TY  - GEN
A1  - Ponomarova, Olga
N2  - Microorganisms  in  nature  live  in  interconnected  communities,  where  the  language  of  biochemistry 
creates means for
communicating, fighting, and cooperating with each other. This work investigates 
one  of  the 
ways
for  microbial  interactions 
-
nutrient  exchange. 
It  is 
focus
ed
primarily  on  co
-
metabolism   of 
Saccharomyces   cerevisiae
and   lactic   acid   bacteria 
-
Lactococcus   la
ctis
and 
Lactobacillus  plantarum
-
community  whose  composition  was  inspired  by  co
-
occurrence  of  yeast 
and  LAB  in 
a 
multitude  of  naturally  fermented  foods.  Specifically, 
I
w
as
interested  in  detecting 
metabolic  interactions  between  budding  yeast  and  lactic  a
cid  bacteria,  identifying  transferred 
molecules,  exploring  metabolic  mechanisms  of  their  biosynthesis  and  excretion,  and  understanding 
possible 
causes
behind them. 
A c
ombination of experimental and computational methods 
was used 
to understand how nutritio
nal 
dependencies  shape  communit
ies
of  microorganisms. 
First  step 
involved 
compos
ing
a  synthetic 
community  of  common  laboratory  strains  of  yeast  and  lactic  acid 
bacteria
.  Following 
a
series  of 
experiments with chemically defined media,
LAB 
revealed 
their me
tabolic dependency on
yeast for 
growth and survival. This m
ixed species community appears
to be
stable and is sustained through 
the 
flow of small nitrogenous 
molecule
s from yeast to bacteria. Nutrient cross feeding was found to be a 
result   of   overflow   meta
bolis
m   in   yeast,   which   release   excess
catabolit
es   under   particular 
combinations of available nitrogen sources. The o
bserved nutrient excretion involve
s
a set of genes 
that  regulate  yeast  nitrogen  metabolism  when  depleted  of  preferred  nitrogen  sources.  We  h
ave 
recreated   co
-
metabolism   of   yeast
-
LAB   community,   as   well   as   multiple   natural   bacterial 
communities, with multi
-
species genome
-
scale metabolic modeling. Simulation results demonstrated 
a 
link  between  metabolic  cross
-
feeding  and  species  co
-
occurrence,  and
proved  its  high  potential 
of 
the method 
for predicting metabolite exchange in microbial communities.
In  this  project, 
the
inter
-
kingdom  model  community  of  wild  type  microorganisms  has  been 
established   and   characterized.   Peculiarities   of   yeast   regulatory   n
etwork,   in   certain   media 
compositions, cause ?wasteful? excretion of amino acids and other metabolites. This in turn cr
e
ates a 
stable  niche  for  growth  of  lactic  acid  bacteria
,  which  are
auxotro
phic  for  multiple  amino  acids. 
D
escribed  scenario  of  metabolic 
dependency  between  yeast  and  lactic  acid  bacteria  demonstrates 
how  survival  of  one  species  can  be  driven  by  metabo
lic  idiosyncrasy  of  the  other.  The  y
east
-
LAB 
interaction  is  established  instantly,  and  thus  can  serve  as  a  first  step  in  evolution  of  cooperat
ion.
AV  - public
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/19856/
TI  - Mapping Metabolic Interactions between S. cerevisiae and Lactic Acid Bacteria
Y1  - 2015///
ID  - heidok19856
ER  -