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Saturday, June 25, 2016

BACTERIA vs HUMAN CELLS: 1 to 1 (FINAL) PT2/3

PART 1 is HERE

by @sciencemug

Oooh, welcome back my dearest English speaking-thinking-reading visitor, welcome to the second part of the postHow to use the hologram of a white rhino called <<Slim Tim>> to cook spaghetti, wash your conscience and put up a bolero dance act in the middle of the dining room of the President of the Guatemalan branch of  <<The Authority For The Perfect Fonduta>> while he/she’s having a private conversation with his/her lawyer about the lawsuit filed for misleading advertising against the city of Cheeseville (43°28′08″N 88°04′50″W”)"… Ooops, nope, sorry, eheh, just confused the posts, this one‘s still under scrutiny of the “Commission of Weary Neurons and Short Sleeve Shirts with Ties” to get the “go” for publication.

Ok, then, let’s start again.

Oooooh, welcome back etc. to the second part of the post which tells the story of a student, a doctor and a professor (Mr. Sender,  Dr. Fuchs & Prof. Milo aka the SFMs) who don’t enter a bar but instead show how the commonly accepted notion that, in the ecosystem the human body is, bacteria outnumber human cells by 10 to 1 (in an adult, healthy, 20-30 years old, 1.70m tall, 70kg* heavy reference man (1) here friendly called Mr. Ref) is not true.

The SFMs first collect evidence –as the Part1 of this post reports- that the number of bugs in&on human bodies is not, as estimated till now, in the order of 1014, but rather of a factor of 10 smaller. It is, indeed, 3.9x1013.

The three happy researchers then proceed to update the second number that is used for the 10 to 1 ratio (the first one being that of the bacteria): the number of the actual human cells in the human body.

And what follows is the tale of how they do that.

Reference  man aka Mr. Ref (by @sciencemug)
Reference  man aka Mr. Ref (by @sciencemug)

The SFMs once again start checking the scientific literature. They find that, in papers from 1985 to 2013, the amount of the human cells is reported as ranging between 1012 and 1014.

Our curious scientists, in their study, mention only three different kind of approaches followed in the years by their colleagues to calculate how many little bricks make the human building.

The first approach switches from the fit 70kg Mr. Ref to a bigger 100kg man, and then divides the mass of this hulk by the 10-12 - 10-11kg mass (“assuming cell volumes of 1,000-10,000 µm3, respectively” Sender et al, 2016; (P)) of what is considered to be the “representative” (P) mammalian cell. This method clearly doesn’t consider that human body’s mass is also made by extracellular stuff, besides the cells themselves. Anyway it is a clear and rather concise way to get to a final result: human cells are between 1013 and 1014.

The second approach is based on DNA. It starts valuating the number of cells in a mouse. No, its name is not Mickey. No, it does not show its compulsive germ phobia by always wearing a pair of white gloves. And no, its best friend is not a talking biped dog with wide spaced beaver front teeth which for some inexplicable reason has evolved while the other dog of the situation just barks, wags its tail, walks on all fours and probably farts regardless of anything and anybody. The mouse here is a 25gr thing, with 20mg of DNA in it (the Mickey guy instead has tons of DNA, but that’s Disney Narrative Appeal, not DeoxyriboNucleic Acid). This total gloveless mouse body amount of DNA is divided by that of a single diploid gloveless mouse cell (namely 6x10-12g) to get a total of about 3x109 cells forming the above mentioned gloveless mouse body.

This second method, then, makes a proportion between a Mr. Ref’s mass and the tiny mouse mass, and, like that, calculates that the 3x109 cells of the gloveless mouse correspond to about 1013 cells in a human body.

by @sciencemug
by @sciencemug

  [The mouse (PC) and mouse (animal) images are Public Domain pics adapted by @sciencemug (source: Wikimedia Commons)]


The third approach to calculate the totality of human cells in a human being that the SFMs mention is the one used by Bianconi et al in 2013 [(2); oh, visitor, try to remember this name ‘cause I’ll mention it again and again in this post since the SFMs often use the Bianconis’ research as a reference source of data to compare their own data to. Ok, let’s help you out on this: let’s make that every time I’ll recall the Bianconis’ study I also contextually write the symbol “§”, that is not logically linked in whatsoever way to the issue, but it’s strange and complicated and unique and mysterious, so it should stick to your mind. So “§” - besides possibly being one of the five symbols (the other four are up to you to be found) that switch on, via hypnotic suggestion, some dormant cell of spies from Planet X that has the order to cut every single bottle of whisky on Earth with 9.576ml of juice of squeezed algae of the Sargasso Sea so to slightly alter and worst the whisky taste, depress the by this confused and disconcerted whisky purists, weaken their will, and start from them to create a fifth column which will help to eventually fulfill Planet X prime directive: to globally destabilize human civilization by stealing every single stamp on Earth which portray the Elvis (the first Planet X undercover agent ever who’s now collecting funds to sustain his 2018 “Khan of Planet X” campaign) - will be there to remind you of the Bianconis’ paper].

