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PROFESSOR: If you're
a teacher and you're

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inventing a course for the first
time, or revising it a lot,

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you sit down with
your teaching partners

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and you put on the
table all the ideas.

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Teaching, you've got an
ever-expanding universe

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of knowledge out
there, and you have

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to cherry-pick the things that
are going to be important.

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It has to hang together.

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One of the strategies
JoAnne and I thought,

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when we went into the current
iteration of teaching 5.07

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biological chemistry, was
to abandon completely,

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higher eukaryotes, namely
us, because genome sequencing

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projects had sequenced so many
bacteria that one could create

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an entire course in biochemistry
that would be very meaningful,

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just focusing on microorganisms.

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We spent a couple of days
reading and thinking about it.

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That would be the course
JoAnne and I would teach,

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if it weren't for the
fact that we actually

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have-- feel as though we have
a commitment to students that

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are going to go on
to medical school

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and therefore, if we avoided
mammalian biochemistry,

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students wouldn't know
anything about the mitochondria

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and organelles, and
things like that that

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are associated with eukaryotes.

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We wouldn't be able to make
these connections to disease,

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the physiological scenarios.

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Nevertheless, why were we
so interested in bacteria?

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What would be an
interesting story,

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that I might be able to tell
you, if we had taken that path.

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So we have a fellow in
biological engineering,

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named Eric Alm.

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And he is an informaticist
and an engineer,

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and an extremely good chemist.

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He really knows his pathways.

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When he looks at
a cell, he thinks

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about what it is, but
also where it came from,

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in terms of how it evolved from
precursors, its family tree,

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so to speak.

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One of the most
interesting organisms

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that he's published
on, not too long ago,

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is an organism
called, Desulforudis.

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And this would be a wonderful
biochemistry course in itself.

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He wondered, if he went out and
dug up a cubic meter of dirt--

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and outside MIT-- and if
he did 16S RNA sequencing,

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how many living things would
be there, many thousands, maybe

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10,000.

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Then he asked the question, what
if you went down 100 meters,

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you know, maybe you see 1,000.

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But what if you go down
until there's really

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only one thing there.

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And that's what he did, going
down two miles into the ground.

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And there was a single, species
ecosystem called, Desulforudis.

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And I remember
seeing this paper,

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and I brought it over to JoAnne.

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I was so excited
because the last picture

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showed its metabolic network,
its metabolic pathways.

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It had everything.

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And it makes sense.

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It can't rely on other things.

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For example, we can't make
all of our amino acids.

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We got to get them
from food that we eat,

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or in our co-factors,
some of our vitamins

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are made by the
bacteria in our gut.

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So, if all the bacteria
disappear, we would too.

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So we rely on other
things, but Desulforudis

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doesn't rely on anything.

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So when you look at it's
biochemical networks,

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what you see is that
it can fix nitrogen. It

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can take N2 and convert
it NH3, and then

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put that into amino
acids, and it can

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make all of its amino acids.

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It has a really good
pentose phosphate pathway.

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It actually uses
radiation in a strange way

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to generate some of the
energy that it needs.

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It uses it to generate
carbon monoxide.

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Ultimately, that CO is going
to form an acetyl group that

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will be able to generate
all of the organic material

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inside the Desulforudis.

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It's got all kinds of
electron transport pathways.

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So it's developed
enormous versatility

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by being a
single-species ecosystem.

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So, again, this
was a course where

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we had to make a compromise
because of our clientele.

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Teachers have to
think about that.

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We have to teach to what
the people need in order

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to go on to the next step.

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But as sort of a
closing thought,

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I think that it
would be wonderful

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for next-generation biochemists
to really turn their attention

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to the microbial world, to
teach this vast biochemistry

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and understand how
bacteria effortlessly,

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swap biochemical pathways,
pick-up entire biochemical

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pathways without even
breaking a sweat.

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Whenever they find
themselves stressed,

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they just pick up a new
pathway and they survive.