Global profiling of Shewanella oneidensis MR-1: expression of hypothetical genes and improved functional annotations.
The gamma-proteobacterium Shewanella oneidensis strain MR-1 is a metabolically versatile organism that can reduce a wide range of organic compounds, metal ions, and radionuclides. Similar to most other sequenced organisms, approximately 40% of the predicted ORFs in the S. oneidensis genome were annotated as uncharacterized "hypothetical" genes. We implemented an integrative approach by using experimental and computational analyses to provide more detailed insight into gene function. Global expression profiles were determined for cells after UV irradiation and under aerobic and suboxic growth conditions. Transcriptomic and proteomic analyses confidently identified 538 hypothetical genes as expressed in S. oneidensis cells both as mRNAs and proteins (33% of all predicted hypothetical proteins). Publicly available analysis tools and databases and the expression data were applied to improve the annotation of these genes. The annotation results were scored by using a seven-category schema that ranked both confidence and precision of the functional assignment. We were able to identify homologs for nearly all of these hypothetical proteins (97%), but could confidently assign exact biochemical functions for only 16 proteins (category 1; 3%). Altogether, computational and experimental evidence provided functional assignments or insights for 240 more genes (categories 2-5; 45%). These functional annotations advance our understanding of genes involved in vital cellular processes, including energy conversion, ion transport, secondary metabolism, and signal transduction. We propose that this integrative approach offers a valuable means to undertake the enormous challenge of characterizing the rapidly growing number of hypothetical proteins with each newly sequenced genome.
Kolker
Eugene
E
BIATECH, 19310 North Creek Parkway, Suite 115, Bothell, WA 98011, USA. ekolker@biatech.org
Picone
Alex F
AF
Galperin
Michael Y
MY
Romine
Margaret F
MF
Higdon
Roger
R
Makarova
Kira S
KS
Kolker
Natali
N
Anderson
Gordon A
GA
Qiu
Xiaoyun
X
Auberry
Kenneth J
KJ
Babnigg
Gyorgy
G
Beliaev
Alex S
AS
Edlefsen
Paul
P
Elias
Dwayne A
DA
Gorby
Yuri A
YA
Holzman
Ted
T
Klappenbach
Joel A
JA
Konstantinidis
Konstantinos T
KT
Land
Miriam L
ML
Lipton
Mary S
MS
McCue
Lee-Ann
LA
Monroe
Matthew
M
Pasa-Tolic
Ljiljana
L
Pinchuk
Grigoriy
G
Purvine
Samuel
S
Serres
Margrethe H
MH
Tsapin
Sasha
S
Zakrajsek
Brian A
BA
Zhu
Wenhong
W
Zhou
Jizhong
J
Larimer
Frank W
FW
Lawrence
Charles E
CE
Riley
Monica
M
Collart
Frank R
FR
Yates
John R
JR
Smith
Richard D
RD
Giometti
Carol S
CS
Nealson
Kenneth H
KH
Fredrickson
James K
JK
Tiedje
James M
JM
D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D020411:Oligonucleotide Array Sequence Analysis; D016366:Open Reading Frames; D020543:Proteome / Q000032:analysis; D020592:Shewanella / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects
D020543:Proteome