The Bianconi’s § lab bunch doesn’t focus on the elusive “average” human cell, but instead estimate the “number of cells in the body by type or organ system [and] the cell count [is] obtained by either a literature reference or by a calculation based on direct count in histological cross sections”(P_Rx). Aaand, like that, dear human visitor, these patient science people check all yours 56 cells types and get to

Friday, June 10, 2016

BACTERIA vs HUMAN CELLS: 1 to 1 (FINAL) PT1/3

bacteria vs humans (by @sciencemug)
by @sciencemug
The ratio between bacteria and human cells in the human body is 1 to 1 and not, as commonly thought till now, 10 to 1.
The updated estimate has been provided by three scientists from Israeli and Canadian universities in a study published on the science journal Cell.
(A pre-print version of the paper is avaiable also on bioRxiv, a free online archive for unpublished research papers in the field of life sciences).


PART 1/3

Ooooh, hallo dear English speaking-reading-hearing visitor, welcome back to me, @sciencemug, the blog/podcast/twitter account which tells science stories, masters the ancient art of napping en plein air, breeds race sloths (for adrenaline addicted betters who like to stretch as much as possible the adrenaline-producing suspense of the races) aaand which sometimes (but not this time) talks to you thanks to the voice that is kidnapped, via a voodoo-wireless trick, from a veeery very very dumb dude.
Aaand which does all of this in Eng?ish, a language that is to proper English what a sneeze is to an authentic expression of free will and a student loan is to a cascade of donuts+pizza which plunges into a pool full of prosecco, gold and diamonds (and beautiful shoes if you’re a lady) and that is surrounded by sexy half naked women/men holding signs that say: “all of this is for you [YOUR NAME], for free. Come and get it!


Today I’m gonna tell you the story of the death of a semi-scientific almost urban legend about numbers, bacteria and human cells!


RIP 10-1  (by @sciencemug)
by @sciencemug

Soo, the story goes like this: a biology student, Ron Sender, a medical doctor, Shai Fuchs and a biology professor, Ron Milo (aka the SFMs) join their efforts to debunk the myth that, in the human body, bacteria outnumber human cells by 10 to 1.
Well, in the human body… Let’s say in the human body of an healthy adult male between 20-30 years of age, weighing 70 kg (oooooh for your brain’s sake, get over all this “I don’t know the Metric System-SI gnè gnè gnè”… Look, it’s more rational, efficient and simple than yours, besides being used worldwide. Stop whining and learn it!) and 170 cm in height that scientists use as the reference human being (aka Mr. Ref) since 1975 [when The International Commission on Radiological  Protection (alias ICRP) publishes the 480 pages long “Report of the Task Group on Reference Man, ICRP Publication 23” which addresses the need to define a reference individual for the studies regarding humans and the risks and consequences of radiations exposition (1)].
 

Ok, let’s say that it’s true that a looot of bacteria (belonging to more than “10,000 microbial species (2))” -at least in the healthy Western population- live in and on you, and that they “inhabit just about every part of the human body (2)” (skin, up the nose, mouth, guts and so on). But the news is that the number of these microorganisms, the SFMs say, is smaller than thought.
 

First of all the science trio gets to the roots of the 10:1 myth, digging deep into the science literature and finding out that all the recent papers that report the 10 to 1 ratio refer to just one study published in 1977 by Savage (aaand good luck if you want to read it for free… By the way, in case you find it, please send me a copy of it).
Now, this study, the SFMs say, is a solid piece of science work, but, althoughreferenced over 1000 times in the literature often in the context of the estimate for the vast overabundance of bacteria over human cells” (Sanders et al, 2016; (P)) its 10 to 1 estimate is just a rough calculation. Above all, Sender and lab coat pals precise, it isn’t meant at all to becomethe cornerstone of an entire field(P), being this one the human microbiome field, namely the research area which sees human beings as ecosystems formed by human cells and a plethora of other life forms, mostly bacteria (i.e. the microbiota).
Moreover, our three science myth-busters add, ironically the very same 1977 Savage study refers to another paper by Luckey dated 1972 (again, good luck if you wanna read it) for the total amount of bacteria harbored by humans (FIG1).
 
The chain of citations (adaptation of a figure of Sander et al, 2016 paper by @sciencemug)
 FIG 1

This 1972 Luckey’s paper says that you human beings live with 1014 bacteria, assuming that your alimentary tract have a capacity of about 1liter (and thus of roughly 1kilogram) and that it contain 1011 bugs per gram (gram: see above, you “gné gné gné”) (FIG2).
 

by @sciencemug
by @sciencemug
[Hamlet's image is a Public Domain pic adapted by @sciencemug (source: Wikimedia Commons)]

FIG2

Soooo, dear listener, being you the smart ecosystem you are, I guess you’re probably wondering why the ‘70s science guys and all the science community after ‘em focus only on the bacterial population of the alimentary tract to determine how many microbes inhabit your whole body, right? I mean, I can feel you thinking “hey, wait a min dude – sorry, pal, but technically I’m not a dude (and also non technically, I’ve to say)…- I’m much more than my mouth stomach and bowels, c’mon, I’ve a couple of lungs (just to mention something) eyes, a lot of skin, those funny thingies I can’t figure out why be there, yeah, those… I mean, really, I’ve got a lot of stuff of me other than mouth stomach and bowels!”.
Aaand yeah, you’re right dear visitor, you’re the proud owner of lungs, eyes, skin and the non-bowel rest, but, science at hand, the ‘70s lab guys were right to focus on the alimentary tract to quantify the microbiota members of the human body, and even our science myth-busters SFMs back ‘em up on this. Well, more or less.
Actually our science trio specifies that, of the whole human alimentary tract, the relevant part is only