The complete genome sequence of Lactobacillus bulgaricus reveals extensive and ongoing reductive evolution.
Lactobacillus delbrueckii ssp. bulgaricus (L. bulgaricus) is a representative of the group of lactic acid-producing bacteria, mainly known for its worldwide application in yogurt production. The genome sequence of this bacterium has been determined and shows the signs of ongoing specialization, with a substantial number of pseudogenes and incomplete metabolic pathways and relatively few regulatory functions. Several unique features of the L. bulgaricus genome support the hypothesis that the genome is in a phase of rapid evolution. (i) Exceptionally high numbers of rRNA and tRNA genes with regard to genome size may indicate that the L. bulgaricus genome has known a recent phase of important size reduction, in agreement with the observed high frequency of gene inactivation and elimination; (ii) a much higher GC content at codon position 3 than expected on the basis of the overall GC content suggests that the composition of the genome is evolving toward a higher GC content; and (iii) the presence of a 47.5-kbp inverted repeat in the replication termination region, an extremely rare feature in bacterial genomes, may be interpreted as a transient stage in genome evolution. The results indicate the adaptation of L. bulgaricus from a plant-associated habitat to the stable protein and lactose-rich milk environment through the loss of superfluous functions and protocooperation with Streptococcus thermophilus.
van de Guchte
M
M
Génétique Microbienne and Mathématique, Informatique et Génome, Institut National de la Recherche Agronomique, 78352 Jouy en Josas Cedex, France. maarten.vandeguchte@jouy.inra.fr
Penaud
S
S
Grimaldi
C
C
Barbe
V
V
Bryson
K
K
Nicolas
P
P
Robert
C
C
Oztas
S
S
Mangenot
S
S
Couloux
A
A
Loux
V
V
Dervyn
R
R
Bossy
R
R
Bolotin
A
A
Batto
J-M
JM
Walunas
T
T
Gibrat
J-F
JF
Bessières
P
P
Weissenbach
J
J
Ehrlich
S D
SD
Maguin
E
E
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D050260:Carbohydrate Metabolism; D019143:Evolution, Molecular; D016680:Genome, Bacterial; D020071:Interspersed Repetitive Sequences; D048668:Lactobacillus delbrueckii / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D048249:Streptococcus thermophilus / Q000378:metabolism; D026801:Synteny; D015014:Yogurt / Q000382:microbiology
D001426:Bacterial Proteins