayesianhorse2• 11 years ago

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.

TeMPOraL• 11 years ago

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.

pbhjpbhj3• 11 years ago

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.

kyberias• 11 years ago

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.

chriswarbo• 11 years ago

"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.

pbhjpbhj3• 11 years ago

"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).

bayesianhorse2• 11 years ago

"As small as life can get" is an interesting claim. Without reading the paper I am wondering if life before bacteria wouldn't have to be smaller. Maybe even devoid of membranes. At the very beginning there should even have been molecules which catalyzed (=enhanced) their own synthesis, first a little, then progressively more until you had something like an RNA replication machine...

And then these bacteria come pretty close to virus and cell organelles, raising questions of when to call a parasite "life" or "not life".

TheSpiceIsLife2• 11 years ago

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.

fabian2k• 11 years ago

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

bazzargh• 11 years ago

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

pjgomez• 11 years ago

Midiclorians... finally!

superfx• 11 years ago

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.

ajarmst• 11 years ago

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.

First detailed microscopy evidence of ‘nanobacteria’

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